| Sulfate-reducing-bacteria(SRB), with the characteristics of using waste sludge to treat wastewater, being suitable for various heavy-metal ions and gaining high removal rate, has been progressed rapidly, which is extensively applied in the treatment of organic wastewater, acid mine drainage(AMD) and electroplating wastewater. However, there exist some defects, such as low-usage of nutrition, high effluent COD and toxicity of heavy metal ion.Immobilized-cells processes could enhance the tolerance and degradation abilities of toxicant. SRB sludge method itself was always considered as an immobilized-cells process, enwrapping SRB to form microbiological flock or particle. However, immobilized SRB sludge method was seldom studied.The study on immobilized SRB sludge of inner cohesive nutrient source has never been reported. Based on this, which provide a reticular structure for SRB sludge to resist outer rigorous environment and gain high removal rate, a novel technology was put forward for treating heavy metal wastewater by immobilized SRB sludge beads of inner cohesive nutrient source in our previous researches, which has the advantage of full utilization of nutrition, without the problem on high effluent COD.This paper optimized beads capability, treated Zn(II)-bearing sulfate wastewater by immobilized SRB sludge of inner cohesive nutrient source, and the mechanism and kinetics model on Zn(II) removal in the process were also studied in systematically.Anaerobic sludge containing high concentration SRB was obtained by anaerboically modification of activated sludge in Postgate's C medium. The study on the composing and distributing of microorganism by the Most Probable Number(MPN) Method explained the competitive process which SRB and methane produce bacteria(MPB) utilized nutrition. And the relativity of TTC-Dehydrogenase activity(DHA) and bacterium number proved that DHA was measured as the sludge activity indexdisplaced bacterium number.The immobilized SRB sludge beads of inner cohesive nutrient source were prepared using Polyvinyl Alcohol(PVA) as entrapment agent. The optimal conditions were chosen in terms of the mechanical stability, mass transfer, and difficulty of forming beads. And the biology-physical-chemistry capability of immobilized beads was improved by adjusting the pH value of boric acid and appending metal salt. In addition, the treatment of Zn(II)-bearing wastewater by immobilized beads was investigated. The result showed that PVA was considered as the best support according to the removal of Zn(II). And the optimal conditions are 9% PVA solutions 30% entrapping agents ratios> 3mm diameters 3Oh in saturated boric acid solution, and 0.1% sodium alginate> 3%SiO2> 0.5%CaCO3 was added to improve the mass transfer and its durability. The pH value of Saturated boric acid solution adding 2% CaCl2 was 6.7.The sorbent of inner cohesive nutrient source was 3% Power Activity Carbon(PAC). The regeneration time was 3 days.In the intermission experiments, the factors of Zn(II) concentrations pH> temperature and the coexistence of heavy metals were investigated in the treatment process of Zn(II)-bearing wastewater. The results showed that immobilized beads can be effectively used to treat 600 mg/L Zn(II)-bearing wastewater under the conditions of 35 °C, element pH=6. In 24h, the removal rate of Zn(II) can get 98% — 99% and Zn(II) concentration reached national wastewater emission standard. The removal rate of SO42" can get 95%. The coexistence of heavy metals produce few effect on the removal of Zn(II)-bearing wastewater.It was analysed that the number of -OH bond decreased as the cross-linking reaction between PVA and H3BO3 was proceeded. 3% PAC was added to immobilized beads as the core of inner cohesive nutrient source, which provided relaxing nutrient source. The results showed that SO42" was reduced to S2" in the way of H2S atmosphere on the surface of SRB sludge beads, and Zn(II) was precipitated outside beads according to the analysis of SEM. EDX and kinetics model data. The reaction kinetics was followed by lVtichaelis-Menten formula as follow:ds 0.018293x5v = --dt 8.992806 + 5... |
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