Orange County Water District: Protecting Groundwater From Pharmaceutical Contamination

Orange County Water District: Protecting Groundwater From Pharmaceutical Contamination

Jason Dadakis in front of a reverse osmosis treatment train.

Orange County Water District (OCWD) is the groundwater basin manager for north and central Orange County, California, providing 77 percent of the water supply for the 2.5 million residents of the area. OCWD is a world leader in water recycling, and its Groundwater Replenishment System (GWRS) is the largest advanced water purification system for potable reuse in the world. OCWD’s focus on water reuse means that it has developed sophisticated protocols for ensuring that the water it provides is clean, safe, and free of any harmful contamination, including contamination by pharmaceuticals and other constituents of emerging concern (CECs). In this interview, Jason Dadakis, OCWD’s executive director of water quality technical resources, tells Municipal Water Leader about how the district monitors and treats its water to mitigate pharmaceutical contamination.

Municipal Water Leader: Please tell us about your background and current position.

Jason Dadakis: I’m a hydrogeologist by training, and I have worked for OCWD for about 16 years. My current title here at OCWD is executive director of water quality and technical resources. I work with our analytical laboratory, water quality monitoring programs, regulatory compliance, and research and development.

Municipal Water Leader: Would you give us an overview of OCWD?

Jason Dadakis: OCWD is what’s known in California as an independent special district. It was created by the state legislature in the 1930s and charged with the role of managing the local groundwater basin. We are the groundwater basin manager for north and central Orange County. There are 2.5 million people in our service area, and the groundwater basin currently provides 77 percent of the water supply. Our major stakeholders are the 19 retail water agencies that have wells that pump from the basin and serve water to residential and industrial customers.

Municipal Water District: Please tell us about the district’s testing for pharmaceuticals and other CECs. When did you start getting involved in this?

Jason Dadakis: The district’s testing for pharmaceuticals and other CECs began in the mid-2000s for a couple of reasons. One was that the necessary analytical technology became available for utilities like ours, which operates a fairly sophisticated water quality laboratory. We now had the resources and expertise to operate the analytical systems required for testing pharmaceuticals that can occur in water at parts-per-trillion-level concentrations. In terms of the drivers, we were getting ready to bring our large potable reuse project, the GWRS, online in 2008. Our permit to operate that facility from the State of California required us to test for some classes of pharmaceuticals, personal care products, and similar CECs, as there was a desire to ensure that its advanced treatment processes were effectively removing those types of constituents.

Municipal Water District: What is included within the category of CECs?

Jason Dadakis: It’s a broad class of pharmaceuticals, personal care products, and industrial contaminants for which there are not currently enforceable drinking water standards or effluent limits.

Municipal Water District: At what points in your water system are you detecting these compounds in your water supplies?

Jason Dadakis: These compounds are most commonly detected in certain environmental waters, such as surface water, particularly if they are influenced by the discharge of conventionally treated municipal wastewater, which can definitely be a source of these types of compounds. In some cases, these environmental waters ultimately become part of the source water for drinking water supplies. That said, we have found that there is some attenuation of these compounds in environmental waters from natural ultraviolet (UV) light and treatment wetlands. We’ve also found that when these surface waters are used to replenish a groundwater basin, a further attenuation and removal of these compounds occurs through the soil-aquifer treatment (SAT) process. Our monitoring is pretty good at documenting the removals that occur as environmental waters migrate along the path to becoming part of the drinking water supply in the groundwater basin.

We also do testing as part of our GWRS recycled water project, which is separate from the surface water I discussed just a moment ago. In conventionally treated secondary wastewater effluent, you will typically detect some residual pharmaceuticals, personal care products, and artificial sweeteners, but we have found that the engineered treatment processes that form part of the GWRS, including the reverse osmosis (RO) process and our UV advanced oxidation process (AOP), are effective in removing them. Even after that, we have the additional barrier of the SAT process that occurs when we introduce this purified water into the groundwater basin.

Municipal Water District: Do you test the water as soon as it arrives at your treatment plants, or after treatment?

Jason Dadakis: We do both. We test the conventionally treated wastewater that is the input to our advanced treatment facility, and we compare the results to the results of testing after each of our major advanced treatment processes. That allows us to track the removal of these compounds. The State of California has developed a list of CECs that it requires projects like GWRS to monitor in their influent and product waters. A limited number of these compounds are associated with potential health concerns. The majority of the listed CECs serve as indicators of treatment performance. Their specific structures and physical or chemical properties allow them to represent a whole class of compounds, so testing for them helps assess how effective the treatment is at removing a wider range of compounds. Testing both what’s coming in and what’s going out of our treatment facilities allows us to assess treatment performance.

