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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-1 

## Chapter 6. Individual and Cluster Clustered (Decentralized) 1 

## Wastewater Treatment Systems 2

6. 

### Contents 3 1 Nitrogen-Reduction Implementation Measures.......

................ Error! Bookmark not defined. 4 2 Introduction and Background ......................

............................ Error! Bookmark not defined. 5 3 Nutrient-Reduction Processes for the Decentralize d Wastewater Sector ..... Error! Bookmark 6 not defined. 7 3.1 Nitrogen .......................................

................................... Error! Bookmark not defined. 8 3.2 Nitrogen Pretreatment..........................

........................... Error! Bookmark not defined. 9 3.3 Permeable Reactive Barriers....................

....................... Error! Bookmark not defined. 10 3.4 System Configuration ......................................

............................................. configuration Error! Bookmark not defined. 11 3.5 Phosphorus.....................................

................................. Error! Bookmark not defined. 12 4 Treatment Technologies and Costs.................

......................... Error! Bookmark not defined. 13 4.1 Conventional Systems...........................

.......................... Error! Bookmark not defined. 14 4.2 Suspended Growth Systems.......................

..................... Error! Bookmark not defined. 15 4.3 Attached Growth Aerobic Systems................

................. Error! Bookmark not defined. 16 4.4 Single-Pass and Recirculating Media Filters ....

.............. Error! Bookmark not defined. 17 4.5 Add-On Anoxic Filters with a Carbon Source.....

........... Error! Bookmark not defined. 18 4.6 Composting Toilet Systems ......................

...................... Error! Bookmark not defined. 19 4.7 Cluster Treatment Systems ......................

....................... Error! Bookmark not defined. 20 4.8 Soil Dispersal Systems.........................

........................... Error! Bookmark not defined. 21 5 Wastewater Planning and Treatment System Manageme nt..... Error! Bookmark not defined. 22 5.1 Public Education and Involvement ...............

.................. Error! Bookmark not defined. 23 5.2 Planning .......................................

................................... Error! Bookmark not defined. 24 5.3 Performance Requirements.......................

...................... Error! Bookmark not defined. 25 5.4 Recordkeeping, Inventories, and Reporting......

.............. Error! Bookmark not defined. 26 5.5 Financial Assistance and Funding ...............

................... Error! Bookmark not defined. 27 5.6 Site Evaluation................................

................................ Error! Bookmark not defined. 28 5.7 System Design ..................................

.............................. Error! Bookmark not defined. 29 5.8 Construction/Installation......................

........................... Error! Bookmark not defined. 30 5.9 Operation and Maintenance ......................

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-2 5.10 Residuals Management ..........................

......................... Error! Bookmark not defined. 1 5.11 Training and Certification/Licensing..........

.................... Error! Bookmark not defined. 2 5.12 Inspections and Monitoring ....................

........................ Error! Bookmark not defined. 3 5.13 Corrective Actions and Enforcement............

.................. Error! Bookmark not defined. 4 6 References.......................................

......................................... Error! Bookmark not defined. 5
6

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-3 

## 1 Nitrogen-Reduction Implementation Measures 1 EPA recommends protecting surface waters in the Che sapeake Bay watershed from nitrogen (N) 2 discharged by decentralized wastewater treatment sy stems by using N-reduction technologies 3 and enhanced system management. 4 Implementation Measures: a) Specify the following risk-based, N-removal perform ance levels for all new and replacement individual and cluster systems:

− 20 milligrams per liter (mg/L) total nitrogen (TN) standard* for all new subdivisions and commercial and institutional developments and a ll system replacements throughout the Chesapeake Bay watershed.

− 10 mg/L TN standard* for all new developments and a ll system replacements in sensitive areas—i.e., between 200 and 1,000 feet of the ordinary high water mark of all surface waters, or between 200 and 500 feet of an open-channel municipal separate storm sewer system (MS4).

− 5 mg/L TN standard* for all new developments and sy stem replacements in more sensitive areas—i.e., between 100 and 200 feet of t he ordinary high water mark of all surface waters, or between 100 and 200 feet of an o pen-channel MS4.

− 100-foot setback from surface waters and open chann el MS4s for all effluent dispersal system components.
* Effluent standards may be met by either system de sign or performance. A 5 mg/L N reduction credit is given when using time- dosed, pressure-drip dispersal within 1 foot of the ground surface.

b) Ensure wastewater treatment performance effectivene ss and cost efficiency by using cluster systems with advanced N-removal technology sufficient to meet the standards specified above for all newly developed communities and densely populated areas. c) Sustain treatment system performance in perpetuity through management contracts with trained and certified operators for all advanced N- removal systems, and responsible management entity (RME) operation and maintenance ( O&M) for all cluster systems. d) Preserve long-term treatment system performance wit h management practices designed to protect system investments, by doing the followi ng:

− Conducting GIS-based inventories of all individual and cluster (i.e., decentralized) wastewater systems in all areas that drain into the Chesapeake Bay or its tributaries. Inventory information includes system location (i.e ., latitude/longitude), type, capacity, installation date, owner, and relevant in formation on complaints, service (including tank pump-out), repairs, inspections, an d dates. Inventory data is stored electronically in a format amenable for use in wate rshed studies, system impacts analyses, and supporting general management tasks. EPA offers The Wastewater Information System Tool (TWIST) as a free resource for managing that infor mation in3/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-4

a user-friendly database. Health departments, state agencies, RMEs and others can adapt, amend, or otherwise modify TWIST without res triction or obligation.

− Requiring inspections for all systems at least once every 5 years; existing systems within sensitive areas are inspected at least once every 3 years; advanced treatment systems and those serving commercial, institutional , or industrial facilities are inspected at least semiannually. A qualified inspec tor inspects all systems on a schedule according to wastewater type, system size, complexity, location, and relative environmental risk. Inspections are consistent with EPA management guidelines for individual and cluster systems. A service professio nal or other trained person conducts routine monitoring on the basis of the sys tem type, operating history, manufacturer’s recommendations, and other factors.

− Repairing or replacing all malfunctioning systems w hen discovered, with new or replacement technologies capable of meeting the N-r emoval standards specified above.

− Requiring reserve areas for installing a replacemen t soil dispersal system that is equal to at least 100 percent of the size of the original effluent dispersal area. Treatment systems using effluent time-dosing (i.e., not deman d-dosing) to the soil can have reserve areas equal to at least 75 percent of the t otal required drainfield area. Systems with pressurized drip effluent dosing and those wit h dual drainfields operated on active/rest cycles (i.e., alternating drainfields) can have reserve areas equal to at least 50 percent of the original required dispersal area. e) Restore groundwater quality in areas where high-nit rate effluent plumes are near the surface and close to receiving surface waters by us ing effective, low-cost technologies such as permeable reactive barriers (PRBs). PRBs ar e low-cost, pH-controlled trenches filled with sand and a degradable carbon source, su ch as sawdust, shredded newspaper, or wood chips, designed to intercept groundwater plume s and reduce the TN concentration.

1 EPA recommends protecting surface waters in the Che sapeake Bay watershed from nitrogen 2 discharged by decentralized wastewater treatment sy stems by using nitrogen-reduction 3 technologies and enhanced system management. Implem entation measures supporting this 4 recommendation are as follows: 5 Specify the following risk-based, nitrogen-removal performance levels for all new and 6 replacement individual and clustered systems: 7

− 20 milligrams per liter (mg/L) total nitrogen stand ard* for all new subdivisions and 8 commercial and institutional developments and all s ystem replacements throughout 9 the Chesapeake Bay watershed. 10

− 10 mg/L total nitrogen standard* for all new develo pments and all system 11 replacements in sensitive areas—i.e., within 1,000 feet of the ordinary high water 12 mark of all surface waters, or within 500 feet of a n open-channel municipal separate 13 storm sewer system (MS4). 143/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-5 − 5 mg/L total nitrogen standard* for all new develop ments and system replacements 1 within 200 feet of the ordinary high water mark of all surface waters, or within 200 2 feet of an open-channel MS4. 3

