Optimization Of Denitrification Filter Process For Advanced Treatment In A Petrochemical Wastewater Treatment Plant

Denitrification filter?DNF?is a new and effective technology developed in Eurepe and the United States for deep denitrification process.After second biochemical treatment,the petrochemical wastewater is always hard to biodegrade?BOD₅/COD=0.06-0.1?,the composition is complex,and the nitrate content is high.To optimize the advanced denitrogenation process of this kind water,exploring the starting performance with different DNF fillers.Four kinds of carbon sources of sodium anhydrous acetate,glucose,residual sludge hydrolysis liquid and residual sludge acidogenic liquid are compared,to screen out the best carbon source.Optimizing the height of DNF packing layer and HRT with the best carbon source and providing technical support for the existing sewage treatment process.Started up the DNF by aerobic prefilming membrane,supplied anhydrous sodium acetate and potassium dihydrogen phosphate to provide environmental conditions for the growth of microbes.Under the condition of pH=7,30?water temperature,volumetric nitrate loading 0.60kg/?m³?d?and 1.9m/h filtration velocity,DNF filled with ceramic filter had a higher start speed than quartz sand filter.In the middle and later stage of film-forming,the filter with the ceramsite media and the quartz sand media had equal performance,reached stable state after the 13th day.The removal rates of total nitrogen reached above 95%and the COD removal rate reached 70%,which showed that film-forming was successful.Due to the better hydraulic condition and adsorption properties of the ceramsite filter material,the ceramic particles were used as DNF filler to carry out the follow-up test.When HRT=2h,C/N=4 was the best carbon source load for sodium anhydrous sodium acetate.Effluent concentrations of total nitrogen was 1.88mg/L,respectively.The figure of COD was under 38.8mg/L.Compared with the carbon source of anhydrous sodium acetate,denitrifying bacteria showed more obvious assimilation when using glucose.The best carbon source load for glucose was C/N=6.The concentration of effluent total nitrogen was about 2.00mg/L,the COD was about64.0mg/L.When using the second settling tank sludge hydrolysis liquid as carbon source,C/N=8,HRT greater than 3h could obtain better denitrification effect.C/N=8was the best carbon source load for acidogenic liquid carbon source,the HRT was needed more than 4h.By comparing and analyzing 4 kinds of carbon sources,selected the anhydrous sodium acetate as the DNF denitrifying carbon source with lower carbon source load,shorter HRT and better effluent quality,and to optimized the subsequent height of DNF filler layer and HRT.The suitable HRT could effectively improve the denitrification performance of DNF.When C/N=4,HRT=1.5h,the total nitrogen concentration in effluent was2.42mg/L,the removal rate was 92.6%,the COD concentration was 36.8mg/L,the removal rate was 76%and the nitrite was almost not detected in water samples.The denitrification effect was the best.At C/N=2 and 3.5,the total nitrogen and nitrate could not increase the removal efficiency by increasing the height of the packing layer.However,at C/N=4,the total nitrogen and nitrate degraded completely at the 70cm packing layer in the DNF along the direction of water flow.Selection of the appropriate carbon source load could effectively reduce the height of the DNF packing layer.Using sodium acetate as the DNF denitrifying carbon source,under the condition of C/N=4,HRT=1.5h,the height of the packing layer needs at least 70cm.The total nitrogen concentration in the effluent is 2.42mg/L,all meets the"urban sewage treatment plant pollutant discharge standard"?DB12/599-2015?limits,and the operating costs is 0.74 yuan/m³.