Wastewater Systems. Dave Lenning Washington Dept. of Health

Transcription

1 Wastewater Systems Dave Lenning Washington Dept. of Health

2 Our Focus: Wastewater issues & options for small communities Decentralized and centralized Relationship to land use planning Wastewater in Washington State Briefly, general issues on technology 2

3 Wastewater System Continuum Decentralized Centralized Treatment Plant Individual Cluster Central Regional Scale of Service Individual Building or Property Part of a community or subdivision Entire town, city, village, or community Two or more towns, cities, villages, or communities Level of Centralization 3

4 Example 1: Typical arrangement for 10 lots Individual Systems

5 Example 2: Possible arrangement for clustering 10 lots Greenbelt Community Area DF DF 5

6 Example 3: Another possible arrangement for clustering 10 lots Greenbelt or Community Area DF

7 Wastewater Systems Both centralized and decentralized: Collect wastewater from each home or business Treat wastewater to reduce contaminant levels Discharge/Disperse treated wastewater in way that won t adversely affect public health or the environment 7

8 Decentralized vs. Centralized Questions: Which does the public like best? Which is best for the environmental protection? Which is most cost-effective? How does an existing small community decide? 8

9 It s a fact: We have experts in centralized systems and experts in decentralized systems Very few are expert in both Some potential for bias when planning the wastewater infrastructure of an area 9

10 Reality to be recognized: Most wastewater infrastructure planning - done by experts in centralized systems Makes getting decentralized systems to be considered more difficult Many engineers, public/private utilities, politicians are convinced - the only good, long-term system is a centralized system 10

11 Decentralized Systems Use same science as centralized systems Can produce high effluent quality But: Not the best reputation Poor history of proper use and care Quality and quantity are variable Is it worth the effort to try and overcome the problems? 11

12 In 1997 USEPA said YES Adequately managed decentralized wastewater treatment systems can be a cost-effective and longterm option for meeting public health and water quality goals, particularly for small, suburban and rural areas. 12

13 Decentralized Wastewater Systems 1997 Response to Congress lists potential benefits: Protection of public health & environment Provides flexibility can target technologies Varying site conditions Varying sensitivities of receiving environments Smaller problem areas Longer service lives for managed systems More cost effective, except in densely populated areas 13

14 Wastewater Systems Need to better understand pros/cons of both centralized and decentralized systems 14

15 Wastewater Systems Characteristic or Attribute Decentralized Centralized Sewage Volume Relatively small amounts Relatively large amounts Type of Collection Gravity effluent + alternatives Gravity sewer + alternatives Treatment Type Dispersal or Discharge Septic tank + alternatives Typically, into the soil Typically activated sludge + alternatives Typically, into surface water or onto land surface 15

16 Wastewater Systems Characteristic or Attribute Applicable Rules Requirements & Standards Convenience for system users I & I Decentralized Vary considerably from state to state & county to county Historically, very prescriptive Can t flush & forget Usually, little concern Centralized Some variance from state to state, but more consistency Performance based Can flush & forget Usually, a concern, especially with conventional gravity 16

17 Wastewater Systems Characteristic or Attribute Decentralized Centralized Ownership Individual or private Public (POTW) Availability of funding Public acceptance Need for easements Historically, more limited and difficult to find this is changing Bad reputation, lack of maintenance has hurt If individual tanks no easements; if cluster some needed Historically, more readily available and easier to obtain Preferred option, most convenient Will be needed 17

18 Wastewater Systems Characteristic or Attribute Decentralized Centralized Consequences of failure Limited to single home or cluster Can be disruptive to large neighborhood Flexibility of technical options Impacts on growth Considerable and growing fast can be very flexible Doesn t promote, but can accommodate, some fit on small lots Many options costly to modify/inflexible once installed Tends to promote growth, more homes = greater return Need for management Critical Critical Sampling frequency Historically, not 7 or 30 day averages Sufficient samples to meet averages 18

19 Decentralized Considerations: Can achieve high pollutant removal rates 95%+ removal BOD/TSS 99%+ removal of FC Can add components for other parameters Often much more affordable for small communities Homeowners/Communities concerned with failure rate 19

20 Decentralized Considerations: Not as convenient as centralized can t flush and forget Just like centralized systems, requires: Proper siting and design Proper installation On-going proper use and care O&M Many benefits and considerations in Rocky Mountain Institute publication 20

21 Centralized Considerations Unaffordable for many small communities Shellfish harvesting prohibited near outfalls Need dense development and population to pay for it affects growth planning Can provide high levels of treatment Management typically is easier 21

22 EPA Guidelines: Models Management Through: Model 1 - System Inventory & Maintenance Awareness Model 2 - Maintenance Contracts Model 3 - Operating Permits Model 4 - Utility Operation and Maintenance Model 5 - Utility Ownership and Management Lower Level Management Higher Level Management 22