− 100-foot setback from surface waters and open chann el MS4s for all effluent 4 dispersal system components. 5 * Effluent standards may be met by either system de sign or performance. A 5 mg/L 6 nitrogen reduction credit is given when using time- dosed pressure drip dispersal within 7 1 foot of the ground surface. 8 Ensure wastewater treatment performance effectivene ss and cost efficiency by using cluster 9 systems with advanced nitrogen-removal technology s ufficient to meet the standards specified 10 above for all newly developed communities and dense ly populated areas. 11 Sustain treatment system performance in perpetuity through management contracts with trained 12 and certified operators for all advanced nitrogen-r emoval systems, and responsible management 13 entity (RME) operation and maintenance (O&M) for al l clustered systems. 14 Preserve long-term treatment system performance wit h management practices designed to 15 protect system investments, by doing the following: 16

− Conducting GIS-based inventories of all individual and clustered (i.e., decentralized) 17 wastewater systems in all areas that drain into the Chesapeake Bay or its tributaries. 18 Inventory information includes system location (i.e ., latitude/longitude), type, 19 capacity, installation date, owner, and relevant in formation on complaints, service 20 (including tank pump-out), repairs, inspections, an d dates. Inventory data is stored 21 electronically in a format amenable for use in wate rshed studies, system impacts 22 analyses, and supporting general management tasks. EPA offers The Wastewater 23 Information System Tool (TWIST) as a free resource for managing that infor mation in 24 a user-friendly database.Health departments, RMEs a nd others can adapt, amend, or 25 otherwise modify TWIST without restriction or oblig ation. 26

− Requiring inspections for all systems at least once every 5 years; existing systems 27 within sensitive areas are inspected at least once every 3 years; advanced treatment 28 systems and those serving commercial, institutional , or industrial facilities are 29 inspected at least semiannually. A qualified inspec tor inspects all systems on a 30 schedule according to wastewater type, system size, complexity, location, and relative 31 environmental risk. Inspections are consistent with EPA management guidelines for 32 individual and clustered systems. A service profess ional or other trained person 33 conducts routine monitoring on the basis of the sys tem type, operating history, 34 manufacturer’s recommendations, and other factors. 35

− Repairing or replacing all malfunctioning systems w hen discovered, with new or 36 replacement technologies capable of meeting the nit rogen-removal standards 37 specified above. 38

− Requiring reserve areas for installing a replacemen t soil dispersal system that is equal 39 to at least 100 percent of the size of the original effluent dispersal area. Treatment 40 systems using effluent time-dosing (i.e., not deman d-dosing) to the soil can have 41 reserve areas equal to at least 75 percent of the t otal required drainfield area. Systems 42 with pressurized drip effluent dosing and those wit h dual drainfields operated on 433/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-6

active/rest cycles (i.e., alternating drainfields) can have reserve areas equal to at least 1 50 percent of the original required dispersal area. 2 Restore groundwater quality in areas where high-nit rate effluent plumes are near the surface and 3 close to receiving surface waters by using effectiv e, low-cost technologies such as permeable 4 reactive barriers (PRBs). PRBs are low-cost, pH-con trolled trenches filled with sand and a 5 degradable carbon source, such as sawdust, shredded newspaper, or wood chips, designed to 6 intercept groundwater plumes and reduce the total n itrogen concentration. 7 

## 2 Introduction and Background 8 Individual on-site and cluster clustered ( decentralized ) wastewater systems treat household and 9 commercial wastes in suburban, exurban, and rural a reas throughout the Chesapeake Bay 10 watershed. The Chesapeake Bay Program ( USEPA 2009) estimates that about 25 percent of the 11 homes in the watershed—2.3 million total—rely on th ese systems, which disperse treated 12 effluent to the soil. EPA predicts that decentraliz ed system installations will increase over the 13 next 20 years by about 35 percent (i.e., 800,000 ne w systems), eventually reaching 3.1 million 14 (USEPA 2009)

. 15 Nearly all the solids and phosphorus (P) discharged from decentralized wastewater systems ar e 16 retained by the soil, through physical filtration, adsorption, and precipitation processes (USEPA 17 2004). However, N nitrogen in wastewater is ultimately converted to nitrate u pon infiltration into 18 aerobic soils, a stable, soluble, and highly mobile form of this nutrient that negatively affects 19 groundwater and surface water quality. 20 Decentralized wastewater systems contribute approxi mately 12.5 million pounds of N nitrogen to 21 the Chesapeake Bay annually, or about 4.5 percent o f the total. According to current Chesapeake 22 Bay nutrient loading models, most of the N nitrogen load from such systems—about 60 percent— 23 comes from the Potomac and Susquehanna river draina ge areas, specifically Pennsylvania, 24 Virginia, and Maryland. The Chesapeake Bay N nitrogen -reduction goal for the decentralized 25 wastewater sector calls for a reduction to 9.4 mill ion pounds per year from the current load of 26 12.5 million pounds annually. With 800,000 new syst ems predicted over the next 15 years, 27 significant reductions in N nitrogen loads from new and existing systems are needed. 28 The Chesapeake Bay nutrient and sediment reduction goals include decreases in current and 29 future pollutant loads from decentralized treatment systems. A new generation of “hardware and 30 software”—treatment technologies and management pra ctices—are needed to achieve the 31 reductions. This section describes those technologi es, management practices, and associated 32 implementation measures. Implementation measures fo r achieving the reductions include 33 installing treatment units with optimal N nitroge n -removal capabilities in sensitive areas near 34 surface waters; using standard N nitrogen removal systems in other areas; and ensuring that all 35 treatment systems are appropriately operated, maint ained, and managed. The measures 36 encompass a range of treatment technologies, planni ng and performance considerations, and 37 management actions needed to address N nitrogen export from decentralized systems. The 38 implementation measures described in this chapter s upport two primary goals for addressing 39 N n itrogen inputs to the Chesapeake Bay from these systems: 403/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-7 • Prevent further impairment of the Chesapeake Bay by significantly reducing N nitrogen 1 levels in wastewater from new residential, commerci al, and institutional developments 2 using decentralized systems 3

• Reduce N nitrogen inputs to the Chesapeake Bay from existing individ ual and 4 cluster clustered wastewater systems by replacing malfunctioning sys tems with better5 performing technologies and by managing all systems to ensure long term performance 6 Implementation measures to achieve those goals incl ude repairing or replacing malfunctioning 7 systems, targeting high-risk systems in sensitive a reas for replacement with advanced treatment 8 units, clustering replacement systems where possibl e to implement better-performing and more 9 efficient community treatment facilities, inspectin g all systems throughout the Chesapeake Bay 10 watershed, and installing PRBs where technically an d economically feasible to reduce N nitrogen 11 concentrations in targeted effluent plumes. Those a pproaches are based on more than 2 decades 12 of research and field studies on decentralized syst em applications. 13 Key findings on the systems’ performance, their eff ects on groundwater, and the opportunities 14 presented by next-generation treatment technologies are summed up in the Final Report for the 15 La Pine National Decentralized Wastewater Treatment Demonstration Project

(2005), a joint 16 effort of EPA and other federal, state, and local a gencies: 17 The groundwater investigations have found significa nt existing nitrogen pollution 18 and the 3-D model has predicted extensive future co ntamination of the aquifer. 19 The model also predicted, based on the field perfor mance of denitrifying systems 20 in the project, that contamination could be slowed or stopped using onsite 21 wastewater treatment technologies, and that, as the region is retrofitted with 22 denitrifying technologies, the existing contaminati on would be flushed from the 23 groundwater system via existing natural discharge p oints. 24 The field test program, in addition to identifying systems that can remove a large 25 proportion of the nitrogen in residential wastewate r, found that conventional 26 systems are not protecting the aquifer from nitrate contamination. Conventional 27 systems that were previously thought to denitrify u p to 50% of the nitrate 28 discharged from septic tanks were found to achieve significantly less 29 denitrification when process and environmental vari ables were accounted for. 30 The La Pine Project, EPA’s Environmental Technology Verification (ETV) program, the 31 National Sanitation Foundation standards program, a nd other research efforts across the country 32 have identified and tested a number of denitrifying wastewater systems and found that 33 performance varies considerably. However, some syst ems do perform optimally in removing 34 TN total nit rogen from the effluent—e.g., to concentrations as low a s 5 mg/L—and others are 35 capable of N nitrogen effluent levels in the 10 and 20 mg/L range. 36 Higher treatment performance levels are needed in s ensitive areas to protect or restore surface 37 water quality. Research and field studies confirm t hat effluent plumes with elevated nitrate levels 38 move laterally over long distances—i.e., greater th an 300 feet in unconfined, sandy aquifers 39 (Walker et al. 1972; Robertson et al

