title: Process control, energy recovery and cost savings in acetic acid wastewater treatment.
abstract: An anaerobic fixed bed loop (AFBL) reactor was applied for treatment of acetic acid (HAc) wastewater. Two pH process control concepts were investigated; auxostatic and chemostatic control. In the auxostatic pH control, feed pump is interrupted when pH falls below a certain pH value in the bioreactor, which results in reactor operation at maximum load. Chemostatic control assures alkaline conditions by setting a certain pH value in the influent, preventing initial reactor acidification. The AFBL reactor treated HAc wastewater at low hydraulic residence time (HRT) (10-12 h), performed at high space time loads (40-45 kg COD/m(3) d) and high space time yield (30-35 kg COD/m(3) d) to achieve high COD (Chemical Oxygen Demand) removal (80%). Material and cost savings were accomplished by utilizing the microbial potential for wastewater neutralization during anaerobic treatment along with application of favourable pH-auxostatic control. NaOH requirement for neutralization was reduced by 75% and HRT was increased up to 20 h. Energy was recovered by applying costless CO(2) contained in the biogas for neutralization of alkaline wastewater. Biogas was enriched in methane by 4 times. This actually brings in more energy profits, since biogas extra heating for CO(2) content during biogas combustion is minimized and usage of other acidifying agents is omitted.
authors.affiliation: Department of Environmental Engineering, Democritus University of Thrace, Vas. Sofias 12, 67 100 Xanthi, Greece. vaiop@env.duth.gr
authors.forename: E
authors.initials: E
authors.lastname: Vaiopoulou
authors.forename: P
authors.initials: P
authors.lastname: Melidis
authors.forename: A
authors.initials: A
authors.lastname: Aivasidis
mesh_terms: D000079:Acetaldehyde / Q000032:analysis; D019342:Acetic Acid / Q000737:chemistry*; D000693:Anaerobiosis; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors; D002245:Carbon Dioxide / Q000737:chemistry; D003246:Conservation of Energy Resources; D017046:Cost Savings; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste / Q000032:analysis; D008697:Methane / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000191:economics* / Q000379:methods*; D014871:Water Microbiology
chemical_list: D007220:Industrial Waste; D002245:Carbon Dioxide; D000079:Acetaldehyde; D008697:Methane; D019342:Acetic Acid; D010100:Oxygen