The Salinity Mediated Release of Ammonium from Treated Wastewate

Science Center, Bent Corridor

The release of nitrogen in effluent from wastewater treatment plants into coastal systems can contribute to eutrophication and coastal degradation, particularly in systems that are nitrogen-limited. One model suggests that ammonium can coulombically bind to dissolved organic matter in wastewater treatment plants, which protects it from removal during the treatment process, only to be bumped off by salt cations as the effluent encounters more saline waters. This presentation analyzes the response of effluent from four sequencing batch reactors, each running a different treatment processes that varied from minimal, nitrification only, to more advanced, biological nitrogen and phosphorus removal. Each of the four effluents produced was then put through one of three disinfection treatments (no disinfection, germicidal UV, or chlorination) producing twelve treatment-disinfection combinations; the combinations were produced twice in the summer and twice in the winter. Each of these combinations was then added to saline solutions producing four final salinities of 0, 10, 20 and 35. The salinity-mediated release of ammonium was observed in almost all of the effluent from two of the sampling periods (one summer and one winter). Effluent that had been chlorinated or received increased aerobic digestion resulted in lower rates of salinity release. These results indicate that salinitymediated release of nitrogen should be considered when selecting the most effective treatment method for effluent released to saline waters.