Graduate (PhD) Student The University of Texas at Arlington Bronx, NY
Irrigation projects are now considering the use of non-traditional water sources, including treated wastewater, to augment supplies. Treated wastewater, however, may still contain many organic pollutants of emerging concern, because traditional wastewater treatment plants are unable to remove all of them. Adsorbents have been demonstrated to effectively remove recalcitrant organics from wastewater more effectively, at lower cost, and using less chemicals and energy than many competing techniques. A single adsorbent with one pre-treatment, however, is not effective for simultaneously removing different types of water pollutants. This work explores a novel solution: waste materials - rice husk and sewage sludge - were modified with different physical/chemical pre-treatments to create a multi-sorbent mixture MultiSorb, to simultaneously remove different organics. Specific objectives were to: 1. Prepare/characterize adsorbents from rice husk and sewage sludge, using varied pre-treatments. 2. Develop and test PreSorb for removing natural organic matter, using batch tests. 3. Develop and test MultiSorb for removing perfluorinated compounds (PFAS) and pharmaceutical and personal care products (PPCPs), using batch tests. 4. Evaluate PreSorb and MultiSorb using column tests, which better simulate actual water treatment systems. 5. Compare costs for wastewater treatment using PreSorb/MultiSorb with commercial activated carbon. To accomplish Obj. 1, 48 powdered adsorbents were made: 4 base materials (RH; rice husk ash, RHA; SS; sewage sludge char, SSC) x [3 chemicals (phosphoric acid, potassium hydroxide, zinc chloride) + 1 physical treatment in steam] x 3 temperatures (500, 650, 800ºC). Adsorbents were characterized for moisture content, CHN analysis, and leaching behavior. Five controls were also characterized: unmodified RH, SS, RHA, SSC; commercial AC. Leaching characterization of adsorbents using the Leaching Environmental Assessment Framework (LEAF Method 1314) showed release of heavy metals and organics from RHA and SSC to be within drinking, irrigation, aquatic standards/guidelines nationally and internationally, except for slightly elevated arsenic levels from RHA. There was no PFAS availability detected in all the samples above the Limit of Detection (LOD). To test the effectiveness of the carbonized and activated adsorbents (Obj. 3), batch tests were conducted. Samples were analyzed by LC-MS. Some waste-made adsorbents showed adsorption of PFAS similar to commercial activated carbon. Objectives 2, 4, and 5 are currently in progress.
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