Study On Wastewater Treatment By New-Designed Biofilter

Biofilter has been applied to wastewater treatment as a secondary treatment process for many years. Compared with traditional wastewater treatment process, it runs without aeration and sludge discharge and can be easily controlled and maintained, however, low efficiency, failure to remove NH₃-N and TN and self-generated odor have limited its wide application in industrial area. Based on both advantages and disadvantanges, according to the principle of energy saving and low cost, research has been focused on the evaluation of biofilters with new stuffs and its best size, and then structure optimization of biofilter would be conducted.First, Volcanics, Bio-ceramic, Ceramic Pall Ring and Multi-faceted hollow plastic ball, all with the size of 10-15mm, are selected as stuff for four biofilters respectively. Experiments are divided into 3 phases with influent velocity of 10L/h,15 L/h and 20 L/h, separately. The results show Volcanics has big size and its surface interstice well developed, which is favor of forming biofilm and enable it to stand high volume loading. While bio-ceramic surface has no interstice, that is to say it has much smaller specific surface area than volcanics, which means it can only depend on its favorable surface harshness to form biofilm. Therefore blockage occurs frequently.Ceramic Pall ring and Multi-faceted hollow plastic ball have big interstice, which is propitious to enrich oxygen. But they tow all have small specific surface area which is unfavorable for forming and maintaining biofilm, so the removal efficiency is far lower than Volcanics and Bio-ceramic. All the four biofilters reach their own removal peak when influent velocity is between10L/h and 15 L/h. Among which the biofilter stuffed with Volcanics achieves the highest efficiency. Its removal efficiency on COD_Cr, NH₃-N, TN and TP are up to 86%, 90%, 58% and 55% respectively with concentration of effluent of 38mg/L, 3 mg/L, 24 mg/L and 2.1mg/L.In line with the conclusion from the previous phase, four types of Volcanics with different size(10-15mm, 15-20mm and 20-30mm) have been selected for the research. As the experiment results indicated, the biofilter with Volcanics of 15-20mm gained the best removal efficiency of both 85% for both COD_Cr and NH₃-N, and 45% and 58% for TN and TP respectively, with the Hydraulic Loading of 10.5-15m³/m²Â·d.To enhance the removal of TN and TP, structure optimizaiton to traditional biofilter has been conducted as following: installation of refluxing, follow-up anaerobic process with supplying Carbon sources and Sponge Iron as stuffing specially for TP removal. Meanwhile, a traditional bioflter has also been set for comparision. As the results shown, the optimized biofilter could maintain its high removal efficiency on COD_Cr and NH₃-N, while for TN and TP, the removal efficiency increased dramatically, up to about 78% and 82%.