Wastewater Treatment Facility Conceptual Design...
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1{ It C IF ; fi \\'iY" [I) JUl t I. \1 REPORT ---- - --- ._ ., ..... --- GlOBAl. PERSPECTIVE. LOCAL lOCUS. Town of Lumsden Wastewater Treatment Facility Conceptual Design Report July 2011
Transcript of Wastewater Treatment Facility Conceptual Design...
1{ It C IF; fi \\'iY" [I)
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REPORT ---- - --- . _., ..... ---
GlOBAl. PERSPECTIVE.
LOCAL lOCUS.
Town of Lumsden
Wastewater Treatment Facility Conceptual Design Report
July 2011
CONFIOENTIALITY AND © COPYRIGHT
This document is for the sole use of the addressee and Associated Engineering (Sask.) Ltd. The document contains proprietary and confidential information that shall not be reproduced in any manner or disclosed to or discussed with any other parties without the express written permission of Associated Engineering (Sask.) Ltd. Information in this document is to be considered the intellectual property of Associated Engineering (Sask.) Ltd. in accordance with Canadian copyright law.
This report was prepared by Associated Engineering (Sask.) Ltd. for the account of Town of Lumsden. The material in it reflects Associated Engineering (Sask.) Ltd.'s best judgement, in light of the information available to it, at the time of preparation. Any use which a third party makes of this report, or any reliance on or decisions to be made based on it, are the responsibility of such third parties. Associated Engineering (Sask.) Ltd. accepts no responsibility for damages, if any, suffered by any third party as a result of decisions made or actions based on this report.
REPORT
v Executive Summary
The Town of Lumsden is proceeding with the planning of a new wastewater treatment facility (WWTF). In
'Wastewater Management Strategy Study' completed by Associated Engineering in 2007, it was determined
that the Town's existing wastewater treatment and storage infrastructure are operating beyond capacity.
The existing infrastructure includes a wastewater treatment lagoon constructed in 1961 and equipped with
mechanical aeration in 1989. Effluent from the lagoon drains to an adjacent oxbow cell for disposal by
evaporation and infiltration. The impoundments are situated adjacent to the nutrient-sensitive Qu'Appelle
River and it is suspected that seepage ultimately enters the Qu'Appelle River without sufficient renovation
by the local groundwater-soil matrix.
The Town has commissioned Associated Engineering to conduct a conceptual study and preliminary design
of a new wastewater treatment facility to replace the existing infrastructure. This document encompasses
the findings of the conceptual study.
The intent of the conceptual study is to position the Town and Associated Engineering to proceed with the preliminary design of the WWTF. The report includes:
• Development of a design basis including:
• Design period;
• Population forecasts; • Projected raw wastewater flows and peaking factors;
• Projected raw wastewater contaminant loading; and
• Effluent quality requirements.
• Evaluation of liquid stream treatment (LST) technologies and selection of the preferred alternative;
• Evaluation of solid stream treatment (SST) technologies and slection of the preferred alternative;
• Selection of a site;
• Identification of odour control options;
• Identification of key issues in the structural, civil, electrical, instrumentation and controls and building mechanical disciplines;
• Discussion on plant hydraulics and treated effluent outfall design; and
• Conceptual level cost estimates.
The study included three workshops with the Town of Lumsden to update on the progress of the project and
allow for input from the Town. Records of these workshops are included along with this report.
At Workshop No.1, a 25-year design horizon projected from expected commissioning in 2015 was agreed
upon for a design year of 2040. The population of Lumsden is projected from a 2011 population of 1700 at
2% annual growth for a 2040 population of 3019.
Current per capita wastewater generation rates are determined by examining recent wastewater flow data.
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Town of Lumsden
v Per capi ta wastewater generation rates are determined to be 325 liters/capita/day average dry weather flow
and 353 liters/capita/day average annual flow. Projected flows and peaking factors for 2040 are summarized in Table 1 below. Flows and peaking factors will continue to be monitored through 2011; flows
and peaking factors may be updated accordingly during preliminary design.
Table E-1
Projected Flows and Peaking Factors Design Parameter/Peaking Factor Projected Flow in 2040 (m'/day)
Average Dry Weather Flow (ADWF) 977
Average Annual Flow (AAF) / ADWF x 1.1 1066
Maximum Daily Flow (MDF) / ADWF x 2.4 2051
Maximum Hour Flow (MHF) / ADWF x 4.2 3321
Maximum Monthly Flow (MMF) / AAF x 1.25 1332
A raw wastewater sampling program conducted between March 1 and 15, 2011 suggests that the citizens from the Town of Lumsden generate less sanitary waste than typical individuals. For design purposes,
projected contaminant loading defaults to typical values lor small communities.
The Saskatchewan Ministry of Environment (MOE) has provided the Town with a set of draft treated
wastewater effluent requirements for discharge to the Qu'Appelle River. A summary of the criteria are included below in Table E-2:
Table E-2 MOE Treated Wastewater Effluent Requirements for Discharge to Qu' Appelle River
Parameter Units Permit Limit
TSS mg/L 15
CBOD, mg/L 15
Ammonia-N (NH3-N) mg/L 4/10 summer/winter
Total Nitrogen mg/L 10/12 summer/winter
Total Phosphorus mg/L 1
Fecal coliform CFU/100 mL 200
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Executive Summary
v Associated Engineering considers the parameters outlined in Table E-2 to be reasonable. However, it is
strongly recommended that the discharge criteria for TSS be raised from 15 mg/L. This should be pursued
in discussions with the MOE.
Initially, a long list of liquid stream treatment (LST) alternatives were identified that can treat Lumsden's
wastewater so that it is suitable for discharge to the Qu'Appelle River. The long list of processes
considered for LST included membrane bioreactors (MBR), extended aeration , oxidation ditch, the BioLac
proprietary process involving earth en ponds and clarifier tanks, sequencing batch reactors (SBR), moving bed bioreactors (MBBR) and integrated fixed film activated sludge (IFAS). An initial screening identified
extended aeration, MBR and IFAS as the alternatives best suited for Lumsden. At Workshop No.2, a peer
reviewer suggested that MBR be eliminated based on high anticipated capital and O&M costs and process
complexity. The peer reviewer recommended that extended aeration be selected as the preferred
alternative which provides flexibility for upgrade to the IFAS process. Following Workshop No. 2, the Town
accepted extended aeration as the preferred LST alternative.
Initially, the triple bottom line (TBL) approach was intended for evaluating LST and solid stream treatment
(SST) alternatives. However, after the Town selected a preferred LST alternative, the TBL analysis was
focused solely on the SST alternatives and was conducted at Workshop No.3 on June 22, 2011. The SST
alternatives evaluated were: 1. Truck the biosolids to the City of Regina for treatment at the City of Regina
wastewater treatment plant, 2. Stabilize the biosolids in an aerobic digester, dewater and truck to the landfill to be spread as cover and 3. Dewater the biosolids, stabilize by composting and truck the compost to the
landfill to be used as cover. Alternative 2 was selected after scoring highest in the TBL analysis.
A site evaluation considered a total of ten sites in and around Lumsden for the location of the WWTF. The
long list of sites was evaluated against a number of economic and non-economic criteria and the long list
was narrowed down to two potential sites: Site CE west of the existing lagoons and Site A 1 down the hill
from the landfill. A preliminary geotechnical investigation on the two sites favoured site A1 for hosting
structural components. Site AI also provides better flood protection, is farther from built up areas and would cost less to develop. At Workshop No.3, the Town selected Site A1 as its preferred site for the
WWTF.
It is recommended that a new WWTF include redundancy for maintenance purposes by providing two
parallel process trains with each train designed to accept 75% average annual flow (AAF) in 2040; both
trains should be constructed at initial build-out. Space provisions should be made for process upgrades if
future effluent criteria require additional treatment to what is required for meeting the MOE's current
proposed discharge criteria. Space provisions should also be made for the addition of further process
trains beyond 2040.
At a conceptual level, the estimated capital cost of a WWTF is $12.4M. This cost includes site
development, outfall construction , an extended aeration facility with nitrification, denitrification, chemical
phosphorus removal, UV disinfection and aerobic digestion and dewatering of biosolids. The cost does not
include upgrades to the pumping station . The conceptual level costs were developed primarily for purposes
of comparing alternatives and should not be used for budgeting. Preliminary design cost estimates would
~ Associated I GLOBAL PERSPEUIVE. ~'Engineering LOCAL FOCUS. iii
Town of Lumsden
v be better suited for that purpose.
The conclusion of the conceptual study positions the Town to proceed with preliminary design of the
WWTF.
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v Table of Contents
SECTION
Executive Summary
Table of Contents
List of Tables
List of Figures
1
2
3
4
Introduction
1.1 1.2 1.3
History
Lim itations of the Report
References
Design Basis
2.1
2.2
2.3
2.4
2.5
2.6 2.7 2.8 2.9
Design Period
Population Forecasts
Raw Wastewater Flows and Peaking Factors
Raw Wastewater Contaminant Loading
Effluent Quality Requirements
Alkalinity and PH
Wastewater Design Temperatures
Site Elevation and Climate
Operating Objectives
Liquid Stream Treatment Requirements and Alternatives
3.1 Introduction
3.2 Unit Processes
3.3 Process Alternatives
3.4 Peer Review
3.5 Conclusions
3.6 Selected Lst Alternative
Solid Stream Treatment Process Requirements and Alternatives
4.1
4.2 4.3 4.4
Introduction
Unit Processes
Process Alternatives
Triple Boltom Line
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Table of Contents
PAGE NO.
v viii
ix
1-1
1-1 1-1
1-2
2-1
2-1 2-1
2-1
2-7 2-12
2-1 2
2-1 3
2-1 3
2-13
3-1
3-1
3-1
3-1
3-4 3-4 3-5
4-1
4-1
4-1
4-3 4-4
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Town of Lumsden
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6
7
8
9
10
11
4.5
4.6 4.7
Risk Factor
Conclusions
Recommendalions
Odour Control
5.1
5.2
Preventing th e Generation of Odours
Minimizing the Release of Odours
Site Selection
6. 1 Introduction
6.2 Criteria
6.3 Site Descriptions
6.4 Short List of Sites
6.5 Geotechnical Results
6.6 Recommendations
Key Issues in Structural, Civil, Electrical, I&C, HV AC
7.1
7.2 Structural
Civil 7.3 Electrical, Instrumentation and Controls
7.4 Heating and Ventilation Systems
Outfall and Plant Hydraulics
8.1 8.2
Outfall Location and Design
Plant Hydraulics
Cost Estimates
Conclusions
Recommendations
Certif ication Page
Appendix A - Technical Memorandums
Appendix B - Annual Reports
Appendix C - Flow Data
Appendix D - Wastewater Sampling
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4-5 4-7 4-8
5-1
5-1
5-1
6-1
6-1 6-1
6-1
6-3 6-4 6-4
7-1
7-1
7-1
7-2 7-2
8-1
8-1 8-1
9-1
10-1
11-1
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1.
Table of Contents
v Appendix E - Workshops
Appendix F - Geotechnical Report
Appendix G - Cost Estimates
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Town of Lumsden
v List of Tables
Table 2-1
Table 2-2
Table 2-3
Table 2-4
Table 2-5
Table 2-6
Table 2-7
Table 4-1 Table 4-2
viii
Town of Lumsden Raw Wastewater Flow 2003-2011
Projected Wastewater Flows
Observed Contaminant Concentrations (15-Day Mean)
Observed Per Capita Contributions (15-Day Mean)
Typical Per Capita Contributions
Projected Contaminant Loading (2040)
MOE Treatment Wastewater Effluent Requirements for Discharge to
Qu' Appelle River Advantages and Disadvantages of the Aerobic Digestion Process
Triple Bottom Line Scoring - Solid Stream Treatment (SST) Alternatives (a
higher score is more favourable)
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PAGE NO.
2-4
2-7
2-9
2-10
2-11
2-11
2-12
4-2
4-6
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v List of Figures
Figure 2-1 Figure 2-2 Figure 6-1 Figure 6-2
Town of Lumsden Raw Wastewater Flows 2008-2011
Diurnal Curve March 24 to May 1, 2011 Location of the Evaluated Sites Sites A1 and CE
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List of Figures
PAGE NO.
