Purification of high-salinity wastewater by activated sludge process

The objective of the present work was the enhancement of the efficiency of microbiological processes in purification of high-salinity oil-field brine by adding the powdered activated carbon (PAC) to the bioreactor and by diluting the brine with surface water. The investigation was carried out in a laboratory setup. Results show that the nature of pollutants and the high salinity (about 29 g/l) of oil-field brine had an unfavourable effect on the activated sludge process. Higher hydraulic loads (above 2.5 d−1) increased wash-out of the activated sludge from the bioreactor, so that an increased concentration of the suspended matter in the settler was observed. The addition of PAC to the bioreactor, combined with the dilution of oil-field brine with surface water, produced a substantial improvement in the sludge volume index. Also, under the given conditions, it was possible to maintain the given concentration of the activated carbon in the bioreactor. The procedure involving PAC and dilution with surface water resulted in an increased rate of pollutant degradation. The positive effect of PAC on the process of oil-field brine purification with the activated sludge was explained by the possibility of immobilization of microorganisms on the activated carbon surface in the form of a biofilm.