On-site Wastewater Treatment Systems: Conventional septic tank ...
On Site Wastewater On-Site Wastewater Treatment – A Treatment A ...
Transcript of On Site Wastewater On-Site Wastewater Treatment – A Treatment A ...
On Site Wastewater On-Site Wastewater Treatment – A Treatment A
Sustainable OptionSustainable OptionJudith Sims
Ut h W t R h L b tUtah Water Research LaboratoryUtah State University
Logan Utah 84322 8200Logan, Utah [email protected]
How Do We Treat Wastewater?How Do We Treat Wastewater?
Two types of treatment facilities used in U.S. Centralized Centralized Decentralized On-site Cluster
All types treat wastewater by: Separating solids (primary treatment) Biologically degrading remaining organic materials Biologically degrading remaining organic materials
(secondary treatment) Some systems may incorporate additional tertiary
treatment processes to remove nutrients Disinfection may be necessary to eliminate pathogens,
depending on receiver system
Features of Features of Centralized SystemsLarge point source of g pdischarge to surface waters
Transfer of water away from point of generationpoint of generation
May even be transferred from one watershed to another
Centralized funding & professional management
FAMILY HANDYMAN Magazine, Home Service Publication, Inc., an affiliate of Reader’s Digest Association, Inc., Suite 950, Minneapolis, MN 55425
Features of Centralized SystemsFeatures of Centralized Systems
Usually more “inviting” to growth
Typically an “all-or-nothing” system for area served Economics dictate that everyone within reasonable
proximity hook up to sewerproximity hook up to sewer
Prone to infiltration/inflow problems that intensify with time Requires rehab projects
Over-sizing of treatment systems to accommodate storm surges or bypassing of poorly treated wastewater during wet weather
How Do We Treat Wastewater?How Do We Treat Wastewater?
D t li d t t t t ( it Decentralized treatment system (on-site system) Serves an individual residence or commercial facilityServes an individual residence or commercial facility
or a group of residences or commercial facilities(cluster systems)
“Decentralized” - no collection sewers or a single treatment plant for an entire service area
How Do We Treat Wastewater?How Do We Treat Wastewater?
“On site” wastewater is treated near where it is On-site - wastewater is treated near where it is generated Also known as septic systems, or “The Beast in the Backyard”
Associated with low density communities and developments such as rural residences and small commercial facilities
Generally consist of a septic tank and a subsurface gravity or y p g ypressurized dispersal system but can include other components such as secondary treatment units and drip dispersal systems
On-Site SystemsOn-Site Systems
Conventional Gravity Flow Septic Tank-Drain
Advanced SystemsExample: Recirculating p
Fieldp gSand Filter
How Do We Treat Wastewater?How Do We Treat Wastewater?
Cluster on site systems Cluster on-site systems Can serve a small to large number of connections (two to
hundreds of structures; most common – 5 to 100) Smaller cluster systems serving a few structures resemble Smaller cluster systems serving a few structures resemble
onsite systems Larger cluster systems serving hundreds of structures tend to
resemble centralized systems Cl t t ll di t t i t Cluster systems generally disperse wastewater into
subsurface dispersal systems Surface discharge or wastewater beneficial reuse (irrigation)
may also be usedy
Decentralized System: A Cluster System
Septic TankSeptic Tank
What About the Solids?
University of Minnesota Cooperative Extension Service
Tank must be pumped periodically to remove solids - referred to as septage
What Do We Mean by Treatment in a Soil-Based On-Site System?
Soil treatment processes Ph i l filt ti d t t f t i t i il Physical filtration and entrapment of contaminants in soil
pores Chemical precipitation of contaminants (for example,
phosphorus)phosphorus) Chemical adsorption of contaminants to soil particles
(especially to clay minerals) Nitrate, the cause of “blue baby” syndrome, does not , y y ,
significantly adsorb to soil particles Biological decomposition of organic contaminants Organic contaminants and pathogens serve as “lunch” for
ti il i inative soil microorganisms Pathogens also die-off if retained in the soil long enough
What Do We Measure to Assess Wastewater Treatment?
