Effect Of Contaminating Bacteria On The Growth Of Photosynthetic Bacteria Z07Utilizing Soybean Processing Wastewater And The Conditions Optimization

Photosynthetic bacteria (PSB) utilizing key pollutants in soybean processing wastewater could not only remove contamination effectively, but also realize their own biomass growth. For obtain PSB from wastewater, pure culture was necessary. However, contaminating bacteria were inevitable in actual wastewater treatment. The existence of contaminating bacteria would cause the drop of treating effect and the impossibility of recycling PSB biomass. How to control the contaminating bacteria in PSB wastewater treatment system was one of the bottlenecks of the technology of PSB wastewater treatment and obtain biomass protein. As a consequence, this paper, based on PSB strain Z07that was separated from wastewater, investigate the effect of contaminating bacteria on the removal of key pollutants in soybean processing wastewater and the yield of PSB biomass, the method of controlling contaminating bacteria in the PSB treating system, the method of isolating PSB with the existing of contaminating bacteria, and the acute toxicity of this process.The results indicated that when coexisting with contaminating bacteria microorganisms, the method is practicable when HPLC was adopted to analyze the concentration of CoQ10and thus obtained the concentration of PSB in water. The average recovery rate was99.13%and the RSD was0.81%(n=5). The method has high precision, good repetitiveness; it could be used in CoQ10extraction and test. The chromatographic condition is as follows: The chromatographiccolumn is SphherisorbC18(10cm×4.6mmID), methanolabsolute alcohol (9:1) as mobile phase at a flowrate of1mL/min, column temperature35℃, Wave Length of UV detector275nm, sample size15μL, column pressure16.4MPa．In pure culture the advantageous conditions of PSB using key pollutants in soybean processing wastewater and realize their own biomass growth were initial soybean processing wastewater3600mg/L, initial PSB160mg/L, nature light micro-aerobic(DO0.5-1.0mg/L), pH of8.0and30℃. The optimal wastewater treatment conditions were nature light micro aerobic, initial PSB160mg/L, initial soybean processing wastewater3600-7200mg/L, pH of8.0-9.0and20-30℃when coexisting with contaminating bacteria microorganisms.The response surface method was adopted to analyze the effect of six kinds of trace elements (Fe2+,Mn2+,Cu2+,Zn2+,Co2+and Mg2+) on PSB biomass production. Based on an overall analysis of PSB biomass production, COD removal and cost, dosing the composition of Fe2+and Mg2+would lead to a remarkable enhancement in the productivity of PSB. The optimum dose of Fe2+and Mg2+was0.66and0.16 mmol/L separately where PSB biomass concentration could reach1483.5mg/L, COD removal of89.1%, the least cost was0.033Yuan/t. Co2+could promote PSB productivity. The predominant trace element was Co2+when cost was not considered.The conditions for PSB having the higher dominance and biomass having recovery value when coexisting with contaminating bacteria microorganisms were the proportion of PSB to contaminating bacteria higher than2:1, light anaerobic, osmotic pressure of0.12atm, pH of8, and30℃.In SBR modle system under light anaerobic condition, PSB culture system could operate stably. PSB biomass increase (2257.2mg/L) and the percentage of PSB to total bacteria (96.3%) were the highest compared with other light oxygen conditions, PSB was the dominate bacteria. And PSB has more advantages under light anaerobic condition. Under dark aerobic condition, PSB biomass only slightly increased by59.8mg/L and the percentage of PSB to total bacteria reached32.7%, and thus PSB was not the dominate bacteria. Under nature light micro aerobic condition, when the percentage of PSB to total bacteria rose from10:1to5:1, PSB biomass increase was basically the same, and PSB biomass increased by186.7-191.3mg/L, and the percentage of PSB to total bacteria reached47.8%-48.3%. Although under nature light micro aerobic condition PSB could treat wastewater effectively, the wastewater treatment effect was provided by contaminating bacteria, and PSB was not the dominate bacteria.PCR-DGGE results indicated that, PSB was the dominate bacteria under three light oxygen conditions. The diversity of the microbial species reached the phase of stable operation from28d to35d. The change of microbial flora was not significant, which proved the system could run stably in this condition.Three kinds of coagulant Al2(SO4)3, Fe2(SO4)3and Al2Cl(OH)5was adopted to separate PSB, the separation rate was51%-92%. The charging weight of coagulant was high; it required at least5000mg/L coagulant in order to bring PSB down. Coagulation is unsuitable for separating PSB. The results compared with ultra filtration membrane to separate PSB display that adopting ultra filtration membrane to separate PSB could lead to the separation rate of99%cheaper and more efficient.The results of the animal acute toxicity test on PSB strain Z07and the mixture of it and contaminating bacteria as bait (or feed) showed that, both strain Z07and the mixture were safe. When releasing the bait at1g/L at one single time, within96hours, we found no observable toxic effect to the carp. When the dose of the soil feed was below5g/kg at feeding Eisenia foetida, within14days, and when the dose below12g/kg·d at feeding mice, within14days, we found no toxic effect, either.