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returns might be reached after enhanced nutrient removal. The additional chemicals and energy needed beyond that point caused a 70 percent spike in greenhouse gas emissions — and resulted in only a one percent drop in nutrient levels. Operational costs also increased more than five times to get to these higher levels of treatment. Researchers found that a more effective solution might be managing these nutrients before they even arrive at the facilities. Integrating best management practices for controlling nonpoint sources, such as the runoff that carries nutrients into our waterways, is a more sustainable solution for protecting our environment as a whole. Another WERF research study took a step back to first assess the impact of various forms of P to help inform regulations and target the P species that are the real offenders. Preliminary studies point to dissolved organic phosphorus (DOP), present after advanced treatment, as a major contributor. Using a newly established test that is based on measures of fluorescence and enzymatic analysis, researchers found a significant portion of lingering DOP could be bioavailable to algae — potentially impacting receiving waters. Finding ways to remove these residual nutrients could be key to meeting future stringent nutrient regulations. In this case, removal of DOP would mean integrating processes that remove hydrophobic organic matter, such as adsorption. This research, Bioavailability and Characteristics of Dissolved Organic Nutrients in Wastewater Effluents (NUTR1R06o), provides valuable information for engineers and facility operators that can help them manage investments on processes to eliminate bioavailable P and N more effectively. Direct determination of P mineralization kinetics in advanced wastewater treatment facility effluents is crucial for developing protective strategies for minimizing eutrophication in receiving surface waters. The research project Mineralization Kinetics of Soluble Phosphorus and Soluble Organic Nitrogen in Advanced Nutrient Removal Effluents (NUTR1R06p) looked at the dissolved P uptake kinetics characterization for five treatment facilities in the Spokane River/ Long Lake System in Washington and Idaho and also tested samples from five other facilities. The researchers tested whether nutrient co-limitation and/or effluent toxicity artificially depressed the percent of bioavailable phosphorus (BAP) estimates for the effluent samples. As it is very expensive to manage dissolved P in effluents using current detection methods, a simpler and less expensive bioassay uptake measurement tool was developed. The research report also presents a general approach for improving models used in managing nutrient impacted waterbodies. Removing P beyond enhanced biological processes usually requires adding chemical coagulants, most often alum. Although this can do a good job of producing effluent with fairly low nutrient levels, it also produces a sizable amount of chemical sludge, which up until now has been largely thought of as waste. However, innovative science is reimagining this product as a useful additive that can be plugged back into upstream treatment processes, resulting in even lower P levels. Researchers for this WERF project, Solids Role in Tertiary Chemical Phosphorus Removal by Alum (NUTR1R06t), found that the most effective points of reentry for sludge in the treatment train took advantage of existing solids separation processes, such as primary clarification, aeration, or secondary clarification. New process flows that take advantage of the sorptive capacity of this sludge could lead to ultra-low P levels while decreasing alum levels. Turning to the importance of real-time information, the WERF research project BNR Process Monitoring and Control with Online Nitrogen Analyzers for Nitrogen Credit Exchange Program in Connecticut (NUTR1R06y) summarizes the use, performance, and reliability of online analyzers by water pollution control facilities in Connecticut. It also considers their use for automated process control to optimize BNR performance. The research report includes case studies which describe practical approaches towards automated online process control for the improvement of BNR process performance. The researchers found that while there is an increasing interest in online N analyzers, their use for automated process control is not typical, that the implementation of automated process control is easier when the treatment facility undergoes an upgrade, and that it is dependent on the facility's existing processes. Looking toward the models that are used to set nutrient limits, the final project, Can TMDL Models Reproduce the Nutrient Loading-Hypoxia Relationship? (U4R09), addressed uncertainty regarding whether current eutrophication models used to determine TMDLs and to forecast the impact of TMDLs on water quality are accurate over longer time periods. The research team sought to calibrate a 55-year watershed simulation in the Chesapeake Bay watershed using several models by constructing a long-term time series (1950 to present) of nutrient loading for that area from nutrient loading observations in the Susquehanna, Potomac, and Patuxent Rivers, as well as proxies for other non-tidal rivers, long-term records of point sources, and proxies for changes in atmospheric loading. They found that there is good agreement between models and measurable results, except in the wet month (July). Based on the findings of this research, regulatory agencies may want to evaluate the agreement between modeled and observed hypoxic volume in future TMDL re-evaluations. Conclusions Although begun several years ago, these recently completed WERF studies illustrate the depth of additional knowledge that is needed to inform the process of setting and meeting nutrient limits. Ultimately, they build the case for WERF's newest research portfolio on the harvesting and recovery of these valuable nutrients. Results from WERF's nutrient recovery research will begin to become available this year. For more information, please visit www.werf.org. n wateronline.com n Water Innovations NUTRIENTS 35 Although meeting lower nutrient levels has become a high priority for many facilities, the benefits of reaching these lower limits can sometimes be offset by the negative impacts that it takes to meet them.