Study On Technique Of High Efficient Biochemical Treatment For Wastewater Of PTA Production

PTA (Pure Terephthalic Acid) is among the top 50 important chemicals manufacturedin the world. It is used in the production of textile fibers, polyethylene terephhalate(PET) bottles, polyester films and etc. Wastewaters are generated with high level oforganic contaminations during process of PTA production. Terephthalic acid, aceticacid, para-toluic acid and benzoic acid are the main components in these wastestreams. Those components can destroy the ecological balance in the water, and havetoxics to the fishes and microbes.The thesis paper introduced the process of PTA production, characteristics of PTAwastewater, technologies for treating this wastewater and the pathways ofbio-degradations for this wastewater.The aims to this thesis paper were studying methods of isolation, identification andcultivation to bacterium for higher efficiently treating PTA wastewater; investigatingeffects of various factors on bio-treatment rates; analyzing metabolic pathways to TAdegradation in the bacterium; devising efficient bio-reactor to treat PTA wastewater;discussing the kinetic functions of the reactor.The thesis paper analyzed the results of experiments and design, conclusions asfollow:(1) A Gram-negative Bacterium, which was able to efficiently biodegrade PTAwastewater, was isolated from activate-sludge in PTA wastewater treatmentreactors. This bacterium is able to biodegrade TA the key pollution in wastestreams of PTA production process. The TA removal rate of the bacterium is 7.11×10-4 mol/(L?h). After series bacteriology experiments, identification to thebacterium was got. The bacterium was named Pseudomonas aeruginosa.(2) The effects of concentrations of TA, NH4Cl, K2HPO4 and Growth factors ongrowth of the bacterium were investigated. The optimized medium for cultivationof the bacterium was as follow: PTA 10 /L;NH4Cl 0.5 g/L;K2HPO40.06 g/L;Growth factors 40 mL/L. The Central Response Surface Method was also used toanalyze effects of temperature and pH on growth of the bacterium that was南京工业大学硕士论文cultivated in the optimized medium. The best-cultivated conditions of thisbacterium were temperature at 36.6 ℃ and pH at 7.3.(3) Factors that affect bio-degradation on PTA wastewater were analyzed.Concentration of COD at 4000 mg/L in PTA wastewater was the best operationcondition under which P. aeruginosa is able to remove above 90 % COD in thewastewater. The surplus ions of Co2+ and Mn2+ from catalyst often degenerate theremoval-rate of bio-degradation for their destroying the structure of enzyme inbacteria. CoCl2 and MnCl2 at the concentration from 0 to 500 ppm were put intothe terephthalate solutions in experiments. The bacteria are able to degradeterephthalate efficiently if concentration of CoCl2 and MnCl2 are less 100 ppm.The method of response surface was applied in the experiments to study effects oftemperature and pH. The optimized operate-conditions of bio-degradation aretemperature at 36.8 ℃ and pH at 7.2. At a large range of temperature and pH, thisbacterium can efficiently degrade terephthalate.(4) The University of Minnesota Biocatalysis / Biodegradation Database (UM-BBD)was used to study metabolic pathways of P. aeruginosa to terephthalate.Experiment showed that pH in the wastewater was the most considerable factorthat affects the bio-degradation of terephthalate, and the experiments onmodification of pH and degradation of protocatechuate showed that pH above 9.0probably greatly abased activities of the enzyme (EC 1.14.12.15). Reasons thatcause pH upswing and effects of Fe2+ on biodegradation are also illustrated bymetabolic studies.(5) Immobile bacterium by PVA was able to solve the engineering difficulties.Although immobile bacterium lost 50 % catalysis activity, the total rate ofbio-degradation was kept by putting into more immobile bacterium. The newdevised three-phase reactor was able to efficiently treat PTA wastewater. Thereactor operation rate was at 4.5 kg/(t·d). With optimizing p...