Bacterial removal of nitrate, nitrite and sulphate in wastewater

Solutions of various concentrations of NO2-, NO3- or SO42-, and equal concentrations of NO2- + NO3- and NO2- + NO3- + SO42- in thrice distilled water as well as in samples of industrial waster-water effluents of Kima company (a factory producing ammonium nitrate coated with limestone powder Fertilizer) at Aswan City and River Nile water collected from Mansoura, Damietta, Kafr el Zayat and Edfina were tested against Bacillus Stearothermophilus Asw 88 and Bacillus Stearothermophilus Asw 129 and autoclaved at 37 and 50 degrees C for various hours using nutrient yeast extract (NYE) medium. Detection and assay of NO2-, NO3- and SO42- in simple salt solutions using NaNO2, NaNO3, Na2SO4 and H2SO4 after screening for 120 h indicates complete depletion of these components as they are good and convenient essential nutrient sources for both strains utilized safely for the treatment of polluted water. The strains are not pathogenic and they have no hazardous effect on human and animal life. The method is efficient and the results of the analysed water samples are consistent with the permissible safety baseline levels desired for domestic, irrigation and industrial purposes and also for drinking purposes after disinfection according to the World Health Organisation Standards. Complete depletion of SO42- after 96 h, NO2- and NO3- after 144 h, COD after 168 h and 23-30% degradation of Cl- after 168 hi are obtained. The biological treatment of industrial wastewater effluents of Kima Company and River Nile water at Damietta, Mansoura, Edfina, and Kafr El Zayat containing NO2-, NO3-, SO42-, HCO3-, Cl- and COD (organic matter) shows a progressive biodegradation of nutrients' levels with time, reaching complete depletion (NO2-, NO3-, SO42- and COD) due to the degradation effect by nitrogen and sulphur reducing bacteria. The decrease or absence (depletion) of nutrients and other parameters' levels may be related to their consumption by bacterial biomass. (C) 1998 Elsevier Science Ltd. All rights reserved.