Study On The Formation Of Disinfection By-Products From Anthracite Coal And The Filtration Effect Of Alternative Filter Media

Anthracite,as a common filter material in traditional filtration process,has the advantages of low specific gravity,good contamination interception effect and relatively uniform particles.It has been used by a considerable number of Waterworks for a long time.In recent years,the research on disinfection by-products has become a hot research direction.In history,the research on chlorine disinfection by-products has increased rapidly since the 1980 s.In recent years,many scholars have paid attention to the problem of disinfection by-products in groundwater overexploitation and seawater backfilling areas.However,the phenomenon that anthracite filter reacts with free residual chlorine to produce disinfection by-products has not attracted attention.The purpose of this study is to explore the regularity of disinfection by-products produced by the reaction of free residual chlorine with anthracite under different conditions,and to explore the turbidity removal effect and the growth law of filtration head loss of a light silica filter material used to replace anthracite filter material.This study is of great significance to reduce the concentration of disinfection byproducts in water plant effluent.Anthracite as filter material reacts with free residual chlorine to produce disinfection by-products,which is a very obvious and fatal disadvantage.This study has a strong guiding significance for the selection of filter material in water plant.The detection method of disinfection by-products in the study was liquid-liquid extraction gas chromatography.Firstly,the production and variation of 24 disinfection by-products under different pH,different concentration of free residual chlorine,different quality of anthracite,different reaction time,different soaking time and different backwashing times were determined.Then,the consumption of free residual chlorine under different pH,different quality of anthracite and different reaction time was analyzed.It was found that with the increase of pH from 5 to 10,the production of trichloro methane increased from 8 ?g/L to 21 ?g/L;with the increase of concentration from 0.2 mg/L to 6 mg/L,the production of most disinfection by-products remained unchanged;with the increase of anthracite quality from 0.001 g to 2 g,the production of disinfection by-products decreased significantly and stabilized after the quality of anthracite reached 0.1 g;and with the increase of reaction time from 5 min to 120 h.The production of disinfection by-products increased,and the production of trichloro acetic acid increased from 0.04 ?g/L to 8 ?g/L;with the soaking time increased from 5 min to 120 h,the production of disinfection byproducts decreased significantly,and the production tended to be stable after soaking time reached 12 h;with the increase of backwashing times from 1 to 10,the production of disinfection by-products decreased slightly,and the output reached 5 times after backwashing.It tends to be stable.The production of disinfection by-products was not significantly related to the consumption of free residual chlorine.The physical and chemical properties of filter media were investigated.The stacking density,solid density,porosity and screening curves of light silica filter media,anthracite filter media,quartz sand filter media and garnet filter media were measured.The filter media were characterized by scanning electron microscopy,transmission electron microscopy,Fourier transform infrared spectroscopy,Zeta potential measurement and specific surface integral analysis.The advantages of light silicon filter material are rough and porous surface,low Zeta potential and high specific surface area.A pilot-scale filtration experiment was carried out with a 120 mm inner diameter and 2 m high PMMA filter column.It was found that the removal effect of light silica filter material on turbidity of influent was slightly better than that of anthracite filter material.The rejection of impurities at 30 cm thickness of filter bed was about 1.1 times that of anthracite filter material.Under the same structure of filter bed,the growth rate of head loss of three-layer filter material system with top layer of light silica filter material in 12 hours was higher than that of anthracite filter material.83.87% of the three-layer system of bituminous coal filter material.