Abstract
A pure culture of any microbial species has not demonstrated phosphorus removal at the same level as EBPR activated sludge in the anaerobic-aerobic (oxic) wastewater treatment process. The reasons for differences in phosphorus profiles between pure cultures of specific species and activated sludge include (1) growth and preservation on agar media, (2) pre-culture with large growth rate, and (3) cultivation with a high concentration of inflow substrate and a low dilution rate without supernatant effluent. The third point was examined experimentally in this study. The results achieved from the lab-scale experiments showed that it was apparent that mixed liquor withdraw operation (MWO) caused deterioration of phosphorus removal in the anaerobic-oxic process, but could enhance phosphorus removal under some specific conditions. High concentrations of sodium, potassium and ammonium nitrogen in the reactors could not be a reason for the deterioration of phosphorus removal in the anaerobic-oxic process with MWO. Similarly, inorganic and organic materials which might be produced during autoclave sterilization did not seem to be a reason for the phosphorus removal deficiency in the anaerobic-oxic process with MWO. Phosphorus to carbon (P/C) ratio of the inflow and aeration level in the aerobic phase were crucial for enhancing phosphorus removal of the anaerobic-oxic process with MWO.
