Research On Nitrogen Removal And Phosophorus Recovery Of Urban Sewage Treatment Plant Secondery Effulent By Ion Exchange

Excessive nitrogen and phosphorus discharge into natural water by secondeffluent of wastewater treatment plants will cause eutrophication of lakes, riversand reservoirs. It can cause the the deterioration of natural conditions, and damgethe health of human beings. In recent years, discharge standards of WWTPsecondary effluent is becoming increasingly rigid. At the same time, phosphorus, asa non-renewable, unrepalceable natural resource, is wasted rather than recoveredand reused in the water treatment process.Based on ion exchange technology, in this article, a dynamic ion exchangesystem was built and commercially available anion exchange resins were used toremove nitrogen and recover phosphorus in the secondary effluent of WWTP.Different anion ion exchange resins were compared and different factorsinfluencing the phosphorus removal process were studied. Optimal operatingparameters of the dynamic nitrogen and phosphorus removal system were chosen.Phosphorus recovery from regeneration wastewater was investigated.Results showed that considerable difference existed among different resins oftheir phosphorus removal performance. Gel-type resins generally had greaterphosphorus removal capacity than macro-reticular resin. When breakthroughoccurred at0.3mg/L,280and220BV reclaimed water phosphorus-free qualitywater were produced using201×7and D201resins. Both resins adsorption andexchange processes followed Freundli ch adsorption isotherm. Static experimentsshowed that, major ions in secondary effluent of WWTP, such as Cl-、NO3-andSO42-, could all negatively impacted the phosphorus removal capacity of the resins,following the impact order of NO3--N> S O42-> C l-.Nitrogen and phosphorus removal of secondary effluent of WWTP wasachieved by using201×7resin. Dynamic experiments showed nitrogen andphosphorus removal capacity of the resin decreased with higher flow rate inproduction and regeneration processes and increased with higher concentration ofNaCl regeneration solution which led to more thorough regeneration and reuses ofregeneration solution When the flow rates of water production and resinregeneration were50BV/h and15BV/h respectively, with5%NaCl as regenerationsolution,1175reclaimed water(TP<0.3mg/L, TN<10.0mg/L) were produced within17.5hours with the recycle use of regeneration solution.Regeneration wastewater contained high concentration of Cl-，SO42-，NO3andPO43-. NaCl, with purity more than95%, were recycled using evaporativecrystallization. More than92%phosphorus was recovered as calcium phosphate by adding CaCl2solution when Ca/P=1.6, pH=10.5. The product was a combination ofHAP and other calcium phosphate with nC a: nP=1.59.