Removal Of Manganese From Surface Water By Sodium Hypochlorite Pre-oxidation Using Modified Filter Material

In recent years,seasonal manganese pollution of surface water sources has led to excessive manganese in water from water works,which has attracted much attention.How to regulate conventional processes to quickly deal with manganese pollutants in surface water has become a research hotspot in the current drinking water industry.Therefore,this topic targeted to investigate the influence of different filter material,combination form,particle size and other factors on manganese removal efficiency,to explore the sodium hypochlorite pre-oxidation coupling modified zeolite single-layer filter filter and modified zeolite/natural quartz sand double-layer filter filter efficiency and optimization path,Using active manganese oxide,manganese removal filter backwash water was prepared by modified quartz sand and used to actual manganese content in the iron surface water purification treatment,at the same time of the filter material surface morphology,chemical composition and microstructure characterization of element content in order to further reveal the manganese removal principle,research results can provide theory for rapid response to surface water pollution problems and technical support.Different material,composition and particle size of the filter material have significant influence on the adsorption and filtration of Mn from surface water.The adsorption of Mn²⁺by natural quartz sand,modified zeolite,natural zeolite and natural manganese sand all satisfied Langmuir adsorption curve.When the initial Mn concentration is 31 mg/L and the adsorption time is 8 h,the adsorption capacity of modified zeolite is increased by about 170%and 400%,respectively,compared with that of natural zeolite and manganese sand.The modified zeolite has a certain catalytic oxidation capacity for Mn²⁺.When the influent Mn²⁺is 0.5 mg/L,the Mn penetration period of the modified zeolite is significantly longer than that of the natural zeolite,and the Mn removal rate is stable at about 75%.The smaller the particle size of the filter material is,the higher the removal efficiency of manganese is.When the particle size of the quartz sand increases from 0.5-0.6mm to 0.8-1.5mm,the removal rate of manganese decreases from 35%to 5%.Manganese sand/quartz sand（1:2）double-layer filter material is significantly better than single-layer filter material of quartz sand,and the manganese removal rate is increased to 50%.The pre-oxidation of NaClO can significantly enhance the manganese removal effect of the modified zeolite.When the NaClO dosage is 0.43 mg/L and the filter speed is 5 m/h,the manganese removal rate at the filter depth of 15 cm is up to 90%,and the manganese removal effect of the modified zeolite/natural quartz sand double-layer filter material（1:2）is basically the same as that of the modified zeolite single-layer filter material.The results show that NaClO preoxidation can greatly reduce the depth of modified zeolite filter layer needed for manganese removal.When the filtration rate increases from 5 m/h to 8 m/h,the manganese penetration period of the filter bed decreases from 40 d to 20 d,and the manganese removal rate decreases from 75%to30%.When sodium hypochlorite was used for pre-oxidation,the increase of filtration rate had little effect on the effluent manganese concentration,but the thickness of effective manganese removal filter layer increased from 15 cm to 35 cm.In the treatment of a reservoir containing iron and manganese in Hainan Province,the modified zeolite filter（filter depth of 900 mm,filter speed of 8 m/h）has a high Fe removal efficiency,but due to the influence of the complex background substances of raw water,the manganese removal efficiency is reduced compared with the laboratory test conditions.Compared with KMn O₄,the removal effect of Fe,chlorophyll A and turbidity by NaClO preoxidation was better,but the removal effect of Mn²⁺was poor.When NaClO pre-oxidation was coupled with the modified zeolite/quartz sand double-layer filter material filtration process,the removal effect of manganese could be significantly enhanced.When the NaClO dosage was 0.97 mg/L and 1.18 mg/L,respectively,the depth of the modified zeolite filter layer only needed 20cm and 10cm to realize the rapid removal of manganese.In the long run（>60 d）,the effluent manganese reached the standard stably.In addition,the use of natural quartz sand,sodium silicate and active manganese oxide,manganese removal water filter backwash water was prepared by modified quartz sand,glue on the surface of the quartz sand,part of the active manganese oxide greatly accelerating the formation of manganese quality,and the active filter film,can significantly strengthen the manganese removal efficiency of contact oxidation manganese removal by a few months to start the cycle 16 d.