THE ROLE OF MEMBRANE BIOREACTORS IN ADDRESSING CHESAPEAKE BAY CHALLENGES. Introduction. Chesapeake Bay Water Quality Challenges

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1 THE ROLE OF MEMBRANE BIOREACTORS IN ADDRESSING CHESAPEAKE BAY CHALLENGES Zohreh Movahed, WATEK Engineering Corporation, 604 S. Frederick Ave, Suite 309, Gaithersburg, MD 20877, (240) Melissa Lin, WATEK Engineering Corporation, Gaithersburg, MD Introduction Sustainable, safe and reliable water service is the lifeblood for every community, one source being the Chesapeake Bay, which covers over 64,000 square miles, bordering six northeast states plus the District of Columbia, with a watershed that is home to more than 18 million people. The Chesapeake Bay is the largest estuary in the United States with a land-to-water ratio of 14:1 and with more than 50% of the watershed population living along or near the shores. The activities on the land have had a direct and in some cases, significant water quality degradation impacts on the Bay. This paper presents some of the current water quality challenges of the Chesapeake Bay, elaborates on effectiveness of Membrane Bioreactors (MBR) for wastewater treatment, and provides an overview of five (5) MBR projects in the region. Chesapeake Bay Water Quality Challenges The Chesapeake Bay watershed encompasses portions of Delaware, Maryland, New York, Pennsylvania, West Virginia, Virginia and the District of Columbia as shown in Figure 1. Figure 1 Chesapeake Bay Watershed Region (Phillips, 2014) 1

2 Numerous parts of the Bay watershed are listed as impaired waterways under the Clean Water Act. Extensive and on-going research continues to demonstrate Nitrogen (N) and Phosphorous (P) loadings as major causes of the water quality challenges to the Bay. While well balanced concentrations of N and P are essential components of a healthy Bay and are critical for production of phytoplankton, which serve the food web, high nutrient levels result in unbalanced, excessive levels of phytoplankton. Since 1985, major upgrades and improvements of nutrient reduction at wastewater treatment plants in the region have helped with reducing over 900 million pounds of nitrogen and phosphorus loadings to the Bay, as demonstrated by the relative size of the charts shown in Figure 2. Figure 2 Chesapeake Bay Watershed Loads (Wastewater Pollution Reduction Leads the Way, 2016) Agricultural, forest, urban runoff, septic tanks and wastewater treatment plants have been identified as major contributors of N and P to the Bay. Although non-point sources continue to pose the greatest risk to water quality, wastewater treatment plant effluents remain on the spotlight, since they are easily identifiable, and public/regulatory agencies have more control over them. Figure 3 Sources of Nitrogen Pollution in the Chesapeake Bay ( Land Use and Pollution Across the Bay Watershed, 2016) 2

3 To protect the Bay from further decay, regulatory agencies continue to establish more stringent Nitrogen and Phosphorus discharge limits for point sources. The Chesapeake Compared to Other Parts of the United States Figure 4 demonstrates states that have developed Total Nitrogen and Total Phosphorus criteria as of September Figure 4 States with Total Nitrogen or Total Phosphorus Criteria ( State Development of Numeric Criteria for Nitrogen and Phosphorus Pollution, 2016) State regulating agencies, depending on the specific conditions of the receiving streams, may implement total maximum daily loads (TMDLs) requirements as well as mandate daily, monthly, annual loads and concentration limits for wastewater treatment plants. For example, Delaware estuaries require discharge limits for Total Nitrogen to be 0.14 mg/l and Total Phosphorus to be 0.01 mg/l ( State Development of Numeric Criteria for Nitrogen and Phosphorus Pollution, 2016). In New York, there are requirements for Nitrate as Nitrogen in lakes/reservoirs, rivers/streams and wetlands to be 0.1 mg/l and 0.02 mg/l in those same waters that are 3

4 considered trout waters. West Virginia limits Total Phosphorus to 0.03 mg/l in cool water lakes and 0.04 mg/l in warm water lakes, which was adopted and has been enforced since 2012 to help inhibit algal blooms. For many states, because of the various receiving water types, nutrient concentrations are project specific. Some project specific nutrient goals will be discussed further in this paper. Moving Forward Utilization of advanced, cutting-edge technology continues to play a significant role in protection and improvement of the Bay. The ten largest wastewater treatment plants in the Chesapeake Bay region are shown below. Figure 5 Top Ten Largest Wastewater Treatment Plants in the Chesapeake Bay Watershed (Wastewater Pollution Reduction Leads the Way, 2016) Although the largest facilities have the potential to have the most significant impacts, still, extensive efforts are taking place in establishing stringent N and P limits at all WWTPs, no matter the size, including the ones that are discussed in this paper. 4

