| Surface water pollution is still serious in China,and water shortage is also a difficult problem that China needs to face.Therefore,the effluent standards of sewage treatment plants are more stringent.In the Plan of Action for Improving Urban Human Settlement Environment in Shanxi Province 2018,it is required that the three major pollutant discharge indicators of chemical oxygen demand,ammonia nitrogen and total phosphorus in some sewage treatment plants meet the V standard of surface water steadily.In Tianjin"Standard for Pollutant Discharge from Urban Sewage Treatment Plant"(DB12/599-2015),the main index of A standard reaches the level of surface water ?.Therefore,it is imperative to improve the degree of sewage treatment.After treatment,municipal wastewater will be discharged into the water body,and the main pollutants such as CODcr,ammonia nitrogen and totalphosphorus will be brought into the water body.These soluble pollutants are mainly biologically treated removal objects.Microorganisms in biological treatment process are greatly affected by environmental temperature and carbon source.Moreover,due to the limitation of microbial activity,biological wastewater treatment alone often fails to achieve the expected results.Therefore,it is particularly important to find efficient,economical and environmentally friendly treatment agents and methods that can effectively remove these pollutants at the same time.Polyaluminium chloride(PAC)is a kind of inorganic flocculant with high cost performance when coagulation precipitation is used in advanced wastewater treatment.Polyacrylamide(PAM)is widely used as coagulant aid because of its excellent water solubility,thickening,flocculation and chemical reactivity.However,with the continuous improvement of effluent standards for advanced wastewater treatment,the use of PAC-PAM alone often fails to achieve the desired results.Past studies have shown that potassium ferrate is a green and efficient water treatment agent,which has the characteristics of coexistence of oxidation and flocculation.At present,the effectiveness of potassium ferrate in sewage treatment has been confirmed.Based on this,this paper studies the effect of K2FeO4-PAC-PAM on simultaneous removal of ammonia nitrogen,total phosphorus and chemical oxygen demand in sewage,and explores the efficient solution for sewage upgrading.In this paper,three experiments were carried out to treat sewage by using PAC-PAM,K2FeO4,and K2FeO4-PAC-PAM.The factors such as dosage,dosage sequence,reaction pH and reaction time were investigated.The first-class A standard for pollutant discharge standards of urban sewage treatment plants(GB 18918-2002),that is,the initial concentrations are CODcr50mg·L.1,ammonia nitrogen 5mg·L-1 and total phosphorus 0.5mg·L-1 in the raw water CODcr,ammonia nitrogen and total phosphorus three pollutants removal rate,and the removal mechanism was studied.The main conclusions showed follows:1.When PAC-PAM treats CODcr,ammonia nitrogen and total phosphorus in wastewater,it has the effect of removing CODcr,ammonia nitrogen and total phosphorus,and the removal effect of total phosphorus is relatively good.When the dosage of PAC was 70mg·L-1,the dosage of PAM was 3mg·L-1,the flocculation pH was 8.0,and the removal rate of CODcr,ammonia nitrogen and total phosphorus was 35.07%,23.53%and 39.23%;2.When K2FeO4 is used to treat CODcr,ammonia nitrogen and total phosphorus in sewage,the effects of CODcr,ammonia nitrogen and total phosphorus are removed,and the removal effect of ammonia nitrogen is relatively good.When the dosage of potassium ferrate was 60mg·L-1,the oxidation stage pH value was 9.0,the oxidation time was 20min,the flocculation stage pH value was 8.0,and the flocculation time was 30min,the removal rates of CODcr,ammonia nitrogen and total phosphorus were 28.44%,59.46%and 50.60%;3.When K2FeO4-PAC-PAM simultaneously removes CODcr,ammonia nitrogen and total phosphorus from sewage,it can effectively increase the removal effect of CODcr,ammonia nitrogen and total phosphorus in water when added in the order of K2FeO4,PAC and PAM.When the dosage of potassium ferrate is 60 mg·L-1,the dosage of PAC is 70 mg·L-1,the dosage of PAM is 3 mg·L.1,the pH of oxidation zone is 9.0,and the oxidation time is 20 min.When the flocculation stage has a pH of 8.0 and the flocculation time is 30 min,the concentration of CODcr in the treated sewage is 22.18 mg·L-1,the ammonia nitrogen concentration is 1.90 mg·L-1,and the total phosphorus concentration is 0.09 mg·L-1.The Class A standard of the Pollutant Discharge Standard for Urban Sewage Treatment Plants(GB 18918-2002)was upgraded to the Class ? water body standard for surface water in the Surface Water Environmental Quality Standard(GB 3838-2002);4.When K2FeO4 is used to treat CODcr,ammonia nitrogen and total phosphorus in sewage,K2FeO4 plays a role in oxidation and flocculation adsorption of self-reduction products during the reaction.When K2FeO4-PAC-PAM simultaneously removes CODcr,ammonia nitrogen and total phosphorus from wastewater,potassium ferrate plays a role in oxidation,flocculation adsorption of self-reduction products and synergistic PAC-PAM flocculation.When K2FeO4-PAC-PAM simultaneously removes CODcr,ammonia nitrogen and total phosphorus from wastewater,the removal effect is best when K2FeO4,PAC and PAM are added in the order,indicating that potassium ferrate has a synergistic effect on PAC-P AM flocculation. |
PDF Full Text Request