Improvement of sludge dewatering performance by persulfate advanced oxidation combined with LDH: Synergistic effect of free radical and non-free radical and reuse of deep-dewatered sludge cake

The high-water content of sludge in wastewater plant will influence the transportation and utilization. In this study, a new method for improving sludge dewatering by pyrite (FeS 2 ) activated persulfate (PMS) combined with layered double hydroxide (LDH) was proposed. After conditioning, the water content (Wc) and specific resistance (SRF) of sludge decreased from 97.12 % and 1.83 × 10 13 m/kg to 71.39 % and 1.84 × 10 12 m/kg, severally. SEM and particle size analysis showed the system could destroy sludge cells effectively.The mechanism analysis of protein and polysaccharide content, 3D-EEM, FTIR, XPS results showed that FeS 2 /PMS-LDH combined system was beneficial to break down the sludge extracellular polymer (EPS), transform and accumulate the organic matter into the EPS outer layer, release the bound water. Both free radical and non-free radical play a role in oxidation, and they cooperate to break EPS. The effective phosphate adsorption performance of the biochar adsorbent prepared from dehydrated sludge cake was also investigated. The adsorption behavior of phosphate on biochar from dewatered sludge cake belongs to uniform chemical monolayer adsorption. When T = 298k, PH = 5, the maximum adsorption capacity is 20.255 mg/g. The introduction of LDH is helpful to enhance the sludge dewatering and the adsorption of phosphate. To sum up, the combined conditioning method considers the effectiveness of sludge dewatering and the feasibility of sludge cake disposal and utilization.