Abstract
Ammonium removal by swim-bed technology using a novel acryl-fiber biomass carrier (biofringe) was conducted to investigate its effectiveness for treatment of Hanoi groundwater contaminated with high levels of ammonium. Two reactors with different amounts of biofringe—single yarn and double yarn—were used in this study. Ammonium removal efficiencies of 95-100% at volumetric loading rates of up to 0.24 and 0.48 kg-N/m3/d, corresponding to hydraulic retention times (HRTs) as short as 3 and 1.5 hours, were obtained for the single-yarn and double-yarn reactors, respectively. The maximum biomass retention capacities of the biofringe carriers and the influences of operational conditions such as temperature, pH, DO, and alkalinity on treatment efficiencies were investigated. Ammonium was converted to nitrate in this process with effluent nitrite concentrations close to zero, and DO concentrations greater than 3.0 mg/l were required for complete removal of ammonium at loading rates of 0.48 kg-N/m3/d. The pH level in the reactor consistently between 6.9 and 7.5 and alkalinity consumption was from 6.5 to 7.5 mg-CaCO3 per mg ammonium-nitrogen oxidized to nitrate. Slowly growing nitrifying bacteria were effectively retained in the reactor using the biofringe with effluent suspended-solids concentrations of less than 3-5 mg/l through out most of this study.
