Process control, energy recovery and cost savings in acetic acid wastewater treatment

• Published in: Journal of hazardous materials Vol. 186; no. 2-3; pp. 1141 - 1146
• Main Authors: Vaiopoulou, E., Melidis, P., Aivasidis, A.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 28.02.2011; Elsevier
• Subjects: Acetaldehyde - analysis; Acetic acid; Acetic Acid - chemistry; acidification; Anaerobic fixed bed loop reactor; Anaerobic treatment; Anaerobiosis; Applied sciences; biogas; Biological and medical sciences; Biological Oxygen Demand Analysis; Bioreactors; Biotechnology; carbon dioxide; Carbon Dioxide - chemistry; Chemical engineering; chemical oxygen demand; combustion; Conservation of Energy Resources; cost effectiveness; Cost engineering; Cost Savings; energy; Energy recovery; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General purification processes; heat; Hydrogen-Ion Concentration; Industrial Waste - analysis; methane; Methane - chemistry; Methods. Procedures. Technologies; Microorganisms; Neutralization; Others; Oxygen - chemistry; pH control; Pollution; Process control; profits and margins; Reactors; sodium hydroxide; Various methods and equipments; Waste Disposal, Fluid - economics; Waste Disposal, Fluid - methods; Waste water; wastewater; Wastewater treatment; Wastewaters; Water Microbiology; Water treatment and pollution; pH control; Energy recovery; Anaerobic fixed bed loop reactor; Acetic acid; Process control; Neutralization; Methane; Carbon dioxide; Acidification; Biogas; Combustion; Pump; Waste water; Biological purification; Bioreactor; Anaerobe; Heating; Chemical oxygen demand; Water quality; pH; Waste water purification; Reactor; Fixed bed
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2010.11.115

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) (10–12h), performed at high space time loads (40–45kgCOD/m3d) and high space time yield (30–35kgCOD/m3d) 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 20h. Energy was recovered by applying costless CO2 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 CO2 content during biogas combustion is minimized and usage of other acidifying agents is omitted.