| Along with the more and more strict demand on the country's emissions targets of wastewater, the effects of ammonia on water resources began to enter people's line of sight.Biological aerated filter is a new type of biological membrane reactor with the removal of nitrogen, which has been in the process of treating ammonia nitrogen wastewater, but most of the research is based on inorganic filler.This experiment mainly studied the treatment of ammonia nitrogen wastewater by the walnut shell-ceramsite aerated biological filter. The influence factors and dynamics of ammonia adsorption by walnuts shell, the start-up of walnut shell, ceramsite, walnut shell-ceramsite combined packing biological aerated filter, optimization of the operation parameters of the reactor,the biochemical characteristics and the filter view along the reactor and the change of biophase were studied.The result indicated:1. The result of the study on the adsorption by walnuts shell showed the optimal pH was 8.5. Through calculating the adsorption kinetics parameters, the adsorption process of ammonia nitrogen was in line with Langmuir model and in accord with the second-order kinetics equation. When the temperature was 285K, 300K,310K, the maximum adsorption capacity could reach 0.58,0.6 and 0.45 g/kg, respectively. As the growing of the Na+ concentration, the ammonia nitrogen adsorption capacity of the walnut shell continued to decline, meanwhile the Cr3+ concentration have no obvious impacts.2. The BAF start-up experiment results showed that three kinds of fillers could be started successfully. The biofilm formation cycle of the walnut shell, ceramic, composite filler BAF were 18d,14d,17d, respectively. The final CODCr removal rate of were stable at 93.25%,80%,94.03%. The final NH4+ -N removal rate of were stable at 73%,54%,65%. The trends of NO3--N and NO2--N showed that three kinds of filler reactor presented nitrification and denitrification. The change of pH, DO could reflect the degree of nitrification. Sufficient oxygen and alkaline is the necessary condition for the success of the successful start-up. In contrast, the BAF with ceramsite as filler starte slightly faster, but another two reactors had more advantages for removal of CODcr and ammonia nitrogen.3. The optimization of technological parameters indicated the operating parameter of walnut shell and the combined BAF is that ammonia nitrogen load was 70mg/L, gas water ratio was 6:1, hydraulic loading was 0.06m3/(m2·h), another reactor is nitrogen load was 70mg/L, gas water ratio was 9:1, hydraulic loading was 0.06m3/(m2·h).Under their respective optimum operation parameters, the ammonia nitrogen removal rate is 81.62%,79.35%,71.43%, respectively.4. Study on biochemical characteristic along the BAF showed that the CODcr removel rate of the walnut shell, ceramic and composite filler BAF was 94.3%,94.2%,91.42%. And the best removal filter layer respectively was 0-30cm,0-15cm,0-15cm. The ammonia nitrogen removel rate is 86.26%, 73.43%,75%. And the best removal filter layer (from bottom to top) respectively was 30-45cm,15-30cm,15-30cm. The change of pH verified the law of ammonia removal.5. The the biofilm quantity along the BAF showed that the determination trend of lipid-P method and MLVSS method were similar. The Maximum amount of biofilm biofilm of walnut shell and the ceramsite BAF appeared at about 30cm,45cm filter layer which respectively was 0.0615 gVSS/g (lipid-P method was16.11 nmo1P/g),0.00305gVSS/g (lipid-P method was 7.81 nmol P/g). The results of SEM images indicated that the amount of biofilm was decreased along the filter height.And the walnut shell showed obvious holes at 0-45cm filter layer. This is because of the presence of cellulose degrading bacteria in the aerobic bacteria, so that the surface is degraded.However,the surface of the ceramic was not changed obviously.6. During the biological aerated filter operation, the appearance of vorticella and rotifers indicated that effluent quality can be kept stable. |
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