5 Why Membrane Bioreactors (MBR)? Membrane technologies, specifically MBR, provide a reliable treatment option that can easily be customized to produce the desired water quality. MBR is typically more expensive in terms of capital and O&M costs per gallon of treated wastewater as compared to the conventional activated sludge processes. However, from a sustainability perspective, the consistency and reliability of effluent water quality and overall long-term effectiveness make MBR the technology of choice as a viable alternative to existing conventional wastewater treatment plants. MBR can consistently meet low nutrient discharge limits by producing an effluent typically lower than a BOD of 3 mg/l; TSS of 1 mg/l; NH3-N of 0.5 mg/l; total Nitrogen of 3 mg/l; total Phosphorus of 0.05 mg/l and Turbidity of 0.2 NTU. Subsequently, this high quality effluent can be used for a long-list of non-potable water reuse applications, producing a valuable commodity rather than a waste product. A Few Membrane Bioreactor Projects in Maryland Many authorities responsible for wastewater treatment plants in the Chesapeake Bay Region have taken proactive measures when planning for upgrades to their ageing WWTPs. This includes considering enhanced nutrient reduction goals to be more in-line with the Bay protection goals. Proactivity, combined with mandatory total maximum daily load requirements, results in more stringent total Nitrogen and Phosphorous removal goals for many WWTPs. Among these authorities is the Maryland Environmental Service (MES), who is responsible for a full range of stormwater, water supply and wastewater treatment services throughout the State of Maryland. MES is commended for their proactive vision and initiatives for such removal requirements. The following is a list of MBR projects that WATEK is involved, within the Maryland Environmental Service region. As shown, the main reason for upgrading to MBR is the more stringent water quality requirements. Southern Maryland Pre-Release Unit WWTP Upgrade The Southern Maryland Pre-Release Unit Wastewater Treatment Plant is located in Charlotte Hall, Maryland and designed for 20,000 gallons per day with a peak flow of 40,000 gallons per day. Instead of discharging to a spray field from spring through fall, the decision was made to discharge to a stream year-round due to more stringent WWTP standards and to avoid interference with the Charles County Police Department shooting range operations. The design criteria for MBR effluent limitations include Total Nitrogen (TN) less than 4 mg/l and Total Phosphorus (TP) less than 0.7 mg/l. The facility has been in operation since October Rocky Gap Wastewater Treatment Plant Conversion to Membrane Bioreactor Rocky Gap State Park is located in Allegany County, in the northwestern part of Maryland, situated among one of the world s oldest mountain ranges, the Central Appalachians. Due to increased attendance at the Rocky Gap Casino Resort, the park has seen increased flows to its independent water and wastewater systems. In response to the ageing infrastructure and more 5

