CLUSTER/COMMUNITY DECENTRALIZED WASTEWATER TREATMENT PLANTS WITH BENEFICIAL REUSE IN NEW JERSEY

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1 CLUSTER/COMMUNITY DECENTRALIZED WASTEWATER TREATMENT PLANTS WITH BENEFICIAL REUSE IN NEW JERSEY Robert R. Sharp, P.E., Ph.D, John Villapiano, and David Interdonato * Introduction The primary goal of this project is to address New Jersey s environmentally proactive regulatory policy regarding new development by providing a high quality wastewater effluent. The technological advances in physical, chemical, and biological processing of wastewater have allowed engineers to look beyond the basic treatment issues and focus on the potential economic, social, and environmental benefits of recycling and reusing treated wastewater. Decentralized wastewater treatment plants (DCWWTPs) are becoming a popular option to treat the raw sewage generated by the residents of cluster and residential developments in New Jersey. This is driven by the New Jersey Department of Environmental Protection (NJDEP) smart-growth philosophy that focuses on maintaining and improving water quality across the State. To protect vital resources in the nation s most densely populated state and to alleviate the social and economic effects of future drought events, new legislation has been passed to encourage water conservation by reusing wastewater and recharging local aquifers via subsurface effluent dispersal. To this end, the NJDEP has established regulatory barriers and provided incentives to promote the concept of effluent reuse in New Jersey. These include 1) denying approval to existing, centralized WWTPs to re-rate or increase capacity of the plant without significant treatment upgrades, 2) promoting the use of secondary treatment technologies in conjunction with new and existing septic tank installations by allowing a reduction in dispersal bed area, 3) issuing general permits for specific reuse type activities to mainstream the applications and decrease the process time, 4) giving tax relief and tax credit to treatment plants and businesses practicing reuse, and 5) protecting nine reservoirs and over 700 miles of streams and waterways from any measurable decline in existing water quality by limiting impacts from development and surface water discharges. The NJDEP estimates that over 15% of the New Jersey population is served by DCWWTPs. The exact number and type of these systems is not known because the NJDEP does not require permits for systems treating less than 2,000 gallons per day (gpd) of domestic sewage. Instead, these smaller plants are regulated by the local Boards of Health, each with their own monitoring and inspection requirements. The NJDEP is currently compiling lists submitted by local health departments identifying existing, proposed, and failing septic systems. The NJDEP also does not delineate between different types of treatment, but rather permits a treatment plant according to the classification of raw sewage, level of treatment, and the means of effluent dispersal. Decentralized treatment regulations are currently under review to address variations in treatment technologies and the desire to decrease septic use and increase beneficial reuse. * Robert R. Sharp, Senior Technical Manager, Schoor DePalma, Inc.; 200 State Highway 9; PO Box 900; Manalapan, New Jersey, 07726; ; rsharp@schoordepalma.com. John Villapiano, Project Engineer, Schoor DePalma; jvillapiano@schoordepalma.com; David Interdonato, formerly of Schoor DePalma

