Preparation Of Low Density Zeolite Composite Paddings And Its Application In Nitrogen And Phosphorus Removal

The unburned spherical low-density zeolite composite paddings4-8mm in particl size are prepared with natural zeolite as the main raw material, cement as the binder, spherical particles of polystyrene as core in the text. Based on testing the void fraction, apparent density, compression strength and other characteristics of materials in the preparation, the authors have concluded the optimal conditions of process combination in the preparation of low density composite paddings as follows. Weight proportion of zeolite:cement=75%:25%and maintenance is7-10d under normal conditions, the void fraction is47.4%, apparent density is1.23g/cm3, compression strength is61.5N, and piled density is0.647g/cm3. Scanning electron microscopy clearly shows that before the biofilm formation the surface is rough, and the interior has numerous pores, whereas after the biofilm formation, a large number of microbes exist on the surface and in the internal. The number of microbes is twice that of the calcinated ceramics.To manually configure the low concentration of ammonia nitrogen and phosphorus simulated wastewater, low-density zeolite composite paddings, build small-scale biological aerated filter test device, biofilm formation and start of the system performance in low temperature environment. The results show that:start the stage of biofilm formation in the BAF, and maintain the water quality ammonia of9.5～12mg/L, the COD of48～60mg/L, the TP of0.5～0.6mg/L, influent flow rate of2.5L/h, the hydraulic retention time of4h, hydraulic load0.5m3/m2h, gas to liquid ratio of3:1, the ambient temperature of2～15℃under the conditions of stable operation of COD, ammonia nitrogen and TP removal rates reached80%,97%and60%. Start in the stage of the reaction system NH4+-N removal by ion exchange, nitrification and denitrification in three parts composed of ion exchange reaction in the filter media height of the NH4+-N in the0-30cm,30-90cm nitrification occurs,90-150cm denitrification occurs, total inorganic nitrogen removal rate of53%; temperature drop has a certain influence on the nitrification in the system.Water quality is secondary effluent for the system by adding ammonia nitrogen and phosphorus to improve the water concentration, restart after a system outage trips and different shock loading univariate analysis and backwash study. The results show that:reboot the system outage can be restored to good treatment effect in the3d time; systems for optimum operating conditions:ammonia nitrogen of20-40mg/L, COD load in the0.8-2.4KgCOD·m-3·d-1, the hydraulic load control in the0.5-2m3/m2h, gas to liquid ratio of1:1～3:1, the ammonia nitrogen and phosphorus removal is good, removal rate reached98%and60%; need3-4h after the backwash can be restored to best to handle state. Due to the packing characteristics, system uptime, reduce the frequency of backwash, thereby reducing energy consumption, to further improve the ability to remove. Low density zeolite composite paddings in wastewater removal of nitrogen and phosphorus have a good application prospect.