Study On Microbial Flocculants Produced By Multiple Microorganisms

Microbial flocculants(MBF) are microorganism-produced special substance that can flocculate suspended solids, cells, and colloidal solids. With the advantages of high efficiency, innocuity and biodegradability, MBF have been paid more and more attention to recently.In term of the mechanism of Effective Microorganisms, multiple microorganisms were constructed with strain BAFRT4 and strain CYGS1. Because of the cooperation of the two strains, multiple microorganisms are able to produce MBF with higher flocculating activity.In order to cut down the cultivating cost of multiple microorganisms, brewery wastewater was tested to replace glucose as the carbon resource and energy resource in the cultivating medium, and the result of experiments confirmed its feasibility. It was studied how the strength of the brewery wastewater, initial pH of culture medium, cultivating temperature, shaking speed and the dose of the germ solution influenced multiple microorganisms to produce MBF. The optimal culture medium of multiple microorganisms consists of 1000 ml brewery wastewater (its COD_Cr is 5000mg/L), 0.5g urea, 0.5g yeast extract, 0.2g (NH₄)₂SO₄, 5g K₂HPO₄, 2g KH₂PO₄, 0.1g NaCl, 0.2g MgSO₄ .7H₂O. The optimal cultivating condition is listed here: 1.0ml germ solution per 50 ml brewery cultivating medium, pH 6.0, 30℃, 160rpm, 72 h. Under this environment, the flocculating activity E₄ of the MBF produced by multiple microorganisms is up to 96.8%.According to the result of preliminary identification, strain BAFRT4 and strain CYGS1 pertain to Staphylococcus sp. and Pseudomonas sp., respectively.The productivity of the partially purified MBF is 15 gram per liter fermentation solution. The main components of the MBF are polysaccharide and protein.The MBF produced by multiple microorganisms excels at treating indigotin printing & dyeing wastewater. The optimized removing COD_Cr scheme is listed here.1.7 ml MBF and 3.5 ml l%CaCl2 were put into 100 ml indigotin printing & dyeing wastewater in 100 ml test tube, and pH of the system was adjusted to 9.0. Then the test tube was stirred and left for 10 min to settle. An aliquot of the supernatant was withdrawn from the test tube, and the value of its CODCr and OD66o was measured. Under this condition, the efficiency of removing CODcr and chroma was 79.2% and 86.5%, respectively. The optimized removing chroma scheme is listed here. 1.7 ml MBF and 3.0 ml l%CaCl2 were put into 100 ml indigotin printing & dyeing wastewater in 100 ml test tube, and pH of the system is adjusted to 8.5. Then the test tube was stirred and left for 10 min to settle. An aliquot of the supernatant was withdrawn from the test tube, and the value of its CODcr and OD660 was measured. Under this condition, the efficiency of removing CODcr and chroma is 69.4% and 87.6%, respectively. The kinetic equations of removing CODa and chroma from indigotin printing & dyeing wastewater with the MBF are Q coD(mg/L) = Co, cod (1—-------------------) , and C, od(A) = Co od (1 ^<sup>--------------------) , respectively.1.8610+ 1.1587/ 3.5697+ 0.9746/According to the components of the MBF and the experiments for flocculating process, the flocculation mechanism of the MBF was considered to be adsorption neutralization and adsorption bridging.In this study, the technology of Effective Microorganisms was employed to construct multiple microorganisms that can produce the MBF of higher flocculating activity. Cultivating cost was cut down greatly by using brewery wastewater as the carbon resource and energy resource of multiple microorganisms. The MBF produced by multiple microorganisms can remove most CODcr and chroma from indigotin printing & dyeing wastewater. It is anticipated that this study could provide valuable reference for the industrialized production and application of MBF.