LONG-TERM EVALUATION OF FINE-PORE DIFFUSERS TO RETROFIT A PETROCHEMICAL INDUSTRY WASTEWATER PLANT

Eastman Chemical Company's Texas Eastman Division (Longview, TX) operates a 15,000 m3/day (4.0 MGD) conventional activated sludge wastewater treatment plant to biologically remove influent organics from its manufacturing wastewater stream. The present wastewater treatment facility has been in operation since May 1990. The aeration system consists of eight 8,265 M3 (2.18 MG) tanks with a side water depth of 5.5m (18 ft) operated in parallel. Oxygen from compressed atmospheric air is supplied for bacterial respiration using a fine-bubble aeration system. Initially, six of the eight aeration tanks were equipped with Brand-A fine-pore diffusers (1200 diffusers per tank) made of 30-cm-long slotted polypropylene tubes covered with plasticized polyvinyl chloride (PVC) perforated membranes. Typically, three of the five single stage centrifugal blowers (each 600 hp, rated at 17,000 standard cubic meters per hour or 10,000 SCFM) provide approximately 5950 SCMH of air per aeration tank. Between 1990 and 1993, six of the eight aeration tanks equipped with the Brand A diffusers treated 20,000 Kg/day to 27,200 Kg/day of BOD5 (Biochemical Oxygen Demand). Additional diffuser systems were installed in the two empty aeration tanks following the plant startup, and normally seven tanks are in service with one standby for emergencies.