2-3
2-5
6-6 6-7
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Town of Lumsden
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2-2
total pump hours for each month. Total flow for each month is determined based on a pumping
rate of 20 Lis as determined through field measurements in the 'Wastewater Management Strategy'
report prepared by Associated Engineering in 2007. The average daily flow for each month is
determined by dividing the total flow for each month by the number of days in the month.
On March 23, 2011, a data logger was installed in the pumping station. The logger measures the
instantaneous flow rate upstream of the pumping station wet well at 15 minute intervals. Flow data
from the data logger is available for this report from March 24 to May 1, 2011. Flow monitoring
continues.
Figure 2· 1 below plots daily raw wastewater flows between January 1, 2008 and May 1, 2011. The
blue line represents average daily flow based on monthly pump run hours. The red line represents
daily flow recorded from the flow meter. The green line represents the daily flow recorded by the
data logger. It appears that the flow throughout most of 2010 (after May 1) was significantly higher than the two year trend prior to 2010. High flows continue to be observed in 2011. This is a likely a ( ,
result of higher than normal groundwater table from the unusually high rainfall experienced during I 2010 and high snowfall levels observed in the winter of 2010/2011 . The wet weather observed in
2010 and 2011 have contributed to significant inflow and infiltration (III) in the Town of Lumsden's
collection system; flows should continue to be monitored. The data used to generate Figure 2·1 is
found in Appendix C.
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Figure 2-1 Town of Lumsden Raw Wastewater Flows 2008-2011
1400.0
1200.0
1000.0
800.0
600 .0
400.0
f-' ~
200.0
0 .0
Oat. _ Average Oailv Flow Based on Monthly Pump Run Hours - Dai lv Flow From M et er - Dai lv Flow from Data Logger
2.3.2 Average Annual Flow
Average annual flow (AAF) is the average daily flow over an entire year. AAF is calculated as the volume of raw wastewater pumped from January 1 to December 31 divided by 365 days.
2.3.3 Average Dry Weather Flow
The average dry weather flow (ADWF) is the flow that occurs on a dai ly basis with no reaction to wet weather events. ADWF is typically observed in the winter months when precipitation is frozen and does not contribute to raw wastewater flows. ADWF for 2008, 2009, 2010 and 2011 are calculated as the average daily flow during January and February of these years. From Figure 2-1, it is apparent that these months represent annual low-flow periods. AAF and ADWF for 2003 to 2005 and 2008 to 2011 are summarized in Table 2-1 below. Data for 2003 to 2005 is taken from the technical memorandum 'Wastewater Characterization and Generation' section Irom Wastewater Management Strategy' by Associated Engineering, 2007.
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Table 2-1 Town of Lumsden Raw Wastewater Flow 2003-2011
Peak Day
Year AAF (m'/d) ADWF (m'/day) MDF (m'/day) Factor
(MDF/ADWF)
2003 385 348 761 2.2
2004 451 437 903 2.1
2005 573 571 1424 2.5
2006 NA NA NA NA
2007 NA NA NA NA
2008 349 335 NA NA
2009 374 319 NA NA
2010 594 360 1175 3.3
2011 (Jan. 1 to NA 576 1304 2.3
May 1)
Note: NA Indicates no data available
2.3.4 Diurnal Pattern
The diurnal pattern is the raw wastewater flow pattern completed every 24 hours and repeated
every 24 hours. This represents the temporal variation in wastewater generation over the course of
the day. The diurnal curve in Figure 2-2 below represents the average flow at fifteen minute
intervals between March 24 and May 1 2011. Over the time period represented in Figure 2-2, Lumsden typically saw peak wastewater flows of approximately 1150 m'/day between 9:00 AM and
11 :00 AM and 8:00 pm and 10:00 pm. Low flows of approximately 800 m'/day were typically
observed between midnight and 5:00 AM. The difference between peak flows and low flows in
Figure 4-1 is a factor of approximately 1.4. The diurnal curve in Figure 2-2 should be observed
noting that the time period represented includes much of the spring melt and does not represent
average dry weather flows . As more daily data is made available by the flow data logger, more
curves should be developed.
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2 - Design Basis
Figure 2-2 Diurnal Curve March 24 to May 1, 2011
1400
1200 " / . ..
. ." '. ...... ~ .'
1000
\ .. / . . 800 "- . / . .
'. -:- "
600
400
200
0 7:12 PM 12:00 AM 4:48 AM 9:36 AM 2:24 PM 7:12 PM 12:00 AM 4:48 AM
Time
2.3.5 Current Flows and Peaking Factors
2.3.5.1 Current Average Dry Weather Flow
Determining the current ADWF at Lumsden is complicated by the wet weather and high water table that has been observed in Lumsden through 2010 and 2011, resulting in high flows due to suspected inflow and infiltration (1/1). An ADWF of 550 m3/day is used for
2011. With a popu lation of 1700, this equates to a per capita ADWF of 324 Ucapitalday wastewater generation.
2.3.5.2 Current Average Annual Flow
An AAF of 600 m3/day is used for 2011. With a population of 1700, this equates to a per capita AAF of 353 L/capitalday.
~ Associated I GLOBAL PERSPECTIVE. ~~ Engineering LOCAL FOCUS. 2-5
Town of Lumsden
v 2.5 EFFLUENT QUALITY REQUIREMENTS
The Saskatchewan Ministry 01 Environment (MOE) regulates the discharge of treated effluent in
Saskatchewan as legislated in the Environmental Management and Protection Act. The MOE has
advanced a draft set of treated wastewater effluent requirements for discharge to the Qu'Appelle River. A
summary of the criteria are included in Table 2-7 below.
Table 2-7 MOE Treatment Wastewater Effluent Requirements for Discharge to Qu' Appelle River
Parameter Units Permit Limit
TSS mg/L 15
CBODs mg/L 15
Ammonia-N (NH3-N) mg/L 4/10 summer/winter
Total Nitrogen mg/L 10/12 summer/winter
Total Phosphorus mg/L 1
Fecal coliform CFU/100 mL 200
Discharge criteria are negotiable with the MOE. One parameter that may be discussed is TSS (total
suspended solids). Under ideal conditions, the liquid stream processes considered in Section 3 are
considered robust enough to meet the discharge criteria in Table 2-7. However raising the TSS criteria
from 15 mg/L would provide more flexibility in process selection and should be pursued with the MOE.
Treated wastewater effluent discharge is currently regulated by the Saskatchewan MOE. However, the
regulatory framework surrounding the release of treated wastewater is influenced by federal legislation and
the Canadian Council for Ministers of the Environment (CCME). Tech Memo No. 1 in Appendix A includes
discussion on the changing regulatory landscape. The technical memorandum 'Qu'Appelle River Receiving
Environment and Estimated Load Increases' by Summit Environmental Consultants Inc. includes a
summary of existing information on water quality in the Qu'Appelle River receiving environment at
Lum sden. The memo also evaluates the potential impact of effluent release on the river. The MOE's
response to the memo is included at the end of the memo in Appendix A.
Historical trends show increasing stringency with respect to effluent discharge requirements. It is therefore
advised that space be included at the facility for process upgrades if future criteria require the addition of
filters or other process equipment to meet future discharge criteria.
2.6 ALKALINITY AND PH
Alkalinity and pH levels in the raw wastewater can affect treatment processes and should be considered in
design. Alkalinity is a measure of the buffering capacity of the raw wastewater, or its ability to neutralize
acids . From Table D-1 in Appendix D, Lumsden raw wastewater has an alkalinity of approximately 550
mg/L as CaC03. The pH is a measure of the hydrogen ion concentration of the wastewater. A low pH
value indicates that a substance is acidic and a high pH value indicates that a substance is basic. A pH of
7 is neutral. Biological nutrient removal processes are often sensitive to pH; the optimal pH for nitrification
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v is between 7.5 and 8 and the optimal pH for denitrification is between 7.5 and 8. From Table D-1 in
Appendix D, Lumsden raw wastewater has a pH of around 7.8.
2.7 WASTEWATER DESIGN TEMPERATURES
A design wastewater temperature of 5°C is assumed. Wastewater temperature should be monitored over
one year to confirm this value.
2.8 SITE ELEVATION AND CLIMATE
The wastewater treatment facility should be protected from severe flooding events to prevent sewer
backups and flooding of the facility. The Town of Lumsden Zoning bylaw requires all development in the
flood plain within dyke protection to be flood proofed to the 1 :500 year flood level plus 0.5 m freeboard. The
facility elevation may be higher to allow sufficient head for the effluent to flow to the river by gravity even
during severe flood events. Further discussion on plant hydraulics is included later in Section 8.2.
2.9 OPERATING OBJECTIVES
Facility operating objectives include:
• Producing treated effluent suitable for discharge to the Qu'Appeile River. The MOE has provided a draft set of discharge criteria (See Section 2.5);
• Stabilize the solid waste stream into a beneficial product;
• Provide treatment capacity to a design year of 2040; and
• Provide flood protection for a 1 :500 year flooding event.
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~I§ 200 m - I I - I I _
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FACILITY FOOTPRINT
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~:~~[CT No. ~~~"_"~~=-~'"_':~w..; ---1
APPROVED:
SCALE:
DWG. No.
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TOWN OF LUMSDEN WWTF UPGRADE
PRELIMINARY SITE PLANS WITH BUFFERS
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Figure 6-2 Sites Al and CE
6 - Site Select ion
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A RESIDENTIAL BUFFERS ~ ,:""
1~ 100 m - - -.3::
FACILITY FOOTPRINT
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~~ ~: 300m - - - -
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P R OJ E CT No. --""'-'-"='"-=-----1
DATE:
APPROVED:
SCALE:
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~ Associated ~'EnJineerlng
TOWN OF LUMSDEN WWTF UPGRADE
PRELIMINARY SITE PLANS WITH BUFFERS
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REPORT
v Liquid Stream Treatment Requirements and Alternatives
3.1 INTRODUCTION
In the Technical Memorandum 'Wastewater Treatment Facility Process Overview (Tech Memo No.2)' in
Appendix A, a description of the required processes for liquid stream treatment (LST) and solid stream
treatment (SST) are provided. The LST processes are required for meeting discharge criteria for disposal
to the Qu' Appelle River as outlined by the Saskatchewan MOE (See Section 2.5). The SST processes are
required to treat the solid waste stream. The finished product can be used as a beneficial resource such as
landfill cover material. Tech Memo 2 was presented to the Town at Workshop No.2 on June 1, 2011 and
can be found in Appendix E.
A number of unit processes are required to treat the liquid stream to the discharge criteria outlined by the
Saskatchewan MOE. These unit processes include screening, grit removal, biological treatment, chemical
phosphorus removal, secondary clarification and disinfection. Initially, a long list of process alternatives
were identified that incorporate these processes. An initial screening process distilled the long list of
alternatives to a short list of three alternatives. A peer reviewer further refined the short list and provided a
recommendation on a preferred LST alternative.
3.2 UNIT PROCESSES
To meet discharge criteria, the requirements for LST are headworks (screening and grit removal), biological
treatment (aerobic biological oxidation, nitrification and denitrification), chemical phosphorus removal,
secondary clarification and disinfection. Descriptions of each of these unit processes are included in Tech
Memo NO.2. When combined in a single system, these unit processes comprise a process referred to as
the activated sludge process. The activated sludge process employs a bulk of microbial biomass, cell
debris and suspended solids (known as mixed liquor suspended solids) where communities of
microorganisms in the sludge are responsible for the treatment of the wastewater.
3.3 PROCESS ALTERNATIVES
A number of configurations are suitable for meeting the LST process reqUirements. In Tech Memo No.2,
the long list of processes considered for LST inCluded membrane bioreactors (MBR), extended aeration,
oxidation ditch, the BioLac proprietary process involving earthen ponds and clarifier tanks, sequencing
batch reactors (SBR), mQving bed bioreactors (MBBR) and integrated fixed film activated sludge (IF AS).
An initial screening of these processes identified the most suitable options for development and evaluation
as extended aeration, MBR and IFAS. Each of these processes would require alum addition for
phosphorus removal and ultraviolet (UV) disinfection. A brief justification for the generation of the short list
of alternatives from the longer list is included in Tech Memo NO.2.
