| Treatment of wastewater containing fluoride has always been an important issue in the field of environmental protection.At the level of national policies and standards,our country put forward higher requirement for the allowable discharge concentration of fluoride in sewage treatment plants.November 4,2015,the Ministry of Ecology and Environmental of the People’s Republic of China issued the"Emission Standards for Pollutants from Urban Wastewater Treatment Plants"（draft for comments）to revise the fluoride emission concentration from 10mg/L to less than 1.5mg/L.The fluoride concentration in the influent water of the Chengdu"HZ"wastewater treatment plant was about 1.5mg/L,was facing the risk of excessive fluoride.This topic aims at the problem of the fluoride exceeding the standard in large-scale and low fluoride concentration municipal sewage treatment plant,and strives for new treatment ideas,so as to provide emergency technical plan for"HZ"sewage treatment plant.In this paper,the non-fluorinated distilled water,the original sewage of"HZ"sewage plant and the tail water of"HZ"sewage plant were taken as the research objects,and the simulated fluorine-containing wastewater was treated by three treatment processes of"chemical precipitation,coagulation sedimentation,and adsorption"We study the optimal defluoridation process for the pretreatment and advanced treatment stages of sewage plants,study the effect of different process section,different kinds of agents,different combination and dosage of agents,different fluoride ion concentration on fluoride removal effect of precipitation process,determine the fluoride removal process,best chemical combination and dosage,and the removal effect of sewage with different background fluoride ion concentration in the pretreatment section and advanced treatment section of the sewage plant;and study the fluoride removal characteristics and effects of different adsorbents,to screen the best adsorbents and determine the best adsorption conditions The main research conclusions were as follows:1)The method of chemical coagulation precipitation+adsorption filter or adsorption filter could reduce the concentration of 2-10mg/L fluorine-containing wastewater below the requirement of the Discharge Standard for Pollutants in Urban Wastewater Treatment Plant（draft for consultation）of 1.5mg/L.2)Chemical coagulation sedimentation method was suitable for fluoride removal at the front end of sewage treatment plant.The results showed that the combination of Ca Cl2+PAC+PAM had better fluoride removal efficiency.The recommended dosage was:Ca Cl2 40mg/L,PAC 600mg/L,PAM 3mg/L,and the cost was 0.31yuan/m3.Among them,PAC accounted for 58.1%of the total cost,and the remaining agents accounted for 41.9%of the total cost.3)Adsorption method was suitable for the end of sewage treatment plant fluoride removal,the experiment shows that:bone charcoal,hydroxyapatite,activated alumina three kinds of adsorbent fluoride removal effect was good,bone charcoal and activated alumina can be used as sewage treatment plant economic practical adsorption filter material.The optimal adsorption time of bone charcoal and activated alumina was 60min and 90min respectively.In view of Chengdu"HZ"sewage treatment plant exceeding the limit,it was proposed to add adsorption filter tank and backwashing pump house at the end of the plant.The initial investment cost was28.957 million yuan,and the single-side water input cost was 0.281 yuan. |
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