Wastewater Systems Wastewater Systems Wastewater Systems Dave Lenning Dave Lenning Dave Lenning Washington Dept. of Health Washington Dept. of Health Washington Dept. of Health
Our Focus: Our Focus: Wastewater issues & options for small Wastewater issues & options for small communities communities � Decentralized and centralized � Decentralized and centralized � Relationship to land use planning � Relationship to land use planning Wastewater in Washington State Wastewater in Washington State Briefly, general issues on technology Briefly, general issues on technology 2
Wastewater System Continuum Wastewater System Continuum Decentralized Centralized Decentralized Decentralized Centralized Centralized Treatment Treatment Treatment Individual Cluster Central Regional Individual Individual Cluster Cluster Central Central Regional Regional Plant Plant Plant Scale of Individual Part of a Entire town, Two or more Scale of Scale of Individual Individual Part of a Part of a Entire town, Entire town, Two or more Two or more Building community city, village, towns, cities, Building Building community community city, village, city, village, towns, cities, towns, cities, Service Service Service or or or or or or villages, or villages, or or or or villages, or Property subdivision community communities Property Property subdivision subdivision community community communities communities Level of Centralization Level of Centralization Level of Centralization 3
Example 1: Typical arrangement for Example 1: Typical arrangement for 10 lots – Individual Systems 10 lots – Individual Systems 5 6 4 7 3 8 9 2 10 1 4
Example 2: Possible arrangement for Example 2: Possible arrangement for clustering 10 lots clustering 10 lots Greenbelt Community Area 6 5 7 4 8 3 2 9 DF DF DF DF 1 10 5
Example 3: Another possible Example 3: Another possible arrangement for clustering 10 lots arrangement for clustering 10 lots Greenbelt or Community Area DF DF 1 2 3 4 5 6 7 8 9 10 6
Wastewater Systems Wastewater Systems Both centralized and decentralized: Both centralized and decentralized: � Collect wastewater from each home or � Collect wastewater from each home or business business � Treat wastewater to reduce contaminant � Treat wastewater to reduce contaminant levels levels � Discharge/Disperse treated wastewater in � Discharge/Disperse treated wastewater in way that won’t adversely affect public way that won’t adversely affect public health or the environment health or the environment 7
Decentralized vs. Centralized Decentralized vs. Centralized Questions: Questions: Which does the public like best? Which does the public like best? Which is best for the environmental Which is best for the environmental protection? protection? Which is most cost-effective? Which is most cost-effective? How does an existing small community How does an existing small community decide? decide? 8
It’s a fact: It’s a fact: We have experts in centralized systems We have experts in centralized systems and experts in decentralized systems and experts in decentralized systems Very few are expert in both Very few are expert in both Some potential for bias when planning Some potential for bias when planning the wastewater infrastructure of an area the wastewater infrastructure of an area 9
Reality to be recognized: Reality to be recognized: Most wastewater infrastructure Most wastewater infrastructure planning - done by experts in planning - done by experts in centralized systems centralized systems Makes getting decentralized systems to Makes getting decentralized systems to be considered more difficult be considered more difficult Many engineers, public/private utilities, Many engineers, public/private utilities, politicians are convinced - the only politicians are convinced - the only good, long-term system is a centralized good, long-term system is a centralized system system 10
Decentralized Systems Decentralized Systems Use same science as centralized systems Use same science as centralized systems Can produce high effluent quality Can produce high effluent quality But: But: Not the best reputation Not the best reputation Poor history of proper use and care Poor history of proper use and care Quality and quantity are variable Quality and quantity are variable Is it worth the effort to try and overcome Is it worth the effort to try and overcome the problems? the problems? 11
In 1997 USEPA said “YES” In 1997 USEPA said “YES” “Adequately managed decentralized wastewater treatment systems can be a cost-effective and long- term option for meeting public health and water quality goals, particularly for small, suburban and rural areas.” 12
Decentralized Wastewater Systems Decentralized Wastewater Systems 1997 Response to Congress lists 1997 Response to Congress lists potential benefits: potential benefits: � Protection of public health & environment � Protection of public health & environment � Provides flexibility – can target technologies � Provides flexibility – can target technologies � Varying site conditions � Varying site conditions � Varying sensitivities of receiving environments � Varying sensitivities of receiving environments � Smaller problem areas � Smaller problem areas � Longer service lives for managed systems � Longer service lives for managed systems � More cost effective, except in densely � More cost effective, except in densely populated areas populated areas 13
Wastewater Systems Wastewater Systems Need to better understand pros/cons of both Need to better understand pros/cons of both centralized and decentralized systems centralized and decentralized systems 14
Wastewater Systems Wastewater Systems Characteristic or Characteristic or Decentralized Centralized Decentralized Centralized Attribute Attribute Relatively small Relatively large Relatively small Relatively large Sewage Volume Sewage Volume amounts amounts amounts amounts Gravity effluent + Gravity sewer + Gravity effluent + Gravity sewer + Type of Collection Type of Collection alternatives alternatives alternatives alternatives Septic tank + Typically activated Septic tank + Typically activated Treatment Type Treatment Type alternatives sludge + alternatives alternatives sludge + alternatives Typically, into surface Typically, into surface Dispersal or Dispersal or Typically, into the soil water or onto land Typically, into the soil water or onto land Discharge Discharge surface surface 15
Wastewater Systems Wastewater Systems Characteristic or Characteristic or Decentralized Centralized Decentralized Centralized Attribute Attribute Vary considerably Some variance from Vary considerably Some variance from Applicable Rules Applicable Rules from state to state & state to state, but from state to state & state to state, but county to county county to county more consistency more consistency Requirements & Requirements & Historically, very Historically, very Performance based Performance based Standards prescriptive Standards prescriptive Convenience for Convenience for Can’t flush & forget Can flush & forget Can’t flush & forget Can flush & forget system users system users Usually, a concern, Usually, a concern, I & I I & I Usually, little concern especially with Usually, little concern especially with conventional gravity conventional gravity 16
Wastewater Systems Wastewater Systems Characteristic or Characteristic or Decentralized Centralized Decentralized Centralized Attribute Attribute Ownership Ownership Individual or private Public (POTW) Individual or private Public (POTW) Historically, more Historically, more Historically, more Historically, more Availability of Availability of limited and difficult to readily available and limited and difficult to readily available and funding funding find – find – this is changing this is changing easier to obtain easier to obtain Public Public Bad reputation, lack of Preferred option, Bad reputation, lack of Preferred option, acceptance maintenance has hurt most convenient acceptance maintenance has hurt most convenient If individual tanks – – no no If individual tanks Need for Need for easements; if cluster – – Will be needed easements; if cluster Will be needed easements easements some needed some needed 17
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