Seeking to Understand and Address the Impacts of Biological Phosphorus Removal on Biosolids Dewatering

While biological phosphorus removal (BPR) is becoming more common, the effect it has on solids digestion and dewatering is just now being recognized and must be confronted. This paper discusses some of the theory behind bioflocculation and dewatering of biosolids, the consequences of BPR and anaerobic digestion on dewatering, and some mitigating measures that are being considered. Amongst these are stripping the phosphorus, magnesium and potassium from the waste activated sludge before digestion which would allow struvite recovery while also diverting potassium cations away from the solids processing train; and the concept of adding magnesium to the digested biosolids to satisfy the two-fold demand for magnesium in struvite formation and bioflocculation.