6 stringent upcoming regulations, the WWTP is being upgraded in two phases. The first phase, which included new duplex coarse screens, a 90,000 gallon equalization tank with pumps as well as headworks building and controls, was recently completed and put in service. The second phase, which will soon begin construction, includes upgrading the wet stream processes by utilizing MBR. The MBR equipment will be retrofitted within the existing concrete tanks, along with new offices, control room and more modern controls being constructed within the existing Filter Building. Due to variations in wastewater flow, which is highly dependent on the season, day of the week, special activities at the casino, coupled with Infiltration/Inflow (I&I), the MBR equipment is sized based on the Maximum Monthly Flow of 150,000 gallons per day. The MBR system is also designed to meet future, more stringent effluent requirements of TN less than 3 mg/l and TP less than 0.3 mg/l. Eastern Pre-Release Unit Wastewater Treatment Plant Upgrade to Membrane Bioreactor Eastern Pre-Release Unit Wastewater Treatment Plant is located in Queen Anne s County in Church Hill, Maryland. This plant currently consists of an aerated lagoon and a Dynasand filtration system, and it is permitted to discharge 20,000 gallons of wastewater per day. However, the WWTP has been operating at more than 80% of its design capacity for the last 3 years, requiring submission of a Wastewater Capacity Management Plan to the Maryland Department of the Environment (MDE). In its latest renewal of the facility permit, dated November 1, 2013, MDE has required prevention of the wastewater from the lagoon to enter the groundwater. Additionally, the lower discharge ammonia limits set in the new permit mandates an upgrade to the WWTP. The new facility is currently being designed to handle an average of 40,000 gallons per day, with a peak flow of 80,000 gallons per day and MBR effluent limitations of TN of 4 mg/l and TP of 0.3 mg/l. Cheltenham Youth Detention Center Wastewater Facility Improvements Cheltenham Youth Detention Center Wastewater Facility is located in Prince George s County, Maryland. The ageing infrastructure at the existing facility is in need of a major upgrade to address: 1) the anticipated wastewater quality and quantity changes resulting from construction of the new Department of Juvenile Services (DJS) Detention Center (currently under construction); 2) compliance with the trends of more stringent nutrient discharge limits from the Maryland Department of the Environment (MDE); and 3) the need for a regional office with adequate laboratory and centralized training facilities for the operators and maintenance staff. The facility is currently being designed for an average daily capacity of 70,000 gallons per day, peak of 200,000 gallons per day and an effluent meeting Total Nitrogen less than 3 mg/l and Phosphorus less than 0.3 mg/l. Eastern Correctional Institution (ECI) Wastewater Treatment Plant Upgrades The Eastern Correctional Institution (ECI) Wastewater Treatment Plant in Westover, Maryland is currently being upgraded by MES to meet a discharge permit effective on January 1, The 6

7 upgrade includes a new equalization tank, new headworks, new MBR systems as well as various other upgrades and polishing to the existing plant. This plant is designed to treat 1.14 million gallons of wastewater per day, including the treatment of ammonia and phosphorus in the concentrate from the existing reverse osmosis water treatment plant. Table 1 Summary of Nitrogen and Phosphorus Discharge Limits Project Location Total Nitrogen (mg/l) Total Phosphorus (mg/l) Southern Maryland Pre-Release Unit < 4.0 < 0.7 Rocky Gap 1 < 3.0 < 0.3 Eastern Pre-Release Unit < 4.0 < 0.3 Cheltenham Youth Detention Center < 3.0 < 0.3 Eastern Correctional Institution < 1.28 < Discharge Limits are shown for designed future requirements. Actual goals required by permit are TN < 6.0 mg/l and TP < 0.7 mg/l. Conclusion Water reuse in the Chesapeake region is at its infancy, perhaps due to lack of economic incentives, regulatory guidelines, and less apparent water shortages. The opportunity to reuse wastewater and meet stricter environmental regulations makes MBR an attractive option for the greater health of the Bay watershed. Many areas are also considering MBR as a sustainable option to upgrade existing facilities that are barely meeting current permit requirements and to help prevent excessive nutrient loads from being discharged into nearby waterways. As examples, this paper provides multiple MBR plants throughout the state of Maryland and depicts the high-quality effluent these plants can produce through the utilization of MBR, which in turn, will help restore clean water to the Chesapeake Bay. 7

8 References 2017 and 2025 Watershed Implementation Plans (WIPs). ChesapeakeProgress. Chesapeake Bay Program Web Team, n.d. Web. 08 Sept < Bay 101: Facts & Figures. Chesapeake Bay Program. N.p., Web. 22 Nov < Wastewater Pollution Reduction Leads the Way. Rep. Chesapeake Bay Progress, June Web. 1 Nov < Land Use and Pollution Across the Bay Watershed. About the Bay/The Issues/Land Use/Land Use and Pollution Across the Bay Watershed - Chesapeake Bay Foundation. N.p., Web. 22 Nov < Phillips, Scott, and Bill Caughron. "Overview of the U.S. Geological Survey Chesapeake Bay Ecosystem Program." U.S. Geological Survey Chesapeake Bay Ecosystem Program. Publishing Service Center, 18 Feb Web. 1 Nov < State Development of Numeric Criteria for Nitrogen and Phosphorus Pollution. US Environmental Protection Agency. N.p., 24 May Web. 08 Sept < Water Quality Standards Attainment and Monitoring. Chesapeake Progress. Chesapeake Bay Program Web Team, n.d. Web. 08 Sept < 8