The “UNOX” system—Oxygen aeration in the activated sludge process

Abstract

AbstractThe UNOX System has been developed to improve upon the conventional activated sludge process. The use of enriched oxygen in a simple and economical multistage gas liquid contacting device allows oxygen to be transferred to wastewater at increased rates with significant decreases in power requirements over those required when using air as the oxygen supply media. The elimination of the mass transfer restriction allows operation at solids levels of 4500–7000 mg/l while maintaining a dissolved oxygen level of 8–10 mg/l in the mixed liquor. Retention times for the process can be correspondingly decreased to 1–2 hr. A highly flocculant sludge is obtained which has excellent settling and dewatering characteristics and is produced in less quantities than normally produced by a conventional air activated sludge process. The process has been demonstrated in a 2.5 mgd activated sludge plant at Batavia, New York. During the Federal Water Quality Administration (FWQA) contract the UNOX process was able to demonstrate consistent BOD and suspended solids removals in excess of 90%. A number of pilot plant programs in municipal waste applications are continuing to verify and confirm the excellent treatment effectiveness and decreased power requirements achieved with the system. Field tests are also being conducted on the treatment of industrial wastes. A pilot plant program is successfully underway treating a mixed petrochemical waste in one of the Union Carbide large petrochemical plants. Plans are being made to pilot plant the UNOX System on a pulp and paper mill waste stream during 1971.