Iron ore waste combined with lysozyme-producing bacteria to promote sludge reduction: Performance and mechanism

Abstract

Due to the complex structure of sludge, sludge hydrolysis becomes the limiting factor for sludge digestion. In this study, a combined treatment system of lysozyme-producing bacteria and iron ore waste was established, and the lysozyme secreted by the enzyme-producing bacteria was used to realize the cracking of the sludge cell structure to achieve the purpose of reducing sludge. The results showed that the best hydrolysis effect could be achieved when the sintered ore dosage was 1.50 g L−1 and lysozyme inoculation dosage was 3 %. At 20 h, the release amount of soluble chemical oxygen demand (SCOD) was 1877.34 mg L−1, and the concentration of protein and polysaccharide increased by 226.64 and 114.51 mg L−1, respectively, which indicated that the sludge microorganisms released a large amount of intracellular substances. The removal rate of suspended solids (SS) concentration in the combined treatment system was 3.37 times that of the control group. The results of sludge morphology analysis showed that the sludge structure was destroyed and the particle size decreased. The addition of sinter reduced the Zeta potential of sludge, promoted electron transfer between microorganisms, and improved lysozyme production efficiency of enzyme-producing bacteria. Proteobacteria plays a dominant role in the combined treatment system. The combined treatment system significantly improved metabolic capacity and iron utilization capacity of the microbial community, which may be the mechanism for the combined treatment system to promote sludge reduction.