~ Ass~ciat~d I GLOBAL PERSPECTIVE. ~ 'Englneermg LOCAL FOCUS. 3-1
Town of Lumsden
v 3.3.1 Alternative 1: Extended Aeration with Alum Addition and UV Disinfection
The extended aeration process provides a relatively long hydraulic retention time (HRT) for aeration
as well as a relatively long solids retention time (SRT) compared with conventional and high rate
activated sludge processes. Because of the relatively long HRT, larger aeration tanks are required
and aeration energy use is higher than for high rate processes such as membrane bioreactors.
However, the process follows a relatively simple design and is easy to operate. Another advantage
of the longer HRT is an increased ability to provide buffering for treating 'shock' loads. As a result
of the long SRT, the extended aeration process provides for some aerobic digestion of solids and
therefore results in a lower sludge yield than a conventional system.
Figure P-01 in Tech Memo No.2 (Appendix A) presents a process flow diagram (PFD) of an
extended aeration facility. Flow would initially enter the headworks building where fine screening
and grit removal remove solids that could potentially damage downstream process equipment. Raw wastewater that has passed through the screens enters aerated equalization tanks which I .
3-2
dampen flow rate variations so that a more constant flow can be delivered through the subsequent
process. Effluent is pumped from the equalization tanks into anoxic tanks (where denitrification
occurs) and overflows into aeration tanks where carbonaceous BOD removal and nitrification occur.
Air bubbles delivered by air diffusers provide oxygen required by the biological processes and also
keep sludge in suspension in the aeration tanks. Alum is added for phosphorus removal at the downstream end of the biological process tanks. Effluent and sludge are passed into the clarifiers
where solids are allowed to settle. Some of the sludge is returned to the anoxic tank as return
activated sludge (RAS) while another stream is wasted as waste activated sludge (WAS) and
pumped to the digesters for solid stream treatment (see Section 4). Effluent overflowing the secondary clarifier weirs is conveyed to the UV disinfection system.
Figure P-03 in Tech Memo No.2 (Appendix A) presents a layout of an extended aeration facility. To provide process redundancy and the capability for performing maintenance without shutting
down the plant entirely, it is advised that two parallel process trains be constructed at initial build
out such that each train is clipable of accepting 75% average annual flow in 2040. Space provision
is made for the addition of a third processirain beyond 2040 (future bioreactor and clarifier in
dashed lines in Figure P-03). Sizing of the process components in Figure P-03 are based on
estimates provided by equipment suppliers. Detailed design calculations for the sizing of tanks and
equipment will follow in preliminary design.
3.3.2 Alternative 2: Membrane Bioreactor with Alum Addition and UVDisinfection
Membrane bioreactors (MBR) combine the activated sludge process with microfiltration or
ultrafiltration membranes for liquid-solid separation. Membrane filtration eliminates the need for
secondary clarification. MBR systems are capable of operating at higher mixed liquor suspended
solids (MLSS) concentrations than other treatment processes such as extended aeration.
Consequently, MBR systems can operate with significantly smaller tanks and have a relatively
small footprint.
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v 3 - Liquid Stream Treatment Process Requirement and Alternatives
An MBR facility would operate similar to an extended aeration facility with the inclusion of
membrane modules submerged in the aerobic zone and the exclusion of secondary clarifiers. The
inclusion of aerated equalization tanks for flow rate dampening is particularly important for MBR
facilities since the MBR process has a maximum treatment rate based on membrane flux and is
likewise sensitive to shock loads.
Regular cleaning of the membranes is important in an MBR facility to prevent fouling of the
membranes. Various cleaning procedures may be implemented with specific procedures for
cleaning the membranes are recommended by the membrane manufacturers.
3.3.3 Alternative 3: Variation on Nitrification/Denitrification with Alum Addition and UV
Disinfection (IFAS Process)
There are a number of variations of the activated sludge process that can provide treatment to
Lumsden's required effluent limits. One process that has been identified as a suitable alternative
for Lumsden is the integrated fixed film activated sludge (IFAS) process. The IFAS process
operates similar to the extended aeration process. It includes neutrally buoyant biofilm carriers which provide large amounts of surface area for fixed film growth in combination with the
suspended activated sludge. When compared with extended aeration, the IFAS process operates
with a higher concentration of biomass in the aerated zone, allowing for operation in smaller tanks. The fixed film growth sustained on the neutrally buoyant media allows the population of
microorganisms in the aerated zone to remain relatively stable during periods of variable flow.
The IFAS process is commonly implemented in retrofitting of existing facilities. By adding the
neutrally buoyant media to existing bioreactor tanks, the treatment capacity of the existing tanks can be increased without the construction of new tanks.
Figure P-02 in Tech Memo No.2 (Appendix A) presents a process flow diagram (PFD) of an IFAS
facility. Flow would initially enter the headworks building where fine screening and grit removal
remove coarse solids. Raw wastewater that has passed through the screens enters aerated
equalization tanks which dampen flow rate variations so that a more constant flow can be delivered
through the subsequent process. Effluent is pumped from the equalization tanks into anoxic tanks
and overflows into the aeration tanks which include the neutrally buoyant biofilm media. Air
bubbles delivered by air diffusers provide oxygen required by the biological processes and also
keep sludge in suspension in the aeration tanks. Alum is added for phosphorus removal at the
downstream end of the biological process tanks. Effluent and sludge are passed into the clarifiers
where solids are allowed to settle. Some of the sludge is returned to the anoxic tank as return
activated sludge (RAS) while another stream is wasted as waste activated sludge (WAS) and
pumped to the digesters for solid stream treatment (see section 4). Effluent overflowing the
secondary clarifier weirs is conveyed to the UV disinfection system.
Figure P-04 in Tech Memo No.2 (Appendix A) presents a layout of an extended aeration facility.
To provide process redundancy and the capability for performing maintenance without shutting
~ Associated I GLOBALPfRSPECTIVE ~ Engineering LOCAL FOCUS. 3-3
Town of Lumsden
v down the plant entirely, it is advised that two parallel process trains be constructed at initial build
out such that each train is capable of accepting 75% average annual flow in 2040. Space
provisions are made for the addition of a third process train (future bioreactor and clarifier in dashed
lines in Figure P-04) beyond 2040. Sizing of the process components in Figure P-04 are based on
estimates provided by equipment suppliers. Detailed design calculations for the sizing of tanks and
equipment will follow in preliminary design.
3.4 PEER REVIEW
The LST treatment alternatives were presented to the Town of Lumsden and peer reviewer Dr. A. Warren
Wilson from WPC Solutions Inc. at Workshop No.2 on June 1, 2011 (see Appendix E for a record of the
workshops). The peer reviewer agreed with distillation of the long list of LST alternatives to the short list
and further suggested that Alternative 2 (MBR with alum addition and UV disinfection) be eliminated based
on the high capital and operation and maintenance costs associated with MBR processes. This shifted
focus to the remaining two alternatives: Alternative 1 (extended aeration) and Alternative 3 (IFAS).
Both extended aeration and IFAS would provide treatment capabilities suitable for discharge to the
Qu'Appelle River. Extended aeration would require a greater footprint however operation would be slightly
simplified without the inclusion of the neutrally buoyant media and would incur slightly lower capital and
operation and maintenance costs. IFAS would require a smaller footprint however would incur slightly
greater capital and operation and maintenance costs.
The peer reviewer suggested that IFAS is most effective in retrofitting applications (increasing treatment
capacity without increasing tank volumes) and is not often implemented at a 'greenfield' site. The peer
reviewer recommended extended aeration as a preferred LST alternative. This would leave the door open
for upgrade to an IFAS process if Lumsden sees higher than expected growth in the future, requiring
capacity upgrades.
3.5 CONCLUSIONS
From Tech Memo No.2 and the peer review process that took place at Workshop No.2, the following
conclusions can be drawn regarding liquid stream treatment:
• A number of activated sludge processes are available for treating raw wastewater to criteria outlined by the Saskatchewan MOE;
• From a long list of process alternatives; three processes are most suited for Lumsden - extended aeration, membrane bioreactors and IFAS. Each alternative would include nitrification and denitrification, chemical phosphorus removal and UV disinfection;
• Extended aeration and IFAS provide the simplest and most cost effective alternatives of the three identified alternatives;
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3 - Liquid Stream Treatment Process Requirement and Alternatives
v • The Peer Reviewer has recommended extended aeration as the most practical alternative for liquid
stream treatment. An extended aeration facility could be upgraded to an IFAS facility in the future if higher than expected growth is seen and capacity of the facility needs to be increased.
3.6 SELECTED LST ALTERNATIVE
On recommendation by Associated Engineering and the peer reviewer, the Town of Lumsden accepted
extended aeration as the preferred liquid stream treatment alternative as Workshop No.2 on June, 2011.
~ Associated I GLOBAL PERSPECTIVE. ~~ Engineering LOCAL FOCUS. 3-5
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v Solid Stream Treatment Process Requirements and Alternatives
4.1 INTRODUCTION
Prior to disposal as biosolids, sludge requires stabilization (through digestion) and dewatering. Digestion
can be accomplished using aerobic digestion, anaerobic digestion, or a composting process. According to
the Saskatchewan MOE, stabilization is the treatment given to sludge in order to reduce pathogenic
organisms, vector attraction potential, odours and putrescibility of the sludge.
Potential aerobic and anaerobic digestion processes were evaluated for the Town of Lumsden. Initially a
long list of alternatives was evaluated. However, for further feasibility assessment the list was narrowed
down to three alternatives. The first alternative is "collecting the sludge (1.2%) from the bottom of the
clarifiers and trucking it to the Regina wastewater treatment plant (WWTP)". The second alternative is
"aerobic digestion plus dewatering of the sludge and then trucking it to the landfill and using it as a cover". The last alternative is "dewatering the sludge, stabilizing it by composting, and then trucking it to the landfill
and using it as a cover". These alternatives were evaluated in a procedure called Triple Bottom Line (TBL).
Using TBL analysis, environmental, social, and economical aspects of the project were evaluated, scored,
and ranked. The evaluation was taken one step further by considering the risk factor for all of the alternatives. The evaluation process and ranking were presented in Workshop NO.3 on June 22, 2011. A
record of the workshop is included in Appendix E.
4.2 UNIT PROCESSES
4.2.1 Aerobic Digestion
Aerobic sludge digestion is an aerobic process used to reduce both the organic content and the volume of the sludge. Under aerobic conditions, a large portion of the organic matter in sludge may
be oxidized biologically by microorganisms creating carbon dioxide and water. This process results
in an approximaiely 50% reduction in solids content. Aerobic digestion is the most commonly used
stabilization process in small wastewater treatment facilities. Aerobic digestion takes place in
completely mixed and aerated tanks designed for a solids retention time of 20 to 45 days. Because
of the aeration requirement, energy requirements are higher for aerobic digestion compared with
anaerobic digestion. However, in comparison with anaerobic digestion, capital costs are lower and
operation is simpler. An aerobic digester is included in the process flow diagrams (PFD's) Figures
P-Ol and P-02 in Tech Memo 2 (Appendix A).
The most commonly used application of aerobic digestion is in the treatment of sludges from
extended aeration systems. Since there is no addition of an external food source, the microorganisms must utilize their own cell content for metabolic purposes in a process called
endogenous respiration. The remaining sludge is a mineralized sludge, with remaining organic
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materials comprised of cell walls and other cell fragments that are not readily biodegradable.
Table 4-1 outlines the advantages and disadvantages of aerobic digestion relative to anaerobic
digestion processes:
Table 4-1 Advantages and Disadvantages of the Aerobic Digestion Process
Advantages Disadvantages
Relatively simple to operate and maintain. • Higher power cost associated with aeration.
Lower capital costs, especially for smaller • No useful by-product such as methane gas that plants. is produced in anaerobic digestion. Lower levels of biochemical oxygen • The process is affected significantly by demand (800) and phosphorus in the temperature, location and type of tank material. supernatant. • Less reduction in volatile solids. Fewer effects from upsets such as the • Aerobically digested sludge is more difficult to be presence of toxic interference or changes dewatered. in loading and pH. • Unfavourable economics for larger wastewater Less odorous process. treatment plants. Non-explosive.
