Laboratory Study On Performance Of Solide Carbon Sources For Biological Denitrification In In-situ Groundwater Remediation

The pollution problem of groundwater of growing concern which as an important part of freshwater resources, particularly the nitrate pollution which has become a global environmental problems. One of groundwater remediation technologies is biological osmotic reaction wall. Due to high efficiency, convenient operation and low cost management this technology which possessed of the potentials of development has become a hot research topic. On the basis of this technology, this study researchs the problem of shortage of carbon source in the process of denitrification, and provide important theoretical basis for biological removal of groundwater nitrate reaction wall technology. The results showed:(1)This study has screened WN1, WN2 and WN16 of three highly efficient denitrification strain from activated sludge of the oxidation ditch in wastewater treatment plant. According to 16 S rDNA sequencing, the WN1 and WN16 strains were generally identified as Pseudomonas sp. and Enterobacter sp., WN2 was not identified due to lost in the process of bacterial identification. Through the three dominant strains composite inoculation tests, we found that nitrate removal capacity of them up to 95.3%, while the total nitrogen removal capacity of up to 92.4%When the initial nitrate nitrogen concentration was 137.4mg·L-1. Therefore the advantage bacterium group formed by three microbes can be used as a species of denitrification(2) This study selected sawdust and bamboo charcoal as denitrification carbon source through the static release experiment. For two kinds of carbon source, the release experiment of wood shavings, bamboo charcoal and mixture was carried out. Found sawdust and mixture which as denitrification energy material can release of high organic carbon, the emission of COD by bamboo charcoal was low, but a lot of potential.(3)In denitrification experiment, relative to sawdust, bamboo charcoal itself less release of nitrogen compounds, and can remove ammonia nitrogen and nitrate nitrogen by adsorption,the denitrification effect also was strong, but its poor denitrification in the early stage of the experiment, to obtain good nitrate nitrogen removal rate a bit long time is needed. A mixture of bamboo charcoal and wood chips use has more advantages relative to both alone. But, the effluent concentration of COD will exceed bid when nitrate concentration was low. The results, the opposite was true of wood, bamboo charcoal and mixture was an advantage. Thus, relatively sawdust, charcoal and the mixture was more advantages.(4) Three factors affecting the denitrification effects(nitrate concentration in the water, N/P values and microorganism amount) study found that microbial optimal dosing quantity was 20 mL water samples with 1 mL bacteria liquid when the value of OD600 around 0.75. When nitrate nitrogen concentration in the water below the 55mg·L-1, the effluent concentration of NO3--N was lower than the national drinking water health standards when sawdust as carbon source. When the water nitrate nitrogen concentration was less than 70mg·L-1, the effluent concentration of NO3--N was lower than the national drinking water health standards when bamboo charcoal and mixture as carbon source.When the value of N/P were 8:1, 10:1 and 12:1 the removal rate of nitrate nitrogen was higher, nitrite accumulation and phosphate concentration was low, the effluent was best.