Decentralized Wastewater Treatment - SSWM · 2018-02-12 · 1 Decentralized Wastewater Treatment: A...

DecentralizedWastewaterTreatmentTechnologies, Management, and Issues

Carl Etnier

Hudson River Watershed Alliance

Garrison, New York

March 16, 2006

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Contents and Take-Home Messages

1 Decentralized Wastewater Treatment: A permanent part of the wastewater infrastructure.

2 Wastewater Planning with Decentralized Options: Understanding what the site allows can save money and lead to more environmentally friendly treatment.

3 Major Issues for the Industry: Nutrient recycling is feasible, and barriers to equitable consideration of decentralized abound.

Plan for an energy-scarce future

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World Oil Discovery vs. Consumption

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“Without massive mitigation more than a decade before the fact, the problem will be pervasive and will not be temporary. Previous energy transitions (wood to coal and coal to oil) were gradual and evolutionary; oil peaking will be abrupt and revolutionary.”

The Hirsch Report (US DOE, 2005)

Peak Oil

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1 Decentralized Wastewater Treatment: A permanent part of the wastewater infrastructure


3 Major Issues for the Industry: Barriers abound to equitable consideration of decentralized


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Decentralized Wastewater Treatment

Source: US EPA

Centralized Approach Decentralized Approach

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Types of Decentralized Wastewater Systems

Cesspools and Drywells

Seepage Beds and Leach Trenches

At-grade and Mound Systems

Sand Filters and Other Innovative/Alternative (I/A) Systems

Cluster Systems

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Decentralized Wastewater Treatment

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Mound System

(Converse and Tyler, 1990)

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At-grade System

(adapted from Converse and Tyler, 1990)

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“Drip” Soil Treatment

virusesip Tubing

solids

groundwater

well

Buffer from well and SW

Air

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Spray Irrigation

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Advanced Treatment

Traditional septic systemI/A system• when to use?• part of management

plan: replacement or sensitive sites

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Sand Filter

(Converse 1999, adapted from Orenco)

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Constructed Wetland

Aerobic biofilter followed by a subsurface horizontal flow constructed wetland using light-weight aggregates: 40-60% nitrogen removal

Illustration source:Jenssen, Petter D. and Lasse Vråle. 2004. Greywater treatment in combined biofilter/constructed wetlands in cold climate. In ecosan - closing the loop: Proceedings of the 2nd international symposium

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Evapotranspiration Wetlands

Dimensioned for complete evapotransporation of water in Danish conditions

Zero discharge of water, organic matter, or nutrients

Source: Zero-discharge of nutrients and water in a willow dominated constructed wetland. Gregersen, P.; Brix, H. Water Science & Technology, 2001, Vol. 44, No. 11-12, pp. 407-412

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Cluster Systems

For properties with limited or no capacity on site

Collection system and piping from 2 or more properties to off-site large dispersal

Private or municipal system and site with permanent easements

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Community Systems

Small Cluster• STEP/STEG systems• traditional or I/A cluster

Large Cluster• services many connections • 40, 50, 100 homes or more

STEP

STEPSTEP

Disposal

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Management Needed

“Adequately managed decentralized wastewater treatment systems are a cost-effective and long-term option formeeting public health and water quality goals.” US EPA 1997Who is responsible? Typically homeowner for onsiteAffected by – Amount of water used, garbage disposals, chemicals, drugs

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Maintenance of Traditional Systems

Check/pump septic tank, check distribution box, check area for ponding

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Maintenance of Pumped Systems

(Converse and Tyler, 1990)

Same as traditional system, plus check pumps, wiring, alarms, flush lines, sample

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Clustering in New Development2-Acre Zoning

Conservation Development and Clustered Treatment

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Needs Assessment for Existing Development

Saves money by helping to avoid unnecessary centralized hookups

Shows where to concentrate wastewater management resources

Reveals wastewater implications of growth proposals

Confers eligibility for State Revolving Fund loans

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Start with the Parcels and Roads

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Add the Buildings and Setbacks

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Add Water Supplies and Protection A

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Add Ponds, Streams, and WetlandsWithSetbacks

Add Ponds, Streams, and WetlandsWithSetbacks

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ROW’s, Drainages, BedrockROW’s, Drainages, BedrockROW’s, Drainages, Bedrock

