Phosphorus Release And Phosphorus Recovery From Rich Phosphorus Sludge In EBPR

Phosphorus is a kind of important resource which is not renewable and replaced in nature.It has important practical significance to study the recycling and utilization of phosphorus. Biological nitrogen and phosphorus removal is the main process of wastewater treatment.But there are still many problems in the treatment and utilization of phosphorus rich sludge.Phosphorus removal by crystallization has good potential for phosphorus recovery. Therefore,the optimization of sludge disintegration method is investigated aiming to achieve the efficient release of nitrogen and phosphorus in phosphorus rich sludge.And then through crystallization method the phosphorus resources after sludge disintegration are recovered.All that can achieve the purpose of phosphorus resource recycling.In conclusion,this article,based on the analysis of the basic characteristics of phosphorus rich sludge in typical enhanced biological phosphorus removal process, discussed nitrogen and phosphorus release rules of phosphorus rich sludge under different intensive treatment conditions.And the phosphorus release and phosphorus crystal reactor of phosphorus rich sludge was exploited to study the effect of its phosphorus removal and phosphorus resources recovery.Hope to provide a new reference for the research and development of new technology for phosphorus removal and phosphorus resources recovery.Firstly,the basic properties of phosphorus rich sludge produced by biological phosphorus removal process(EBPR) were investigated,mainly including A/A/O process,CAST process,and Oxidation ditch process.The disintegration effect of phosphorus rich sludge in typical process and the basic law of nitrogen and phosphorus release were studied under normal conditions(static/mixing) and physical and chemical strengthening cracking conditions(pyolysis,alkali cracking,acid cracking).And the optimum technological conditions of different sludge cracking were analyzed.At the same time,using FLUENT software to analyze the flow pattern in simulated phosphorus recovery reactor,the optimum operating mode and operating parameters were put forward.The above analytical data provide a basis for optimal design and preparation of phosphorus recovery reactor.The effects of phosphorus removal and recovery by crystallization method under different influent p H value were investigated using homemade phosphorus recovery reactor.Final crystalline products were characterized and analyzed by XRD and EDS scanning electron microscopy.The results showed that, with the increase of the standing time, the concentration of phosphorus and nitrogen in the typical EBPR process was increased.And using stirring treatment,different EBPR process has different cracking effects.When the stirring speed is 100r/min,phosphorus release from phosphorusrich sludge was better for A/A/O process and the Oxidation ditch process.For phosphorus rich sludge of CAST process,200 r/min stirring speed is more conducive to the release of phosphorus.The concentration of phosphate, total phosphorus and ammonia nitrogen in the supernatant,discharged by phosphorus rich sludge cracking, were related to the pyrolysis temperature and time.Optimum pyrolysis conditions of phosphorus rich sludge in A / A / O process, cast process and oxidation ditch process were50℃ and 8h,60℃ and 6h,40℃ and 4h,respectively. The concentration of phosphate in the supernatant under above Optimum pyrolysis conditions was 13.55 mg/L, 10.41 mg/L, 86.95 mg/L, respectively.The positive phosphate concentration, total phosphorus concentration and ammonia nitrogen concentration in the supernatant by alkaline hydrolysis treatment of phosphorus rich sludge increased with the extension of the alkaline hydrolysis time. The study found that when the p H value was 12 or 12.5, it was more favorable for the release of phosphate.In rich phosphorus sludge acid hydrolysis process, sludge disintegration effect decreased with the increase of p H.When the acid hydrolysis p H value was 3,the maximum phosphate release concentrations of A/A/O process,CAST process,and oxidation ditch process were obtained,followed by 3.87 mg/L, 10.95mg/L and 76.88 mg/L.Using the FLUENT software to analyze the flow pattern of the phosphorus recovery reactor,we found that the way that water enters from the upper part of reactor is more conducive to control current speed.And when the inlet height is 0.05 m,flow pattern in reactor is more conducive to the formation and precipitation of magnesium ammonium phosphate crystals.When the influent, the abortion ratio is 10:1,reactor internal velocity distribution was not effected.This velocity ratio can save operation costs and reduce the load operation.Based on the above, the optimal operation mode and operating parameters of the phosphorus recovery reactor were put forward.And model reactor for phosphorus recovery was designed and prepared.The water and drug inlet and the flow rate of influent and drug were controlled by creeping pump.And the experimental water was simulated phosphorus rich sludge digestion supernatant of the A/A/O, CAST and oxidation ditch three different EBPR processes.Through upper inlet,the flow rate of influent and drug was 10:1,and aging time was 0.5h.The crystallization product which extracted by the vacuum pump was characterized.On the conditions that influent phosphorus and magnesium ratio is 1:1,nitrogen and phosphorus resources were recovered through the reactor actual operation for sludge disintegration.The phosphorus recovery rate of phosphorus rich sludge digestion solution for A/A/O process,CAST process,and oxidationditch process,reached 35.47%, 11.54% and 58.79% respectively.Through the SEM,SEM-EDS and XRD,the magnesium ammonium phosphate crystals were found in the product.It was found that increasing the influent p H value could increase the phosphorus and nitrogen recovery rate of the sludge release phosphorus supernatant.When the p H value increased from 7.0 to 10.0,inlet phosphate concentrations were 40 mg / L, 60 mg / L, 80 mg / L and 100 mg / L,and n(P): n(mg): n(n) =1:1:1, the phosphorus recovery rate were raised from 4.94%, 3.72%, 9.47% and 3.73 to 39.55%, 60.21%,72.57% and 71.54%.