Isolation And Identification Of Sulfate-reducing Bacteria And Its Application In Karst Water

Taiyuan Southern Region belongs to the arid or semi-arid area, lack of water resources. Despite having a large number of underground karst water resources, its high hardness and high salinity and high sulfate content which can not be used as domestic water and was also not suitable for industry. Therefore the karst water can be put into use after appropriate treatment.The karst water is a special kind of water body, contains a variety of anions and cations such as Ca2+, Mg2+, Na+, K+, SO42-.The water is neutral or alkaline, slightly bitter taste. Directly discharged without treatment or put into use directly will not only bring harm to the ecological environment, but also affect the distribution of the industrial production and cause the waste of resources. This experiment focused on dealing with the sulfate ions in the karst water.At present, there are several ways to remove sulfate, which mainly include ion exchange, reverse osmosis, activated carbon adsorption method, BaCl2method, CaCl2method, freezing method and biological method and so on. Physical and chemical methods have high processing efficiency, but the cost is high and easily lead to secondary pollution. However biological methods are not only low-cost, good effect and also no secondary pollution. In recent years, the immobilized microbial technology in the water treatment technology has attracted much attention. This technology not only has the characteristics of high efficiency, stable, easy to control, and easy separation of the solid-liquid, also has many advantages such as can maintain biological activities and so on. The study will use immobilized sulfate-reducing bacteria (SRB) to degradate sulfate of karst water. The purpose is to make the sulfate content of karst water reach the standard of drinking water, namely sulfate content reduced to250mg/L.This research mainly includes three aspects:(1)A strain of sulfate-reducing bacteria (SRB) was isolated and screened from sewage purification plant secondary sedimentation tank return sludge of Yang Jiabao in Taiyuan, then it was studied by morphological and physiological and biochemical characteristics;(2) SRB will be made immobilized beads using different embedding agent. And the best strains immobilization conditions was selected by measuring the degree of difficulty of the ball into a ball, the mechanical strength and the mass transfer rate;(3) Degradation of SRB immobilized on karst water sulfate was studied in order to obtain the amount of ball, processing time and processing temperature which can make the sulfate content of karst water to reach the drinking water standard.Isolating a strain of sulfate-reducing bacteria from return sludge, while using the dilution-fold culture dish sandwich culture method to separate and purify the bacteria, and for further studying characterization of strains of Gram staining, spore staining observation, physiological and biochemical characteristics of the bacteria. It was found that SRB is rod-shaped or fine shape, and the cell was dyed in red in Gram staining. It indicated that SRB is Gram-negative bacteria; in the spore staining, we found that SRB spores were stained green, while the sporangium and nutrition were red. It indicated that SRB had bacillus. Through the determination of the bacteria OD600value, SRB on different carbon sources, sulfur source utilization situation was different, in different temperature and different PH conditions have different growth conditions; When sucrose, sodium acetate, sodium lactate as carbon source, SRB strains growed well and had higher bacterial density, and sodium lactate is the best; With the sodium sulfate, magnesium sulfate, sodium thiosulfate, sulfite as sulfur source SRB, growth is good, when using sodium thiosulfate as sulfur source, the highest SRB cell density, growth of the best. SRB growth and proper temperature was22～32℃, and the optimum temperature was32℃; the suitable pH range was8.28～10.36, and the optimum pH is9.62(The pH value was measured before sterilization, calcium chloride, potassium hydrogen phosphate two is not added to the medium at that time, the purpose is to prevent the nutrients in the sterilization response, thereby affecting the components of culture medium). Based on the above factors, we identified the bacteria desulfovibrio.In order to improve the treatment effect of sulphate karst water, this experiment will be used immobilized microorganism technology. So it is particularly important that find out the optimum immobilization conditions of SRB strain. This experiment will use four different embedding agent composition which were sodium alginate (SA), SA and zeolite, SA and polyvinyl alcohol (PVA), SA and gelatin. Then making immobilized beads in different concentrations of CaCl2saturated boric acid solution. And then the optimum immobilization conditions of SRB strain was determined by measuring the balls into the ball difficult easy degree, mechanical strength and mass transfer rate to prepare for the subsequent water treatment experiment. The experiments showed that:when SA and zeolite as entrapment agent, and SA was2.4g, zeolite was2.4g, CaCl2saturated boric acid solution at the concentration of2%, small spherical variables was small and complete dyeing time was short.Based on the above experimental results, in the third part of the experiment, we will use the zeolite-SA embedding agent composition to make SRB immobilized beads, and then degradated sulphate of karst water. Respectively adding different amounts (0.5g,1.0g,1.5g,2.0g) of the ball (SRB immobilized bacteria embedded15%) to35mL karst water, and then placed in different temperature (27℃,32℃,37℃), respectively, processing0,12,24,36,48h. After the end of the treatment, the sulfate content of OD420of the karst water was determined by Barium Chromate Spectrophotometry. Before and after SRB treatment of immobilized beads sulfate content of karst water by sulfate standard curve calculated, then exploring SRB immobilized amount and the processing time and temperature which can make the sulfate content of karst water to reach the drinking water standard. The results show that, degradation of SRB immobilized ball the karst water sulfate, the best conditions for the:at37℃for2.0g SRB immobilized onto the35mL karst water, the treatment time was36h, sulfate content in karst water reduced the most, from1856mg/L to61mg/L, the degradation rate of96.71%.Taking all these experiments can be seen, the SRB immobilized beads degradation of karst water sulfate results significantly improved the water quality of the karst water, and to some extent alleviate the water shortage situation Taiyuan Southern Region, at the same time as Taiyuan Southern Region ecological the environment and the economy in the form provided strong protection.