Study On Denitriifcatiun Of Groundwater With Solid Carbon Source And Mineral Filler

Nitrate nitrogen becomes the most popular pollution factor in the groundwaterworldwide, and the pollution level has been increasing year by year. To this end, thereaches on technologies of nitrate nitrogen removal has become the research hot spotboth at home and abroad. Bioremediation technology is the best method which hadalready been put into practical. In the traditional heterotrophic denitrificationprocess,usually use soluble carbon as carbon source. This method still exists somedisadvantages, such as high cost, and the amount of carbon source is difficult tocontrol. In order to explore one efficient, secure and cheap carbon source,we usedbagasse and sawdust as carbon source. Use solid carbon source as biologicalmembrane carrier in the experiment, with the decomposition and consumption ofcarbon, the stability of the biological membranes will be affected. In view of this, inaddition to solid carbon,we also added volcano rock as carrier of biologicalmembrane.Most of the denitrifying bacteria belongs to the medium temperature bacterium,the most appropriate growth temperature were between25℃and40℃.Therefore,this experiment studied the removal effect of nitrate nitrogen at room temperature.The results showed that: at room temperature, use volcano rock as carrier and sawdustas carbon source, nitrates can be effectively removed and no significant accumulationof nitrates. The average removal rate was95.3%. But during the early stage of theexperiment, the concentration of COD and ammonia nitrogen were relatively high. Aswe know, the temperature of the underground water is14~18℃, the temperature ofon the ground water is also very low in winter and spring,to meet the need ofremediation of contaminated groundwater, it’s necessary to study bioremediationtechnology under low temperature. We studied the removal effect of nitrate nitrogenat14±1℃. The results showed that: at14±1℃, the average removal rate of nitratenitrogen was95%, but in this reaction produced high concentration of ammonia andnitrite.Taking into account the high level of ammonia and nitrite occurred in the preceding experiment, we carried out further experiment to study the effect of carbonsource and dissolved oxygen on denitrification process. We adopted controlexperiment, excluding the effect of microbial life activities and external factors, inorder to find factors influence the production of by product. Finally, we found:dissolved oxygen did not affect the nitrate nitrogen removal, but impact the amount ofbyproducts in the effluent. The reactor with high dissolved oxygen also has high levelof ammonia and nitrite nitrogen in the effluent, suggesting that the inhibitory effect ofdissolved oxygen on nitrite reductase was greater than on nitrate nitrogen reductase.At the same time, dissolved oxygen promotes the conversion of nitrate nitrogen intoammonia. However, the overall trend of Ammonia nitrogen, nitrite nitrogen dependson the changes of carbon source. We also found that the accumulation of nitritenitrogen and ammonia nitrogen is related to the carbon source types. Compared to theusage of bagasse, use sawdust as carbon source, we detected higher level of nitritenitrogen, but lower level of ammonia in the effluent. Wheather to use bagasse orsawdust as the carbon source, the PH of the effluent were reduced(both between7and8), but the effluent pH dropped even more sharply when used bagasse as carbonsource.