A Study Of Removal Phosphorus Treatment Process On CRI

Traditional sewage land treating systems have ubiquitous problems of lower hydraulic load rates and lower wastewater treating capabilities per unit area.To solveThe problem,based on the summarization of all kinds of land treating systems,constructed rapid infiltration sewage treating system(CRI for short)was developed.During the development course,rapid infiltration land treating system and constructed wetland system were mainly used for references.By learning from their advantages and offsetting their weaknesses,the CRI system,a new wastewater treatment technique with its special characteristics was developed step by step.But study of CRI is just in the initial stage in China,and many of its aspects need to be further studied.Most people research about COD,LAS,BOD, NH3-N and so on,but there are few research about treat TP and by CRI,therefore in this paper we study CRI in detail,basing on the treatment of TP.Based on this consideration and combined the current situation in domestic and abroad, a detailed research on CRI has been condueted from lab—scale experiment to on—site experiment and finally to practical engineering.The lab—scale CRI systems have been designed to treat domestic wastewater by adopting artificial quartz and alluvial sands.The effects of operation pattern and workmanship upon the Pollutant removal effect of CRI have been studied at a higher Hydraulic Loading (HL) condition.The on—site experiment has been designed to treat polluted river water by adopting alluvial sands.The removal effeets of CRI system on CODcr, TP and the clogging situation of the System are mainly diseussed. The results show that the average removal rates for CODcr and BOD5 are80% and 85%; and for TP are quite low.Study on the clogging problem of CRI system show that the accumulating of organic suspended material in top medium of the rapid infiltration tank is the main reason for clogging.Constructed rapid infiltration system has been built in chengdu, which is running normally and stably with high outlet water quality and high capability of bearing shock load.Outlet quality indexes,such as COD,BOD,SS, NH3-N can reach the A criterion,standard I in Contaminant Emission Standard for Civil Sewage Treatment Works,and can be ensured in long-term running.However, TP can not measure up the standards.Pretreatment process is very important for the normal and stable running of the whole system,which reduces the contaminant concentration into the rapid infiltration tank,enhances the hydraulic load of the system,reduces the land area of the system, and prevents the block-up phenomenon.After technically compare,Coagulation and sedim entation process is an ideal pretreatment process,which can be the technical combination of CRI. It can effectively remove the SS in sewage and the phosphorus with Special filtration media,which offsets the weakness of lower TP removal rate of rapid infiltration.The special infiltration medium adsorption experiment by means of marble, zeolite,coke,haydite and sponge iron shows that the sponge iron adsorption quantity to phosphorus in 50mg/l KH2PO4 solution is maximum and reaches 0.47mgTP/g sponge iron.Besides,the sponge iron adsorption quantity to phosphorus in 10mg/LKH₂PO₄ solution is also maximum and reaches 0.095 mgTP/g sponge iron.Although CRI technique has a lot of advantages,as a newly developed technique, it still needs further study.Problems like running in winter,effective removal of N and P,treatment of high concentration wastewater need to be solved.It is suggested that systemic study be strengthened,techniques be consummated,outlet water quality be improved,and application extension be developed.Then it will contribute more in utilization of sewage resource and economization of water resource.