| Energy crisis and environmental pollution have become global problems which hinder the development of global economy and society. Oil-rich algae can be used as raw materials for production of biodiesel, which has very good prospects as a fuel. Therefore, the use of sewage water for cultivating high-fat microalgae will be an effective way to turn wastewater into resource. However, the microalga is inefficient for the removal of organic pollutants that can be efficiently removed by bacteria. Thus, the system of microalgae using the sewage water in combination with bacteria, not only cultures the microalgae for biodiesel production, but also treats the wastewater efficiently. This study will focus on the selection of highly-efficient LAS degrading bacteria and their applications of the bacteria in combination with the algae in a rotating biological contactor (RBC).In this work, efficient bacteria and carrier were firstly selected and added to the RBC. Then, effect of the addition of the bacteria on the performance of the RBC was investigated. The relationship between the performance and bacteria amount, distribution and community structures in the RBC was investigated by the PCR-DGGE technique.Finally, we have reached the following conclusions.1. Surfactants contaminated activated sludge was sampled from Luofang WWTP and sewages were taken from Shenzhen University Town. Enrichment and isolation of surfactant degrading bacteria were carried out using LAS as a sole carbon source. Finally, three LAS degrading strains (L3, L7 and H6) were obtained. Through physiological and biochemical identification and 16S rDNA sequencing, L3 and L7 belong to Plesiomonas sp, and H6 is Pseudomonas sp. When the LAS concentration was less than 100 mg/L, the strain H6 achieved the 80% degradation of the LAS. The strains cannot be cultured when LAS concentrations was more than 500 mg/L2. Biofilm formations and activities on 5 kinds of carriers were investigated. The results show that among these, the YL-XHΦ25×12 carrier is the most suitable to be used in the pneumatic-driven RBC. Its consumption rates of glucose and CODCr were 35.59±0.40 mg/L(carrier)/min and 7.85±0.95 mg/L(carrier)/min, respectively.3. After the highly-efficient LAS degrading bacteria were added into the RBC, the average effluent CODCr concentration from the 3rd reactor was 24.3 mg/L, and the average effluent CODCr from the membrane was 15.8 mg/L. Thus, the average removal rate was 90.5%. Compared with the RBC without the addition of the bacteria, the effluent CODCr concentrations from the 3rd reactor and the membrane were decreased by 55.7% and 46.4%, respectively, in the bacteria-added RBC. Thus, the addition of the highly-efficient LAS degrading bacteria was helpful for the removal of the CODCr.LAS average effluent concentration was 0.20 mg/L, and the average removal rate was 94.6% in the bacteria-added RBC, and the effluent concentration was decreased 81.7% compared with the LAS effluent concentration of the RBC without the addition of the bacteria. It is below the LAS limitation concentration (0.5 mg/L) of the 1A standard of the "Municipal Wastewater Treatment Plant Pollutant Emission Standards" (GB18918-2002).4. DGGE profile analysis showed that there were two dominant kinds of LAS degrading species in the system, band 4 and band 7. The sequence analysis shows that the band 4 and the band 7 belong to Plesiomonas sp. and Pseudomonas sp., respectively. That the LAS removal capacity of the RBC system was improved after the addition of the highly-efficient LAS degrading bacteria is not because the change of the bacteria consortia structure but the increase of the amount of the LAS degrading bacteria in the system.In the end, technical and economic feasibility analysis of this bacterium augmentation RBC process was investigated. The results showed that this process is feasible for the wastewater treatment plant modification project. |
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