Decentralized Wastewater Treatment Technologies, Management, and Issues Carl Etnier Hudson River Watershed Alliance Garrison, New York March 16, 2006
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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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: Barriers abound to equitable consideration of decentralized
Plan for an energy-scarce future
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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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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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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 -
Parcels withfew limitations
Parcels withsome limitations
Parcels withsevere limitations
Deep Pits, PercTestsSoil Mapping Units
Add Soils Data -
Parcels withfew limitationsParcels withfew limitations
Parcels withsome limitationsParcels withsome limitations
Parcels withsevere limitationsParcels withsevere limitations
Deep Pits, PercTestsSoil Mapping Units
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Results – Application Rate (Capacity)
Parcels withfew limitations
Parcels withsome limitations
Parcels withsevere limitations
Results – Application Rate (Capacity)
Parcels withfew limitationsParcels withfew limitations
Parcels withsome limitationsParcels withsome limitations
Parcels withsevere limitationsParcels withsevere limitations
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Confirmation based on -Field survey and public input
Parcels withfew limitations
Parcels withsome limitations
Parcels withsevere limitations
Confirmation based on -Field survey and public input
Parcels withfew limitationsParcels withfew limitations
Parcels withsome limitationsParcels withsome limitations
Parcels withsevere limitationsParcels withsevere limitations
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Final Result –Recommendations based on need
Parcels withfew limitations
Parcels withsome limitations
Parcels withsevere limitations Final Result –
Recommendations based on need
Parcels withfew limitationsParcels withfew limitations
Parcels withsome limitationsParcels withsome limitations
Parcels withsevere limitationsParcels withsevere limitations
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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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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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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
Maintenance required
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
Maintenance required
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
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
55
Questions and Discussion
http://www.stone-env.com
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