Development Of Diatomite-based Water Treatment Agent And Its Application In Advanced Treatment Of Urban Sewage

Water is an indispensable resource for people’s daily life and production,and China’s natural water resources are very limited.The deterioration of water environment and the shortage of water resources are two major problems facing the economic and social development of C hina.Advanced sewage treatment is an important way to solve the problem of water environment deterioration and water shortage.Since the implementation of the new environmental protection law and the implementation of the treatment of black and odorous water bodies in recent years,the Ministry of Ecology and Environment has imposed stricter requirements on the quality of water discharged into surface water bodies,requiring the effluent of urban sewage treatment plants to meet the"Urban Sewage Treatment Plant Pollutant Discharge Standard"（GB18918-2002）C lass A standard,and even some cities require the water quality of C lass IV water bodies in the"Environmental Q uality Standard for Surface Water"（GB 3838-2002）.To achieve advanced treatment and resource reuse of sewage,it is necessary to develop and prepare new water treatment agents.The purpose of this article is to prepare a new type of water treatment agent by diatomite modification/combination,to explore diatomite modification and compounding schemes,and to compare the main pollution of the modified/combined diatomite water treatment agent on the removal of the secondary treatment system.The development of advanced sewage treatment water treatment agents based on diatomaceous earth applications is expected to provide a new technical route for upgrading sewage treatment plants to meet higher effluent standards.The main conclusions of this article are as follows:（1）After single factor experiment and response surface optimization experiment,the best preparation conditions of chitosan modified purified diatomite（CMPDE）are:mixing time 90min,chitosan solution concentration 1.0g/L,diatomite and chitosan The ratio of the added mass is 12:1;the best preparation conditions for fly ash modified purified diatomite（FAMPDE）and fly ash modified original diatomite（FAMODE）are:raw material ratio 5:5,The calcining temperature is 800℃,and the calcining time is90min.Under the above conditions,the removal rates of COD,NH₃-N,TN,TP,and SS in the sewage can reach 29.47%,26.39%,14.48%,54.39%,65.72%;63.39%,31.82%,23.41%,respectively.85.96%,50.66%,71.42%,30.82%,29.47%,86.73%,51.49%.（2）The SEM characterization results showed that natural diatomite contained more impurities.After purification and chitosan modification,the surface impurities decreased and the diatomite pore diameter increased;modified by fly ash after the properties,a new multi-layered structure is formed;BET characterization results show that the adsorption isotherms of original diatomite（ODE）,purified diatomite（PDE）and modified diatomite all appear type II isotherms,and there are for H3 hysteresis rings of different sizes,after purification and modification of ODE,the specific surface area,pore volume and pore d iameter are all increased to a certain extent,which is conducive to the adsorption of impurities;XRD characterization results show that the main component of diatomite is quartz.A new diffraction peak appears after the test,which may be a new p H ase;FTIR characterization results show that the peak of FAMPDE and FAMODE at 927 cm^-1 disappears,which is most likely due to the high temperature causing the Si O₂structure in the diatomite structure to be damaged.To failure,the isolated Si-OH bonds appearing at 3633cm^-1 and 3710cm^-1 may disappear with high temperature.（3）By comparing the removal rate of pollutants in sewage with different diatomite compound and different flocculants under different reaction conditions,the best reaction conditions are as follows:p H value is 7,stirring at 150r/min for 10min,shaking time for6h,standing still after measuring the concentration of COD,NH₃-N,TN,TP,and SS in the supernatant,the removal rates are as follows:when ODE is mixed with PAC at 1:11,the removal rates can reach 68.94%,34.29%,29.42%,91.37%,97.28%;when PDE is compounded with calcium aluminate according to 5:5,the removal rate can reach82.09%,39.28%,29.39%,89.55%,93.89%;when CMPDE is compounded with PAFC according to 1:11,the removal rate can reach 73.22%,61.38%,22.47%,62.18%,94.81%;when FAMPDE is mixed with calcium aluminate according to 6:4,the removal rate can reach 83.99%,72.69%,20.01%,96.20%,98.46%;FAMO DE according to 1:11The removal rate of compound PAC can reach 84.38%,73.46%,21.54%,96.79%,95.39%.Through experiments,it is found that the modified/compounded diatomite has a poor removal effect on nitrogen,but also has a good removal effect on pollutants under other compound conditions,and the effluent quality can reach the"Urban Wastewater Treatment Plant Pollutants Emission Standard"（GB18918-2002） Class A standard.