Expanded bed groundwater treatment

Dempsey, Michael J., Cowl, James, Štembal, Tamara and Sipos, Laszlo (2000) Expanded bed groundwater treatment. In: Society for General Microbiology/Society for Applied Microbiology Millennium Meeting, 10-14 April 2000, Warwick, UK.

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Abstract

Groundwater normally has to be treated before it is suitable for potable use. For example by aeration, to supply oxygen; passage down through a sand filter, to filter out fine particulates and remove dissolved materials by microbial action; followed by a disinfection step, often using hypochlorite. However, many groundwaters contain trace quantities of ammonia, which reduces the anti-microbial efficiency of chlorination. We have investigated the potential of ammonia removal via oxidation to nitrate in a fluidized bed bioreactor. A laboratory-scale expanded bed column (2·5 cm diameter by 50 cm height), containing coke colonised by a mixed population of nitrifying bacteria, to form biofilms approximately 0.5 mm thick (40-50 gdm-3 dry weight) was fed an artificial groundwater containing 1.9 mg/l NH3-N. The bacteria were able to oxidise virtually all the ammonia to nitrate in a single pass, with a residence time of about 100 s through the bed (upward velocity approximately 0.5 cm s-1 ). This equates to a throughput of 60 m3 groundwater per m3 expanded bed per hour.