Municipal Water District: Has the focus on pharmaceutical compounds in drinking water been driven by state regulators and legislators, by the industry, or both?

Jason Dadakis: I would say both. OCWD was interested in assessing CECs in advance of formal regulations. It definitely has been a topic of interest for California regulators. The State of California’s formal requirements for the testing and treatment of pharmaceuticals and other compounds is largely focused on recycled water because of the known occurrence of CECs in conventionally treated wastewater. For certain types of potable reuse in the state, there is a requirement to use RO and AOP to help control the potential chemical risk associated with those compounds. The state is also evaluating similar monitoring requirements for environmental discharges of wastewater, but I don’t believe there are consistent formal effluent limitations as of yet. On the drinking water side, there are to my knowledge no formal testing requirements or regulatory thresholds for pharmaceuticals in drinking water in California.

Municipal Water District: What are the risks associated with the human consumption of these compounds?

Jason Dadakis: Pharmaceuticals and certain food additives have to go through a U.S. Food and Drug Administration approval process or another similar approval process, so we have pretty good information about the doses and concentrations that are required to have an effect on people. Based on that available information, it is possible to develop drinking water guidelines that correspond to those dosing thresholds. Even in conventionally treated wastewater, the concentrations that are typically observed are orders of magnitude below the level that would elicit a response. There isn’t thought to be much risk of consumption at those levels because they’re so far below medicinal doses. The concentrations observed in drinking water supply source waters are even lower, for the reasons described previously. That’s likely why in California there are currently no drinking water limits in place for specific pharmaceuticals.

Municipal Water District: How do you select the particular compounds to test for?

Jason Dadakis: Typically, the targets that are used in the analytical methods are based on a variety of factors, including public interest, occurrence, and efficacy as a treatment indicator. Sometimes the community wants to know about the presence, absence, or level of a particular constituent. Another factor is a given constituent’s value as an indicator. Some constituents are widely used and are almost certain to be found in conventionally treated wastewater or other environmental discharges, so you may want to use them as treatment indicators. Perhaps a given constituent has a relevant structure that can cover a larger class of compounds. Indicator compounds ideally occur in the influent or source water at reasonably high and consistent concentrations so that their removal during treatment can be effectively quantified.

Municipal Water District: What treatment methods does OCWD employ?

Jason Dadakis: In our potable reuse project, which purifies water to reintroduce into our groundwater basin, our core treatment process for chemical contaminants is RO. RO is a robust process across a wide range of contaminants, including both pathogens and chemicals. It removes contaminants based on their molecular size and charge. Most pharmaceutical molecules are simply too big to get through the RO membrane, so when we test afterward, we rarely, if ever, have any detectable pharmaceutical traces.

After that, we have our UV AOP, which includes the addition of hydrogen peroxide, which is an oxidant. Any small, neutral molecule that was able to get through the RO process is either oxidized through the AOP or destroyed by the UV light. It is an effective supplemental barrier.

Finally, the water is introduced to the groundwater basin via injection wells or surface-spreading recharge ponds. The SAT process occurs as the water infiltrates or migrates into the ground and provides us another opportunity for removal through absorption, volatilization, and/or biodegradation. That series of barriers constitutes a robust overall process for removing pharmaceuticals.

Municipal Water District: Were those treatment methods developed for this particular issue, or were they used previously for other contaminants?

Jason Dadakis: RO, AOP, and SAT are each part of the California regulations that govern our project. Control of organics, specifically constituents of emerging concern and pharmaceuticals, is a goal of that overall multibarrier process. That is why that treatment train is required for the type of work we’re doing in California.

Municipal Water District: What should OCWD’s customers know about pharmaceutical contamination in drinking water?

Jason Dadakis: It is really not an issue for us because of the treatment and monitoring processes we have in place. We’re able to reliably test for these contaminants and ensure that they’re being removed through both natural and engineered treatment. The combination of treatment and verification from monitoring means that pharmaceutical contamination is not a significant issue for our customers.

Jason Dadakis is the executive director of water quality technical resources at the Orange County Water District. He can be contacted at jdadakis@ocwd.com.