Why Dewaterability of Sewage Sludge Occurs Upstream: A Model to Quantify the Effects

Successful dewatering optimization requires a good understanding the dewaterability of a particular sludge. To help with this a model was developed to explain the main influences on dewaterability in wastewater treatment plant as well as the impact of different sludge conditioning technologies (i.e. cell lysis or phosphate sequestration) on its water binding characteristics. Dewaterability herein is expresses as DS(A)KBKopp, which represents the achievable cake dryness through mechanical dewatering. The DS(A)KBKopp is measured through thermogravimetric analysis with an accuracy of ±0.5%DS. The model was informed by results from nearly 1,000 dewaterability tests conducted since 1995. Thanks to this extensive database it was possible to create a model that describes dewaterability at treatment plants as a function of the process but also factoring in seasonal changes. The model determined the three most dominant influences: the fraction of waste activated sludge to PS before digestion, phosphate quantity, and volatile suspended solids. While this model cannot replace measuring sludge dewaterability it can be used to improve one's understanding of the dewatering performance, once calibrated to historical data. Armed with a better understanding of the current dewatering process performance, operators and engineers can develop optimization strategies to reduce the overall dewatering and disposal cost. Note: facility names in this section are omitted for confidentially reasons.