Study on Microorganisms’ Immobilization by Different Support Materials in the UASB System

Abstract

Four up-flow anaerobic sludge blanket reactors (UASB) filled with oyster shell (R1), activated carbon (R2), quartz sand (R3), zeolite (R4), respectively had been selected to inspect their effects on the COD removal efficiency, and to compare with the traditional UASB reactor (R0). System stability and pH variation were also inspected. All the reactors were inoculated with sludge from a local sewage treatment plant, and fed with the synthetic wastewater. The organic load rate was 0.96 kgCOD.m-3.d-1during 1-20 days (StageⅠ), 1.86 kgCOD.m-3.d-1during 21-57 days(StageⅡ), and 5.32 kgCOD.m-3.d-1during 58-97 days(StageⅢ), the system temperature was controlled at 35 °C. The influent pH was 7-8. The results reveal that: (1) The average removal rate was 94.5%, 78.0%, 91.4% for R1; 93.6%, 87.7%, 92.5% for R2in the three stages, respectively. R1and R2reactors are suitable to treat low organic load wastewater( 0.96 kgCOD.m-3.d-1) to high organic load wastewater(5.32 kgCOD.m-3.d-1). R3, R4and R0are not suitable for high organic load wastewater. (2) R1and R2reactors can resist the continuous organic shock load, and the system can recover in a short time; R3, R4and R0reactors could not recover during StageⅢ. (3) The system was sensitive to temperature variation, so temperature was an important factor to the system. (4) Anaerobic granular sludge were formed in R1, R2, R3, R4reactors, the amount of granular sludge sequencing was 89.02%, 82.46%, 16.44%, 36.54%, respectively. Compared to the support material size which was 0.15-0.20 mm; the size of granular sludge larger than 0.90mm was 41.5% in R1reactor, and 28.8% in R2reactor. (5) All the reactors had the ability of pH value moderation, so the pH value of all the system were stable. Since oyster shell is a solid waste, oyster shell powder used as the immobilization material not only has good effects of immobilization, but also has a strong economic competitiveness.