Irrigation with Recycled Wastewater: The NDMA Story

BACKGROUND The scarcity of water supply in many arid regions, combined with the need for disposal of large volumes of wastewater, has led to an increased use of recycled water for landscape irrigation. Although this practice has been employed for decades in many parts of the world, public health officials recently have begun to express concerns about the potential for wastewater-derived trace contaminants to contaminate potable water supplies. The trace contaminants in recycled wastewater include steroid hormones, pharmaceuticals, personal care products, and chlorination byproducts such as Nnitrosodimethylamine or NDMA. Known for its high cancer potency, NDMA is detected frequently in municipal wastewater effluent at concentrations up to 1000 parts per trillion (ppt), including at a number of wastewater treatment plants in California. California Department of Health Services (CDHS) has set a reporting level of only 10 ppt for NDMA. As a result of such stringent guidelines, reuse of wastewater is being scrutinized for potential to introduce NDMA into groundwater, particularly through practices such as use of recycled wastewater for groundwater recharge and landscape irrigation.