Adaptability of organic matter and solid content to Fe 2+ /persulfate and skeleton builder conditioner for waste activated sludge dewatering.

Sludge conditioning is important for improved dewatering, with the sludge characteristics impacting the effect of conditioning. A composite conditioner, Fe ²⁺ -activated sodium persulfate (Fe ²⁺ /SPS) combined with phosphogypsum (PG), was used to examine its impact on sludges with different organic contents (34.6-43.8%) or different solid contents (2.8-5.9%). Response surface optimization analysis shows that when the best conditioning is achieved, the reduction of the specific resistance to filtration (SRF) is not sensitive to organic matter content, but the dewatering performance of the sludge is greatly affected by the solid content. The oxidation role of Fe ²⁺ /SPS and the skeleton builder role of PG together affect the conditioning, oxidation playing a major role in conditioning, especially for greater organic matter content. The organic content (maximum η _SOL value was 0.32) also affects the effectiveness of the skeleton builder more than the solid content (Maximum η _SOL value was 0.25). Changes in PG significantly impacts the optimal molar ratio and dosage of Fe ²⁺ /SPS. Sludge with greater solid content requires greater Fe ²⁺ /SPS dosage to provide stronger oxidation to destroy flocs, and the maximum Fe ²⁺ :SPS molar ratio was 1.14 with solid content of 5.9 wt%. The composite conditioning decreases the content of extracellular polymeric substances and proteins/polysaccharides. This study provides new insight into the relationship between the oxidation role of Fe ²⁺ /SPS and the skeleton builder role of PG for sludge conditioning strategies according to the optimal conditions.
(© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)