. 1989; Robertson and Cherry 1992). N Nitr ogen 40 concentrations in effluent plumes are affected by s oil oxygen levels, soil composition, plant 41 uptake, labile carbon content, travel distance, rat e of movement, mixing, and other factors. The 423/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-8 measures listed in this chapter incorporate the gen eral availability of treatment and dispersal 1 systems that can meet the performance standards nee ded to protect the Chesapeake Bay and its 2 tributaries with more stringent treatment levels in sensitive areas near waterbodies. States have 3 been adopting treatment zone setbacks and standards to address N nitrogen and other pollutants in 4 coastal areas (Joubert et al. 2003). 5


## 3 Nutrient-Reduction Processes for the Decentralize d 6 

## Wastewater Sector 7 Nutrients—primarily P phosphorus and N nitrogen —are present in somewhat significant levels in 8 domestic and commercial wastewater. Nutrient treatm ent and removal involve processes that 9 occur either in treatment system components or in t he receiving environment, as summarized 10 below. 11


### 3.1 Nitrogen 12
N Nitrogen is the primary pollutant of concern along the coas tal areas of the United States, 13 including the Chesapeake Bay. N Nitrogen discharges are a concern for both nitrate 14 contamination of drinking water wells and as an aqu atic plant nutrient, particularly in N nitrogen

15 sensitive surface waters and nearshore marine water s. N Nitrogen is not readily or consistently 16 removed in conventional individual and cluster soil -based systems because most soils have a 17 limited capacity to retain or remove N nitrogen . Conventional soil-discharging systems are not 18 designed to remove N nitrogen . Organic N nitrogen in wastewater generally is converted to 19 ammonium N nitrogen in the septic tank. Ammonium N nitrogen is quickly nitrified as the 20 wastewater infiltrates the aerobic soil. Nitrate- N nitrogen is stable, soluble, and highly mobile in 21 the subsurface environment. Biological denitrificat ion of the nitrate is usually limited because 22 the soil is often aerobic near the ground surface a nd usually has very little organic carbon, which 23 is required by the heterotrophic denitrifying micro organisms. Therefore, where N nitrogen 24 removal is required for dispersal, pretreatment tha t achieves both nitrification and denitrification 25 usually is necessary before the wastewater is dispe rsed to the soil. 26


### 3.2 Nitrogen Pretreatment 27 Many reasonably priced natural and mechanical pretreatment systems, specifically designed for 28 individual and cluster systems, are available today . The most popular example of such systems is 29 the recirculating media filter, with timed dosing a nd drip or pumped effluent dispersal. The filter 30 media is typically sand, gravel, textile or peat. A portion of the filtered effluent is recycled 31 several times back to the septic tank (or pump/reci rculating tank) before further filtration and 32 discharge. Denitrification is supported by the low- oxygen, high-carbon environment that exists 33 in the recirculating or septic tanks. Those systems are able to consistently remove an average of 34 50 percent of the TN total nitrogen in the septic tank effluent—reducing the TN total nitrogen 35 from a typical influent range of 40–50 mg/L for sin gle family homes to 15–20 mg/L (Otis 2007; 36 USEPA 2002 ETV 2009 ; Jenssen and Siegrist 1990; Higgins et al. 2002; S mith et al. 2008; Rich 37 et al. 2003). 383/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-9 To achieve TN total nitrogen levels of 3–5 mg/L and lower, a denitrifying proce ss unit is usually 1 installed after the nitrification stage (e.g., aero bic attached or suspended growth media filter) in 2 the pretreatment system. To sustain a denitrificati on process, a reactive carbon source must be 3 added to complete the nitrate removal. For larger i nstallations methanol, acetic acid, molasses, or 4 other organic chemicals are added to the anaerobic reactor. However, the costs of constructing 5 and O&M of an external chemical feeding system and the cost of chemicals, power for a feed 6 pump, controls, and chemical storage increase remov al expenses substantially. 7 Proprietary denitrifying units, which avoid the nee d for feed pumps, controls, and chemicals are 8 now available. Such units include a slowly degradab le organic material in the reactor tank that 9 can last several years. Field testing has documente d TN total nitrogen effluent concentrations of 10 3–5 mg/L and even lower (Smith et al. 2008; Lombard o et al. 2005). 11
Further N nitrogen removal occurs after pretreated effluent is unifor mly dosed and rested during 12 discharge into the soil, where soil oxygen levels, carbon sources, temperature, and residence time 13 are key factors. That removal is quoted to be about 50 percent (Long 1995; Otis 2007). 14 Additionally, some Some soils do contain sufficient labile carbon to denitrify efflu ents regardless 15 of the method of dispersal (Anderson 1998; Gold et al. 2002; Starr and Gillham 1986; Bushman 16 1996; Hiscock et al. 1991). Other variables include seasonal use (Postma 1992), in-stream 17 processes, including the matrix through which the groundwater enters nea rby surface waters 18 ( Birgand 2000; Stewart and Reneau 1984 Hoover 2003 ), and the distance from the source to the 19 receiving surface waters (Stacey 2002). One British study (Hiscock et al. 1991) estimates that the 20 average groundwater carbon content would account fo r removal of 3 mg/L of nitrate. 21



### 3.3 Permeable Reactive Barriers 22 One recent development that can be applied to remov e groundwater nitrate from plumes that 23 have adversely already aversely affected the quality of nearby receiving water is the PRB 24 concept. Those barriers, which consist of a trench filled with a degradable carbon source (e.g., 25 sawdust, newspaper), are sited to intercept high-ni trate groundwater plumes (WE&T 2009) . As 26 the plumes pass through the low-oxygen, carbon-rich barrier, bacteria break down nitrate 27 molecules to use the oxygen for cell respiration. I n areas where receiving waters are already 28 eutrophied, the trenches can provide immediate reli ef by removing nitrate from the incoming 29 groundwater. Addressing the source of the high-nitr ate plume—densely sited septic systems— 30 would also produce results, but any measureable eff ects would likely take several years. 313/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-10 PRBs are installed as long, 1 narrow trenches perpendicular 2 to the incoming plume and 3 parallel to shoreline. A calcium4 based source of alkalinity is 5 usually included with the 6 carbon media to assure high 7 rates of denitrification. Such 8 systems have been successfully 9 demonstrated in North America 10 and Europe (Robertson and 11 Cherry 1995; Lombardo et al. 12 2005; USEPA 1998). PRB costs 13 range from about $5,000 to 14 $15,000 per equivalent dwelling 15 unit (i.e., in the plume sourcing 16 area), depending on soils, 17 geology, depth to groundwater, 18 subsurface hydrology, 19 construction access, existing infrastructure, and o ther factors. 20


### 3.4 System Configuration configuration 21 As noted above, a certain level of treatment proces s unit sophistication and soil discharge 22 technique (e.g., pressure dosing, drip tube dispers al) are required for optimum N nitrogen 23 removal. Their cost in terms of both hardware and m anagement needs can be significantly 24 mitigated through the use of cluster systems that t reat wastewater from multiple homes or 25 businesses. Cluster Clustered systems, also called community or distributed syst ems, have 26 become extremely popular in areas where high levels of wastewater treatment are required, 27 where space is too limited for on

- site conventional soil-discharging systems, and loc al funding 28 capacity precludes conventional sewage collection a nd treatment. 29


### 3.5 Phosphorus 30 In general, most regions of the Chesapeake Bay wate rshed have soils that retain P phosphorus 31 from decentralized systems. The process involves ch emical adsorption to soil particles and 32 precipitation reactions with soil minerals, includi ng iron, calcium, and aluminum (Tyler et al. 33 2003; Stone Environmental 2005). The soil’s capacit y to remove P phosphorus is significant both 34 spatially and temporally. Saturation fronts of P phos phorus move only inches or less per year 35 through all but coarse sandy or gravelly soils. 36 Wastewater system designers maximize P phosphorus removal rates by locating the infiltration 37 system in medium- to fine-textured soils that are a s far from surface waters as possible, and 38 extending the infiltration system along the contour of the installation site. Also, uniform dosing 39 and resting dispersal by pressure or drip distribut ion will maximize P phosphorus removal by the 40 Source: USEPA 1998 Figure 6-1. Permeable reactive barrier conceptual a pproach

