Operating Conditions Optimization Of MAP Precipitation Recovery Device

One important cause of water eutrophication is phosphorus which is one-way loop in nature. And to control the emission of the phosphorus is an effective way of preventing the water eutrophication. At the same time, phosphorus is a kind of the valuable non-renewable resources, so recycling phosphorus from waste water is a good solution to sustainable use of resources of phosphorus. In recent years, the recycle of the phosphorus from the waste water has received more and more attention by the researchers.This project of research based on the past research results of the MAP method, to aim to develop a suit of structures of recovering MAP deposit which is simple and good performing. And I will adopt a small laboratory study of the physical model test method to study the optimization of operate and control conditions of the reactor of the recovering of the MAP precipitation. Simultaneously I will analyze the precipitation collected by MAP reactor to explore the possibility of its use as fertilizer.The main contents and results of this research are as follows:(1) According to the structural design theory of wastewater treatment reactor and design method of physical model experiments, I designed and made a recovering device of MAP precipitation on a scale of laboratory. From making use of this device, orthogonal tests and single factor optimizing tests of the simulate waste water has been made to study the performance of recovering MAP precipitation affected by operate and control way of pH, amount of aeration, HRT and n(Mg):n(P).And results of the tests show that the size of the affection performance of selected four factors to the simulate waste water of n(N):n(P)=20:l and the concentration of P is 60mg/L are listed as pH, n(Mg):n(P),HRT and amount of aeration. And the optimum combination of the process is pH=9.8, n(Mg):n(P)=1.4:1, HRT=70min and amount of aeration is 1.2L/min. Under optimal conditions, the recovery rate of phosphorus and precipitation stabilized to 95% and 65% separately made by this device to treat the simulate waste water.(2) Application of the actual wastewater containing nitrogen and phosphorus to investigate the efficiency of recovery of precipitation of this MAP recovering device and to study the affection of the value of SS, pH and the amount of aeration to the efficiency of the removal of the phosphorus and nitrogen and the performance of the recovery of MAP precipitation. It was found that the value of the raw water SS has a great impact on the treatment effect and so before the experiment the raw water should be done a stable and sink treatment to reduce the value of the SS. When the pH is 9.5-10.1 and the amount of aeration is 1.2L/min, this plant has a best performance of treating the sludge dewatering supernatant. Under the optimum conditions of the process, the plant can run in stable and the rate of removal of phosphorus is about 97%, the rate of removal of the Ammonia-Nitrogen is about 16% and the recovery rate of precipitation is about 71%.(3) Analysis of major components and features of sediment. Thermo gravimetric analysis and Chemical analysis have been used to determine the contents of N, P, Mg in the precipitation. The results show that the major components of sediment is MgNH4PO4·6H2O. Experiment also has investigated the physical and chemical properties of sediments and confirmed that the water absorbent of sediments are poor and the sediments is hard to agglomerate. So the sediment just requires a simple process to be the fertilizer and it would be convenient of storing.