Struvite Phosphorous Recovery Processconditions Influencing Factors Of Solubility Product

In nature, phosphate is a non-renewable resource. And the reserves are extremely limited.In the reality of the shortage of phosphate resources, phosphorus is also a key factor in the eutrophication of water bodies. The phosphorus removal from waste water in the form of struvite can be used to remove nitrogen and phosphorus from the waste water. And the recycled product can be used as an efficient release of phosphate fertilizer, which can be used to recycle phosphorus resources. It is commonly found in wastewater that contains a large amount of organic material, which is closely related to the efficiency of the process of reclamation. This study selected four kinds of typical existing in practical rich phosphorus wastewater organic matter (sodium alginate, bovine albumin, glucose, humic acid sodium) in the form of simulated wastewater, organic solubility product of struvite conditions and affect the efficiency of phosphorus recovery; In order to recover the nitrogen and phosphorus in the liquid in the form of guano, the optimal recovery conditions were explored. The comprehensive benefit analysis was made for the recycling of phosphorus by struvite. The results of the study are as follows:(1) The effects of different pH on the solubility of struvite were studied under different phosphorus concentration conditions. The results showed that the crystallization process was beneficial to the crystallization reaction when the pH control of the crystal process of the struvite was controlled in the range of 9.0 ～ 10.0. Using the response surface optimization method of Box - Behnken experimental design method, analysis the influence factors of struvite method of phosphorus recovery, examines the initial solution pH value, initial phosphate concentration, reaction time effect on phosphorus recovery rate. Using the box-behnken experiment design, a second triomial mathematical model was obtained, and the optimum conditions for the recovery of phosphorus and phosphorus were obtained. Initial pH = 9.5 ,stirring time 30 min, solution initial phosphorus concentration 10 mmol/L, the phosphorus recovery rate reached 96.12%.(2) Effects of different organic matter concentration on recovery of struvite from phosphorus. The results showed that: (a) there is sodium alginate, bovine albumin and sodium humate to equilibrium conditions of struvite solubility increases, is not conducive to the crystallization reaction. The presence and absence of glucose equilibrium conditions of struvite solubility product has little effect. (b) the residual phosphorus concentration increased with the increase of the concentration of the four kinds of organic compounds. Adding sodium alginate,bovine albumin and glucose concentration to 1000 mg/L, the residual phosphorus concentration were 26.23mg/L, 19.22 mg/L and 17.37mg/L; adding humic acid concentration to 200 mg/L,the residual phosphorus concentration increased to 23.44mg/L; (c) the struvite purity decreased with the increase of sodium alginate, bovine serum albumin and sodium humate concentration,glucose and smaller effect of struvite purity; (d) effects of crystals are four organic compounds.With the increase of the concentration of sodium alginate, the crystal is a short column, and the crystal length becomes shorter; with the increase of BSA concentration, crystal crystal from needle deformation is in X shape, feather shape, and eventually become three prismatic; with the increase of sodium humate concentration, crystal form into feather shape; with the increase of the concentration of glucose, crystal form change, crystal surface roughness. (e) Solution was added into the organic matter is not conducive to the coordination of struvite formation, the equilibrium conditions of struvite solubility increases,the phosphorus removal rate decreased,the supernatant residual phosphorus concentration increased, decreased struvite purity, crystal form by organic matter type and concentration of the synergistic effect of changes(3) The recovery of nitrogen and phosphorus acid fermentation of excess sludge supernatant in the form of struvite. The results showed that: the sludge in acid (pH=4) and alkali (pH=10) under the conditions of fermentation for 2 days, the best effect of nitrogen and phosphorus release. pH=4, 2 days after fermentation, the release of ammonia nitrogen and phosphorus were 59mg/L and 85mg/L,pH=10, fermentation for 2 days,ammonia nitrogen and phosphorus release of 78mg/L and 105mg/L. The phosphorus was recovered in the supernatant after acid and alkali fermentation. When n (Mg) : n (P)=1.2:1, the phosphorus recovery rate was 81% and 73%, respectively.(4) On struvite phosphorus recovery method, analyzes the social, environmental and economic aspects of the three, has a good development prospect and practical value of the struvite precipitation.This study provides a theoretical basis and reference for the engineering of phosphorus in wastewater by struvite recovery.