Organic materials BOD5 - Biochemical oxygen demand - amount of
oxygen used in the breakdown of organic matter Is an indirect measurement of the organic content of a water Is an indirect measurement of the organic content of a water
sample
Pathogens Indicator organisms - Fecal coliforms/E. coli
(bacteria whose presence indicates that the water may be contaminated with human or animal wastes))
What Do We Measure to Assess Wastewater Treatment?
N i Nutrients Phosphorus
i f Nitrogen forms NH4
+, NO3-, Organic nitrogen
Total Nitrogen is all of the forms Total Kjeldahl Nitrogen measures
i d i iammonium and organic nitrogen
NitrogenNitrogen
Nit i th f f it t i l f Nitrogen, in the form of nitrate, is also of human health concern Nitrate levels in drinking water above Nitrate levels in drinking water above
regulated levels (10 mg/L (ppm)) may be toxic when consumed by infants less than 6
h ldmonths old “Blue Baby” Syndrome Also implicated in other health problems Also implicated in other health problems
Case Study: On-Site TreatmentThrough 4 ft of Fine SandThrough 4 ft. of Fine Sand
EPA/625/R-00/008Parameter
(Units)Septic Tank
EffluentSoil Water at
0.6 mSoil Water at
1.2 m( )
BOD(mg/L)
93.5 <1 <1
TKN(mg/L)
47.4 0.77 0.77
NO3—N
( /L)0.04 21.6 13.0
(mg/L)
Total P(mg/L)
8.8 0.4 0.18
E. coli(Log # per 100 mL)
4.57 Non-detect Non-detect
How Do We Treat Wastewater When Site Conditions are Limiting?
I l h diffi l i di i h In places where difficult site conditions prevent the use of septic tank/drain fields, some jurisdictions allow the use of advanced (usually more complex -allow the use of advanced (usually more complex often called alternative) systems
Also sometimes used to provide a higher level of Also sometimes used to provide a higher level of treatment than can be obtained with conventional system
How Do We Treat Wastewater?Limiting Conditions
Difficult conditions that may prevent use of conventional systemconventional system Small lot sizes High ground water Shallow depth to bedrock High permeability soils with excessive amounts of
gravel rocks or sandgravel, rocks, or sand Low permeability soils with large amounts of clays Proximity to water sources
May need higher levels of contaminant removal for pathogens and nutrients, especially nitrogen
Benefits of On-Site SystemsBenefits of On-Site Systems
If l l d i d d i d i ll d If properly planned, sited, designed, installed, operated and maintained, on-site systems can provide level of treatment necessary to protect provide level of treatment necessary to protect public health and meet water quality standards
F ll i i i h l l i For small communities with low population densities, often are most cost effective option
Benefits of On-Site SystemsBenefits of On-Site Systems
Avoid transfer of water from one watershed to Avoid transfer of water from one watershed to another
Recharge local aquifers through subsurface Recharge local aquifers through subsurface disposal, maintaining the groundwater supply and a base flow for surface waters
Other water reuse opportunities include irrigation close to point of wastewater generation Use of drip irrigation is becoming more commonp g g
Challenges of On-Site SystemsChallenges of On-Site Systems
Many older systems in use today do not provide adequate treatment, resulting in adverse effects on q , gpublic health and the environment and negative effects on property values Were installed as temporary systems assuming centralized Were installed as temporary systems, assuming centralized
system would replace them
Were installed in unsuitable sites and locations
More than half of existing systems are over 30 years old
At least 10% of these older systems cause wastewater to back up into the home or surface in the yard
Many local health departments do not have records of many of these old systems
Management ProgramsManagement Programs
In many small towns and rural areas, where houses are spaced widely apart, septic systems may be the most practical & least expensive way to treat household wastewater
H f i i h d l d However, few communities have developed organizational structures for management of on-site wastewater systems Though such programs required for centralized
wastewater facilities and for other services (e.g., electric, telephone, water, etc.) to provide
f i l professional management
Management ProgramsManagement Programs
To protect ground and surface waters, an on-site
