Wet Air Oxidation: A Review of Commercial Sub-Critical Hydrothermal Treatment
by Clayton B. Maugans and Claude Ellis, Siemens Water Technologies

Wet air oxidation (WAO) is a hydrothermal treatment process that has been commercialized for approximately 50 years. Over 200 industrial or municipal WAO systems have been constructed. The process is operated in a pressurized hydrothermal reactor in the sub-critical water temperature and pressure range with the system conditions usually under 320°C and 214 bar (608°F/3100 psig). This process is usually applied for the treatment of high strength wastewaters with components that are difficult or uneconomical to treat via conventional biological treatment or incineration. WAO has also been used for the treatment of municipal sludge to minimize the consumption of landfill capacity. In the majority of WAO wastewater applications, subsequent biological treatment of the WAO effluent is required. Another application of WAO includes the integration into industrial processes for insitu removal of impurities, such as in crystallization.

Improvement of Industrial Synthesis of Methyl Methacrylate Application of a Wet Air Oxidation Process
by Dario Giudici - ATOFINA; and Clayton Maugans - Siemens Water Technologies

A process in which the blow down from an ammonium sulfate crystallizer is treated in a wet air oxidation system has been developed by ATOFINA Italia and Siemens Water Technologies (formerly USFilter). The process has been installed and operated at ATOFINA Italia's methyl methacrylate production facility in Rho, Italy, and eliminates the need for off-site disposal of a crystallizer blow down stream, as well as increases ammonium sulfate recovery.

This paper discusses the MMA process and by-product generation, application of wet air oxidation to the stream, and treatment results.

The Use of Wet Oxidation and PACT® for the Treatment of Propylene Oxide/Styrene Monomer (PO/SM) Industrial Wastewaters at the Repsol PO/SM Plant in Tarragona, Spain
by Juan Pedrerol Gallego - Repsol Quimica, S.A.; Salvador Ruiz Lopez - Repsol Quimica, S.A.; Clayton B. Maugans - Siemens Water Technologies

In 1999, Repsol YPF constructed a sophisticated industrial wastewater treatment plant in Tarragona, Spain to accommodate the new 678,000 tons per year propylene oxide/styrene monomer (PO/SM) and derivatives chemical production plants. The high strength aromatic and polyol compounds in the PO/SM wastewater are unaffected by conventional biological treatment processes and a more sophisticated wastewater treatment approach was necessary.

This paper describes the wastewater treatment plant in detail, and use of the wet air oxidation and PACT systems.

Wet Air Oxidation of a Pharmaceutical Waste Stream
by David J. Best - Sterling Organics

In early 1990, ministers of the European countries on the North Sea declared that ocean disposal of industrial wastes should cease by the end of 1992. To comply with the mandate, the Sterling Organics' facility at Dudley, Northumberland, England, had to investigate treatment of a high-strength, highly colored para-aminophenol (PAP) wastewater generated in the production of the pain reliever Paracetamol.

They chose to use a wet air oxidation from Siemens Water Technologies (formerly USFilter). This paper discusses the treatment challenge, the decision to use wet air oxidation, and the treatment results.

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