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-11 soil through maximizing the contact time between th e effluent and the soil. System age reduces 1 the capacity of the soil to remove P phosphorus

. 2 If native soils are not amenable to adsorption remo val, other adsorption methods also are 3 available (Stone Environmental 2005; Dimick et al. 2006; USEPA 2002 ; Robertson et al. 1989 ). 4 Although some P phosphorus can be removed by pretreatment systems that contai n high 5 concentrations of adsorptive elements or by biologi cal P phosphorus removal, soil adsorption is 6 by far the most common, and least expensive, means of removal. 7 

## 4 Treatment Technologies and Costs 8 Key considerations in treatment system selection ar e wastewater flow, strength (i.e., biochemical 9 oxygen demand) , the presence of nonconventional organic or inorga nic constituents, the 10 sensitivity of the receiving environment, and the c apacity of system managers to operate and 11 maintain it over the long term. Given those factors
, note that both the selection and ongoing use 12 of a specific technology is driven by management co nsiderations. For example, wastewater 13 characterization and assessment of the receiving en vironment are planning-level activities that 14 result in establishing performance standards, which begin to identify the narrow range of 15 treatment technology options and related design con siderations. Once a specific system is 16 selected, construction oversight, operation, inspec tion, maintenance, and residuals removal—all 17 management program elements—become paramount in ens uring perpetual performance. 18 The subsections that follow discuss the primary tre atment system technology classes. The final 19 section of this chapter summarizes management progr am elements that support the 20 implementation measures provided at the beginning o f this chapter recommendations listed 21 above

. 22


### 4.1 Conventional Systems 23 Conventional treatment systems featuring septic tan ks and soil infiltration systems are the most 24 commonly used wastewater treatment technologies. Th e soil dispersal absorption system 25 facilitates aerobic treatment, degradation, filtrat ion, and adsorption of contaminants not treated or 26 retained by the septic tank. However, N n itrogen removal is somewhat limited, with TN total 27 nitrogen concentrations before soil application typically i n the 40–50 mg/L range. In sandy soils 28 with little organic content, high oxygen levels, an d poor downgradient mixing N nitrogen 29 concentrations can remain high even after several h undred feet of effluent plume movement 30 (Walker et al. 1973; Robertson and Cherry 1992; Robertson et al. 1989; Cogger 1988; Joubert et 31 al. 2004). Given the low N nitrogen removal rates of conventional systems (i.e., avera ging 20 32 percent TN total nitrogen removal; Otis 2007; Smith et al. 2008; Jenssen and Siegrist 1990 1989 ), 33 they are no longer appropriate for use in new commu nities or densely developed areas in the 34 Chesapeake Bay watershed. 35


### 4.2 Suspended Growth Systems 36 Suspended growth systems, such as activated sludge- based aerobic treatment units, are generally 37 effective in nitrifying septic tank effluent. Denit rification, however, is limited. Aerobic units that 383/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-12 feature with aeration that stopped and started periodically stops and starts show improved improve 1 denitrification. Sequencing batch reactors , which first fills and then draws, in with fill/draw 2 alternating aerobic/anoxic cycles in a single tank may also meet the 20 mg/L recommended 3 effluent limit for areas more than 1,000 feet of su rface waters in the Chesapeake Bay watershed, 4 when effluent is dispersed to the soil via time-dos ed
, pressure

- drip lines (Washington State 5 Department of Health 2005). Capital costs for on-si te suspended growth systems range from 6 $7,500 to $15,000, with O&M expenses of $400 to $80 0 per year when all suggested O&M tasks 7 are performed (Tetra Tech 2007). 8


### 4.3 Attached Growth Aerobic Systems 9 These systems (sometimes called trickling filters) use natural aeration instead of mechanical, 10 produce less sludge for disposal, and require less power and O&M than the suspended growth 11 units in performing the same tasks. They also requi re a recirculation step to meet more stringent 12 TN total nitrogen removal objectives. Commercially available systems come in lightweight 13 packages and employ lightweight media for easy inst allation. They also require about 20 percent 14 less physical footprint than typical trickling filt ers. When properly loaded and operated, they can 15 produce very high nitrification levels that must be followed by a denitrification step to exceed 16 the typical 50 percent N nitrogen -removal rate. On-site capital costs are slightly h igher in general 17 than the suspended growth ATUs ($10,000 to $16,000) , but O&M costs are significantly less, 18 e.g., about $200–300 per year (USEPA 2010; Tetra Tech 2007)

. 19


### 4.4 Single-Pass and Recirculating Media Filters 20 Single-pass media filters—sand filters, textile fil ters, peat systems, mounds, and other packed 21 media bed units—achieve excellent nitrification lev els but generally do a poor job with 22 denitrification unless some, or all, of the effluen t passes through a carbon-rich, low-oxygen 23 environment after the nitrification stage. That can be accomplished by recirculating a portion of 24 the effluent back to the septic tank or a pump tank , or by adding a denitrification unit to the 25 system (see below) , or both. Media filters have a long record of exce llent performance, with 26 nitrification rates as high as 95 percent (Otis 200 7; Smith et al. 2008; USEPA 2002). The 27 treatment process is stable year-round and can be e mployed through either custom-built, 28 nonproprietary engineered systems or commercial uni ts that can be installed in a single day. 29 Capital costs for single-pass filters range from $5 ,500 to $13,000, with O&M expenses of $200 30 to $400 per year

(USEPA 2010; Tetra Tech 2007)

. 31 Recirculating media filters have been in use for ma ny years and feature high nitrification rates 32 with about 50 percent denitrification. The systems recycle part of the effluent back to the septic 33 tank or the recirculating tank, where the anoxic en vironment and available carbon facilitate 34 denitrification processes. Design considerations in clude the ratio of effluent recirculated and the 35 configuration of the recycle plumbing, i.e., ensuri ng that the recycled effluent is discharged to a 36 tank location with low oxygen and some carbon. TN Total nitrogen effluent concentrations can be 37 as low as10 as10 mg/L, which can be further reduced in the soil by u sing time-dosed, 38 pressure press urized -drip effluent dispersal. Engineered systems and pr oprietary units are widely 39 available and can serve single homes or large subdi visions. Capital costs for recirculating 403/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-13 systems range from $9,500 to $20,000, with O&M expe nses of $350 to $600 per year (USEPA 1 2010; Tetra Tech 2007; Washington State Department of Health 2005)

. 2



### 4.5 Add-On Anoxic Filters with a Carbon Source 3 As noted in the discussion on recirculating media f ilters above, optimal denitrification can be 4 achieved by passing nitrified effluent through a lo w-oxygen, carbon-rich environment before soil 5 discharge. Engineered and proprietary systems featu ring add-on anoxic filters with an external 6 carbon source (e.g., methanol, sawdust, newspapers, and such) have performed successfully in 7 single-home or cluster clustered applications. For example, commercially available products 8 regularly produce an effluent with N nitrogen concentrations of less than 5 mg/L. Other system 9 designs discussed above can also achieve this level when paired with time-dosed
, pressure

- or 10 drip dispersal. Capital costs for add-on denitrific ation systems range from $3,500 to $5 7 ,000, 11 with O&M expenses of less than $100 per year (Washington State Department of Health 2005)

. 12 Note that this does not include the septic tank, ni trification step, or soil dispersal system—just 13 the add-on component. 14


### 4.6 Composting Toilet Systems 15 Composting toilet systems that contain and treat to ilet wastes can reduce watershed N nitrogen 16 discharges significantly, because such wastes accou nt for 70–80 percent of the TN total nitrogen 17 load in domestic wastewater. Composting systems hav e been successfully used in both private 18 and public facility settings. Like all systems, the y require appropriate design and ongoing O&M 19 attention. A greywater treatment system will be nee ded if the facility generates sink, laundry, or 20 other greywater. Capital costs for composting syste ms range from $2,500 to $10,000, with O&M 21 expenses of $50 to $100 per year (USEPA 1999) . The single-house viability of such systems 22 depends on the owner’s attitude. The systems are mo re commonly used in public settings. 23