32 Results – Area Available (Suitability

Parcels withfew limitations

Parcels withsome limitations

Parcels withsevere limitations

Results – Area Available (Suitability

Parcels withfew limitationsParcels withfew limitations

Parcels withsome limitationsParcels withsome limitations

Parcels withsevere limitationsParcels withsevere limitations

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Add Soils Data -




Deep Pits, PercTestsSoil Mapping Units

Add Soils Data -




Deep Pits, PercTestsSoil Mapping Units

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Results – Application Rate (Capacity)




Results – Application Rate (Capacity)




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Confirmation based on -Field survey and public input




Confirmation based on -Field survey and public input




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Final Result –Recommendations based on need



Parcels withsevere limitations Final Result –

Recommendations based on need




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Example: Aesthetics/Drainage Analyses (1 of 2)

Properties with older systems identified

Properties with high groundwater identified

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Example: Aesthetics/Drainage Analyses (2 of 2)

Properties with low average slopes identified

Combination of older systems, high groundwater, and low slope

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Source Diversion

Divert and recycle nutrients

Microflush toilets (1.0 L or less per flush), with holding tanksfor blackwater and separate treatment of graywater

Composting of feces and separate treatment of graywater

”No-mix” toilets that keep urine separate from feces

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Phosphorus in Wastewater

Source: Vinnerås et al. (submitted)

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Use small amounts of water; air transports the feces, urine, and toilet paper

Usually connected to holding tank

Household applications more common in Scandinavia

Maintenance required

Can divert up to 75% of phosphorus from waste stream

Source Diversion: Microflush Toilets

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A vacuum toilet with generator and holding tank. Source: http://www.folkeweb.no/cgi-bin/webadm.cgi?gid=1022&c=1058.

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Feces collected and retained in the toilet system

Feces may be composted in the toilet system or collected and retained for treatment elsewhere

Many designs and models available


Can divert up to 75% of phosphorus from waste stream

Source Diversion: Composting Toilets

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Separate bowls for urine and feces; urine diverted to separate holding tank

Urine can be recycled to agriculture

Proven track record in Europe


Can remove 30-50% of phosphorus from waste stream

Source Diversion: “No-Mix” Toilets

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Urine-diverting toilets. BB Innovation’s Dubbletten Toilet (left) and the Wost Man Ecology DS Toilet, both constructed from porcelain. Source: Johansson 2000.

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This project focuses on barriers to engineers givingequitable consideration to decentralized solutions

Examples of inequitable consideration

Facilities plans that summarily dismiss decentralized options

Utilities install sewers at the margin of their service area, where decentralized can be competitive

Regulations discourage or prevent the use of decentralized technologies

WERF Research on Barriers

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Task 1: Identify barriers to equitable consideration of decentralized wastewater treatment within the engineering community

Task 2: Develop ways to overcome the barriers

Task 3: Communicate and publicize the findings

Project Work Plan

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Objectives

Research function: Help identify barriers

Communication function: Introduce barriers in the report

Five case studies are included

Austin, Texas

Holliston, Massachusetts

NorthStar Engineering, California

BETA Group, New England

University of Wisconsin

Case studies

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The community

Growing city of 657,000; 812,000 in Travis County

Austin Water Utility’s wastewater system serves 168,000 connections. Treatment at 3 plants with 130 MGD capacity.

Explored decentralized at edges in 1990s

Case study – Austin, Texas

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Numerous barriers encountered

Status

Decentralized wastewater approach never really got off the ground

Austin, Texas (cont.)

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The community

Growing unsewered community of 15,000 approx. 25 miles southwest of Boston

Case study – Holliston, Massachusetts

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Key barriers encountered

Early engineering consultants told community what to do; did not gather local desires. May have upsized system for economies of scale.

Inadequate methods of needs assessment: “Study area” analysis based on generalized criteria determined most areas (23 of 28) needed centralized solution.

Lack of systems thinking: Regionalization proposals did not adequately address hydrologic impacts.

Holliston, Massachusetts (cont.)

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Engineers’ lack of knowledge of decentralized systems

Engineers’ unfavorable perception of decentralized systems

Engineers’ financial reward for using centralized systems

Unfavorability of the regulatory environment for decentralized systems

Lack of systems thinking

Five Barrier Categories

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p(engineers consider

decent ralized equit ab ly)

Engineers’f inancial rew ard

f or using cent ralized

Unf avorab il i t y of regulat ory

cl im at e

Engineers’ lack of know ledge of

decent ralized

Engineer ’sunf avorab le

percep t ion of decent ralized

– –

– –+

+

+ +

+ +

+

+ + +

+

Lack of syst em t h inking+

+ ++ +

+

+–

+

+

Relationships among the five barrier categories

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Take-Home Messages





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Questions and Discussion

http://www.stone-env.com

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