Research On Removing Phosphorus From Wastewater By Modified Particles Calcite

Phosphorus is an important element to life activities. And it is the main cause which could lead to eutrophi cation. So if we want to improve the water environment, phosphorus removal is the key. Phosphorus is mainly coming from phosphate mining. But nature reserve of phosphate is limited, so phosphorus recycling become necessary. The research summarized the study on phosphorus removal of the domestic and foreign area, used the phosphorus removal property of calcite to remove phosphorus. The purpose of calcite surface modification is improving the capability of phosphorus removal and recycling.The crystalline structure of calcite is different, and the apparent properties and phosphorus removal ability varied from different areas. The research compared the calcite form Hebei, Guangxi, Jiangxi, Hubei province, then find the calcite from Hubei province has excellent experimental effect.Using high concentration Ca2+, P solution to modify particle calcite by undertaking it in the solution,which could improve the ability of phosphorus removal of particle calcite.Ca2+, P, HCO3-have great influence to the surface modification of calcite. The effect of Ca2+, P to surface modification of calcite is bigger than HCO3-. The proportion of Ca2+,P, HCO3-have little effect on surface modification of calcite. Soak time also did not have obvious influence of calcite modification. The calcite soaking1day to4day almost had the same removal ability of phosphorus removal. Through a series experiment of using modified calcite to remove phosphorus, the research concluded the best condition of calcite surface modification. It is as follows:1、using Distilled water configurating modification water and controlling temperature at20℃;2、the initial Ca2+concentration is120mg/L; the initial P concentration is93mg/L; the initial HCO3-concentration is244mg/L;3、soaking time is2days;4、soaking the calcite with the proportion of calcite to modification water at50g:250ml.Using the modified calcite removing phosphorus in wastewater.The element of Ca2+concentration, HCO3-concentration, pH, temperature, particle size all have effect on the capacity of modification calcite to remove phosphorus. Ca2+had bigger effect on phosphorus removal than HCO3-. And higher Ca2+concentration make the calcite have a better capacity of phosphorus removal in low phosphorus concentration. The capacity of modified calcite to remove phosphorus increases with the increasing in pH and temperature, so the course of calcite to remove phosphorus is an endothermic process. The capacity of calcite to remove phosphorus increases with the decreasing in particle size, which means specific surface area is big. The existence of microbes in sewage could improve capacity of calcite to remove phosphorus. But the influence time is short. Almost after48h, the influence form microbes is not obvious.Using modified particle calcite to filter phosphorus wasterwater has some of the continuous phosphorus removal ability, but phosphorus removal capacity gradually decreased. When the phosphorus concentration, Ca2+concentration, HCO3-concentration, pH of life sewage was2.19mg/L,71.06mg/L,373.63mg/L,7.53respectively, the effect of phosphorus removal was great.9h was the best retention time,and could meet the effluent P concentration less than0.5mg/L continued operation12d. Filter bed in the process of operation, filter layer top about0to0.2m place is the efficient phosphorus removal part,and the amount of phosphorus removal of total amount to54.9%. the phosphorus removal efficiency of the modified calcite under0.2m were relatively low. The calcite efficiency in the use is low.The concentration of phosphorus of inflow has effect on the phosphorus removal, and the contact time could be longer with the phosphorus concentration of inflow sewage becoming larger to get much better effluent.