WateReuse Research Foundation Report Engineered DPR delivers reliable water quality A WateReuse Research Foundation study compares engineered direct potable reuse with de facto potable reuse, in terms of reliable water quality in the United States. Investigators Glen Boyd, Guy Carpenter, Nupur Hiremath, Deniz Demirkanli, and Mary Ellen Tuccillo explain the study results. e facto reuse occurs when waste- ment prior to treatment for meeting water treatment plant effluent is potable standards. The end product is Ddischarged to surface water or drinking water derived from municipal Engineered DPR groundwater, which is subsequently wastewater, after extensive treatment used as source water for drinking water and water-quality monitoring. Advanced systems can provide treatment. Utilities that rely on surface treated reclaimed water can be introduced water resources frequently are located into the potable water supply system by greater reliability and downstream from wastewater treatment blending the purified water with source plant discharges into rivers or lakes. water prior to treatment. Or, it can be better water quality Historically, the 1972 US Clean Water Act blended directly with the treated potable (which regulates discharges of impaired water supply at the point of distribution. than de facto reuse water to the environment), and the 1974 The limited number of DPR facilities US Safe Drinking Water Act (which could be evidence of the public’s adverse systems. regulates the quality of potable water), perception of the “toilet-to-tap” concept, have been relied upon in tandem to protect and reluctance to accept DPR technology. quality parameters considered in the public health. However, water scarcity is driving model were the following: dissolved WateReuse Research Foundation Report Conversely, direct potable reuse (DPR) additional communities in the US states oxygen and carbonaceous biochemical is an intentional, engineered approach of Texas and New Mexico to design and oxygen demand representing general to provide advanced treatment of the obtain permits for DPR implementation. aquatic systems health; indicator bacteria wastewater treatment plant effluent (E. coli) signifying potential health (reclaimed water) so that it can be used as Study approach hazard; and trace organic compounds a source of supply for potable purposes. To make this comparison, case studies (carbamazepine, sulfamethoxazole, The quality of water produced by were developed to evaluate the effects acetaminophen, and atenolol) engineered DPR systems provide greater of upstream wastewater effluent on representing occurrence of trace organic reliability and consistently better quality surface water bodies used as downstream contaminants in natural surface waters. than de facto reuse, according to the drinking water sources. Three utilities The analytical model was used to predict findings of a WateReuse Research – serving different population sizes, concentrations of the selected parameters Foundation-funded project (WateReuse- representing different geographic regions, in the water resource recovery effluents 11-05). Factors, such as climate and source and located in different land use settings at downstream drinking water treatment water quality, were found to affect the – were selected. The three utilities, all plant intake locations. Modeling results quality of de facto reuse. In comparing the river discharge systems, were Greater of the de facto reuse scenarios were two drinking water approaches, the study Cincinnati Water Works, Ohio; Frederick compared with available water-quality evaluates the quality of surface water as a County, Maryland; and Philadelphia Water data that resulted from more fully source for drinking water, and the quality Department, Pennsylvania. Available engineered approaches, such as DPR. of highly treated effluent sourced directly water-quality data and other information from water resource recovery facilities. were collected from wastewater utilities, Modeling results Trace organic contaminants, such as drinking water utilities, other regional The quantitative assessment of the endocrine-disrupting compounds, water organizations, and publicly study suggests river systems – such as in pharmaceutically active compounds, available data sets (for example: United Cincinnati and Frederick County, where and personal care products, are typically States Geological Survey stream gauges) to the individual discharge volumes are not targets of conventional wastewater characterize their de facto reuse settings. notably less than the total flow conditions or drinking water treatment processes. No sampling program was specifically in the surface water – most likely need Yet, a large body of scientific literature designed for this evaluation or conducted dilution as a significant attenuation demonstrates that these contaminants as part of this study. process for constituents in the treated frequently occur at very low levels in A quantitative assessment was effluents. Results indicate, if the effluent treated effluent and finished water conducted to estimate the effects of flow is small relative to river discharge, the supplies. Although not conclusively effluent discharges on the water quality effect of an individual facility discharge determined to be a public health concern, of the receiving water bodies. Analytical point in a river de facto reuse setting is published studies provide evidence of models of the three utility systems were likely to be small as well. A modeling occurrence of trace organic contaminants developed to represent steady-state flow assessment was also conducted with a in downstream drinking water resources. conditions, point source discharges of the lake discharge system. Results similarly There are only two DPR operations in wastewater treatment plants, transport indicated the importance of background the world today – Windhoek, Namibia, mechanisms of advection and dispersion, concentrations. In addition to treatment and Big Spring, Texas – and both of and major removal or generation reactions plant discharge points, surface water them employ advanced effluent treat- for the selected compounds. The water systems are subject to runoff, and careful 30 World Water: Water Reuse & Desalination / Spring 2014 WateReuse Research Foundation Report analysis is needed to estimate the relative Secondary Effluent and Finished Product Water Quality Data from Orange County contributions of various point and non- point sources of pollutants. Parameter OCSD Secondary Effluent OCWD Finished Product Water Overall, the predicted water-quality Dissolved Oxygen (DO) Not Available 4.43 − 16.5 mg/L (average 6.95 mg/L) values, resulting from the analytical models, were consistent with available Fecal coliform (MPN) 1,600 −2,600,000 ND (<2 MPN) water-quality data describing the system Carbamazepine (ng/L) 190 −263 (average 237) ND (<1 ng/L) characteristics and de facto reuse settings. Sulfamethoxazole (ng/L) 1,300 −2,130 (average 1,921) ND (<1 ng/L) In particular, predicted source waters’ Acetaminophen (ng/L) <5 −110 (average 64) ND (<5 or <10 ng/L) dissolved oxygen concentrations Atenolol (ng/L) 555 −1,200 (2 samples) ND (<5 ng/L) displayed positive agreement with Triclosan (ng/L) 280 −520 (average 415) ND (<1 ng/L) monitoring profiles. However, finer temporal and spatial fluctuations in water Table 1. Data indicate that the treatment combination of microfiltration, reverse osmosis, and advanced oxidation reliably removes quality – likely affected by non-point the parameters of interest to below analytical method detection levels – regardless of the variability of the recycled water quality. sources of contamination – were not captured in this study that used only available water-quality data. Coordinated systems, representative water-quality data is assumed that the treatment technology sampling is therefore needed, which is derived from analogous membrane and – as demonstrated by other projects like temporally and spatially planned, to better advanced oxidation treatment processes Orange County Water District’s Ground understand the relative contributions of were used to characterize DPR finished Water Replenishment System project, various contaminant sources in de facto water quality. coupled with the dilution that occurs reuse settings. Since January 2008, California’s Orange because of blending – renders trace County Water District Groundwater organic contaminant concentrations very Comparison of water quality Replenishment System has been low and of little concern. Engineered The project compared the case study producing up to 70-million gallons per DPR systems employing a combination findings of de facto reuse to the water- day of high-quality advanced treated of microfiltration, reverse osmosis, and quality performance levels demonstrated recycled water for augmen-tation of the advanced oxidation process appear to for engineered advanced water treatment regional aquifer. The Orange County Water provide robust removal of pathogens and systems, which are designed for direct District treats secondary effluent from trace organic contaminants – regardless potable reuse. Since 1969, the DPR the Orange County Sanitation District of influent water quality. operation in Windhoek, Namibia, has with microfiltration and reverse osmosis, Findings from this research demon- been implementing potable reuse without followed by advanced oxidation (of strate that, as a source for drinking water an environmental buffer (NRC, 2012). hydrogen peroxide