Spray Irrigation : RIBs Spray

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1 Spray Irrigation : RIBs DNREC s Perspective on Beneficial Reuse in Delaware Ronald E. Graeber Program Manager I Ground Water Discharges Section Ronald.graeber@state.de.us (302) On-Site Wastewater Treatment and Disposal Systems (OWTDS) 128 Large (> 2,500 gpd design flow) land based disposal/reuse systems in Delaware 91 systems using subsurface disposal 24 Spray Irrigation i Facilities i 12 systems using Rapid Infiltration Basins Design flows vary from 2,500 gpd to 3.8 MGD Level of Treatment Required Spray Irrigation Facilities required to limit total nitrogen percolate to < 10 mg/l (1988) Effective 3/11/02 All Large On-Site systems with design flow > 20,000 gpd required to treat to secondary standards Effective 1/1/06 all Large On-Site systems with design flow > 20,000 gpd required to reduce Total Nitrogen to < 10 mg/l Effective October 2008, PCS for the IBB requires all new Large On-Site systems > 20,000 gpd to reduce Total Nitrogen to < 5 mg/l: existing facilities to 10 mg/l Proposed Requirements (2010) Perform Surface Water Assessment Report (SWAR) Demonstrate Surface Water Quality Standards will not be violated by proposed OWTDS Would include a nutrient fate and transport analysis Alternative to SWAR for Community Systems would be to meet established Performance Standards for Nitrogen and Phosphorus(when applicable) This would not be applicable to Regional or Municipal systems Proposed Performance Standard Requirements OWTDS with a design flow > 20,000 gpd: New Systems: N < 5 mg/l; P < 3.9 mg/l* Existing Systems: N < 10 mg/l; P < 3.9 mg/l* OWTDS with a design flow > 2500 gpd, but < 20,000 gpd New Systems: N< 10 mg/l; P < 7.8 mg/l* Existing Systems: N < 20 mg/l; P < 7.8 mg/l * Only required if disposal site has a high potential for phosphorus mobility based on in-situ soil conditions Rapid Infiltration Basins (RIBs) Wastewater disposal option, not a Beneficial Reuse activity in and of itself Treated effluent is discharged to the surface of the basin Effluent passes through the soil to recharge the ground water Basin is flooded then allowed to dry before flooding again Multiple Basins are required No credit for nitrogen removal 1

2 History of RIBs in Delaware Cape Henlopen State Park: first RIB permitted in Delaware Operating permit issued in 1987 Secondary Treatment via Imhoff Tank Design Flow: 80,000 gpd 8 Rapid Infiltration Basins, 5400 sq. ft. total 12 facilities currently permitted to discharge to RIBs Sizes vary from 3,360 gpd (Seaford Burger King) to 540,000 gpd (Island Farms, under review) Advantages of RIBs Recharges aquifer Requires smallest footprint Least expensive to construct Easier to repair and maintain Can accommodate the greatest quantity of water, up to 3 gpd/ft*ft Spray irrigation 90 in/year Septic system 171 in/year RIB 1757 in/yr RIBs: Disadvantages and Concerns Detailed hydrogeological evaluation is necessary May clog over time, causing ponding 2

3 RIBs: Disadvantages and Concerns Detailed hydrogeological evaluation is necessary May clog over time, causing ponding Exposed wastewater may generate odors Safety concerns Preferential pathway to surface waters may be established Adversely impacting local surface water quality May discharge large quantities of nitrogen and phosphorus to local surface waters, exceeding TMDL limits locally Pounds of Nitroge en per acre per Year Comparison of Nitrogen Loading Rates for Various Wastewater Disposal Options Septic Systems Spray Irrigation RIBs: Disadvantages and Concerns RIBs: Disadvantages and Concerns Detailed hydrogeological evaluation is necessary May clog over time, causing ponding Exposed wastewater may generate odors Safety concerns Preferential pathway to surface waters may be established May discharge large quantities of nitrogen and phosphorus to local surface waters, exceeding TMDL limits May require a more sophisticated ground water monitoring network Detailed hydrogeological evaluation is necessary May clog over time, causing ponding Exposed wastewater may generate odors Safety concerns Preferential pathway to surface waters may be established May discharge large quantities of nitrogen and phosphorus to local surface waters, exceeding TMDL limits May require a more sophisticated ground water monitoring network Very high hydraulic loading rates Comparison of Hydraulic Loading Rates for Various Wastewater Disposal Options per Year Inches Septic Systems Spray Irrigation gpd/sq.ft 3

4 Future of RIBs in Delaware DWR funding RIB study by DGS Evaluate potential benefits and risks to ground water and surface waters Develop more detailed procedures for permitting and monitoring RIB s Phase 1 of 3 completed Phase 1 characterized wastewater treatment processes and quality of effluent to RIB s in the region Spray Irrigation of Treated Wastewater A Sensible Approach to Wastewater Management Promotes Beneficial Reuse of Reclaimed Water Preferred Method of Wastewater Management in Delaware GWDS has initiated process to amend and update On- Site and Spray Irrigation Regulations into one comprehensive document 4

