Study On The Nitrification Performance Of Biological Activated Carbon Packed Reactor

Two-step salinity gradient treatment was adopted to cultivate the nitrification of the saline biofilter, using granular activated carbon as the filter. HRT (Hydraulic Retention Time, HRT), ammonia loading and COD/TAN were changed to investigate the influence on nitrification performance. The results demonstrated: 25²7℃, 73 days would be spent to cultivate the nitrification of the saline biofilter. It needed 28 days to cultivate the nitrification of the freshwater biofilter. The treatments of freshwater to salinity 15 and salinity 15 to salinity 30 were taken 19 days and 26 days, respectively. The biomass was up to 10¹⁰E.coli/g^-BAC in BAC reactor under experimental conditions. When the influent ammonia was 2 mg.L^-1, the optimal HRT was 1.0h, and the removal rate reached 84.98%, meanwhile, the OUR (Oxygen Uptake Rate, OUR) of ammonia oxidizing bacteria and nitrate bacteria were 2.091 and 1.948 mgO₂ / (g^-BAC.h ) , respectively. The ammonia removal efficiency reduced with the increase of influent ammonia loading, when the HRT was 1.0h. The ammonia removal efficiency decreased from 84.98% to 41.68% and the OUR of ammonia oxidizing bacteria decreased from 2.091 to 0.625 mgO₂ / (g^-BAC.h), when the influent ammonia loading changed from 0.12 to 0.48 g^-N/(kg^-BAC.d). With the increase of COD_Mn/TAN, the ammonia removal rate decreased, however, the COD_Mn removal efficiency increased. When COD_Mn/TAN changed from 1 to 8, ammonia removal rate decreased from 84.98% to 53.64%, but COD_Mn removal rate increased from 40.86% to 93.59%. The OUR of heterotrophic bacteria increased with the rise of COD_Mn/TAN and was up to 0.914 mgO₂ / (g^-BAC.h). Although, the application of BAC in salinity water treatment is still less, as a physical, chemical and biological treatment, with its increasing of technology and practical level, it will have broad prospects in salinity water treatment. The study provided a theoretical basis for biological filter design and optimization.After the determination of single influencing factor, Response Surface Methodology was used to investigate the effect of HRT, influent ammonia concentration, COD and their interaction of ammonia removal rate within the BAC-packed biofilter. The prediction model was established to forecast ammonia removal rate with the fluctuations of water quality. It provided a theoretical guidance for design and operation in aquaculture system. The results showed that: by means of RSM central composite design, the quadratic polynomial regression model of ammonia removal efficiency was built with the influencing factors of HRT, influent ammonia concentration and COD, prediction model described as: Y = 1.13+ 0.119x₁ - 0.139 x₂ - 0.0380 x₃ - 0.0378x₁² + 0.00623 x₂²+ 0.000530 x₃²+ 0.00508 x₁*x₂ -0.00029x₁*x₃+0.00247x₂*x₃Where Y is ammonia removal efficiency, X₁ is influent ammonia concentration, X₂ is hydraulic retention time, X₃ is COD. Model was good fitting degree by analysis of variance and R² was 98.9%, could analysis and predict the ammonia removal efficiency of the reactor. According to the significance test of the factor influence, ammonia removal efficiency could be greatly impacted by constant, x₂, x₃, x₂², x₃²and x₂*x₃. Standard deviation of x₁, x₁², x₁*x₂ and x₁*x₃ were larger than regression coefficient, p>0.005, so these factors had no significance. We could get the same conclusion from the contour. When influent ammonia concentration was from 0.6364 to 5mg·L^-1, COD was from 2.546 to 20mg·L^-1, ammonia removal efficiency was more than 60%. Therefore, comprehensive and complete considerations must be needed during the running of reactor.Poly Butylenes Succinate as a biodegradable polymer, could act as both carbon resource and microbial carrier. According to pre-test, mixing BAC and PBS as a filter, studied the effect of nitrification and denitrification in different proportions reactor. The results showed that: the effluent level of DOC and nitrite was low in different proportions reactor, and could achieve the requirements of aquaculture water, had no harm to aquatic animals. When BAC/PBS was 1:1, the filter had the best nitrification and denitrification, the ammonia removal efficiency was up to 84.11%, the removal efficiency of nitrate and TN were 63.1% and 63.34%, respectively. The reactor of 1:1 showed significant change with the change of ammonia loading. The removal efficiency was better, when the concentrations of ammonia and nitrate were 2mg.L^-1 and 20mg.L^-1, respectively. The test only did preliminary study on BAC/PBS reactor performance, further study should be done, such as specific conditions, the stability of reactor operation, biological characteristics of reactor and the dynamic model of nitrogen and phosphorus removal.