Study On Application Of Immobilized Microorganisms In In-situ Repair Of Black Odorous Water And Sediment

With the rapid economic development and the acceleration of urbanization,different degrees of balck-odorous pollution has occurred in most rivers of our country.It not only seriously affects the lives of residents,but also restricts the development of society.It has increasingly becoming the focus and focus of people's attention.Sediment is the "sink" and“source”of pollutants in river.It is also one of the main causes of black odor in the river.Therefore,sediments remediation is the key to solving the problem of black odor in water.This paper is based on the research project of the water remediation demonstration project in balck-odorous river in Yangzhou City and Systematically carried out researches on the selection of dominant microorganisms,the selection of carrier for microbial solidification,and the effect of immobilized microorganisms for in situ remediation of sediments in the balck-odorous river.Besides the laboratory test results are used for practical application.The main achievements of this paper include the following points:(1)10 strains of dominant photosynthetic bacteria(numbered G1?G10)and 9 strains of dominant denitrifying bacteria(numbered F1?F9)were screened from the sediment of the local typical balck-odorous river.Experimental results showed that bacterial strain G3 has the best purification effect on balck-odorous water and bacterial strain G3 has the best degradation of nitrate nitrogen and total nitrogen in the screening medium.Accordingly,bacterial strain G3 and F8 are selected as the dominant bacteria in indigenous microorganisms of sediment.(2)Zeolite and activated carbon are selected as microbial carriers and analysed their performance.The results are shown as follows:1)The carriers shows a good activation effect at a temperature of 400?;2)the results of isothermal adsorption test shows that both carriers have a good ability to absorb ammonia nitrogen,and zeolites are slightly better than activated carbon.3)The methylene blue adsorption values of activated carbon and zeolite are 102.56 mg/g and 26.82 mg/g respectively.It shows that activated carbon has a greater adsorption capacity than zeolite.4)The maximum adsorption capacity of the carrier to denitrifying bacteria is 2.39×107 cfu/g,while the maximum adsorption capacity of the carrier to photosynthetic bacteria is 2.39×107 cfu/g.Both carriers showed good adsorption capacity of microbial bacteria.(3)20g activated zeolite carriers and 20g activated carbon carriers were respectively added to the photosynthetic bacteria solution and the denitrifying bacteria solution to microaerate the films for 48 hours.Scanning electron microscopy showed that photosynthetic bacteria and denitrifying bacteria adhered to the carrier in the Photosynthetic bacteria-zeolite group(GF group),photosynthetic bacteria-activated carbon group(GH group),denitrifying bacteria-zeolite group(FF group)and denitrifying bacteria-activated carbon group(FH group)had good growth effect on the carrier.The immobilization of microorganism is successful.(4)Immobilized microbial carriers were used to carry out simulated repair experiments under laboratory conditions.A total of 5 groups experiment devices were divided into blank group,GF group,GH group,FF group,and FH group.At the end of the 88-day trial period,the main test indicators for overlying water in each test group were improved except for the control group.The GF group had the best purification effect,the CODcr concentration decreased from 84.33 mg/L to 41.98 mg/L;the concentration of NH3-N and TN dropped from 12.59 mg/L to 0.78 mg/L,23.12 mg/L to 1.20 mg/L respectively,and their change trends were similar.The TP concentration decreased from the initial value of 1.48 mg/L to 0.19 mg/L.(5)At the end of the 88-day trial period,the main indicators of sediment in each test group are obviously different.The sediment organic matter of GF group decreased from an initial value of 88.31 g/kg to 62.07 g/kg,a drop of 26.24 g/kg,while the organic matter in the GH group,FF group,and FH group decreased by only 13.89 g/kg,14.91 g/kg,11.20 g/kg,respectively.However,there was almost no change in organic matter in the blank group.The GF group also has the largest increase in sediment G value(biodegradability of sediment)which increased from an initial value of 0.25×10-3kg/(kg · h)to 1.44×10-3kg/(kg · h).(6)At 90-day trial period,The best transfer effects of the four heavy metal contents of Cu,Zn,Ni,Pb,Cd,and Cr in sediment of each test group were 7.40%,3.64%,18.39%,6.43%,respectively.The contents of Pb and Cd were relatively low,and the best transfer effects of the two ions were that reduced from 49.21 mg/kg and 2.15 mg/kg to 38.57 mg/kg and 1.41 mg/kg,respectively.While the contents of Cu,Zn,Ni,Pb,Cd,and Cr in the blank group were only transfered by 1.49%,0.79%,8.31%,5.23%,6.64%,and 1.25%,respectively.Although the transfer effect of heavy metals in the GF group was significantly better than that of other test groups,the overall effect of the test on the transfer of heavy metals was not satisfactory.(7)Microbial community structure analysis of sediment showed that immobilized microorganisms in the loaded carrier significantly increase the richness and diversity of the microbial communities in the sediment.Moreover,the changes of microbial community in sediment are consistent with the change of indicators in sediment and overlying water.(8)The results of laboratory tests show that the cured photosynthetic bacteria of zeolite(GF group)has the best repair effect on contaminated sediment and overlying water.(9)Immobilized Microorganisms were used to carry out application test of in situ remediation of black odorous water and sediment.The cured photosynthetic bacteria of zeolite(once every 7 days)was evenly thrown into the sediment of the test river for a period of 5 months at a strength of 0.5 kg/m2.After 5 months,the concentrations of CODcr,NH3-N,TN and TP of the overlying water decreased from 90.11 mg/L,16.43 mg/L,30.59 mg/L,2.53 mg/L to 38.29 mg/L,1.05 mg/L,1.48 mg/L,0.33 mg/L,respectively.And their rates were 60.04%,93.61%,95.16%,86.96%,respectively.The sediment organic matter reduced from 95.34 g/kg to 69.41 g/kg.G value of sediment increased from the initial 0.57 × 10-3 kg/(kg · h)to 1.91 × 10-3 kg/(kg · h).The water quality improvement effect is obvious,but the transfer of heavy metals in the sediment is not effective.