Study On Advanced Treatment Process Of Coking Wastewater

Coking wastewater is a kind of industrial wastewater which is difficult to be biodegraded because of its complex components,includingcyanide,phenols,polycyclic aromatic hydrocarbons and heterocyclic compounds.After the upgrading of wastewater discharge standard in coking industry,many coking enterprises urgently need to upgrade the wastewater treatment station and add advanced treatment process after the original biochemical treatment to meet the wastewater discharge requirements.In view of the unstable treatment effect of biochemical treatment process in a wastewater treatment station of a coking plant and the failure of the effluent to meet the new discharge standard,a pilot scale test was carried out to verify the treatment effect of different advanced treatment processes on biochemical effluent in a small scale,and the operation cost of advanced treatment process was carried out based on the pilot scale test data.The main conclusions are as follows:1)The characteristics of organic matter in different units of wastewater treatment station were determined.The characteristic organic pollutants in the influent of wastewater treatment station mainly include phenols,nitrogen heterocycles,ketones,alcohols,esters,alkanes and polycyclic aromatic hydrocarbons.The concentration of some phenols and nitrogen heterocyclic organics in the effluent of acidification unit decreased slightly;there were no phenols and nitrogen heterocyclic organics in the effluent of aerobic unit,and the remaining refractory organics were ketones,alcohols,esters,chain hydrocarbons and polycyclic aromatic hydrocarbons.2)A suitable combination process of advanced treatment was selected through lab-scale experimentsLab-scale experiments were carried out to study the treatment effect of different advanced treatment processes,such as coagulation,membrane filtration,Fenton oxidation,ozone oxidation and sodium hypochlorite oxidation.The"coagulation precipitation+Fenton oxidation"was determined as the appropriate combination of core advanced treatment process,and the main process parameters were preliminarily determined.3)Through pilot experiment,the parameters of the advanced treatment were optimized and the operation cost was calculatedField pilot experiment was carried out to treat the effluent of the biochemical process with"coagulation sedimentation+Fenton oxidation+sand filtration"advanced treatment process.During the operation period of 21 days,under the condition that the COD_crr of the influent water in the advanced treatment section is lower than 300mg/L,the effluent water quality can meet the first level discharge standard in Emission standard of pollutants for coking chemical industry?GB16171-2012?.The optimized process parameters are:dosing100mg/L¹20mg/L PAC,fast stirring for 2min at 160r/min,dosing 1mg/L cationic PAM and slowly stirring for 12min at 70r/min,settling for 30min;controlling the initial pH value of Fenton oxidation process at 2.8³,dosing 0.6⁰.7mL/L hydrogen peroxide and 0.7⁰.85g/L ferrous sulfate heptahydrate,reaction time 30min,adjusting the pH value to 8.5,precipitation time 30min.The unit direct operation cost of the advanced treatment section is 4.34 yuan/m³waste water?only including reagents and electricity cost?.