### 4.7 Cluster Treatment Systems 24 Generally, cluster systems collect wastewater from multiple houses through low-cost sewerage 25 and treat and disperse the effluent to soil-based d ispersal systems similar to on-site systems. 26 Many homes and businesses can be served by a single treatment facility. Most cluster systems 27 feature septic tanks on each building lot; collecti on piping that operates via gravity, vacuum, or 28 pressure; a treatment facility with attached growth process units; and a soils-based dispersal field 29 for the effluent. Add-on anoxic denitrification fil ters can be included. Effluent is typically 30 dispersed to the soil under pressure (e.g., pressur e, drip, time or demand dosing) to assure 31 uniform application throughout the larger drainfiel d. Collection technologies include grinder 32 pump systems, which macerate and transport all sewa ge; effluent sewers, such as the septic tank 33 effluent pump (STEP); the septic tank effluent grav ity (STEG) collection system; and vacuum 34 systems. 35 Advanced treatment systems can facilitate local reu se of the treated effluent for toilet flushing, 36 irrigation, industrial purposes, or just be used to replenish aquifers. The cost of a cluster 37 collection system varies significantly according to the number of users, collection system 38 logistics, treatment facility design, land availabi lity, materials/labor costs, and other factors but 393/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-14 averages around $10,000 per dwelling served. Cluste r systems can achieve significant economies 1 of scale to provide high levels of treatment at cos ts significantly less (25 percent to 50 percent) 2 than centralized sewer systems. New cluster systems generally range from $8,000 to $18,000 per 3 connection, depending on the treatment technology u sed (USEPA 2010; Tetra Tech 2007)

. 4 Replacement and / retrofit systems have similar costs, but collection system installation can drive 5 costs higher. An RME with the technical, financial, and managerial capacity to ensure viable, 6 long-term, cost-effective performance is needed for cluster system applications. Total system 7 annual O&M costs range from $450 to $750 (Tetra Tec h 2007). 8
Table 6-1. Examples of biological N nitrogen removal performance from the literature 9

Technology examples TN removal efficiency (%) Effluent TN

(mg/L) Suspended growth Aerobic units w/ pulse aeration 25%–61% a 37–60 a Sequencing batch reactor 60% b 15.5 b Attached growth Single-Pass Sand Filters (SPSF) 8%–50% c 30–60 c Recirculating Sand/Gravel Filters (RSF) 15%–84% d 10–47 d
Multi-Pass Textile Filters 14%–38% e,i 9–83 e,i
RSF w/ Anoxic Filter 40%–90% f 7–23 f
RSF w/ Anoxic Filter w/ external carbon source 74%–80% g 10–13 g RUCK system 29%–54% h 18–53 h
Nitrex 96% j 2.2 j3/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-15 1
Source: Adapted from Washington Department of Health 2005

. Notes: a. California Regional Water Quality Control Board 1997; Whitmeyer et al. 1991 b. Ayres Associates 1998 c. Converse 1999; Gold et al. 1992; Loomis et al 20 01; Nolte & Associates 1992; Ronayne et al. 1982 d. California Regional Water Quality Control Board 1997; Gold et al. 1992; Loomis et al 2001; Nolte & Associates 1992; Oakley et al. 1999; Piluk and Peters 1994; Ro nayne et al. 19823/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-16 e. Leverenz et al. 2001 f. Ayres Associates 1998; Sandy et al. 1988 g. Gold et al. 1989 h. Brooks 1996; Gold et al. 1989 i. Loomis et al 2001 j. Rich et al. 2003 

### 4.8 Soil Dispersal Systems 1 Gravity-based
, soil dispersal systems generally include conventio nal perforated pipe; laid in 2 stone-filled trenches or purchased with Styrofoam b eads surrounding the pipe and wrapped in 3 netting; and gravelless, open-bottomed leaching cha mbers. Soil dispersal increases its level of 4 N nitrogen removal when it occurs in a time-dosed manner and uses pressure-drip irrigation 5 piping installed within one 1 foot of the surface of the ground. Using time-dose d
, pressure-drip 6 dispersal in the top 12 inches of soil is credited with a 50 percent reduction in TN total nitrogen 7 (Long 1995), making this option an important featur e for achieving the performance standards 8 recommended in this chapter. 9 Also, because most conventional systems continuousl y load drainfields resulting in reduction of 10 the soil’s capacity to treat effluent over time, al ternating dosing systems (active/rest cycles) that 11 extend the useful life of the soil dispersal system should be favored over conventional gravity12 flow drainfields. These systems require relatively low additional investment and can greatly 13 extend the life of the soil dispersal system (Noah 2006). for many years. Maintenance programs 14 for such systems should be designed and implemented in concert with the local health 15 department or RME to ensure that flow-diversion dev ices are operated on schedule. This 16 recommendation applies primarily to areas of new de velopment outside sensitive areas. 173/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-17 1 Source: La Pine Demonstration Project 2005. Figure 6-2. Effluent TN Total Nitrogen concentrations for systems tested in the La Pine P roject. 22-22-10 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote

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Chapter 6. Individual and Cluster (Decentralized) W astewater Treatment Systems 6-18Table 6-2. Products that have completed the EPA ETVprocess forNnitrogenreduction in domestic wastewater from individual homes,as of May 2005.System nameTechnologyDescription of processPerformanceCostWaterloo Biofilter® Model 4-BedroomWaterloo Biofilter Systems, Inc.143 Dennis St.: PO Box 100,Rockwood, OntarioCanada N0B 2kOhttp://www.nsf.org/business/water_quality_protection_center/pdf/Waterloo-VSSIGNED.pdfFixed film tricklingfilter.The biofilter unit uses a patentedlightweight open-cell foam that provides alarge surface area. Settled wastewater froma primary septic tank is applied to thesurface of the biofilter with a spraydistribution system. The system can be setup using a single pass process (without anyrecirculation of biofilter treated effluent) orcan use multi-pass configurations. The ETVtesting results were generated by returning50% of the biofilter effluent back to theprimary compartment of the septic tank.It averaged 62%removal of totalnitrogen with anaverage totalnitrogen effluent of14 mg/L over the 13-month testingperiod. Earliertesting of thisproduct in a singlepass modedemonstrated that itcould produce a 20–40% TN reduction.$13,000–$1 7,000 for totalsystem installation. TheWaterloo Biofilter unit onlywould cost approximately$7,000.AmphidromeTM Model Single FamilySystem:F.R. Mahony & Associates, Inc.273 Weymouth St.Rockland, MA 02370http://www.nsf.org/business/water_quality_protection_center/pdf/Amphidrome_VS.pdfSubmerged growthsequencing batchreactor (SBR)inconjunction with ananoxic/equalizationtank and a clearwell tank forwastewatertreatmentThe bioreactor consists of a deep bed sandfilter, which alternates between aerobic andanoxic treatment. The reactor operatessimilar to a biological aerated filter, exceptthat the reactor changes from aerobic toanoxic conditions during sequential cyclingof the unit. Air, supplied by a blower, isintroduced at the bottom of the filter toenhance oxygen transfer.It averaged 59%removal of totalnitrogen effluent of15 mg/L over the 13-month testing periodat theMassachusettsAlternative SepticSystem Test Center(MASSTC).$7,500 for unit only. Themanufacturer estimates it wouldcost $12,000–$15,000 for a totalinstallation.Septitech® Model 400 SystemSeptitech, Inc.220 Lewiston RoadGray, ME 04039http://www.nsf.org/business/water_quality_protection_center/pdf/SeptiTech_VS.pdfTwo-stage fixed filmtrickling filter usinga patented highlypermeablehydrophobic mediaClarified septic tank effluent flows by gravityinto the recirculation chamber of theSeptiTech unit. A submerged pumpperiodically sprays wastewater onto theattached growth process and thewastewater percolates through the patentedpacking material. Treated wastewater flowsback into the recirculation chamber to mixwith the contents. Treated water flows intoa clarification chamber and is periodicallydischarged to disposal unit (drainfield, dripirrigation, etc.)Averaged 64%removal of totalnitrogen with anaverage totalnitrogen effluent of14 mg/L over the 12-month testing periodat MASSTC.$11,000 for SeptiTech unitincludes shipping andinstallation. The manufacturerestimated that a total systemwith pressure distributiondrainfield would costapproximately $20,000.2-22-10 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote

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Chapter 6. Individual and Cluster (Decentralized) W astewater Treatment Systems 6-20Table 6-2.Products that have completed theEPAETV process for nitrogen reduction in domestic wastewater from individual homes, asof May 2005.(continued)System nameTechnologyDescription of processPerformanceCostBioclere TM Model 16/12Aquapoint, Inc.241 Duchanine Blvd.New Bedford, MA 02745http://www.nsf.org/business/water_quality_protection_center/pdf/Bioclere-VS-SIGNED.pdfFixed film tricklingfilter.Septic tank effluent flows by gravity to theBioclere clarifier unit from which it issprayed or splashed onto the fixed filmmedia. Treated effluent and sloughedbiomass are returned to the clarifier unit. Arecirculation pump in the clarifierperiodically returns biomass to the primarytank. Oxygen is provided to the fixed film bya fan located on the top of the unit.Averaged 57%removal of totalnitrogen with anaverage totalnitrogen effluent of16 mg/L over the 13-month testing periodat MASSTC.$7,500 for unit itself. Price fortotal system would need toinclude primary septic tankBioclere unit and disposaloption, with costs in the range of$12,000–$15,000. Themanufacturer recommends usein clusters to reduce per homecosts and facilitatemaintenance. Experience with27 home cluster resulted incosts of $6,800– $8,000 perhome.Retrofast 0.375 System:Bio-Microbics8450 Cole ParkwayShawnee, KS 66227http://www.nsf.org/business/water_quality_protection_center/pdf/Biomicrobics-FinalVerificationStatement.pdfSubmergedattached-growthtreatment system,which is inserted asa retrofit device intothe outlet side ofnew or existingseptic tanks.The RetroFAST 0.375 System is insertedinto the second compartment of the septictank. Air is supplied to the fixed filmhoneycombed media of the unit by aremote blower. Alternate modes ofoperation include recirculation of nitrifiedwastewater to the primary settling chamberfor nitrification. Intermittent use of theblower can also be programmed to reduceelectricity use and to increase nitrification.Averaged 51%removal of totalnitrogen with anaverage totalnitrogen effluent of19 mg/L over the 13-month testing periodat MASSTC.Product and installation cost forthe Retrofast 0.375 Systemranges is estimated to be$4,000–$5,500 depending onexisting tankage. That costincludes the FAST unit, blower,blower housing and controlpanel. The local The localrepresentative for Bio-Microbicsunits believes costs could be aslow as $3,500 for multiple units.Recip® RTS-500 System:Bioconcepts, Inc.P.O. Box 885Oriental, NC 28571-0885http://www.nsf.org/business/water_quality_protection_center/pdf/Bioconcepts_Verification_Statement.pdfFixed film filterThis is the newest product to completeEnvironmental Technology Verification(ETV) Program testing. It is a patentedprocess developed by the TennesseeValley Authority (TVA) and uses a fixed filmfilter medium contained in two adjacent,equally dimensioned cells. Timers on eachof the two reciprocating pumps control theprocess.Averaged 58%removal of totalnitrogen with anaverage totalnitrogen effluent of15 mg/L over the 12-month testing periodat MASSTC.Very limited experience with thissingle-family unit. The unit builtfor ETV testing was a prototype.The cost per unit. by itself. isestimated to be $8,000–$10,000. Cost of the septic tankand disposal unit would be extraand the cost would depend onsite conditions. Conservatively,cost for a total system could be$11,000– $15,000.2-22-10 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote

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Chapter 6. Individual and Cluster (Decentralized) W astewater Treatment Systems 6-212-22-10 Chesapeake Bay Executive Order Section 502 Guidance — Do Not Cite or Quote

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Chapter 6. Individual and Cluster (Decentralized) W astewater Treatment Systems 6-22Table 6-2. Products that have completed the EPA ETVprocess for nitrogen reduction in domestic wastewater from individual homes, asof May 2005.(continued)Source:Adapted fromWashington Department of Health 2005.3/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-23 

## 5 Wastewater Planning and Treatment System Manageme nt 1 The implementation measures in this section are N nitrogen -removing individual or 2 cluster clustered wastewater systems in sensitive areas coupled with management considerations 3 such as inventory systems, wastewater planning, per formance standards, siting and installation 4 guidelines, operation, inspection, maintenance, and residuals handling. Management tasks are 5 paramount for reducing nutrient inputs to the Chesa peake Bay because they establish the 6 framework for selecting and using specific treatmen t systems in particular locations. For 7 example, advanced cluster systems are the best appr oach for protecting and restoring the 8 Chesapeake Bay when considering wastewater faciliti es for new subdivisions and replacing 9 significant numbers of malfunctioning systems in ex isting subdivisions. 10 The following subsections summarize key management program elements viewed as important 11 for controlling the input of nutrients and other po llutants to the Chesapeake Bay. EPA has 12 provided extensive guidance, case studies, resource s, references, and links on these management 13 program topics (USEPA 2005, 2010). 14



### 5.1 Public Education and Involvement 15 Decentralized wastewater management programs requir e public support. The success of such 16 programs will depend on how well homeowners, system service providers, and other 17 stakeholders are involved in the development proces s. Unless people understand the need for a 18 management program, there is little chance it will be adopted. Once in operation, the program 19 must keep the community involved and informed. Mana gers should give special consideration to 20 explaining the need for new requirements for system upgrades, inspections, or other performance 21
measures. 22


### 5.2 Planning 23 Planning can be used to integrate management strate gies for areas served by both centralized and 24 decentralized wastewater treatment facilities, serv e as the basis for ordinances and subdivision 25 regulations, and synchronize the community growth p lan in harmony with the water and 26 wastewater infrastructure investments. Integrating wastewater planning functions provides better 27 long-term management of facilities and can help loc al officials deal with a number of needs such 28 as sewer overflows, National Pollutant Discharge El imination System (NPDES) effluent 29 limitations, Total Maximum Daily Loads (TMDLs), and antidegradation requirements. 30 Integrated planning, which can minimize stormwater management problems created by new 31 developments, is useful in anticipating and prevent ing adverse water quality effects, often by 32 using LID and green infrastructure approaches. Vari ables to consider during the planning process 33 include wastewater flows, proximity and uses of nea rby water resources, landscape topography, 34 hydrology, hydrogeology, soils, environmentally sen sitive areas, infrastructure system options 35 and locations, population densities, and need/poten tial for clustering treatment/reuse facilities. 36 EPA supports a wide range of water resource plannin g and management functions through 37 programs such as the Clean Water Act section 319 no npoint source management program, the 38 Clean Water Act 305(b) assessment reports, TMDLs, w ellhead and source water protection 393/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-24 programs, watershed planning initiatives, coastal m anagement, National Estuary Program, 1 wetlands protection programs, water quality standar ds, continuous planning processes under 2 section 303(e), water quality management processes under section 205(j) and 604(b), the Clean 3 Water State Revolving Fund, and so on. Ideally, the planning and management activities 4 supporting decentralized wastewater treatment would be integrated—or at least coordinated— 5 with these and other water resource programs, many of which the states operate. 6


### 5.3 Performance Requirements 7 Performance requirements for systems are derived by characterizing the risks they pose to health 8 and water resources and by setting pollutant loadin g limits on the basis of limiting those risks to 9 specific levels. Performance requirements specify o bjectives for each wastewater management 10 system, which can include physical, chemical, and b iological process components. Performance 11 compliance is based on cumulative, extrapolated pol lutant removals for the various system 12 components (e.g., septic tank, suspended-growth or fixed-film reactors, lagoons, wetlands, soil, 13 disinfection). Performance can be measured via nume ric or narrative criteria. Numeric criteria 14 reflect time-based, mass loadings or pollutant-conc entration limits designed to protect sensitive 15 water resources. Pollutants commonly targeted in pe rformance requirements include nutrients, 16 bacteria, oxygen demand, and solids. 17


### 5.4 Recordkeeping, Inventories, and Reporting 18 System inventories provide the nuts and bolts for o n-site management. Basic system 19 information—GIS location, type, design capacity, ow ner, installation, and servicing dates—is 20 essential to an effective program. The best record- keeping programs feature integrated electronic 21 databases with field unit data entry (i.e., using a handheld personal digital assistant), save-to-file 22 computer assisted design drawings, and user-specifi ed reporting formats. 23