2 Beneficial Reuse in New Jersey Beneficial reuse is a relatively new concept in New Jersey, especially when compared to Florida and California. New Jersey first started considering beneficial reuse in 1999, after a series of droughts that resulted in water restrictions and slowed economic growth and productivity. In 2002, 230 million gallons of effluent was reused for beneficial purposes in New Jersey. However, approximately 700 million gallons per day (MGD) of treated effluent continues to be discharged to the oceans, bays, and rivers of New Jersey. Currently, New Jersey s beneficial reuse program is based on guidelines established by the EPA. The NJDEP separates beneficial reuse into two categories: 1) public access applications and 2) restricted access applications. The majority of permitted reuse applications in New Jersey include spray irrigation, industrial reuse, sewer washing and street cleaning. Several larger reuse projects (2 10 MGD) are being considered and developed that will ultimately reuse wastewater for industrial applications and golf course irrigation. These projects will require the design and construction of infrastructure to treat raw sewage onsite or convey treated effluent back to large industrial or commercial water users. As of 2003, only 17 NJ Pollutant Discharge Elimination System (NJPDES) permits were approved to practice some form of beneficial reuse. Residential DCWWTPs have been practicing reuse through a groundwater discharge permit by utilizing subsurface dispersal systems. Other beneficial reuse of treated wastewater produced at DCWWTPs is approved and permitted by NJDEP on a case by case basis, with strong consideration given to category of reuse (public or restricted access) and the quality of treatment. Currently, the NJDEP offers the newly updated Technical Manual for Reclaimed Water and Beneficial Reuse (RWBR) to assist operators and owners of DCWWTPs in effectively implementing reuse. As with most reuse programs, the permitting process drives New Jersey s program. New Jersey has included the following in its permit process to address reuse applications: NJPDES (New Jersey Pollutant Discharge Elimination System) permits o Discharge to surface water (DSW) o Discharge to ground water (DGW) Module in Part IV of NJPDES permit Module may incorporate additional limits and conditions as well as submittal requirements for: o User/Supplier Agreement o Operations Protocol o Engineering Report DCWWTPs and Reuse in New Jersey In order for DCWWTPs to meet more stringent DSW and DGW requirements and to attempt some method of reuse, plants must utilize advanced treatment technologies. The key to making a treatment process viable for these onsite applications is to be able to attain and maintain a strict level of treatment, while keeping capital, operation and maintenance costs at a minimum. Because of New Jersey s stringent surface water standards and anti-degradation policies, most DCWWTPs favor DGW and onsite reuse as the fate of the treated effluent. The NJPDES-DGW and RWBR minimum treatment plant performance requirements are presented in Table 1 and Table 2.

3 Table 1. Discharge limits for typical monitored sanitary parameters Effluent Parameter Standard Total Nitrogen (NO 3 +NH 3 -N) 10 mg/l (max.) Fecal Coliform 200 colonies/100 ml (daily max.) Chlorine Not an acceptable means of disinfection Volatile organics Discharge of non-sanitary wastes is prohibited Table 2. Effluent Quality for Reclaimed Water for Beneficial Reuse - Public Access Systems: Effluent Parameter Standard Fecal Coliform 2.2/100 ml, 7 day median, 14/100 ml maximum any one sample Minimum Chlorine Residual 1.0 mg/l after 15 minute contact at peak hourly flow or design UV dose of 100 µw/cm 2 under maximum daily flow. Total Suspended Solids 5 mg/l Turbidity (UV only) 2 NTU maximum Total nitrogen 10 mg/l Hydraulic loading rate 2 inches per week Secondary treatment required Filtration required All discharge permit levels must be met In Schoor DePalma s design and permitting experience with DCWWTPs utilizing DGW and/or beneficial reuse in New Jersey, it has been determined that the most cost effective means to achieve ground water quality standards and standards for beneficial reuse is to employ a membrane bioreactor (MBR) system followed by UV disinfection. Schoor DePalma has completed several feasibility studies comparing various treatment and dispersal options on the basis of water quality, capital costs, O&M costs, required area, odors, and aesthetics. From a performance perspective, Schoor DePalma has found the MBRs with UV disinfection compare favorably to other technologies such as SBRs, conventional activated sludge plants, and other proprietary treatment technologies. From a cost perspective, the key issues in these studies have typically been capacity of the plant and operational familiarity. Our experience has also proven that subsurface drip irrigation is an excellent option for DGW, even when soil and site limitations are present onsite. The following is a description of a specific MBR/UV DCWWT that was designed for DGW and reuse. Regardless of make or model, the general technologies and design of the treatment and dispersal systems presented below are becoming a cornerstone of onsite treatment in New Jersey. These systems continue to prove themselves as one of the most attractive treatment scenarios available to meet New Jersey s strict discharge requirements and desire to improve water quality and availability across the State.

