Immobilization of activated sludge in PVA matrix using innovative methods
聚乙烯醇固定化微生物新方法的研究

The immobilization methods using polyvinyl alcohol (PVA) and sodium alginate (SA) as carriers was developed and used for entrapment of activated sludge. Mechanical stability and microbial activity was compared for five kinds of PVA-immobilized beads of activated sludge, which were PVA-boric acid beads, PVA-sodium nitrate beads, PVA-orthophosphate beads, PVA-sodium sulfate beads and PVA-freezing-thawing beads. The results showed that PVA-sodium sulfate method was the best immobilized one in terms of the microbial activity and mechanical stability. The immobilization conditions for ctivated sludge were optimized. With the PVA concentration of 12%, Na2SO4 concentration of 0.5 mol·L-1, cross-linking in saturated boric acid containing 2% CaCl2 for 1 h and cross-linking in Na2SO4 solution for 4 h, the formed immobilized beads had higher microbial activity. The long-term performance of the PVA-sodium sulfate beads was also studied. The physical characteristics and microbial activity of the beads changed with time and stabilized finally, with the service span more than 30 d.