Research And Design Of Acid Wastewater Treatment Process In A Chemical Plant In Henan Province

The total wastewater from nitrocellulose production in a chemical plant in Henan is 2800m3/d.The content of organic matter in wastewater is 200～300mg/L,BOD5 is 70～105mg/L,and acidity is 15～16g/L.The treated wastewater should meet the first-class discharge standard of the Integrated wastewater discharge standard(GB8978～1996),Discharge standard of water pollutants in the Haihe River Basin of HaNan and the local environmental protection standard,the effluent CODCr should be less than 40mg/L,the effluent BOD5 should be less than 10mg/L,the effluent suspended solid should be less than 10mg/L,the pH value should be 6～9.This paper mainly studies the acid waste water produced by the factory.So as to determine the treatment plan and process parameters,and complete the engineering design.These results are applied to practical projects.The results show that:Lime method is the most economical method for neutralization test of acidic wastewater.When the dosage of lime is 16.4g/L,the effluent pH after coagulation and sedimentation is higher than 6.Experimental study on COD degradation by Fenton oxidation show that the optimum process conditions are:H2O2 dosage 600mg/L,n(Fe2+):n(H2O2)=2:3,does not adjust the pH value of raw water,reaction time 60 minutes.Under this condition,the removal rate of CODCr can reach 81%.During the degradation of COD by activated carbon adsorption,when the acid wastewater filtered through granular activated carbon(filtration column length 3meters)directly,the removal rate of CODCr was 14.3%.Acid wastewater is neutralized by lime and then filtered through granular activated carbon column,the removal rate of CODCr was 14.7%.When the dosage of powdered activated carbon is 1000mg/L,the pH value of raw water is not adjusted and the reaction time is 60min,the removal rate of CODCr by powdered activated carbon adsorption is 24%.It is impossible to discharge the treated wastewater to the standard only use Fenton oxidation or activated carbon adsorption method.Adopt the method of Fenton oxidation activated carbon filtration combined or Fenton oxidation combined with powdered activated carbon adsorption To deal with organic matter,the removal rate of organic compounds in wastewater is about 84%.When the concentration of organic matter in raw water is low,the effluent can be discharged after treatment.However,when the concentration of organic matter in the raw water is high(CODcr>240mg/L),it is still impossible to guarantee the effluent reaching the standard.Therefore,it is considered to treat biochemical treatment after neutralization of acidic wastewater.When the residence time of hydrolytic acidification tank is 6 hours,the operation cycle of SBR process is 6 hours and the discharge ratio is 1/2,the final effluent CODCr can be reduced to less than 40 mg/L,which meets the discharge requirements.According to the test results and the actual situation,the "lime neutralization +biochemical treatment" treatment scheme is finally determined.The specific process is:Neutralization reaction→Coagulation sedimentation→Hydrolysis acidification→DAT—IAT→Biological aeration filtration→Ordinary fast filtration→Effluent reaches the standard.The main structures and auxiliary structures such as sludge thickener,sludge dewatering workshop,dosing room and blower room were designed,and the construction drawings of main structures were drawn.After the completion of the project,a month of commissioning has been carried out,and achieves the desired results:the effluent CODCr is below 40mg/L,pH value is 7～8.The total investment of the project is 6.2642 million yuan and the treatment cost is 8.61 RMB/t of water.The environmental and social benefits are remarkable.