Bioremediation Of Acid Mine Drainage Using Immobilized SRB Sludge With Inner Cohesive Corncob In A Permeable Reactive Barrier

Environmental pollution contributed by acid mine drainage (AMD) is deteriorating with rapid development of coal industries in our country recent years. And it is of more importance to control and reuse AMD, to keep sustainable flourish, for those plants which are short of potable water and destroying brittle ecosystem service as exploiting coal mine. Nowadays, great progresses in the application of new technologies based on SRB have been achieved, which are used to bioremediate acid wastewater containing organic matter or heavy metals. With a lot of advantages of bioremediation, more and more concerns were paid to utilize SRB for treating AMD.In the paper, a new carbon source slowly released as hydrolyze microorganism decomposed corncob under anaerobic condition was used to maintain SRB’s metabolism. Moreover, in order to create a suitable minienvironment for SRB, scrop iron and maifan stone were also added in this immobilized gelatum. To determine optimum dosage ratios among SRB sludge, scrap iron and maifan stone, an orthogonal test was conducted which was evaluated by variance analysis. In addition, the effect of immobilized methods and cross-linking times on both activity and stability of particles fabricated within optimal condition were investigated, respectively. Then, a series of paralleled batch experiments were executed to indentify factors that influenced particles’ metabolic properties significantly, including dosage of inner cohesive corncob and polluted load in AMD, and estimate particles’capacity to treat AMD as well as resistance to manganese toxicity. Finally, tow anaerobic reactors were prepared using immobilized particles as packed medium to examine the feasibility of remediating AMD in-situ. The main results achieved show below:(1) The optimal dosage ratio to fabricate particles when polyving akohol (PVA) and H3BO3 were used as immobilization materials were as follows:SRB sludge of 30%, scrap iron of 2% and maifan stone of 3%. Significant negative correlations were observed between cross-linking time and expansion rates of the particles as well as reduction rates of sulfate. To maintain favourable stability and activity of the particle simultaneously, it is reasonable to the select cross-linking time of 4-8 hours.(2) The average rate of organic matter produced by decomposed corncob is 932mg/(L·d). with the maximum released quality of 478mgCOD per lOg particles. High activity of SRB was observed within a large range pH values, from 2 to 6. When the concentration of manganese was less than 55mg/L, the absorption behavior occurred on the particles’surface could be described by pseudo secondary dynamic model well (R2=0.995). And the absorption curve of manganese could be fitted by both Frundlich (R2=0.996) and Langmuir (R2=0.983) well, which indicated the maximum absorption quantity of 0.998mg/g.(3) The maximum rate of sulfate reduced by actived particles was 94.88mg/(L-d). Meanwhile, the reduction curve could be fitted by first order kinetics model (R2=0.962, K1=0.0997h). Manganese at higher concentration could not only decrease particles’ability to promote pH value of solution, but also inhibit the activity of immobilized microorganism directly, including SRB and hydrolyze microorganism, when it diffused into particles from aqueous solution, drived by the impetus of concentration gradient. When it occurs, an obvious decline was observed in both rates of sulfate reduced and organic matter produced.(4) There was litter distinction between up-anaerobic packed bed reactor (UAPB) and permeable reactive barrier (PRB) in neutralizing acidity of AMD. However, the values of OD600 in UAPB, a turbid effluent with a hint of beige, were higher than in PRB. In addition, the dramatically changing concentration of organic matter lowered stability to reduce sulfate in UAPB which was inclined to fluctuate as pollution load increasing. On contrast, PRB was stronger to resist the effect of changing pollution load. The concentration of organic matter was stable, 1000mg/L, and the maximum reduction rate of sulfate was 1256mg/(L-d). Based on chemical principle to form precipitate after absorprion, the removal rates of total iron and manganese were up to 99.9% and 3.74mg/(L-d), respectively, in this reactor.Above studies show that combination of corncob with mixed bacterial in the sludge was feasible to make the carbon source released slowly and pollutants removed simultaneously. This new kind PRB packed with the immobilized particle could become effective method for bioremediating AMD in-situ.