Greater redUction in grease and hexane solubles than anaerobic digestion. Like anaerobic digestion, produces an odourless, humus-like, biologically stable end product that has fertilizer value. Effective alternative for smaller wastewater treatment plants.
Aerobic digestion is capable of producing stabilized biosolids for surface disposal (e.g. landfill final
cover to establish vegetation).
4.2.2 Anaerobic Digestion
Anaerobic digestion is a naturally occurring biological process in which anaerobic bacteria convert
organic matter into methane and carbon dioxide in the absence of air. This process stabilizes the
organic matter in wastewater sludge, reduces pathogens and odours, and reduces the total
solids/sludge quantity by converting part of the volatile solids (VS) fraction to biogas. Anaerobic
digestion results in a product that contains stabilized solids as well as some available forms of
nutrients such as ammonia-nitrogen. Anaerobic digestion has the advantages of low energy
demand, potential for recovery of methane gas and good pathogen inactivation. However,
anaerobic digestion may require alkalinity and/or specific ion addition. This process is very
sensitive to the adverse effect of lower temperatures on reaction rates and it may need heating
(often by utilization of process gas) to achieve adequate reaction rates. There is an increased
chance of production of odours and corrosive gases. This process has a slow recovery from
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4.3
4 - Solid Stream Treatment Process Requirements and Alternatives
process upset and there are safety concerns with methane gas handling and odour issues.
Significant mechanical equipment and complex process operation is involved. The process has significant capital and operational costs.
4.2.3 Composting
Composting is a controlled microbial process that converts organic materials into carbon dioxide,
water, heat and compost which can then be used as soil conditioner/amendment. Composting is a
slow process that can produce foul-smelling gases. The important parameters in composting
include: carbon:nitrogen (C:N) ratio, moisture content, and aeration. At the optimum C:N ratio,
moisture content level and level of aeration, composting begins spontaneously. As the organic
matters decompose, the compost heats to temperatures in the pasteurization range of 50"C to 70"C, which kills off pathogenic bacteria. Composting of wastewater sludge most often involves
mixing dewatered sludge (in the 20% to 25% dry solids range) with a wood based amendment such
as wood chips,saw dust, or yard wastes to provide a carbon source as well as porosity to permit
aeration through the compost mixture. Once mixed, the compost mixture needs to be kept aerobic.
4.2.4 Dewatering (Belt Filter Press or Centrifuge)
Prior to final disposition, it is necessary to reduce the water content of the sludges. This is
particularly the case if the sludge is to be received at a landfill or is to be com pasted. If the sludge
needs to be trucked a significant distance, dewatering will also save transport costs. Screening of the various options for the Lumsden WWTF suggests using a belt filter press or centrifuge for
dewatering. Centrifuge dewatering employs centrifugal force to separate of solids from water. The
process is characterized by high energy demands and high capital and operating costs however the
operator attention requirement is minimal and the footprint is small. Belt filter presses press and dewater biosolids between two moving belts. Belt filter presses have lower capital and operating
costs however they require a greater footprint and tend to release more odour than a centrifuge.
Dewatering equipment is included in the PDF's in Figures P-Ol and P-02 in Tech Memo 2 (Appendix A).
PROCESS ALTERNATIVES
4.3.1 Alternative 1: Collecting from the bottom of the clarifiers (1.2%) and trucking it to
ReginaWWTP
In this process sludge is collected from the bottom of the clarifiers. Then the sludge is shipped to
Regina and dumped in the Regina wastewater treatment plant (WWTP) receiving station for further
processing. This alternative has very low capital cost, minimum maintenance, and no odour as the
major advantages. However, high operational costs (i.e. trucking the sludge regularly to Regina),
noise, high consumption of fossil fuels, and emitting significant amounts of Green House Gas
(GHG) into the atmosphere are the main disadvantage of this alternative. Further processing on
the receiving sludge would need to be carried out at the Regina WWTP.
~ Associated I GLOBAL PERSPECTIVE. ~E:7 Engineering LOCAL FOCUS. 4-3
Town of Lumsden
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4.3.2 Alternative 2: Aerobic digestion plus dewatering of the sludge and then trucking it to
the landfill and using it as a cover
Sludge can be stabilized by digestion in an aerobic digester with approximately 20 to 45 days solids
retention time. This process would be followed by a dewatering process. The advantages of
aerobic digestion are its simple process operation, low capital costs (compared to anaerobic
digestion), minimal odour issues and end product with good dewatering properties. The dewatering
process decreases the volume of the sludge almost 16 fold. However, the dewatering process can
cause some odour issues within the plant. Also, dewatering instruments can have a large footprint
depending on the type of dewatering process being used. For example, more space is needed for
a belt filter press than a centrifuge. Alternative 2 requires more capital expenditure in comparison
to Alternative 1; however there is a residual value for the facility in Alternative 2.
4.3.3 Alternative 3: Dewatering the sludge and stabilizing it by composting then trucking it
to the landfill and using it as a cover
Sludge produced by municipal wastewater treatment plants should meet quality standards before
its disposal in the environment. Environmental sewage sludge is classified as a hazardous waste
because it contains high levels of organic compounds and pathogenic microorganisms. Alternative
3 relies on composting to stabilize the solids. The sludge is dewatered to approximately 20%
solids. This allows the sludge to be self-supporting in a pile or stack to facilitate composting. It is then mixed with a bulking agent to dry out the blended mix. Bulking agents can include sawdust,
leaves, or wood chips; wood chips are most commonly used. Compost is mixed in a ratio of three
parts wood chips to one part sludge. Composting offers an environmentally friendly approach
towards disposal of wastewater sludge. However, the cost of acquiring woodchips in Lumsden is
significant. Also, windrow composting is a labour intensive process. As a result, the cost of
operation and maintenance (O&M) is relatively high for Alternative 3. Composting is a complex
process and there are many factors that have to be considered in order to achieve a well
functioning process. It is very common to have odour issues with the composting process.
Collection of leachate due to runoff and placing a liner underneath the windrows would increase the
capital cost of the project.
4.4 TRIPLE BOTTOM LINE
The triple bottom line (TBL) methodology is one approach employed by Associated Engineering for
assessing public infrastructure projects. It recognizes that a balance between environmental efficiency,
social acceptance and economic feasibility must consider and accommodate stakeholder values. In other
words, a truly "sustainable" solution seeks to maximize environmental benefits in a socially acceptable
manner while at the same time being affordable. This framework recognizes that the best idea in the world
is worthless if people will not embrace it or it is beyond their financial means. The TBL framework is thus
appropriate for this project.
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4 - Solid Stream Treatment Process Requirements and Alternatives
v TBL was initially intended to be used to evaluate LST and SST alternatives. At Workshop No.2 on June 1,
2011, the peer reviewer extensively evaluated a nurnber of LST process alternatives against economic and
non-economic criteria. Following the peer review, the Town accepted extended aeration as the preferred
LST alternative. Therefore, TBL was only carried out for the SST alternatives
Table 4-2 provides the list of all indicators which were analyzed in the TBL analysis. Each indicator is
assigned a weight depending on the how important the indicator is. Also alternatives were assessed and
given a value ranging from 0 to 5 depending on the indicator. Weighted scores are calculated for each
indicator. For example, minimizing GreenHouse Gas (GHG) emissions is the first indicator in the
environment category. GHG is weighted high since it is a very important concern to the citizens of
Lumsden. The amount of GHG emitted into the environment is calculated for each alternative. Based on
the calculations, the alternative with the least amount of GHG generation gets the highest mark which is 5 and in this case it is composting. The score for the other alternatives are calculated proportionally. The
other indicators are weighted and marked based on previous experience, well known pros and cons, and in some cases precise calculations.
4.5 RISK FACTOR
Process risk analysis, like all risk analyses, must be implemented using a graded approach. For each
alternative, issues and concerns that may significantly affect the project were determined. The most important concerns were selected, weighted and scored. Since risk is considered of high importance to the
viability of the project, risk is assigned a higher weight than the other factors. As shown in Table 4-2,
"Regina Not Receiving the Biosolids" is a big risk for Alternative 1. The second risk is "Increase in O&M
Cost Greater than Inflation". It is important to select a process with a minimal reliance on gas, electricity, and labour cost so that the O&M costs never exceed the inflation rate. The last risk which was analysed is
"Process Risk". Process risk includes: safety of the project and successful outcome. For example, there
are some risks with the composting process, such as odour issues and leachate runoff.
In Table 4-2 three SST alternatives were analyzed according to the TBL plus Risk evaluation. Each
indicator is weighted based on how important it is for the stakeholders. Alternatives were scored for each of
the indicators. The total weighted score shows Alternative 2 received the highest score which is 354 out of
maximum 500. Evaluation shows that Alternative 2 has the least risk among the three and it also ranks the
highest in the social index. Alternative number 1 ranks second with the best score in the economic index
and Alternative 3 ranks third with the highest score for the environmental index.
Alternative 2 offers the least amount of risk out of the three and it ranks the highest for the overall
evaluation.
~ Associated I GLOBAL PERSPECTIVE. .~ Engineering LOCAL FOCUS. 4-5
Table 4-2 Triple Bottom Line Scoring - Solid Stream Treatment (SST) Alternatives (a higher score is more favourable)
Alternative
2: Digest 3: Dewater, Weight
Equivalent 1: Truckto Aerobically, Compost, Spread
Index Indicator (High! Percentage ReginaWWTP Dewater, Spread as Landfill Cover
Mediuml Weight as Landfill Cover
Low) Score Weighted Score Weighted Score Weighted
Score Score Score Minimize greenhouse gas
Environmental emissions (measured as
High 50% 0.8 8.0 0.6 6.0 5.0 50.0 equivalent CO2 emissions)Jrom
(20%) the use of non-renewable fuels. Operational Health and Safety High 50% 4.0 40.0 3;0 30.0 2.0 20.0 Off Site Social Impacts - Odour
Medium 33% 2.0 13.3 5.0 33.3 1.0 6.7 Social (20%)
and Noise Process Simplicity, Robustness,
and Serviceability High 67% 5.0 66.7 4.0 53.3 2.0 26.7
Economic Capital Cost High 50% 5.0 50.0 1.1 11.0 1.5 15.0
(20%) 25-Year Net Present Value High 50% 5.0 50.0 4.0 40.0 2.4 24.0
(NPV) Life Cycle Cost Regina Not Receiving. the
High 50% - - 5.0 100.0 5.0 100.0 Biosolids Risk (40%) Increase in O&M Cost Greater
Medium 25% 2.0 20.0 4.0 40.0 3.0 30.0 than Inflation Process Risk Medium 25% 5.0 50.0 4.0 40.0 2.0 20.0
Total 100% Environmental 48 36 70
Total Social 100% 80 87 33 Total
100% Economic 100 51 39
Total Risk 200% 70 180 150 Total
Weighted 500% 298 354 292 Score
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4.6 CONCLUSIONS
A number of conclusions have been drawn from the comparison and evaluation of the alternatives:
• Aerobic and anaerobic digestion processes were evaluated. Anaerobic digestion needs significant mechanical equipment and is a complex process operation. The process has significant capital and operational costs. On the other hand, aerobic digestion needs less capital cost than anaerobic digestion and it is the most commonly used stabilization process in small WWTFs.
• Composting is a green way to stabilize the sludge. However, it is a slow and high maintenance process. Composting requires mixing wastewater sludge with a wood based amendment. The cost of providing woodchips in Lumsden is significant.
• Belt filter press or centrifuge for dewatering are two feasible options for Lumsden WWTF. Centrifuge dewatering is characterized by high energy demands and high capital and operating costs however less operator attention is required. Belt filter presses have lower capital and operating costs however they require a greater footprint and tend to release more odour than a centrifuge.
• Alternative 1: Collecting from the bottom of the clarifiers (1.2%) and trucking it to Regina WWTP. This alternative has very low capital cost, minimum maintenance, and no odour as the major advantages. However, this alternative has high operational costs, noise, and would emit significant amounts of GHG into the atmosphere.
