Sludge reduction using polyvinyl alcohol-sodium alginate (PVA/ SA)-immobilized refined iron ore and microorganisms: Optimization and mechanism

To enhance sludge digestion efficiency and sludge reduction, polyethylene glycol (PVA) and sodium alginate (SA) were employed as carriers to immobilize the lysozyme-producing strain SJ25, the surfactant-producing strain WH11 and refined iron ore (RO), prepared the above materials into PSR B. The optimal conditions for sludge hydrolysis in the experimental group PSR B were found to be as follows: the dosing amount and pH was 0.45 g/g SS and 9.0 respectively. Compared to the control group, the suspended solids (SS) and volatile suspended solids (VSS) reduction efficiencies increased by 29.6 and 29.4 % in turn. In addition, the soluble chemical oxygen demand (SCOD) increased by 1560.99 mg/L. Meanwhile, the polysaccharides (PS) and proteins (PN) concentrations rose by 165.43 and 202.23 mg/L respectively. The RO in PSR B would promote the transfer of electrons and the secretion of lysozyme and biosurfactants. These compositions could synergistically promote the destruction of cell walls and sludge. Furthermore, High-throughput sequencing analysis indicated that the PSR B would enhance the metabolism of carbohydrates and proteins and membrane transport, thereby improving sludge reduction outcomes.