Water Online

September 2017

Water Innovations gives Water and Wastewater Engineers and end-users a venue to find project solutions and source valuable product information. We aim to educate the engineering and operations community on important issues and trends.

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discharge is not available. Therefore, inland locations considering potable reuse are either planning very expensive RO-based treatment trains with brine-handling facilities, or they are exploring alternative treatment trains that are equally effective in providing barriers for pathogens, CECs, and DBPs. To address the One Water project needs of inland communities, the question was asked whether RO (a desalination process developed decades ago) was truly the best technology for removing CECs, which are primarily organics. The answer to this question may well be no; it's ozone-BAC technology. The ozonation step oxidizes CECs that are residual from conventional wastewater treatment processes into short-chain organic compounds that are biodegradable. Next, the BAC step metabolizes these short- chain organics into even simpler organics. A schematic of an ozone- BAC process is shown in Figure 2. As shown, treated wastewater must be filtered prior to ozone-BAC treatment. This filter may be part of the wastewater treatment plant or part of the water reuse treatment process. A description of the ozone- BAC process relative to the Figure 2 schematic is presented below. Ozone-BAC Technology Development And Maturation While some communities have been utilizing ozone-BAC for decades, engineering services company, Stantec, reported one of the earliest data sets on the CEC removal capabilities of ozone-BAC when treating filtered wastewater. That data set was based on the field performance of an ozone-BAC process operated from 2008 to 2010 at the City of Reno's Reno-Stead Wastewater Reclamation Facility (WRF). CEC removal in ozone-BAC was extensive and reliable and was achieved mainly via three treatment mechanisms: 1) oxidation, 2) biodegradation, and 3) adsorption, resulting in true treatment, not just concentration. Since then, Stantec has been working on the optimization and design of ozone-BAC for potable reuse applications, including water treatment in Gwinnett County. Since reporting the Reno project findings, several full-scale ozone-BAC projects have been implemented in New Mexico and Texas, and field investigations are being conducted in Virginia and Florida. Stantec is currently designing full-scale ozone-BAC processes for agencies in Southern California. Optimization Of Ozone-BAC For Potable Reuse Applications Water Environment & Reuse Foundation (WE&RF) Project 15-10 is a research project in collaboration with American Water, Stantec, Washoe County, Nevada, Xylem, and WE&RF. The goals of the project are to: 1. Understand water quality differences between ozone-BAC and RO effluents. 2. Optimize ozone-BAC treatment mechanisms and design parameters. 3. Develop an ozone-BAC guidance manual for potable reuse applications. The project team is currently conducting diagnostic pilot testing at Washoe County's South Truckee Meadows WRF in Reno, NV. This research project has been providing valuable insights on the roles of the ozone and BAC steps in controlling DBP formation and maximizing CEC removal. The guidance manual is considered as the next step in ozone-BAC technology maturation as it allows regulators and designers to better understand the technology's capabilities and limitations. Ozone-BAC And Its Role In Future Water Management Ozone-BAC has an important role in removing CECs found in municipal wastewater prior to reuse as part of One Water resource planning. Ozone-BAC-based treatment trains are proven to be effective in providing pathogen log reductions and minimizing DBP formation as well. RO still has a place in One Water planning, but primarily for use in its original role to remove salt if needed, and only to the extent needed based on One Water project-specific factors. In such cases, the RO unit would treat just a portion of the reuse water downstream of the ozone-BAC process. n 20 wateronline.com n Water Innovations RESOURCERECOVERY Vijay Sundaram, a chemical engineer by training, has 15 years of experience designing advanced water and wastewater treatment systems using physical, chemical, and biological processes. He is the water resource technology leader at Stantec, and as a resident of drought-sensitive California, he's focused on creating safe, cost- effective, and reliable water sources. About The Author The ozonation step oxidizes CECs that are residual from conventional wastewater treatment processes into short-chain organic compounds that are biodegradable. Next, the BAC step metabolizes these short-chain organics into even simpler organics. Filtration tanks for biological activated carbon treatment.

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