• Alternative 2: Aerobic digestion plus dewatering of the sludge and then trucking it to the landfill and using it as a cover. Aerobic digestion is a simple process operation, has low capital costs (compared to anaerobic digestion) and minimal odour issues. The dewatering equipment can have a large footprint depending on the type of dewatering process used. Alternative number two requires more capital cost in comparison to alternative number one; however this process provides full treatment at one facility and carries a residual value as an asset.
• Alternative 3: Dewatering the sludge and stabilizing it by composting then trucking it to the landfill and using it as a cover. This alternative relies on composting to stabilize the solids. Composting is a complex process and there are many factors that have to be considered in order to achieve a well-functioning process. It is very common to have odour issues with a composting process. Collection of leachate due to runoffs and placing a liner underneath the windrows would increase the capital cost of the project.
• The TBL analysis was used to assess and assign weights and marks to the indicators and alternatives. Weighted scores are calculated for each indicator. Alternative 1 ranks first in the economic index. Alternative 2 ranks first in the social index. Alternative 3 ranks first in the environmental index.
~ ASs?ciat~d I GLOBAL P[RSPECTIVE, .,.£:7' Engmeenng LOCAL FOCUS. 4-7
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• Important risks were determined, weighted, and scored for each alternative. Alternative 1 has the highest risk therefore it receives the lowest score in the risk category. Alternative 2 has the least risk and Alternative 3 ranks second due to the process risk associated with composting.
4.7 RECOMMENDATIONS
Based on the conclusions presented above, AE recommends that the Town of Lumsden proceed with Alternative 2, aerobic digestion plus dewatering of the sludge and then trucking it to the landfill and using it as a cover as the preferred SST alternative. Alternative 2 received the highest score using the TBL analysis. This alternative has the following advantages:
• a complete solid stream process;
• less odour and process issues related to stabilizing the sludge;
• a residual value for the facility;
• useful end products to be used as a landfill cover;
• relatively simple to operate and maintain; and
• least risk.
We believe that the above advantages outweigh the disadvantages that have been identified with Alternative number 2. The Town Council passed a motion accepting alternative number two which is an aerobic digestion plus dewatering of the sludge and then trucking it to the landfill and to use dried biosolids as a cover material for its municipal landfill operation.
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Odour Control
Wastewater treatment facilities have the potential to generate odours which when released, may have a
negative impact on the surrounding community. Odour generation is a problem associated with both the
solid stream and liquid stream at a wastewater treatment facility. In wastewater treatment, odours are
typically associated with anaerobic compounds created by microbial digestion of organic material. The
potential for odour generation is greatly increased when anaerobic conditions (absence of oxygen) are created. Locating odourous facilities away from sensitive areas is a means of mitigating public exposure to
odour. The MOE states that mechanical treatment facilities should be located at least 300 m from
developed areas. If this buffer distance cannot be achieved, additional odour control measures might be
required. Odour control at a wastewater treatment facility can be considered in the context of a) preventing
the generation of odours and b) minimizing their release (Franz and Frechen, 2001).
5.1 PREVENTING THE GENERATION OF ODOURS
Odour generation is typically related to the treatment process employed - some processes generate more odour than others. Typically, processes that include longer storage periods of wastewater or sludge under
anaerobic conditions generate more odour than processes that include shorter storage periods under
aerobic conditions. Adequate mixing and aeration can prevent the generation of odour. Minim izing the
amount of turbulent flow of raw wastewater through the facility, designing inlets/outlets below the water surface level, increasing the frequency of disposal of grit and screenings and frequent cleaning of the
facility are additional means of reducing odour.
5.2 MINIMIZING THE RELEASE OF ODOURS
At an activated sludge facility, the processes with the highest potential for odour generation are typically the biosolids handling components and headworks (screening and grit removal) where raw sewage which may
have been exposed to anaerobic conditions in the collection system enters the plant. In these areas, odour
potential cannot always be mitigated and the odour may require treatment. Odour control systems include
biological filters, passing foul air through an adsorbent media such as activated carbon or the Bentax
system which pushes ionized air inio a foul air environment to oxidize volatile organic compounds and
cause air borne particles to fall out of the air.
Biological filters draw odourous air through a biomass media which oxidize the odour causing anaerobic
compounds in the air. If filters are properly maintained so as to provide a suitable environment for biomass,
biofilters can significantly minimize the release of odours.
~ Ass?ciat~d I GLOBAL PERSPECTIVE ~ 'Engmeerlng LOCAL FOCUS. 5-1
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REPORT
v Site Selection
6.1 INTRODUCTION
This chapter discusses and evaluates a long list of sites for the Town of Lumsden's WWTF. Associated
Engineering identified 10 potential sites for the WWTF.
6.2 CRITERIA
This chapter identifies the most practical location for the new WWTF by evaluating potential sites against a
set of criteria considered important to the Town of Lumsden. Initially, a long list of sites was prepared for
initial screening. These sites were labeled Sites A, B, C, D, E, F, G and H. The list was presented to the
Town in the February 22, 2011 Workshop. Sites are shown on Figure 6-1 at the end of this section. Site A 1 and CE were added as alternatives to Site A and Sites C and E. The sites were evaluated based on the
following criteria.
• Flexibility for future expansion;
• Proximity to utilities, road access; • Aesthetics and proximity to developments ('Guidelines for Sewage Works Design' (EPB 203) by
Saskatchewan;
• Odour buffer; • Financial parameters (land availability and cut and fill); and
• Flood protection and environmental constraints.
This section assesses the potential of locating the WWTF on one of ten selected sites identified in Figure
6-1 and 6-2.
6.3 SITE DESCRIPTIONS
The locations of the following sites are indicated on Figure 6-1 at the end of this section.
6.3.1 Site A
Site A is situated on land owned by the Town of Lumsden. It is approximately 200 m outside of the
Town's residential area, adjacent to the Town's landfill and 850 m from the Town's maintenance shop. This site is above the 1 :500 year floodplain and would require construction of an access road
off of Highway 734 to the south. A slight adjustment to the location of this site could make this site
a good candidate for the WWTF location.
6.3.2 Site 8
Site B is situated on land owned by the Town of Lumsden. It is within the Town's residential area
~ Ass~ciat~d I GLOBAL PERSPECTIVE. ~~ Engmeerlng LOCAL FOCUS. 6-1
Town of Lumsden
v therefore all services and utilities are within close proximity. It is also 350 m from the Town's
maintenance shop. This site is below the 1 :500 year floodplain. The main issues with constructing the facility in the Town are: land availability, plant operational activities and noise and odour issues
arising from close proximity to surrounding commercial and residential buildings.
6.3.3 Site C
Site C is situated on privately owned land. It is approximately 100 m outside of the Town's
residential area, therefore within close range to all utilities and 550 m from the Town's maintenance
shop. This site is below the 1 :500 year floodplain. The main issue with this site is the short
distance to residential areas placing it well within Ministry of Environment's 300 m development
buffer. The site also requires significant fill to reach the 1 :500 year flood elevation. Improvements
to road access would be required at this site and even with these improvements, issues around
crossing the railway remain difficult to resolve. Placing the WWTF at this location would limit future
recreational use of the surrounding land. Special geotechnical requirements are required to control
the soil preloading on the site. A costly pile support system is anticipated given the high water table
and soil characteristics.
6.3.4 Site 0
Site 0 is situated on land owned by the Town of Lumsden. It is approximately 100 m outside of the Town's residential area, therefore within close range to all utilities and 70 m from the Town's
maintenance shop. This site is adjacent to the Qu'Appelle River and is below the 1 :500 year
floodplain. The main concerns with this site are the odour problems that could arise due to the
short distance to residential areas. Also, land requirements for the WWTF would crowd the
available maintenance shop site.
6.3.5 Site E
Site E is situated on privately owned land. It is located more than 300 m outside of the Town's
residential area and 300 m from the Town's maintenance shop. This site is adjacent to the
Qu'Appelle River and below the 1 :500 year floodplain. The site would require fill to reach the 1 :500
year floodplain. Special geotechnical requirements would be required to control the soil preloading l .
6·2
on the site. A costly pile support system is antiCipated given the high water table and soil
characteristics.
6.3.6 Site F
Site F is situated on land owned by the Town of Lumsden. It is located more than 300 m outside of
the Town's residential area and 1400 m from the Town's maintenance shop. This site is below the
1 :500 year floodplain and would require a significant amount of fill. Access would be off the
Qu'AppeJle River dyke which is not recommended. Special geotechnical requirements would be
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6 - Site Selection
required to control the soil preloading on the site. A costly pile support system is anticipated given
the high water table and soil characteristics.
6.3.7 SiteG
Site G is situated on privately owned land. It is located more than 300 m outside of the Town's
residential area and 1500 m from the Town's maintenance shop. This site is above the 1 :500 year
floodplain and a forcemain would need to be bored under the Qu'Appelle River to convey raw
wastewater to the facility. The main concerns with this site are its relatively long distance from the
shop, landfill and lift station.
6.3.8 Site H
Site H is situated on privately owned land. It is located more than 300 m outside of the Town's
residential area and 1900 m from the Town's rnaintenance shop. The site is above the 1 :500 year floodplain and the forcemain would need to be bored under the Qu'Appelle River and HWY #11 to
convey raw wastewater to the facility. This site is farthest from the lift station. The main concern
with this site is its relatively long distance from the shop, landfill and lift station.
6.4 SHORT LIST OF SITES
Initially, the eight sites described in Section 6.3 were evaluated. All have strengths and weaknesses. The
over-riding concerns for the Town were the distance from the residential areas, potential for future expansion and development of the site and flooding issues. Sites A, S, C, and D do not have the
recommended buffer to the residential area and Sites Sand D do not have enough space for future
expansion. Sites S, C, D, E, F and H need significant fill to bring the elevation to above the 1 :500 flooding
elevation, which can be very costly. Sites G, F, and H are far from the shop, landfill and lift station. After
this initial screening, Sites A1 and CE were defined by slightly adjusting the locations of Sites A, C, and E. In Workshop No.2 on June 1 st the Wastewater Committee agreed that Sites A 1 and CE are the most
favourable sites for the WWTF. Sites A 1 and CE are indicated on Figure 6-2.
6.4.1 SiteA1
Site A 1 is situated on land owned by the Town and located down the hill from the landfill and south
of the existing lagoon. Site A1 is at a higher elevation in comparison to Site CE, as it is located
slightly up the valley wall. A survey at Site A 1 confirms that the site could easily be established
above the 1 :500 year flood. The site is approximately 275 m from residential development.
Topographical surveying was performed on the Site A 1 and the adjacent lands. The potential
access road location was evaluated. The land around Site A 1 belongs to the Town and this would
enable the Town to have more flexibility for the future expansion. Site A 1 is approximately 650 m
from the landfill which is favourable from a sludge handling viewpoint. One option for the solid
stream treatment is to use the solids as a landfill cover. Therefore, proximity to the landfill would be
~ Ass?ciat~d I GLOBAL PERSPECTIVE. "---~ Englneermg LOCAL FOCUS. 6-3
Town of Lumsden
v an advantage. The preliminary estimated baseline cost for developing and servicing Site A1 is
$900,000. The baseline estimated cost includes servicing the site with utilities and road access as
well as the required soil balance.
6.4.2 Site CE
Site CE is located on privately owned land. Site CE is located to the west of the existing lagoon
and north of the railway and is approximately 200 m from residential developments. The site would
require fill to bring the ground level to above the 1 :500 year flood elevation. Site CE is close to the
lift station as well as the river. This site is relatively flat which is an advantage; however it requires
extensive compaction. The preliminary estimated baseline cost for Site CE is $1,200,000. The
baseline cost includes servicing the site with utilities and road access, the required soil balance,
purchase of the land from the existing landowner and pre-loading the site to address future
settlement issues.
6.4.3 Comparison between Site A1 and CE
Site A 1 is situated on land owned by the Town and it is above the 1 :500 year flood elevation.
However, Site CE needs to be purchased and it requires substantial fill to bring the ground level to above the 1 :500 year flood elevation shown on Figure 6-2 at the end of this section.Furher, site A 1
is a greater distance from the residential area in comparison with the Site CEo
On the other hand, Site CE is close to the lift station as well as the river, and this site is relatively
flat in comparison with Site A 1. Considering all of the information about these two sites, Site A 1 is
deemed to be the more favourable site for the WWTF. The preliminary baseline cost for Site A1 is $900,000 which is considerably lower than Site CE's cost of $1,200,000.
