AWWA WQTC69408

AWWA WQTC69408 An Innovative Approach to Predicting Nitrogen Removal in Repurified Wastewater
Conference Proceeding by American Water Works Association, 11/01/2008

Kinser, Karla; Cassanova, Regina; Nelson, Michael; Jacangelo, Joseph

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Decreasing regulations on nutrient limits worldwide are requiring careful processconsiderations to provide reliable nutrient removal in reuse plants. A key design concern of the13.2 MGD Gibson Island Advanced Water Treatment Plant (AWTP) in Brisbane, Australia, isremoval of nitrogen from influent levels as high as 5.4 mg/l as N to 0.8 mg/l as N in the treatedwater. Reverse osmosis is a key process technology integral to achieving the low level ofnitrogen.Understanding nitrogen rejection of commercially available reverse osmosis (RO)elements was required to become more precise as design advanced. While RO manufacturerprojection software may be an effective way in which to predict rejection of nitrate and ammonia,it does not predict the removal of organic nitrogen. Since organic nitrogen is one of theconstituents that comprise total nitrogen, projection software is unable to confirm itsconcentration in treated water. Additionally, organic nitrogen varies greatly in differentsecondary effluent sources, and is highly dependent on industrial waste contributions. Theobjective of this study was to discuss the methods of determining RO nitrogen rejection andprovide information on the results of those methods applied to a specific project. Of most importance, and a driver to have reverse osmosis, is the needto reduce Total Nitrogen to 0.8 mg/L as N. Total nitrogen is comprised of organic nitrogen,ammonia, nitrate, and nitrite compounds. Nitrate is the only compound that can be modeled forrejection by reverse osmosis. Therefore, to accurately predict the amount of organic nitrogenthat would be rejected by the full-scale AWTP, a pilot study was conducted. Furthermore, eachreverse osmosis manufacturer has different rejection properties, so the pilot study had toevaluate several manufacturers to understand the rejection that could be achieved.Two pilot studies were conducted to model the nitrogen rejection for the AWTP, a singleelement RO pilot and a demonstration pilot designed similar to the full-scale. Includes tables, figures.