Optimization Of Anaerobic Treatment Process Of Citric Acid Wastewater

Anaerobic biological treatment was a method which combines wastewatertreatment and energy recovery. Citric acid industrial wastewater containes highconcentration organic and has good biodegradability, it could be treated efficiently withanaerobic biological treatment and achieve resources recovery.Citric acid industrial wastewater was treated with inter cycle reactor by Singlefactor experiment and response surface method to optimize the anaerobic treatmentprocess. Pilot scale experiment was carry out. Results were listed below.The influence of anaerobic reflux involved in the acidification, acidification time,anaerobic hydraulic retention time and COD concentration to anaerobic biologicaltreatment were studied. Anaerobic reflux involved in the acidification could improve theCOD removal rate but had a smaller effect on biogas volume. COD removal rate wasthe biggest when acidification time was3hours, but biogas yield reached highest whenthe acidification time was adjusted to4.5hours.Then we studied the influence of the anaerobic hydraulic retention time on theOperation results of anaerobic reactor. Biogas yield was the highest when the anaerobichydraulic retention time was2hours. With the extension of anaerobic hydraulicretention time the COD removal rate was increased and reached the maximum when itwas5hours.The Anaerobic treatment presses were affected by influent COD concentration. Itwas showed that the COD removal rate was the highest when influent CODconcentration was3000mg/L, and biogas yield had a peak value when it was5000mg/L.Response surface methodology was used to design and optimization the CODremoval rate and biogas yield and got the following results. The COD removal ratereach its maximum of93.31%, validation test of removal efficiency was93.23%, whenAcidification time was1.5hours, anaerobic hydraulic retention time was3.5hours, andinfluent COD concentration was2700mg/L, and the biogas yield was0.65m~3/kg CODunder this conditions.When acidification time was3.7h, anaerobic hydraulic retention time was4.2h,influent COD concentration was4000mg/L, the biogas yield reaches its top value of0.71m~3/kg COD contrast0.66m~3/kg COD in the validation test, and the COD removalrate was92.5%under this condition.The pilot-scale test was carried out in two groups, groupⅠwas to verify theresponse surface result for COD removal rate, groupⅡ for biogas yield, both of them were conducted normally for45days with pH7.1of the anaerobic effluent. Both twogroups had a higher COD removal rate than the present technology and groupⅠ was0.64%higher than groupⅡ. The biogas yield of the groupⅠ was0.04m~3/kg higherthan groupⅡ. Granular sludge of both groups had good settling performance of72m/hand a specific methanogenic activity of0.83and0.81g COD/(gVSS d),respectively.