### 5.5 Financial Assistance and Funding 24
Financial assistance is needed to : (1) develop or enhance a management program; (2) p rovide 25 support for constructing and modifying wastewater f acilities; and (3) support operation of the 26 program. Funding for program development and operat ion is often available from public and 27 private loan or grant sources, supplemented by loca l matching funds. It can also be derived from 28 some form of resource sharing among management prog ram partner organizations such as 29 planning departments or health and water resource a gencies. Developing an RME and financing 30 for constructing and operating facilities require l arger investments that might come from grants 31 and loans or public-private partnerships. Long-term operating costs are usually borne by system 32 users through payment of fees and tax assessments. 33



### 5.6 Site Evaluation 34 Evaluating a proposed site in terms of its environm ental conditions, physical features, and 35 characteristics provides the information needed to size, select, and locate the appropriate 36 wastewater treatment system. Regulatory authorities issue installation permits on the basis of the 37 information collected and analyses performed during the site evaluation. Prescriptive site 383/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-25 evaluation, design, and construction requirements a re based on experience with conventional 1 septic tank/soil dispersal absorption systems and empirical relationships that have evol ved over 2 the years. A soil analysis using core sampling to a depth of 4–6 feet or a backhoe pit, rather than 3 a simple percolation test, provides the best approa ch for assessing soils, seasonal water table 4 fluctuations, and other subsurface site features. P erformance-based approaches require a more 5 comprehensive site evaluation. Site evaluation prot ocols can include some presently employed 6 empirical tests, specific soil properties tests and soil pits to characterize soil horizons, mottling, 7 and a variety of other properties. 8


### 5.7 System Design 9 Decentralized wastewater treatment system design re quirements focus on protecting public 10 health and water resources. However, systems should also be affordable and aesthetically 11 acceptable. Prescriptive codes that specify standar d designs for sites meeting minimum criteria 12 simplify design reviews but limit development optio ns and the potential for meeting performance 13 requirements. Where management programs rely on the state code for design, there might not be 14 any need for special design protocols. However, in sensitive environments where performance 15 codes are employed, there is a need to include a de sign protocol even if it only expands the 16 number of prescriptive system choices and site para meters for sites that do not meet the 17 conditions for conventional systems. Design protoco ls should address the potential implications 18 of water conservation fixtures, effects of differen t pretreatment levels on hydraulic and treatment 19 performance of soil-based systems, and the O&M requ irements of different pretreatment and soil 20 dispersal technologies. 21



### 5.8 Construction/Installation 22 Poor installation can adversely affect performance of both conventional and advanced systems 23 that rely on soil dispersion and treatment. Most ju risdictions allow installation or construction to 24 begin after issuance of a construction permit, whic h occurs after the design and site evaluation 25 reports have been reviewed and approved. Performanc e problems linked to installation/ 26 construction are typically related to soil moisture conditions during construction, operation of 27 heavy equipment on soil infiltration areas, use of unapproved construction materials (e.g., 28 unwashed aggregate containing clay or other fines), and overall construction practices (e.g., 29 altering trench depth, slope, length, location). Th e effects of improperly installed soil-based 30 systems generally occur within the first year of op eration in the form of wastewater backups. 31 Some improper construction practices might not be a s evident, and could take years to manifest 32 themselves in the form of degraded groundwater or s urface water. The regulatory authority or 33 other approved professionals should conduct inspect ions at several stages during the system 34 installation process to ensure compliance with desi gn and regulatory requirements. 35


### 5.9 Operation and Maintenance 36 O&M for most systems includes some user awareness o f inputs that might affect treatment 37 processes, such as strong cleaners, lye, acids, bio cides, paint wastes, oil and grease, and the like. 38 Gravity-flow, soil-infiltration systems require lit tle O&M beyond limiting inputs to normal 39 residential wastes, cleaning effluent screens/filte rs, and periodic tank pumping (e.g., every 3 to 7 403/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-26 years). Systems employing advanced treatment techno logies and electromechanical components 1 require more intensive O&M attention, e.g., checkin g switches and pumps, measuring and 2 managing sludge levels, monitoring and adjusting tr eatment process and system timers, checking 3 effluent filters, monitoring effluent quality, and maintaining disinfection equipment. Operators 4 and service technicians should be trained and certi fied for the types of systems they will be 5 servicing; services should be logged and reported t o the management program so that long-term 6 performance can be tracked. The use of a dial-up mo dem or Internet-based monitoring 7 equipment can improve operator efficiency and perfo rmance tracking when large numbers of 8 systems are involved. 9


### 5.10 Residuals Management 10 The primary objective for septage management is to establish procedures for handling and 11 dispersing the material in a manner that protects p ublic health and water resources and complies 12 with applicable laws. Approximately 67 percent of t he estimated 12.4 billion gallons of septage 13 produced annually in the United States is hauled to publicly owned treatment works or other 14 facilities for treatment, while the remaining 33 pe rcent is land applied. Federal regulations (under 15 40 CFR Part 503) and state/local codes strive to mi nimize exposure of humans, animals, and the 16 environment to chemical contaminants and pathogens that are often present in septage. Residuals 17 management programs include tracking or manifest sy stems that identify sources, pumpers, 18 transport equipment, final destination, and treatme nt or management techniques. 19


### 5.11 Training and Certification/Licensing 20 A variety of professionals and technicians includin g planners, regulators, designers, installers, 21 operators, pumpers, and inspectors, are all involve d in some aspect of a decentralized wastewater 22 management program. Training, along with certificat ion or registration, provides system owners 23 and users with competent service providers and rais es the bar in promoting professionalism 24 among the industry. Service providers need to have a solid working knowledge of treatment 25 processes, system components, performance options, O&M requirements, and laws/regulations. 26 Universities, colleges, technical schools, agency-s ponsored training programs, regional/local 27 workshops, or formal/informal apprenticeship progra ms can provide such training. Service 28 providers should have extensive and detailed knowle dge of their own service areas and a general 29 grasp of other related activities (e.g., planning o r site evaluation). Service providers should 30 pursue opportunities for cross-training, joint accr editation/certification, and sharing of training 31 resources wherever possible. 32


### 5.12 Inspections and Monitoring 33 Perhaps the most significant shortcoming in existin g management programs is the lack of regular 34 inspections and performance monitoring. Area-wide m onitoring regimes include testing 35 groundwater and surface waters for indicators of po or treatment, such as the presence of human 36 fecal bacteria and excess nutrients. All systems ne ed to be inspected, at an interval defined by the 37 technological complexity of system components, the receiving environment, and the relative risk 38 posed to public health and valued water resources. The best approach is to establish an inspection 39 regime and schedule on the basis of the system’s re lative reliance on electromechanical 403/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-27 components combined with health and environmental r isk. Less effective surrogate approaches 1 include, in order of descending effectiveness (1) r equiring comprehensive inspections at regular 2 intervals; (2) third-party inspections at the time of property transfer; (3) inspections only as part 3 of complaint investigations. 4



### 5.13 Corrective Actions and Enforcement 5 A decentralized wastewater management program shoul d be enforceable to assure compliance 6 with laws and to protect public health and the envi ronment. Management agencies should have 7 the legal authority to adopt rules and assure compl iance by levying fines, fees, assessments, or by 8 requiring service providers to respond to system ma lfunctions. Program administrators should 9 emphasize those tools that encourage compliance, ra ther than punishment. It also helps to have 10 the support of the courts to implement an effective enforcement program. To assure compliance, 11 management agencies typically need authority to do the following: 12

• Respond promptly to complaints 13

• Issue civil and criminal actions or injunctions 14

• Provide meaningful performance inspections 15

• Condemn systems or property 16

• Issue notices of violation (NOVs) 17

• Correct system malfunctions 18

• Implement consent orders and court orders 19

• Restrict real estate transactions 20

• Hold formal and informal hearings 21

• Issue fines and penalties 22



## 6 References 23 Anderson, D.L. 1998. Natural denitrification in gro und water impacted by onsite wastewater 24 treatment systems. In Proceedings of the 8th National Symposium on Indivi dual and Small 25 Community Sewage Systems , American Society of Agricultural and Biological E ngineers, 26 Orlando, Florida, March 8–10, 1998, pp. 336

– -345. 27 Bedessem, M.E. 2005. Nitrogen removal in laboratory model leachfields with organic-rich 28 layers. Journal of Environmental Quality 34:936–942. 29 Anderson, D.L. 2002. Pollutant attenuation below onsite wast ewater treatment systems in 30 Florida

. In Proceedings of Northeast Onsite Wastewater Treatmen t Short Course , Newport, 31 Rhode Island, March 24