4 Case Study DCWWTPs Design for DGW and Reuse in New Jersey Project Summary In response to New Jersey s commitment to protecting sensitive and threatened waterways, developers have sought the expertise of wastewater treatment professionals to provide site-specific systems to treat wastewater from housing developments, institutions, and commercial facilities. One such development is a small commercial center and residential community consisting of a total of 120, 2- and 3-bedroom town homes located in rural, northwestern New Jersey. The projected maximum wastewater flow from this development is 37,750 gallons per day. Due to the remote location of the development, there is insufficient infrastructure and support utilities to handle the additional wastewater flow. Additionally, the southern and eastern boundaries of the property consist of two recently designated C-1 streams. The New Jersey C-1 classification protects a water body from any further degradation or diminished water quality resulting from either a point or nonpoint discharge. Both streams are also designated as impaired water bodies. With these limitations and New Jersey s commitment to protecting its resources, developers and engineers collaborated on the design of an advanced onsite wastewater treatment and reuse systems for the development. Onsite Wastewater Treatment Facility (WWTF) Description The following is a description of the proposed wastewater treatment facility and dispersal system. The wastewater treatment facility was designed in accordance with the New Jersey Administrative Codes and guidelines detailed in the Public Access Reuse Manual. The raw municipal wastewater flows to the head of the plant via a standard pump station. From the influent pump station, the wastewater flow is conveyed to a 25,000 gallon trash trap located within the treatment building, where grease, scum and other flotables are removed. After the trash trap, the flow continues to a 25,000 gallon equalization tank via a siphon. The equalization tank was utilized to eliminate flow surges during times of peak water usage and to allow for a constant flow to the treatment system and minimize the potential for system upsets. The pre-treatment arrangement keeps wastewater loadings constant and can accommodate elevated organic loads at periods of high flow and organic discharge. After consideration of the amount and type of residential and nonresidential wastewater to be treated in the plant, an MBR system was chosen as the optimal method. The plant was designed with twoultrafiltration membrane bioreactor treatment trains. The specific MBR used in this project was designed to carry out biological nitrogen removal via an anoxic tank and aerobic tank in series. Each of the treatment tanks has a volume of approximately 7,000 gallons. After the anoxic and aerobic treatment tanks, the wastewater is pumped to the modular ultrafiltration membrane units, as designed and constructed by Zenon, Inc. The membrane units contain submerged ZeeWeed ultrafiltration membrane cassettes. The hollow-fiber membranes operate under a slight vacuum to draw the treated effluent across the membrane to separate the solids (>0.10 micron) from the treated flow. The modular filtration systems are aboveground units and are equipped with backpulse and permeate pumps, and an effluent storage tank for periodic backpulsing events. A recirculation line runs from the modular units to the anoxic tanks to return a portion of the wastewater for further treatment.