system should be managed throughout the life of that
system to ensure that the system performs satisfactorily
over its service life
When homeowners are responsible for managing their systems,
inadequate operation and lack of routine maintenance often inadequate operation and lack of routine maintenance often
leads to system failures, with a resulting perception that on-site
systems are not reliable
Given a choice, people would just rather flush and forget
about what they put down the drain
Management is a Good IdeaManagement is a Good Idea
Implementation of a management program can control the effectiveness of wastewater treatment to protect the effectiveness of wastewater treatment to protect public health and the environment
Management programs can take on many forms and g p g yvary in level of responsibility assumed by the program and by the system owners
A management program is especially important when A management program is especially important when alternative systems are used Alternative systems are usually more complex than
th ti l ti t k/ il b ti t the conventional septic tank/soil absorption system and require more frequent and specialized maintenance
Goals of an On-Site Management Program
R d i k t bli h lth b Reduce risks to public health by: Wastewater backup into homes or onto soil surfaces Prevent groundwater and well contamination Prevent groundwater and well contamination Minimize risks from public contact with system
components Mi i i i k f i d di l f Minimize risks from inadequate disposal of septage
Goals of an On-Site Management Program
Prevent and reduce effects on water resources Prevent and reduce effects on water resources, including nutrient over-enrichment and pathogen and contaminant discharges
Protect sensitive aquatic habitat and life
Abate public nuisances by eliminating odors Abate public nuisances by eliminating odors from systems or from transportation and disposal of septage
Approaches to Achieve On-SiteManagement Program Goals
Local Health Districts may: Administer a permitting program for on-site systems Administer a permitting program for on-site systems Manage or oversee on-going monitoring and maintenance of
systems Implement corrective action programs for failing systems Implement corrective action programs for failing systems Provide or require certification and licensure for on-site
system professionals Facilitate appeals and variances Facilitate appeals and variances Comply with UIC (underground injection control) and storm
water programs Offer inspections of on-site systems during real estate p y g
transactions Develop a public education and outreach program
The Utah On-Site Training ProgramThe Utah On-Site Training Program
Utah Administrative Rule R317-11
Persons who design, inspect, and maintain underground disposal systems, and who conduct percolation tests or soil evaluations for these percolation tests or soil evaluations for these systems, must be certified by the State of Utah
The Utah On-site Wastewater Treatment Training C U h S U i i h b d i d
gCenter at Utah State University has been designated as the provider of training as well as the administrator of examinations for certification of those persons who design, inspect, maintain, or p g , p , ,conduct soil and percolation tests for underground wastewater disposal systems
MOU for Decentralized Wastewater Treatment
In 2005 EPA developed a Program Strategy for the Decentralized Wastewater Program identifying EPA’s vision, mission and actions to improve performance of onsite wastewater treatment p psystems
One of the components of the Program Strategy is a M d f U d di (MOU) b EPA d Memorandum of Understanding (MOU) between EPA and fourteen organizations involved in managing decentralized wastewater systems. I l di G d W P i C il d NOWRA Including Ground Water Protection Council and NOWRA
MOU is intended to: Upgrade the professionalism within the industry leading towards Upgrade the professionalism within the industry, leading towards
efforts to improve system performance, promote education, expand knowledge levels, and increase communication concerning onsite issues
Resources National Onsite Wastewater Recycling Association NOWRA.org
U.S. EPA Onsite Program cfpub.epa.gov/owm/septic/septic.cfm?page_id=260
Consortium of Institutes for Decentralized Wastewater Treatment www.onsiteconsortium.org/g
MOU Partners