Study On Phosphorus Recovery Process By Co-processing Biochemical Methods

The existing and new sewage treatment plant is the most traditional of the two biological Phosphorus removal process, this process faced with problems like expensive infrastructure, high running costs and energy consumption issues, and had the shortage that can not be simultaneously nitrogen and Phosphorus compliance. With the increasingly stringent emission standards, the process is more difficult to meet the latest standards. In addition, the Phosphorus are non-renewable resources, with the Phosphorus exhausted, the recovery of Phosphorus from urban sewage becomes more important. Thus, the Phosphorus recovery technology needs to study imminently. In this article, the removal efficiency and capacity of Phosphorus, the effectiveness and feasibility of recycling were evaluated by experiment using enhanced biological Phosphorus technology.In this study, aluminum, iron and lime was selected as Phosphorus removal agents. The removal effectiveness was assessed by chemical precipitation, respectively; with the same experiment conditions ferric chloride was most effective, the second was aluminum sulfate, and the third is calcium hydroxide. When the dosage of 250mg/L, the aluminum and iron salts for Phosphorus removal are more than 95% calcium hydroxide on the Phosphorus removal rate is also higher than 91%. From an economic point of view, with three major pharmaceutical and recycling of Phosphorus removal, Phosphorus removal were selected the most appropriate agent.Then, efforts were taken in the laboratory study to recover the Phosphorus from the Phosphorus-rich wastewater in the form of calcium phosphate, and during which, the effects of different reaction time, pH, calcium and Phosphorus ratios and temperature on the recovery of Phosphorus were also investigated. The results showed that, with the increase of reaction time, the Phosphorus recovery rate raised and reached 92.3% after 30 minutes. After that, it had no significant change. Besides, the Phosphorus recovery rate rose with the increase of pH and when the calcium hydroxide was sufficient, an excellent Phosphorus recovery rate as high as 95% could be achieved as long as the pH was adjusted to around 8.5. The Phosphorus recovery rate increased with the calcium and Phosphorus ratio under the optimal pH and finally kept still. When the calcium and Phosphorus ratio was 2.5:1, the Phosphorus recovery rate could reach 90%. Moreover, the Phosphorus recovery rate increased with temperature and went higher than 90% after 30 minutes'reaction at the temperature of 25℃.The combined biological and chemical Phosphorus removal technology and lateral-way Phosphorus recovery technology for urban sewage possessed a highly efficiency of removing CODcr, ammonia-nitrogen, and TP from sewage, with an average removal efficiency of 92.4%,93.0% and 93.9%, respectively. The pH of effluent was below 8.0. Each index of effluent reached the primary standard level A of discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002).In addition, more than 90% of phosphate rock had a grade of less than 26% in our country and the mean grade was only 17% calculated by P2O5, converted into a Phosphorus content of only 8.17%, which was the least all over the world. However, the Phosphorus content reached 16.43% and without any harmful element in the sediment collected from this study, which was suitable to serve as a raw material for the phosphate industry.It was indicated that the combined biological and chemical Phosphorus removal technology and lateral-way Phosphorus recovery technology realized an effective Phosphorus removal as well as good removal of other pollutants in municipal wastewater. Besides, it could achieve Phosphorus recovery preliminarily with the effluent met the primary standard level A of discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002), therefore the process will have a broad application prospect.