5 What is Spray Irrigation??? Reuse and Recycling of Treated Wastewater Controlled application of treated wastewater (Reclaimed Water) onto vegetated land surface Application rate based on crop nutrient needs Nutrients in reclaimed water used to grow crops Level of wastewater treatment based on reuse type: Restricted Public Access Sites Limited Public Access Sites Unlimited Public Access sites Parameter Typical Waste Water Characteristics Prior to Treatment Treated WW/ Prior to Spray Irrigation 3 feet Below the Soil Surface Nitrogen 50 mg/l 25 mg/l <5 mg/l Phosphorus 12 mg/l 8 mg/l 0 mg/l Fecal Coliforms >1,000,000 col/100ml * col/100m L 0 col/100ml BOD 250 mg/l * mg/l 0 mg/l TSS 220 mg/l 10-50* mg/l 0 mg/l Chlorides 30 mg/l 30 mg/l 30 mg/l * The lower concentrations must be met if the public may come into contact with the reclaimed water, such as in Golf Course Irrigation Benefits of using reclaimed water include: Aquifer recharge Reduces current demand on aquifer Keeps water in watershed Maintains Open Space Preserves agricultural ral lands Reduces agricultural operating costs Reduces import of nutrients to Watershed Alternative to Surface Water Discharge Helps protect surface water quality, meets TMDL goals Advanced wastewater treatment not required, Lagoon treatment acceptable Types of Beneficial Reuse Agricultural Applications Dedicated Ag Sites Voluntary Ag sites Irrigation of Wooded Tracks Golf Course Irrigation Irrigation of Open Spaces Irrigation of Residential Lawns Agricultural Applications Irrigate fields Supply supplemental nutrients Promotes fertigation Nutrient content of reclaimed water is known Nutrient application based on crop needs Conventional irrigation equipment used, such as: Center pivots Traveling guns Solid set sprinklers 5

6 Agricultural Benefits to Using Reclaimed Water Provides supplemental nutrients Provides water at pressure suitable for irrigation Reduces electrical and equipment costs Reduces demand on ground water supply Available even during drought restrictions Improves crop yields Allows for accurate nutrient loading rates, at all stages of crop growth (FERTIGATION) Types of Agricultural Reuse Sites Dedicated Agricultural Reuse Sites Purchased by WWTF, or long-term contract Maximize hydraulic loading rates Year-round round application Grass and hay, or grain crops Monitoring wells required Buffers to property lines, surface waters Public access restricted Ag. field is permitted Secondary treatment required ~125 to 150 acres of irrigatable land needed per MGD Types of Agricultural Reuse Sites (continued) Voluntary Agricultural Reuse Sites All activities controlled by farm manager Hydraulic loading rates based on crop needs Most crops can be grown Only prohibition is on crops that will be consumed raw Tertiary treatment is required (Unlimited Public Access Criteria) Minimal buffers No public access restrictions May use lands under Ag Preservation Agricultural Land Preservation 2005 MOU between DNREC and DDA encourages Spray Irrigation on Ag Preservation Lands: For production of conventional cash crops Requires treatment to Unlimited Access levels 2009 Irrigation Preservation Legislation Preservation of Agricultural lands Maintain/improve farming economy Preserve ground water resources Promote utilization of reclaimed water on farm Reclaimed water utilized on an As-Needed basis Activity incorporated into farms Nutrient Management Plan Beneficial Reuse in Delaware Started in the 1970 s Currently, 24 permitted spray irrigation facilities Sussex County operates 3 Regional Spray Irrigation Facilities in Inland Bays Basin 3100 acres of land currently permitted Over 200 individual, id and community drip irrigation i systems currently in use Applied to agricultural sites, golf courses, wooded tracks, open spaces and residential lawns 650,000 pounds of Nitrogen and 210,000 pounds of Phosphorus reclaimed through reuse in

7 How Land Treatment Systems Reduce Nutrient Loads and Help Meet TMDL Goals Agricultural Setting Nutrients supplied by treated wastewater Reduces or eliminates nutrient import to farm Nutrient loading rates are limited, matched to crop uptake needs Nutrients are applied in small quantities, over time Maximizes nutrient uptake, reduces nutrient loss to water table Vegetated buffers reduce erosion and runoff Phosphorus control Eliminates Surface Water Discharges Wastewater runoff is prohibited Ground Water Considerations Impact to Ground Water Improve ground water quality under site Promotes local recharge of aquifer No appreciable mounding of water table Verified through on site ground water monitoring Comparison with Disposal Options Hydraulic Loading Rates Comparison of Hydraulic Loading Rates for Various Wastewater Disposal Options Ground Water Considerations per Year Inches Septic Systems Spray Irrigation gpd/sq.ft 1757 Impact to Ground Water Improve ground water quality under site Promotes local recharge of aquifer No mounding of water table Verified through on site ground water monitoring Comparison with Disposal Options Hydraulic Loading Rates Nitrogen Loading Rates Pounds of Nitroge en per acre per Year Comparison of Nitrogen Loading Rates for Various Wastewater Disposal Options Future uses of reclaimed water in Delaware Eliminate current surface water discharges Wetland restoration / Wetland creation Greenhouse production of ornamental flora Residential and commercial lawn watering Grey water reuse Industrial/Commercial reuse Septic Systems Spray Irrigation 7

8 Q U E S T I O N S? C O M M E N T S 8