6.5 GEOTECHNICAL RESULTS
A geotechnical investigation has been performed on Site A1 and CE by Clifton Associates Ltd (included in
Appendix E). For the geotechnical investigation of the sites, two boreholes were drilled at Site A 1 and one
at Site CEo Samples were collected to analyze ground water level, subsurface condition, slope stability,
depth of frost and excavation issues. The preliminary assessment provides various recommendations with
regard to both sites with a preference to Site A 1. It also advises a more comprehensive geotechnical
investigation at the selected site for the WWTF. Preliminary comments from Clifton Associated Ltd places
site A 1 in a more favourable position. Associated Engineering's structural review of the geotechnical report
aligned with the geotechnical finding's in terms of preference for Site A 1.
6.6 RECOMMENDATIONS
Associated Engineering recommends that Site A1 be selected for the new WWTF. Site A 1 was brought
forward from the initial screening of the long list of sites along with Site CEo After further evaluation of these
two sites, Site A1 is more attractive eoonomically. Site A1 also has non-economic characteristics that make
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6 - Site Selection
v it favourable when compared with Site CE including: natural flood protection, close proximity to landfill and
farther distance from developments. At Workshop No 2 on June 1,2011, the Town indicated that they
supported Associated Engineering's recommendation of Site AI.
The estimated site footprint for the WWTF is approximately 100 m x 100 m (1 hectare). This footprint would
include the facility itself with consideration for civil works such as parking and drainage and spatial
provisions for process upgrades during the design life of the facility and the construction of additional
process trains beyond the design life of the facility.
~ Ass?ciat~d I GLOBAL PERSPECTIVE. ~ Engmeerlng LOCAL FOCUS. 6-5
Town of Lumsden
v Figure 6-1
Location of the Evaluated Sites
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\.:: ..... SUNlNlIT ~ ENVIRONMENTAL CONSULTANTS INC.
A Melllbel of the Associated Engineering Group of (ompanie"s
Date:
To:
From:
Project:
Subject: Memo
May 13, 2011 File: 2010-4796.000
Saskatchewan Ministry of Environment
Hugh Hamilton
Lumsden WWTP
Qu'Appelle River Receiving Environment and Estimated Load Increases
This memo provides a brief summary of existing information on water quality in the Qu'Appelle River receiving environment at Lumsden. Of particular interest is information on water quality just upstream of the potential locations of a new outfall pipe from the planned wastewater treatment plant (WWTP) that will replace the existing lagoons. The primary parameters of interest are those that Saskatchewan Ministry of Environment (MOE) has indicated preliminary treatment standards for the WWTP - total suspended solids (TSS), carbonaceous
biochemical oxygen demand (CBOD5), ammonia-N, total nitrogen (TN), total phosphorus (TP), and fecal coliform bacteria. The key questions are:
• How do baseline water quality concentrations compare against the MOE treatment standards arid Water Quality Objectives/Guidelines?
• What are the baseline loads of these parameters? • How would the concentrations and loads change with the addition of the treated Lumsden effluent?
1 SUMMARY OF PREVIOUS STUDIES
1.1 CITY OF REGINA PLANNING STUDY
In 2002, the City of Regina commissioned Stantec Consulting Ltd. to prepare a detailed study of Regina's wastewater treatment system and the environmental impact downstream. The final Stantec (2006) report described the existing wastewater treatment system, effluent output, environmental effects with respect to the regulations in place at the time, and recommendations for treatment targets. A number of improvements have since been made, but the major upgrades to improve downstream water quality have just begun.
Effluent from the Regina wastewater treatment plant is discharged into Wascana Creek, which is a tributary to the Qu'Appelle River. Wascana Creek joins the Qu'Appelle River about 3 km upstream of Lumsden (Figure 1). The
total wastewater effluentfrom Regina's WWTP can contribute up to 85% of the flow in WaSC8ria Creek during the winter and other low flow periods. While the effluent quality is considered to be good for BOD, TSS, TP, and fecal coliforms,only 15% to 20% of nitrogen is removed prior to releasing the effluent (Stantec 2006). Asa result a large portion of the nitrogen released into Wascana Creek is in the form of ammonia. Un-ionized ammonia is toxic to fish and aquatic organisms and increases' in concentration with increased temperature and pH. The additional nitrogen also contributes to increased algal productivity in fish-bearing lakes downstream as these lakes have been shown to be nitrogen-limited (Stantec 2006; citing Dixit et ai, 2000; Hall et al. 1999, Quinlan et al. 2002; and others). The effect of Regina's discharge on downstream lakes is potentially compounded by other point and non-point sources of nutrients between Wascana Creek and the lakes.
The effluent output from Regina's WWTP increases the nitrogen in Wascana Creek and the Qu'Appelle River and reportedly causes eutrophication of the watercourses and lakes downstream. The increased input of ammonia raises the un-ionized ammonia concentrations above 0.48 mg/L which is reported by Stantec to be within the .
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\...~ ~R~E~O~A~TJ.C. ~lcll\h(" oi the Associated EnginecJing Group of Companies
Memo To: Ministry of Environment May 13, 2011 - 2 -
range that is potentially toxic to rainbow trout. The discharge of treated effluent from the Regina WWTP also caused significant downstream dissolved oxygen depletion in vVascana Creek (Stantec 2006; 1977-2001 data). ,,. Fecal coliforms from Regina's effluent are controlled with.AJV disinfection in the summer, but not in the winter. The impact on fecal coliform levels in Wascana Creek does not extend as far as the confluence with the
Qu'Appelle River (Stantec 2006).
The key conclusions from the Stantec report that have a bearing on the Lumsden WWTP upgrades are:
• Eutrophication of Qu'Appelle River basin lakes is largely controlled by nitrogen loads;
• The ratio of nitrogen to phosphorus (N:P ratio) is critical for affecting algae growth and the proportions of algae and cyanobacteria in overall algae biomass, and needs to be considered in managing any
discharge; and • Total ammonia-N reduction in the treated effluent to 4 mg/Land 10 mg/L were predicted to be sufficient to
avoid ammonia toxicity to fish and other aquatic organisms.
1.2 RESEARCH BY THE UNIVERSITY OF REGINA
Research from the University of Regina led by Dr. P. R. Leavitt and A. Patoine focused on the effects of nitrogen from urban waste water on the aquatic environment in southern Saskatchewan. In general, it is known that the
soil in the Northern Great Plains region is rich in phosphorous and carbonate from glacial till (Finlayet al. 2009) and that long-term agricultural practices can saturate soils with phosphorous (Benette et al. 2001). Phosphorous loading in soil increases phosphorous export to surface waters which can create condition~ where lakes are nitrogen-limited; and small changes in nitrogen inputs can potentially degrade water quality (Bunting et al. 2005).
In the Qu'Appelle valley, the high availability of phosphorous in soils and effective sequestration of nitrogen into
sediments causes nitrogen limitation in lakes (Patoine et al. 2006). Nitrogen-rich effluent from Regina has degraded water quality in Pasqua and Echo lakes since the 1930s (Hall et al. 1999), but as nitrogen use in agriculture is expected to increase in the coming decades, eutrophication of lakes in the northern great plains remains a concern. A number of studies show that cha:nges in nitrogen influx from urban and agricultural sources are correlated with increased lake primary productivity (Hall et al. 1999; Dixit et al. 2000; Quinlan at al. 2002) and
that cyanobacteria playa greater role in the nitrogen flux of eutrophic lakes than was previously recognized (Patoine and Leavitt 2008).
Patoine and Leavitt (2008) observed spatial gradients of water chemistry in lakes along the Qu'AppeUe Valley.
Lake catchment area, conductivity, salinity, chlorophyll g and nutrient values increase from headwater to downstream lakes; but patterns of nitrogen fixation varied unrelated to location. Nitrogen outputs from the Regina
WWTP accounted for 85% of the total nitrogen in the Qu'Appelle River when assessed in 2002 and 2004. Earlier studies concluded the aquatic systems downstream of Regina were phosphorous-limited, so measures were taken (e.g. alum chemical precipitation and other phosphorous control programs) to reduce phosphorous loading
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Technical Memorandum Wastwater Treatment Facility
Process Overview (Tech Memo No.2)
in the receiving waters. During aerobic biological oxidation, organic material in the influent is oxidized and converted to new heterotrophic biomass. In order to
maintain the proper balance of incoming organic material (substrate) and heterotrophic biomass, a certain amount of the new biomass must be regularly
removed from the system and a certain amount must be recycled back into the
system.
3.1.2.2 Biological Nit'rification
Biological nitrification is a two-step process in which ammonia (NH4 +) is first oxidized to nitrite (NO/) and nitrite is then oxidized to nitrate (N03-
1). Removal of
ammonia prior to discharge to the Qu'Appelle River is required because of
ammonia's toxicity to fish and as an overall effort to limit the addition of nitrogen to the Qu'Appelle. In the activated sludge process, two different types of aerobic autotrophic bacteria are responsible for each of the two steps of nitrification.
Nitrification can be achieved alongside cBOD'removal in the same bioreactor using the same single-sludge process, however the bacteria responsible for nitrification grow much slower than the bacteria used for cBOD resulting in a longer hydraulic
and solids retention time in systems designed for·nitrification.
3.1.2.3 Biological Denitrification
Biological denitrification is the term used to describe the biological reduction of nitrate (N03-
1) to nitric oxide (N20 2) and nitrogen gas (Ni). Nitrate reduction is
achieved by heterotrophic microbial activity in the presence of organic carbon. In
the activated sludge process, this is achieved in an anoxic (absence of dissolved I I oxygen) zone separate from the aerated zone where cBOD removal and
nitrification take place. Removal of nitrate is required to limit the amount of total
nitrogen discharged to the Qu'Appelle River.
3.1.3 Chemical Phosphorus Removal
Phosphorus can be removed from raw wastewater biologically (Le. incorporated in cell biomass) or chemicallyby precipitating it with the addition of aluminum or iron salts.
Biological removal of phosphorus is effective for removing phosphorus in solution to
relatively low levels however it requires the inclusion of an anaerobic zone in the bioreactor
process and adds complexity to the plant. In large facilities, the complexity is warranted by significant savings in chemical costs. In small facilities, the chemical approach is usually
favoured on the basis of operational simplicity.
Chemical phosphorus removal by adding aluminum sulphate (AI2(S04h) (alum) followed by secondary clarification without further solids removal is typically effective for meeting a total
phosphorus (TP) discharge limit of 1 mg/L. For lower phosphorus limits, tertiary filtration or
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membrane filtration would likely be required. The presence of phosphorus in wastewater is
largely in the form of phosphate ions (P04-3
) which react with alum to form an aluminum
phosphate precipitate. The precipitated aluminum phosphate is removed along with
excess aluminum hydroxide after settling in secohdary clarifiers.
3.1.4 Secondary Clarification
Secondary clarification is the process of separating the solids (sludge and precipitated phosphorus) from the treated liquid after biological oxidation, nitrification and denitrification
and chemical phosphorus removal. Separation is achieved by gravity settling in secondary
clarifiers. The settled sludge is collected at the bottom of the clarifiers and either pumped back into the aeration basin as return activated sludge (RAS) or wasted and pumped for
solid stream treatment as waste activated sludge (WAS). Clarifiers can be circular or rectangular in geometry however circular clarifiers are more common for a number of
reasons related to design and operation. The base of a circular clarifier is typically conical, sloping to a central low point where solids are collected in a hopper. A mechanism on the base of the clarifier plows settled solids to the central hopper. In some designs, sludge is withdrawn at openings along the length of the plow device to provide for more rapid
removal of sludge. This reduces the potential for the sludge to become anoxic or anaerobic which in the case of biologically enhanced phosphorus removal, could result in phosphorus
release.
3.2 Solids Stream Treatment
The activated sludge process produces a continuous stream of waste activated sludge (WAS) which requires stabilization and dispOsal. The objective of the stabilization process (after which
sludge is referred to as biosolids) is to reduce pathogens, eliminate offensive odours and minimize the potential for putrefaction of organic matter. Biosolids are sometimes thickened in a dissolved
air flotation process, gravity belt thickener or rotary drum thickener in order to reduce the volume of sludge prior to stabilization. Stabilization can be achieved in either aerobic or anaerobic digesters or via several other processes including composting, autothermophilic aerobic digestion or lime
stabilization.
