Processes Selection Test On Treating Calcium-phosphorus Wastewater By Biological Treatment

Calcium-phosphorus wastewater, which is discharged wastewater recycled by calcium hydrophosphate (CaHPO₄) resulted from the wastewater mixed by acid leaching process and liming process,is high concentration of organic wastewater.The high concentration of Cl^- is about 30000 mg/L,Ca²⁺ about 15100 mg/L,and TP 418 mg/L in this wastewater. It is very difficult to treat and the cost is high.Because most of organic pollutants from gelatin manufacturing wastewater is protein, and biological method is becoming research hot spot in recent years due to its low cost and convenient.Activated sludge process and Photosynthetic bacteria (PSB) membrane process were used for treating calcium-phosphorus wastewater from gelatin production respectively in this paper.The feasibility of the two kinds of biological treatment process are researched comparatively.The characteristics in aspect of biological treatment and influencing factors are discussed.The experimental result indicates the following:(1)It has some effect to treat calcium-phosphorus wastewater by activated sludge.Aerobic treatment could be up to 88% of COD removal rate. However, COD removal rate could be reduced with activity sludge weakened. The biological activity of sludge maintained only 7 8d due to high Cl^- and accumulation of CaCO₃ during the treatment of calcium-phosphorus wastewater.In practical engineering, changing sludge is frequent and difficult to treat.While PSB membrane process has good biodegradable to treat calcium-phosphorus wastewater, PSB membrane process could achieve 85% of COD removal rate within 48 60h retention time, even above 92% in 84h. It had little influence on treating Calcium-phosphorus wastewater by PSB membrane process to high concentration of Cl^-.(2) Two methods have obvious effect on dephosphorization, especially PSB membrane process can reach 83% of TP removal rate in the first 2h, but sludge treatment can reach 64% of TP removal rate in the first 2h. So the TP removal rate was quicker by PSB membrane and the effect was prior to that of activated sludge.Two kinds of biochemical methods had little effect on denitrification.(3) The influence of Cl^- and Ca²⁺ on two biological treatment systems are different. In PSB processing system mature domesticated PSB can tolerate high concentration Cl^-(>30000mg/L) in Calcium-phosphorus wastewater.The concentration of Calcium was relatively small and CaCO₃ on the mature domesticated PSB was relatively less on the filler. So the effect of PSB membrane process is better.(4)Treating Calcium-phosphorus wastewater by PSB domesticated can not only assure COD removal, but also resolve problem of the free bacteria with easy erosion and difficult separation. PSB, as a fertilizer, can be recycled, so without disposal problem of bacteria sludge.It has certain directive significance for engineering practice of gelatin manufacturing wastewater.