Treatment Of Comprehensive Chemical Industrial Wastewater Using A PAC-AS Process

In this study, a PAC-AS and a traditional AS process were established to treat akind of refractory comprehensive industrial wastewater from a chemical industrialpark in Tianjin, China. According to the analysis of this wastewater, the removalperformance of the system was evaluated and the mechanism of PAC-AS effects onactivated sludge was studied. An optimized adding method of PAC was proposed.These measurements and analyses could provide economic and efficacious technicalsupport to the efficacious treatment of chemical industrial wastewater in full-scaleindustrial wastewater treatment plants.Selected PAC No.785from four different carbon materials. PAC No.785hasmedium granularity.The multipoint BET, total pore volume, average pore diameterand saturated adsorption capacity of PAC No.785were great. In order to overcome theproblem of instability in removal performance with one-time dosing PAC, anoptimized dosing method was proposed to enhance the efficiency of PAC. Bystudying about the utilization of adsorption capacity of different kinds of PACs, CODremoval and decolorization performance of the process, one of the most economicaldosing way was selected: Initial value of the dosage was10g, supplement1g everythree days. As much as to say, adding36g PAC per ton wastewater or0.036g PAC fora gram COD, supplying1g PAC every three days.The PAC-AS system under the optimization scheme of PAC has been running for70days, and the AS reactor run at the same time. The experimental results show thatthe PAC-AS process obtained higher COD removal and decolorization performancecompared with AS process under the operating conditions: the waste water averageCOD concentration of950mg/L, BOD5/COD of0.16~0.22, volume load of0.94kgCOD/m3·d, HRT of40h. The average removal efficiencies of COD of the A/Oprocess increased from20%to39%, nearly doubled respectively after PAC addition.The removal of COD by biodegradation of PAC-AS process was13%higher than thatof the AS system. Chromaticity could not be reduced in the AS process, however, thecolor removal rate of PAC-AS system maintained in60%~70%. Further studies haveproven that PAC enhanced biomass accumulation, sludge settleability and specificoxygen uptake rate inside the biological system. In PAC-AS system, the organic matter in HPO fractions preferred to be removedby PAC adsorption while the compounds in HPI and TPI-N fractions were removedmore easily by AS biodegradation. Moreover, PAC could adsorb metabolic products,this eliminated the adverse effects of metabolite accumulation on the system andpromoted the organic matter removal.The microbial community structures in the PAC-AS system and AS system weremonitored using Biolog-ECO microplates periodically during the experiment. Theresults showed that the average well color development (AWCD) in PAC-AS systemwas higher than that of AS system. The utilization of various substrates bymicroorganisms in two reactors presented no difference. Non-similarity index was farless than1. After a long-term operation, the similarity of metabolic characteristics ofmicrobial communities in two reactors was higher. This showed that microbialcommunity structures of the two system has no difference.In summary, in addition to play a role of adsorption, adding PAC into traditionalAS process also reinforcement to biodegradation. However, adding PAC will notchange the system of microbial community structure and the microbial degradationprocess of organic matter. The performance improvement by adding PAC into the ASprocess effects to improve the system environment and improve the properties ofactivated sludge, etc.