A new method for the simultaneous online measurement of sulfide and nitrate in wastewater is developed. A UV-VIS spectrometer was used. The sensor was calibrated by means of simultaneous online and offline measurements of sulfide and nitrate in batch tests carried out on a laboratory-scale sewer system. The developed calibration algorithm was successfully validated for both sulfide and nitrate measurement, with confidence limits of 2.7 mg S/L for total dissolved sulfide, and 7.5 mg N/L for nitrate. The online measurement of sulfide and nitrate enabled detailed evaluation of seven nitrate dosing strategies in the laboratory-scale sewer system, providing strong support to process optimisation. The dosage optimisation revealed that nitrate should be added at a location close to the point of sulfide control rather than at the beginning of a rising main, at a rate proportional to the expected hydraulic retention time (HRT) of the wastewater in the sewer section between the point of nitrate addition and the point where sulfide control is desired.

dosage optimisation, nitrate, sewer, sulfide, UV-VIS spectrometry
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© IWA Publishing 2010
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