Study On Pretreatment Technology Of Helional Production Wastewater

The Helional wastewater is characterized by high COD and high content offormaldehyde, its strong biological disincentives leaded to low efficiency ofbiochemical treatment directly. In this paper a study has been made on researching thiskind of wastewater of a perfumery plant. the efficient and reasonable pretreatmenttechnology was sought to improve biodegradability and make for the subsequentbiochemical treatment.The results of experiments showed as follows:(1) At the conditions of pH=9,ferrous sulfate15g/L, lime15g/L, the reaction time20min, settling time45min, theremoval rate of lime-ferrous sulfate method were COD28.88%and formaldehyde43.79%; At the conditions of pH=4, FeCl31.75g/L, PAM0.01g/L, settling time30min,the results of FeCl3coagulation were COD removal rate19.59%and formaldehyde21.38%.(2) The oxidation style of alkaline hydrogen peroxide and Fenton reagent hadsiginificant effect on the formaldehyde removal of the wastewater. When the conditionwas saturated NaOH12.5mL/L, H2O215mL/L, the reaction time5min and temperature30℃for the former method, the removal rate of COD and formaldehyde wererespectively14.55%and99.73%, the rest concentration of formaldehyde was9.93mg/L.The optimum conditions for Fenton reagent were: pH=3, the mole ratio H2O2andferrous sulfate5:1, H2O2112.5mL/L, ferrous sulfate61.25g/L, reaction60min andsedimentation time40min. Under the optimumconditions, the removal rate of COD andformaldehyde were respectively52.66%and99.40%, the rest concentration offormaldehyde was3.74mg/L.(3) There was no obvious change of COD andformaldehyde before and after reaction of micro-electrolysis treatment separately. Theeffect of subsequent processing was enhanced, an addition of H2O2can make a Fentonsystem by Fe2+that was ionized from micro-electrolysis, which had32.98%and90.07%of removal rate of COD and formaldehyde.Experiments of biochemical treatment after pretreatment of wastewater proved asfollows:(1) Both basic hydrogen peroxide and Fenton oxidation reduced the wastewaterbiological inhibition significantly, the biodegradability was greatly improved that couldmeet the requirements of biochemical treatment;(2) Although the results ofanerobic+physical chemistry experiment and anerobic+aerobic treatment had somevariance, they can meet the discharge requirements. The basic hydrogen peroxide had slightly lower effect of COD than Fenton oxidation,but the process was easy to control and operate, As pretreatment technology, there wasno need to adjust pH, actual project had also obtained satisfactory results by this method,efficiency of the biological treatment system was improved, which could fully meet theprimary wastewater discharge standard. So, basic hydrogen peroxide oxidation waschose to be the optimum pretreatment of Helional production wastewater.