The digestion process promotes microbial breakdown of the microbial cells to reduce the solids
content. Digestion also reduces, but does not eliminate odours and the potential to attract insects
or animals. Digestion contributes to partial disinfection of the sludge, depending on the temperature and duration of the process.
Prior to final disposition, it is necessary to reduce the water content of the digested sludges. This is particularly the case if the digested sludge is to be received at a landfill or is to be composted. If
the sludge needs to be trucked a significant distance, dewatering will also save transport costs. In
Lumsden's case, it is recommended that biosolids be stabilized in a digester without thickening.
Although the digester tank volume would be higher than with thickening the benefits of eliminating
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Technical Memorandum Wastwater Treatment Facility
Process Overview (Tech Memo No.2)
the thickener override the advantages of providing it. The process would be simpler from an operations and maintenance (O&M) perspective and the capital cost would be smaller. Separate
sludge thickening is seldom practiced in small facilities.
3.2.1 Aerobic Digestion
Aerobic digestion is the mosf commonly used stabilization process in small wastewater treatment facilities. Aerobic digestion takes place in completely mixed and aerated tanks
designed for a solids retention time of 20 to 45 days. Because of the aeration requirement,
energy requirements are higher for aerobic digestion compared with anaerobic digestion. However, in comparison with anaerobic digestion, capital costs are lower and operation is
simpler.
3.2.2 Mechanical Dewatering
Typical dewatering processes include treatment in centrifuges, belt filter presses and
pressure filter presses. In some cases, dewatering may be achieved intermittently with the use of mobile dewatering equipment. Centrifuge dewatering employs centrifugal force to
accelerate the separation of solids from water. The process is characterized by high energy demands and high capital and operating costs however the operator attention requirement is minimal and the footprint is small. Belt filter presses press and dewater
biosolids between two moving belts. Belt filter presses have lower capital and operating
costs however they require a greater footprint and tend to release more odour than a centrifuge. Pressure filter presses dewater biosolids using a positive pressure differential
as the driving force. Pressure filter presses have high capital and operating costs and
require considerable amounts of operator attention.
3.2~3 Sludge Drying Beds
Prior to disposal, further dewatering can be achieved with sludge drying beds. Sludge is spread over a layer of sand overlying a gravel bed with underdrains. Moisture is removed
by drainage and evaporation. Sludge drying beds have a large land requirement however
operation is simple.
4 Liquid Stream Treatment Alternatives Description
4.1 Introduction
A number of variations on the activated sludge process can provide treatment of Lumsden's raw
wastewater to the preliminary effluent standards that have been suggested by the Saskatchewan
Ministry of Environment (MOE). Each variation is characterized by a different footprint, operational complexity, odour potential and lifecycle costs. Activated sludge processes initially considered for
evaluation included membrane bioreactor (MBR), extended aeration, oxidation ditch, the Biolac
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proprietary process involving earthen ponds and clarifier tanks, sequencing batch reactor, moving bed bioreactor and integrated fixed film activated sludge (IFAS). Initial screening identified the
most attractive options for development and evaluation as extended aeration, MBR and IFAS as a variation of a continuous flow nitrification/denitrification bioreactor. Each of these processes would
require alum addition for phosphorus removal and ultraviolet (UV) disinfection.
The following is a brief justification f6r the generation of the short list of processes from the longer list. Both the oxidation ditch and Biolac processes were eliminated due to their reliance on
relatively large, open aeration ponds. These ponds were not sufficiently compact to meet the requirements of the new facility and would contribute to heat loss in winter - a disadvantage when
trying to maintain nitrification. The sequencing batch reactor option was eliminated due to its batch
mode of operation. Batch operation introduces a level of control complexity and several design
complications that make the process less attractive than a continuous flow process. The moving bed bioreactor process was eliminated because of its similarity to the IFAS process and its
relatively low level of application in western Canada.
4.2 Alternative 1 - Extended Aeration with Alum Addition and UV Disinfection
The extended aeration process is designed to provide a relatively long hydraulic retention time
(HRT) for aeration as well as a relatively long s()lids retention time (SRT) compared with conventional and high rate processes. Because of the relatively long HRT, larger aeration tanks
are required and aeration energy use is higher than for high rate processes. However, the process
follows a relatively simple design and is easy to operate. Another advc:mtage of the longer HRT is an increased ability to provide buffering for treating 'shock' loads. To some degree, the extended aeration process provides for aerobic digestion of solids and therefore results in a lower sludge
yield than a conventional system.
An extended aeration facility would include initial fine screening and grit removal to remove solids
that could potentially damage downstream process equipment. Raw wastewater that has passed through the screens enters aerated equalization tanks which dampen flow rate variations so that a more constant flow can be delivered through the subsequent process. Effluent is pumped from the
equalization tanks into anoxic tanks (where denitrification occurs) and overflows into aeration tanks where carbonaceous BOD removC!1 and nitrification occur. Air bubbles delivered by air diffusers provide oxygen required by the biological processes and also keep sludge in suspension in the
aeration tanks. Alum is added for phosphorus removal at the downstream end of the biological process tanks. Effluent and sludge are passed into the clarifiers where solids are allowed to settle. Some of the sludge is returned to the anoxic tank as return activated sludge (RAS) while another
stream is wasted as waste activated sludge (WAS) and pumped to the digesters. Effluent
overflowing the secondary clarifier weirs is conveyed to the UV disinfection system.
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4.3 Alternative 2 - Membrane Bioi"eactor (MBR) with Alum Addition and UV Disinfection
Membrane bioreactors (MBR) combine the activated sludge process with microfiltration or ultrafiltration membranes for liquid-solid separation. The membranes eliminate the requirement for
secondary clarifiers. MBR systems are capable of operating at higher mixed liquor suspended
solids(MLSS) concentrations than other treatment processes such as extended aeration or
conventional activated sludge. Consequently, MBR systems can operate with significantly smaller
tanks than other processes and have a relatively small footprint.
An MBR facility would include initial fine screening (typically through 1 mm diameter openings) and
grit removal to remove solids that could potentially damage downstream process equipment. Raw wastewater that has passed through the screens enters aerated equalization tanks which dampen
flow rate variations so that a more constant flow can be delivered through the subsequent process. This is particularly important for the MBR process that has a maximum treatment rate based on membrane flux.
Effluent is pumped from the equalization tanks into the anoxic zone (where denitrification occurs) and continues into the aerobic zone where carbonaceous BOD removal and nitrification occur and alum is added to precipitate phosphorus. Air bubbles delivered by air diffusers provide oxygen
required for the biological processes and also generate mixing to keep the sludge held in
suspension. Membrane modules that separate liquids and solids are submerged in the aerobic zone. Some of the sludge is recovered and returned to the anoxic tank as return activated sludge
(RAS) while another stream is wasted as waste activated sludge (WAS) and pumped to the digesters. Effluent that passes through the membranes then flows through the UV disinfection system.
Various cleaning procedures are used to overcome fouling of the membranes. These consist of
frequent, relatively short procedures and less frequent more intensive cleaning operations to restore membrane flux. Slight variations in the operational approach are recommended by different manufacturers.
4.4 Alternative 3 - Variation on Nitrification/Denitrification with Alum Addition and UV Disinfection
Several other variations of the activated sludge process could provide treatment to the required effluent limits. One example developed f()r comparison with the extended aeration and MBR
processes is the integrated fixed film activated sludge (IFAS) process that includes neutrally
buoyant biofilm carriers. In this process, the carriers (or media) provide large amounts of surface
area for fixed film growth in combination with the suspended growth of the activated sludge
process. The carriers are contained within carrier retaining screens in the aerated zone and
provide a stable environment on which the microorganisms can grow. The fixed film growth sustained by the carriers allows the population of microorganisms in the aerated zone to remain
stable during periods of variable flow. This is advantageous for the retention of nitrifying bacteria that have slow growth rates especially in cold temperature water. Whereas the suspended nitrifiers
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would be susceptible to a wash out event, the attached growth nitrifiers would be retained in the fixed film environment. This would help to prevent the temporary loss of the ability of the process to
provide nitrification.
The high surface area to volume ratio of the carriers results in a high concentration of biomass in
the aerated zone, allowing operation in smaller aeration tanks than an extended aeration process. Detached biomass from the carriers1s held in suspension by diffused air bubbles. The detached biomass is separated in the secondary clarifier and pumped back into the aerated zone as RAS or wasted as WAS ..
In a variation of the IFAS process, moving bed biofilm reactors (MBBR) operate without a RAS
stream. This allows for a more basic settling basin than the fully functional secondary clarifier required for IFAS however the aeration tank volume is greater.
5 Solid Stream Treatment Alternatives Description
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5.1 Introduction
Prior to disposal as biosolids, sludge will require stabilization (through digestion) and dewatering. Digestion can be accomplished aerobically or anaerobically. Dewatering alternatives include belt filter press, centrifuge, pressure filter press and drying beds. An initial screening selected three
process alternatives for evaluation and development. These include aerobic digestion with a belt filter press, aerobic digestion with centrifuge and anaerobic digestion with centrifuge. In each of these alternatives, final drying would be achieved in sludge drying beds. The Town has indicated
its preference to use dried biosolids as a cover material for its municipal landfill operation.
5.2 Alternative 1 - Aerobic Digestion with Belt Filter Press
Sludge can be stabilized by digestion in an aerobic digester with approximately 20 to 45 days solids retention time. In alternative one this would be followed by belt filter press dewatering. The advantages of aerobic digestion over anaerobic digestion are its simple process operation, low capital costs, minimal odour issues and end product with good dewatering properties. The
disadvantages of aerobic digestion are its high energy demand, poor performance at low temperatures and potential for foaming. Belt filter press dewatering has the advantages of low capital costs, low energy demand, low polymer dose and easy visual observation of process
performance. The disadvantages of belt filter press dewatering are odour issues, greater space requirement than centrifuge and sensitivity to feed sludge variations.
5.3 Alternative 2 - Aerobic Digestion with Centrifuge
Alternative 2 differs from Alternative 1 in the use of centrifuge dewatering as opposed to belt filter press dewatering. A centrifuge applies centrifugal force to the solids through high speed rotation,
accelerating the separation of solids from water. In comparison to a belt filter press, a centrifuge
carries the advantages of having fewer odour issues, flexible operation control with respect to feed
P:1201 04796100_Lumsden_ WW _ UpgradlEngineeringl03.00 _ ConceptuaLFeasibility_Designl Tech Memo 2ltcm_2drafC20 11 0704.doc
, I
Technical Memorandum Wastwater Treatment Facility
Process Overview (Tech Memo No.2)
variation, small space requirement and low operator attention requirements. However, centrifuge
dewatering has higher capital costs, higher energy demands, higher operating costs and more
noise than a belt filter press.
5.4 Alternative 3 - Anaerobic Digestion with Centrifuge
An alternative to aerobic digestion isanaerobic digestion. Mesophilic anaerobic digestion takes
place in completely mixed anaerobic tanks at37"C with an SRT of 15 to 20 days. Anaerobic digesters are typically two-stage systems with an unheated and unmixed second stage. Anaerobic digestion has the advantages of low energy demand, potential for recovery of methane gas and good pathogen inactivation. Disadvantages of anaerobic digestion are high capital costs, significant mechanical equipment, heat input requirements, slow recovery from process upset,
complex process operation, safety concerns with methane gas handling and odour issues.
6 Liquid and Solid Stream Treatment Evaluation Criteria
The short listed processes for liquid stream treatment and for solid stream treatment are developed to an extent sufficient for further comparison and evaluation. The external peer reviewer will consider the process development and provide comments pertaining to the liquid and solids streams treatment alternatives. From those comments two alternative technology packages are to be advanced for further consideration and evaluation using a Triple Bottom Line (TBL) analysis.