5 The MBR treatment trains were designed with complete redundancy, and each train is capable of handling the projected maximum wastewater flow for up to 3 days. The design arrangement allows for maintenance and replacement of all process and structural equipment without temporary interruption of the treatment process. The system is capable of handling peak flow and loading events without compromising performance. The higher capital cost associated with MBRs is offset by numerous operational advantages. First, the MBR system is capable of operating at a much higher mixed liquor and suspended solids concentration. This permits longer sludge retention time and a subsequent decrease in sludge production over time, further reducing sludge wasting and sludge hauling events. Second, the entire operating and monitoring system is controlled using PLC and SCADA systems equipped with a dialin/dial-out alarm network. Therefore, the operator must only be present to perform mandatory and routine operation and maintenance. Next, the membrane cassettes are clean in place and only require disinfection once a month. The membranes are also designed to be highly efficient in regards to energy use. Finally, the small footprint required to construct an MBR treatment plant results in much lower construction costs. The two-mbr effluent streams are combined in an effluent trough and proceed to one of two ultraviolet light (UV) disinfection units. The UV units consist of bundles of shielded, horizontal UV lamps placed in a pressurized stainless steel tanks. The treated effluent then flows to a dosing tank to be pumped to the subsurface drip irrigation system. The treated effluent as it exits the UV units meets the discharge limits for restricted access beneficial reuse. The treatment parameters are attained at the end-of -pipe as the soil is not relied on for any further reduction in contaminant concentrations. A detailed diagram of the treatment process is presented in Figure 1. To control the release of odors, the treatment building was equipped with a state-of-the-art carbon adsorber to scrub the air inside the building and eliminate any odors before release into the atmosphere. All air within the building is collected and released through a ventilation system. The building is maintained at a negative pressure to prevent the unintentional release of gases from the interior of the building. Drip Irrigation System Description Following UV disinfection, the high quality treated effluent is discharged to groundwater to recharge the aquifer via subsurface drip irrigation. The subsurface drip irrigation system is designed using a system manufactured by Geoflow TM Inc. The treated effluent is pumped slowly and uniformly through the dispersal field. The treated effluent travels through the field in polyethylene dispersal tubing that are connected to the supply and return headers with compression fittings. A conceptual layout of the drip irrigation system is presented in Figure 2. The dispersal tubing is spaced 24 inches apart and located approximately 6 to 18 inches below the ground surface in the rhizosphere (root zone) with pressure compensating emitters spaced 24 inches apart along the tubing to evenly distribute the effluent throughout the drip field. The drip irrigation

6 Figure 1 Schematic of MBR Treatment System for Reuse. system is separated into 4 zones of equivalent size with the piping elevations following the surface contours. The drip irrigation system was designed by inputting the results from multiple subsurface soils and hydrogeologic investigations into a MODFLOW analysis program with a redundancy of 150%. Because the soils are not relied on for any further treatment of the wastewater constituents, the drip irrigation system was sized for the volume of discharge as opposed to the chemical make-up. The drip irrigation system is located in the open space between the commercial building and residential lots. Local ordinances require an 80 vegetative buffer between commercial and residential buildings. The drip irrigation system is located within the buffer zone allowing the developer to maximize the number of units in the residential development. There are several advantages to using subsurface drip irrigation systems, including: Human contact with high quality treated effluent is minimized; DGW standards apply; Evapotranspiration and attenuation maximize the dispersal of water; Any excess carbon and nitrogen may be utilized as nutrients in the soil; Uniform application across the dispersal area;

7 Automated controller monitors system performance and controls the distribution; No need for artificial fill or excavation; Can be installed directly into native soils, maintaining the natural landscape of the site; Most manufacturers have 10 year performance guarantees; and The system is cost effective when compared to other discharge to groundwater technologies with minimal maintained required. Figure 2 Subsurface Drip Irrigation Conceptual Layout The Decorative Pond Beneficial reuse of the high quality treated effluent helps with local aquifer recharge and watering of landscape greens. There is a decorative pond located in the center of the development designed to serve as a storm water retention basin. During periods of dry weather flow, treated effluent will be used to fill the pond. Treated effluent can be diverted from the supply header of the drip irrigation system to the decorative pond as needed.

8 Conclusion In 1999, the State of New Jersey and the NJDEP announced a major shift in environmental policy regarding the responsibility and control of residential, commercial, and industrial development decisions. The purpose of the legislation is to minimize the environmental impact of and to accommodate for the expected addition of 1 million people over the next two decades; to preserve and improve the water resources that are vital to public health, the environment and the economy; and to alleviate the financial and social impacts of increasingly common droughts. With the change in regulatory policy and the implementation of more stringent discharge permit requirements, the need for innovative and cost effective wastewater treatment plants for small flow applications became the focus of many developers and civil engineers. This project provided an opportunity to achieve multiple objectives by combining effluent reuse with water use requirements. As evident by this case study, a coordinated effort between the NJDEP, developers, and wastewater professionals can help maintain the economic prosperity of New Jersey without further degrading the natural resources that are vital to sustaining the residents and businesses of the State.