23 Management of Wastewater is a Major Challenge in the Puget Sound Basin Issue Population Served (projected increase of 35% by 2025) Total Volume Groundwater Recharge Nitrogen Reduction Operation and Maintenance Water Quality Impacts Shellfish Acres Permanently Closed Shellfish Area Closed/Outfall or Failure Pipe breaks, Sewer Overflows, Failures Public Swimming Beach Closures Sewers (discharge to surface water) 2.85 Million (71%) 400 Million GPD Limited (reclaimed water; upland spray) 10-40% 1 (much more with tertiary treatment) Daily 28,000 (excluding urban bays) Large areas (100s 1,000s acres) >1.3 billion gallons/year 3 57 Short-term ( ) Septic Systems (discharge into soils) 1.15 Million (29%) 175 Million GPD High (but greater risk if failure) 10-40% Basic System 2 (Much more with nitrogen removal) Limited < 2,000 acres (where only source) Small, localized areas (1-2 acres) Variable depending on location 10 long-term ( ) SUMMARY Both meet or exceed secondary treatment standards Both are capable of higher treatment Both create water quality challenges 1 LOTT: 5% of 400 million GPD Ecology CSO Focus Sheet 2 Onsite Wastewater Systems Manual, EPA/625/R-00/008, Table 3-17, February 2002 Data source: DOH Office of Shellfish and Water Protection 11/

24 Consider: Wastewater Systems Stop using labels All systems part of wastewater infrastructure All systems need adequate management Why are labels then needed? 24

25 Wastewater Infrastructure Planning Using land use plan - consider all options USEPA Response to Congress: Combination of individual, cluster, and centralized may be best choice for many communities Rocky Mountain Institute: Optimal architecture for wastewater systems should be much more a mixture of centralized and decentralized than commonly encountered today 25

26 Consider: Wastewater Systems Population Density LOW HIGH GOOD Soils POOR Individual Cluster Wastewater Systems Sewer/TP 26

27 Wastewater Infrastructure Planning All systems in jurisdiction part of jurisdiction s wastewater infrastructure 27

28 Wastewater Infrastructure Planning Different Approaches 28

29 Wastewater Infrastructure Planning BUT community must first plan its future - how it will grow/sustain itself Then, wastewater infrastructure plan - dependent on land use/growth management plan 29

30 Pacific Northwest Differences 30

31 On-site Sewage Regulatory Framework Washington Regulatory Authority Local Health Current (Gallons/Day) 3,500 Proposed (Gallons/Day) 3,500 Dept. of Health Dept. of Ecology Approximate equivalencies: 3,500 14,500 (Non-mechanical) All: > 14,500 Mechanical: > 3,500 3,500 gpd 10 houses or a small strip mall 14,500 gpd large restaurant or grocery store, 45 houses 100,000 gpd 300 houses All: 3, ,000 Systems >100,000 31

32 Washington Agencies Reclaimed Water Use shared review responsibility Health greywater, industrial Ecology Other projects with assistance from Health 32

33 Philosophy - Rules SBOH Applies to both local and state health State rules are minimum rules for local health Washington local government is where the action is, where final decisions made DOH review and approve local rules Ecology promulgates its own rules 33

34 Philosophy - Permitting Ecology Discharge permits 5 years, conditions can be changed, extensive sampling, PH & environment Performance standards Little technical detail in rules Health System Approvals, construction permits Want on-going observations & measurements Conditions typically not changed Historically, prescriptive standards a lot of technical detail in rules 34

35 Philosophy Technology Review Ecology No real up-front verification of technology Depend on intensive monitoring/sampling Health Centralized review Level playing field For smaller flows - up-front verification Specific testing protocol Must be on state list 35

36 SBOH rules Technology reviews Assure good designs State license Assure good site evaluation Match site s sensitivity with appropriate levels of treatment Treatment Levels (show table) Design to simplify monitoring/maintenance Proper repairs of failures Minimum lot sizes area for installation, nitrogen LHJs management plans & rules Consistent with land use planning 36

37 CTED Growth management Assumptions OSS not desirable, not long-term No OSS within GMAs No sewers outside GMAs Version of land use planning by utilities opposite of way it should be Takes options away from communities 37

38 Decentralized Technologies Collection/Transmission Application/Distribution Pretreatment Final Treatment/Dispersal 38

39 Core Concept P = S + T ns + T s Where: P = Pollutant load to be removed by system S = Pollutant removed at the source T ns = Treatment by non-soil components = Treatment by soil T s 39

40 Core Concept We normally depend on the soil to provide the bulk of treatment to sewage Pollutant load (CBOD, TSS, FC, TN) T ns + T s 40

41 Core Concept As site s treatment capacity decreases, pretreatment levels must increase. Pollutant load (CBOD, TSS, FC, TN) T ns + T s 41

42 System Selection Strategies Soil depth Restrictive layer 42

43 System Selection Strategies Parameter Suspended solids Organic material (BOD 5 ) Pathogens Nitrogen Phosphorous Removal Processes Sedimentation, filtration Aerobic processes Filtration, predation, inactivation, disinfection Nitrification-denitrification, ion-exchange Adsorption in soil, physical-chemical Adapted from USEPA,

44 In conclusion: We have huge responsibility to assist small communities We do not do them a favor when we limit the wastewater choices Individual and cluster systems can be viable, long-term alternatives Just like a centralized sewerage system, decentralized systems need on-going O&M We need to understand the technologies to make good choices 44

45 Thank You! 45