– 26, 2 002. 32
Barnard , et al. 2003. Biological Phosphorus Removal

. publisher/journal details. 333/15/20 2

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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-28 Behrends, L.L., L. Houke, P. Jansen, K. Rylant, and C. Shea. 2007. Recip Water Treatment 1 System with U.V. Disinfection for Decentralized Was tewater Treatment: Part II: Water 2 Quality Dynamics. In Proceedings of the National Onsite Wastewater Recyc ling 3 Association Annual Meeting , Baltimore, MD, March, dates? 4 Benisch, et al . 2006. How Low Can You Go ? publisher/journal details. 5 Blankenship, K. 2007. Terms and trends. Bay Journal , Alliance for the Chesapeake Bay, January 6 2007. Vol (no):pp–pp 7 Birgand, Francois. 2000. Quantification and Modeling of In-stream Processes in Agricultural 8 Canals of the Lower Coastal Plain . North Carolina State University, Biological and 9 Agricultural Engineering Department, Raleigh, NC. 10 Blankenship, K. 2009. New research finds nitrogen l oads to the bay underestimated by 20%. Bay 11 Journal , Alliance for the Chesapeake Bay. Vol (no):pp–pp 12 Boivin, M., R. Lacosse, and M.C. Belanger. 2007. An innovative wastewater treatment approach 13 for commercial and community applications. In Proceedings of the National Onsite 14 Wastewater Recycling Association Annual Meeting , Baltimore, MD, dates?. 15 Brown, W.E., W D. Hankins, and E.J. Leonard. 2009. Nitrogen pollution solutions. Water & 16 Wastes Digest .49(9):pp–pp. 17 Bushman, J.L. 1996. Transport and Transformations o f Nitrogen Compounds in Effluent from 18 Sand Filter-Septic System system Draintile Fields. MS Thesis, Oregon State Universi ty. 19 Cogger, C. 1988. On-Site Septic Systems: The Risk of Groundwater Con tamination. Journal of 20 Envir. Health, 51(1):12–16. Sept/Oct, 1988. 21
California

State Water Resources Control Board . 2008. Draft EIR: AB885 Onsi te Wastewater 22 treatment Systems. < http://www.swrcb.ca.gov/water_issues/programs/septi c_tanks / >

. 23 Accessed date? 24 Chesapeake Bay Program. 2009. [Insert reference cit ation for Bay model & assumptions here] 25 Corr, S.H., and A. Blodig. 2006. Installation and O perational Problems with Innovative 26 Alternative Wastewater treatment Systems. National Onsite W astewater Recycling 27 Association Annual Meeting; Denver, CO , dates?

. 28 Corr, S.H. and N. Brown, 2002. Field performance of innovative/alternative technologies in the 29 Title 5 program in Massachusetts, In Proceedings of State Onsite Regulators Alliance 30 Conferen ce , New port, R I, dates?

. 31 Corry. 2006. E

- mail from USEPA Decentralized Wastewater Listserv r egarding n itrogen m ass 32 b alance. 33 Costa, J.E, G. Heufelder, S. Foss, N.P. Milham, B. Howes. 2002. Nitrogen removal efficiencies 34 of 3 alternative septic system technolo gies and a conventional septic system

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deBarbad illo, C., R. Rectanus, S. Lambert, D. Parker, J. We lls, and R. Willet. 2005. Evaluating 11 denitrification filters. Water, Environment and Technology

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– - 31, 17 2006. 18 Etnier, C.D.,D. Braun, A. Grenier, A. Macrellis, R. J. Miles, and T.C. White. 2005. Mico-Scale 19 Evaluation of Phosphorus Management: Alternative Wa stewater systems Evaluation. 20 Project No. WU-HT-03-22,. Prepared for the NDWRCDP, Washington University, St. 21 Louis, MO, by Stone Environmental, Inc., Montpelier , VT. 22 Dix, S.P. 2003. Biological Denitrification Evaluati on for Piranha at MASSTC. In Proceedings of 23 the Twelfth Northwest On

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28 FlammableProprietary Carbon source (Micro C)for Den itrification in Onsite and 29 Decentra lized Industries In Proceedings of the 2006 NOWRA Conference Proceedings, 30 Denver, CO. 31 Lombardo Associates, Inc. 2009. Fact Sheets on Nitr ex systems. Lombardo Associates, Inc
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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-31 Lombardo, P. 2006. E

- mail to EPA Decentralized Wastewater Listserv regar ding applicability of 1 MBRs to small flow systems. 2 Lombardo, P., N. Brown, J. Barnes, K. Foreman, and W. Robertson. 2005. Holistic Approach for 3 Coastal Watershed Nitrogen Management. In Proceedings of the 2005 National Onsite 4 Wastewater Recycling Association Annual Meeting Conference Proceedings, Cleveland, 5 OH, October, 2005 dates?

. 6 Long, T. 1995. Methodology to predict nitrogen load ing from on-site sewage treatment systems. 7 In Proceedings of the Northwest Onsite Wastewater Trea tment Short Course, ed: R.W. 8 Seabloom. University of Washington, Department of C ivil Engineering, Seattle, 9 Washington, September, 1995 dates?

. . 10 Loomis, G., D. Dow, L. Green, M. Stolt, E. Herron, B. Moore, and A. Gold. 2003. A Summary 11 of Alternative Onsite Wastewater Demonstration Syst em Performance in Rhode Island. In 12 Proceedings of the Twelfth Northwest On

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. 14 Loomis, G., D. Dow , T. Gentes, M. Stolt, L. Green, and A. Gold. 2002. Nitrogen removal 15 performance of advanced onsite wastewater treatment systems in Rhode Island. In 16 Proceedings of Northeast Onsite Wastewater Treatmen t Short Course , Newport, Rhode 17 Island, March 24

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. 25 Noah, M. 2006. Drainfield rehabilitation. Small Flows Quarterly . Winter 2006. West Virginia 26 University, National Environmental Services Center, Morgantown, WV. 27 Omni Environmental Systems, Inc. 2010. Information on OMNI denitrification process

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. 30 Otis, R.J. 2007. Can we afford performance ? In Proceedings of the National Onsite Wastewater 31 Recycling Association Annual Meeting
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Chapter 6. Individual and Cluster Clustered (Decentralized) Wastewater Treatment Systems 6-32 Pedros, P.B., A. McBrearty, and W.W. Bruce. 2007. A submerged attached growth bioreactor 1 and membrane filtration for water reuse . In Proceedings of the National Onsi te Wastewater 2 Recycling Association Annual Meeting , Baltimore, MD , dates?

. 3 Pedros, P.B., H. Metghalchi, and W.K. Dobie. 2006. Total nitrogen removal in a single 4 submerged attached growth react or. In Proceedings of the National Onsite Wastewater 5 Recycling Association Annual Meeting
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The Pinelands Comm. 2001. Final Report of Ad Hoc Committee on Alternative Sep tic Systems

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– 26, 2002. 15 Smith, D.P., R.J. Otis, and M. Flint. 2008. Florida Passive Nitrogen Removal Study . Prepared for 16 the Florida Department of Health, City, FL. 17
Sm ith , et al. 2008. FLDOH Report entitled Florida passive Nitrog en Removal Study. 18 Stacey, P.E. 2002. Nitrogen effects and management: Implementing the Long Island sound 19 study. In Proceedings of Northeast Onsite Wastewater Treatme nt Short Course , Newport, 20 RI R hode Island , March 24–26, 2002. 21 Starr, R.C., and R.W. Gillham. 1989. Controls on Denitrification in Shallow Unconfined 22 Aquifers. In Contaminant Transport in Groundwater, Proceedings o f the International 23 Ssymposium on Contaminant Transport in Groundwater, Stuttgart, Germany, April, 1989. 24 Stewart, L.W., and R.B. Reneau Jr. 1984. Septic Tank Disposal Experiments using 25 Nonconventional Systems in Selected Coastal Plain S oils . Prepared for the Virginia 26 Department of Health, Richmond, VA, and Virginia Po lytechnic Institute and State 27 University, Blacksburg VA. 28 Stensel, et al. 2000. Modification of Ox Ditch Systems for Nitroge n Removal

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Tetra Tech. 2005. Approaches for Identifying Methodologies to Quantif y the Nationwide 10 Environmental Impacts of Failing Decentralized Wast ewater Systems

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