Study on Fe-rich sludge biochar as conditioner to improve sludge dewatering performance
Biochar derived from Fe-rich sludge through pyrolysis was utilized as a substitute of iron reagents in the Fenton reaction for sludge conditioning so as to enhance its dewatering capability.The results indicated that the pyrolysis temperature significantly affected the conditioning performance of the Fe-rich sludge biochar,with the biochar produced at 800 ℃(RS800)demonstrated the best dewatering efficiency.The optimized conditioning paramenters were as follows:initial sludge pH of 2.00,with RS800 and H2O2 dosages of 0.2 and 0.08 g/g based on volatile solids(VS)in sludge,respectively,followed by a 15-minute reaction after the addition of H2O2.Under these conditions,the capillary suction time(CST)of the conditioned sludge decreased to 39.4 s,representing an 84.33％reduction compared to the raw sludge(CST=251.5 s),thus significantly improving the sludge dewatering performance.The Fenton reaction initiated by the leached Fe2+from the Fe-rich sludge biochar effectively promoted the decomposition of H2O2,yielding a substantial amount of hydroxyl radicals(·OH).These radicals effectively disrupted the structure of extracellular polymeric substances(EPS)within sludge flocs,causing the release of organic matter,proteins,and polysaccharides from the inner layer to the outer layer of the flocs,accompanied by the release of bound water.Concurrently,the flocculation action of Fe3,produced during the Fenton reaction,aggregated fine sludge particles into larger and denser particles,further releasing bound water and ultimately achieving deep sludge dewatering.
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