The TBL approach evaluates facility development based on three sets of criteria - economic, environmental
and social. The goal of TBL evaluation is to screen alternative approaches based on environmental and
social sustainability in addition to the traditional economic bottom line. Economic criteria include capital
costs, operation and maintenance (O&M) costs and 25-year lifecycle costs. Environmental criteria include energy demand, greenhouse gas emissions, chemical demand, odour potential, process reliability and
robustness and land requirements. Social criteria include visual and noise impacts, ease of operation and
ease of maintenance. Adopting the holistic approach to facility development in the context of TBL enhances the probability of the overall successful outcome for the Town.
During Workshop 3, Conduct TBL Evaluation of LST and SST Options, the weights of the three general
categories; economic, environmental and social, as well as the weights of individual evaluation criteria will
be discussed and confirmed with the Wastewater Committee. This process of assigning weights is an important component of the overall process. Further, the assignment of scores to each alternative for how well it meets each specific evaluation criterion will be made jointly with the participants of the Workshop.
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Town of Lumsden
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6.1 Triple Bottom Line Criteria and Weights ..
6.1.1 Economic
6.1.1.1 Capital Costs
Capital costs includ~estimates for land, process equipment, civil works, structural components, building mechanical systems, electrical, instrumentation, controls and
" related costs applicable to provision of the wastewater treatment facility. Costs for
the lift station upgrades, installation of forcemain extensions and new river outfall
are not included in the wastewater treatment facility costs.
6.1.1.2 O&M Costs
Operation and maintenance (O&M) costs are estimates for costs related to operating and maintaining the facility on an annual basis. O&M costs include
labour, power, chemicals, maintenance and administration.
6.1.1.3 25-year Lifecycle Costs
The 25-year lifecycle cost of a facility is the net present value (NPV) of all of the capital and O&M costs incurred over the 25-year life of the facility.
6.1.2 Environmental
6.1;2.1 Energy Demand
Although energy demand is also considered in O&M costs, it is reconsidered here
in the context of sustainability. Using less energy implies lesser use of resources and a reduction in greenhouse gas emissions.
6.1.2.2 Chemical Demand
Similar to energy.demand, chemical demand is considered here in the context of sustainability. The energy input and emissions associated with the production and
transport of chemicals imply that a facility that minimizes chemical use is a more
sustainable facility than one that relies heavily on chemical input.
P:1201 04796100_ Lumsden_ WW _ UpgradIEngineeringI03.00_ ConceptualJeasibility_ DesignlTech Memo 2Itcm_2draft_2011 0704.doc
6.1.2.3 Process Robustness
Technical Memorandum Wastwater Treatment Facility
Process Overview (Tech Memo No.2)
The robustness of the chosen process will determine the impact on the receiving
environment, the Qu'Appelle River. Technologies are evaluated based on their capability for consistently removing contaminants and producing a high quality
effluent in the face of variable input conditions.
6.1.2.4 Footprint
The facility's areal requirement or 'footprint' will dictate the amount of land required
for construction of the facility. A smaller footprint will minimize the disruption of wildlife habitat and allow for a less conspicuous facility. Until the wastewater liquid stream technology is selected the conceptual footprint is deemed to be one hectare. Not only must the plant requirements be addressed but also other factors. Considerations for onsite parking, truck access for grit and sludge removal, truck access for servicing the facility, truck access for receiving treatment chemicals, and
certainly not least, provision for expandability. Future development of the site could be driven by larger population and therefore more flow through the plant or it may be driven by regulatory forces. For example, should total phosphorus permit levels be reduced to less than 1 mg/L, then additional filtration may be needed.
6.1.2.5 Grade
The facility is to be established at a grade that adheres to certain criteria. The
plant site is to be flood proof to an accepted return period flood such as one in 500 year return, or to be suitable for flood proofing. Operating staff rieed year around
access to the site to operate the plant. Energy consideration may result in an elevation that allows gravity flow to the outfall. Such a decision may also require
modifications to the lift station pumps.
6.1.3 Social
6.1.3.1 Visual and Noise Impacts
The aesthetics of the facility will affect public perception of the infrastructure. A facility that is aesthetically unpleasing and noisy will not be met with the same degree of public acceptability as a facility that appears spatially efficient and
unintrusive.
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Town of Lumsden
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6.1.3.2 Odour Potential
Odours generated by wastewater treatment technologies can have significant
impact on residences and visitors to the plant. Technologies that minimize the generation of odours or include measures to control odours will be met with greater acceptance by the overall community.
6.1.3.3 Ease of Operation
The ease of operation of the facility reflects the complexity of the system and the
potential for problems that may impact system performance. Systems with excessive mechanical components and electrical controls require a higher degree of operator attention than systems that favour simplicity over complexity.
6.1 ;3.4 Ease of Maintenance
Similar to ease of operation, ease of maintenance is related to the complexity of the facility. Facilities that follow simple operating procedures and have fewer components are easier to repair than complex systems with many moving parts.
7 Presentation of LST and SST Options
Two liquid stream/solid stream treatment options are presented. These include 1) extended aeration with nitrification and denitrification, and 2) IFAS. Each option includes UV disinfection, aerobic digestion of biosolids and centrifuge dewatering of biosolids. Appendix A includes process flow diagrams (PFD's) and
site layouts for Options 1 and 2.
Capital and 25-year lifecycle costs for each option are included in Table 10-1. Costs include site
development and outfall construction. Costs do not include pumping station upgrades.
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Table 10-1
Technical Memorandum Wastwater Treatment Facility
Process Overview (Tech Memo No.2)
Capital and Lifecycle Cost Estimates ($M)
1) Extended 2) IFAS
'" Aeration with
Option: "
Nitrification and Den itrificatio n
Base Construction Cost Estimate (Mid 2011 Dollars, Including 8% for General
6.3 6.8 Conditions and 7% for Overhead & Profit)
Contingencies (20% Design, 15% Construction, 10% Market - Total 45%) 2.8 3.0
Indirect Costs (Engineering 12%, Administration 3%, Misculaneous 2%) 1.5 1.7
Financial Adjustments (PST 5%, Interim
Financing 4%, Inflation to Midpoint of 1.8 2.0
Construction 2%/yr)
Total Capital Cost Estimate 12.4 13.5
25-year Lifecycle Cost Estimate 15.0 16.1
These costs are for comparison purposes and should not be taken for budgeting. From Table 10-1, the total capital cost estimates for each option are almost 100% more than the base construction costs as a result of contingencies, indirect costs and financial adjustments. There is considerable room to adjust and reduce these factors as design progresses.
8 References
Tchobanoglous, George, et al. (Metcalf and Eddy). 'Wastewater Engineering Treatment and Reuse, 4th
Edition'. McGraw Hill, 2003, New York, NY.
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Town of Lumsden
Appendix A - Figures
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St.VDGET~ SUPERNATANT
:--;r------------------!l~~~~~~~~~=_----------------------------------------------------------------------------------------------~ . ~ '--------------TOLANDFILL
... ~~------------------------------------- """"'"0 SOURCE
FEED
!1.0
RAW SANITARY WASTEWATER
K1\I\I\/\}~ ~ LIFT STATION
MJlNUALBAR SCREEN
SCREENINGS WASHER/COMPACTOR
:"
"",""0,,","'",," • BIOREACTORS '--1
Or----------i : .
SECONDARY CLARIFIERS
W REACTORS
--------------------------~------------------------------~'" > TOLANOFILL
r-------------------------------------------------------------------------~
I ~IT~. : ~----/1)-:;c---~~oeG:~e~ .....:0..:=""""" /{7- 0,. -
'0' r-______ ::z:;G~':~~~::~'_______ 'WOCET~' r--( ~ I ~~ -----------'~·:_OR~~ CENTRIFUGE .
~,:: OR CONVEYOR -~ T BE~~~~TER -------------------.:~-------------------~ TO HEADWORKS
D-· POlYMER SYSTEM
PROJECT No. 'OJ 04796 DATE: !l !NE 2011
APPROVED: 8 HEYWOOD
SCALE: --"'N"'""'S _____ __
owe. No. FIGURE P 01
~Assoclated ~jEngineerlng
TOWN OF LUMSDEN WASTEWATER UPGRADES
PROCESS FLOW DIAGRAM
EXTENDED AERATION
SWOOET~K f~~~~~~~~~~~-------------------------------------------------~ ~>---------
' SCREENINGS
~ ==--'
RAW SANtT ARY ,WASTEWATER
i I I "",e"", '.
L/J--MANUAlllAR
SCREEN
SCREENINGS WASHERICOMPACTOR
e,,"BOND SOURCE "EO
10 0 "'" "'0
--..~
:;~~;~?;0~
• or-------~
DISINFECTED .... ____ EFF~ueNT.
l~~~ ~ TO QU'AP?E1.LE RIVER
W REACTORS
~ . § ",--. --,-s <V ' GRIT v:
SEPARATOR CLASSIFIERS
---------------------~ -'---,' TO LANDFILL
)IV My "V""
"R""e i or------D-'''-''-''_ .. i
r-____________________________________ ~:SU~RNMANT )
IT~ . .-------:::::'" T "",,,;e
# ~ TOTRUCK
~ I StUDGECAKE
. "'DG"~'. &, ~ "''-''<V ---TOOR"'G'EI" >
;~ :~?£:: __________ "'-/_~ __ . ee _"'"'_"''''_''_OR _______ CENTRATE
.
D-' POLYMER SYSTEM
PROJECT No. 2C:l C~Z9fi DATE: BltllE 2Q:ll APPROVED. 8 I::IEn:YQQQ SCALE: t!tIS DWG. No. EIG\IBE ~-Q2
: > rOt1EAOWORKS
TOWN OF LUMSDEN WASTEWATER UPGRADES ,,-Enstneerlns PROCESS FLOW DIAGRAM
IFAS ALTERNATIVE
SECONDARY CLARI!'IER (FUroRE)
~~~~CTEl): DC TO RIVER !
::---------1
SLUDGE PUMPINC :---STATION
SOliDS DEWATERING/UV
aUILDING
BIOREACTOR (FUTURE)
--------- , , ,~-----~~,
: INFUJENTFROM • LIFT STATION
. SITE OUTliNE SHOWN FOR REFERENCE • APPRDX90M x 10M(O.63 hD) ,
'--- - - -- - - -- - - -- -- -- - - -- -- -- - --- - - -- - - -- - - -- - - -- - - -- - - -- - --
PROJECT No . .,-"J20JjlLCO",471J9,,6'-_-i
DATE: !llNE 2Q11
APPROVED: 6 HEY'vVOOD
SCALE: 1 '20Q
DWG. No. Elm lRE P-Q3
~ AssocIated ~'Enslneerlnl
TOWN OF LUMSDEN WASTEWATER UPGRADES
SITE PLAN
DRAWING REDUCED TO HALF SIZE
EXTENDED AERATION LAYOUT L-_________________ _
OISINF'ECT'ED EFFtUENT TO RIVER
SECONDARY CLARIFIER (Furur<E)
,~ '.",. - .~ .. , .. ', ~ ~y
/~ ;, \\ .' \\ i\ SECONOARV CLARll'IER
\~\ ,~: \ j //~
/ . . ~. -,-,--; /
, SlUOGE: , : PUMPIfIlG ;---; ---------,
STATION
~~~ /1 ' ,,\, r· :? ' ,
:~\ ,ECONOARVCLARIFIER t \ /' ~'
(.---------~ SOliDS
O~WATERINGIUV
BUILDING
IFAS BIOREACTQR (FUTURE)
,.-._._.- _. __ .- _._ ..
--1 ~ --{) - ----- - - - ----- ~ ;;..., ----+--j, '
--+
,INFlUENTFRQM I LlFl ~'TATION
i SITE OUT\.INE SHOWN FOI~ REFERENCE" APPROX!IOM • 10M (O.li3h<1)
'-- - - --- - -- - - -- - - -- - - -- - - -- - --- - - -- - - -- - - -- - - -- - - -- - - -- - --'
PROJECT No . .....,20""""0=.47,-,9,,,6 __ -.< DATE: !lIN[ 2011
APPROVED: A HeywOOD
SCALE: 1 '200
DWG. No. fiGURE P 04 L-__________________________________________________________ _
~AssocIated ~Enrrlneerl ...
TOWN OF LUMSDEN WASTEWATER UPGRADES
SITE PLAN
IFASLAYOUT
DRAWING REDUCED TO HALF SIZE
TECHNICAL MEMORANDUM
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