Treatments Of Alkaline Waste Water And Soil By Exiguobacterium And Their Mechanism

Environmental pollution of alkaline waste water and soil salification andbasification are serious ecological and environment safety issues of our country.Although treatment of alkaline environment by physics and chemistry methods haveobtained the certain achievements, obvious shortcomings also exist. The use ofbiotechnology, especially microbial biotechnology gives new hope of treatment ofalkaline environment. In this study Exiguobacterium aurantiacum was used to dealwith alkaline waste water and soil, and their mechanism was preliminarily studied.Alkaline waste water used in this study was from water flushed pipe lines ofTianjin Zhongfen Dairy Co. Ltd. with initial pH12.80. Treatment results of alkalinewaste water with different initial pH values, different dealing methods and additionsof bacteria solution, and different treatment temperatures were studied by individualfactor experiment. The pH value of alkaline waste water can reduce from10.00to7.42within12h, but the strain has little effect on strongly alkaline waste water whichpH value is always above11. The treatment effect was better when bacteria solutionwas suspended in saline or added directly with addition10%-15%in temperatureabout30?. The COD value of alkaline waste water reduced from425to330within12h.Soil samples were taken from Guxie wetlands in Beidagang, Tianjin. The pH of itis8.84, the water holdup is8.26%, and the electrical conductivity is1.549×103?S/cm,it is a kind of typical saline-alkali soil.20g soil sample was shaken by10mesh sieves,and added with5mL fermentation liquor with bacteria density of5.1×109cfu/mL. ThepH value of it can reduce from8.84to7.75with in72h, while with hardly any changein conductivity. When bacteria with different concentration of were added in it, theone with5.1×107cfu/mL has the best effect on the treatment of it which can reduce thepH value from8.84to7.45within48h.In order to determine the variety and output of the organic acid inExiguobacterium fermentation liquor, Fourier transform infrared spectrometer (FT-IR)and high performance liquid chromatography (HPLC) were performed. In FT-IRspectroscopy2peaks corresponding to carbonyl group (at1408.38cm-1) and hydroxylgroup (at3420.13cm-1) were detected. It shows that Exiguobacterium aurantiacumculture supernatant contains a compound having a carboxylic acid group. The typesand amount of acid were detected by HPLC. Formic acid, acetic acid, propionic acid,malic acid and succinic acid were detected in it. The amount of acetic was highest andit was risen to the highest at22h which is12.448mg/mL. Total acid in thefermentation liquor was highest at10h with the production of27.120mg/mL. Theseresults may explain the mechanism of the pH value reduce of alkaline waste wateradded with Exiguobacterium aurantiacum, the amount of acid produced by thebacteria was highest at10h, while the pH of alkaline waste water was lowest at10h,and the biomass growth entered in stable condition at10h. So it established arelationship among biomass growth, acid production and pH value of alkaline wastewater. This research adopted Exiguobacterium aurantiacum to deal with alkaline wastewater and soil, and favourable results were obtained, while at the same time theirmechanism was preliminarily explored. It laid the foundation for the handling ofalkaline environmental issues using miacrobial biotechnology in industry.