This eastern USA chemical plant produces polyester resins and wastewater containing terephthalic acid and ethylene glycol. Like many wastewater treatment facilities, this plant has had its share of treatment challenges. 'Our waste is rapidly oxidized and tends toward filamentous growth,' said the site engineer. Poor sludge settleability was a problem too. But, it was reduced biological activity during winter that sent the company on a search to find help.
The chemical plant staff chose the AIRE-O2® aspirator aeration system 'because it represents the best compromise between agitation and aeration needs, with the least temperature loss,' said the engineer. Two x 20 hp (15 kW) units were installed in the 0.325 MG (1230.13 m 3) equalization basin for a trial. Results were so good that two additional AIRE-O2® aerators were installed in the 0.95 MG (3595.75 m 3) aerated basin.
The 0.5 MGD (1892.5 m 3) flow had an influent BOD (biological oxygen demand) of 2,500 mg/l. After the addition of the AIRE-O2® aerators, the plant now boosts a removal rate of 99 percent or 20 mg/l…even in winter. Effluent quality was improved with the warmer basin temperatures that increase biological activity. The plant was also able to increase flow rates through the treatment plant as a result. This site caught the attention of an EPA official who used it as a fine example of winter treatment performance efficiency.