DEVELOPMENT OF NEW TREATMENT FACILITIES FOR WASTEWATER AT ESSO LONG ISLAND POINT TERMINAL, WESTERN PORT VICTORIA

Abstract

Occasional high loadings of ethylene glycol have caused problems for Esso in meeting an existing Environment Protection Authority (EPA) licence condition for total organic carbon (TOC) in a discharge of waste water to Western Port. The main constituent of the waste stream was crude tank water (CTW) which is mainly residual formation water that separates in oil tanks at Long Island Point terminal. Discussions and co-operation between Esso, the EPA and government laboratories has led to the development of a new water treatment process and a revised licence. The process and licence are both oriented to minimising the toxicity of the effluent, rather than to meeting traditional chemical criteria alone.

The median lethal concentration (LC30) and chemical characteristics of CTW were determined before and after modification of the effluent by a range of laboratory treatments. The test organism for toxicity was the marine gammarid amphipod Allorchestes compressa. This combination of toxicological and chemical testing showed that the toxicity of CTW to marine organisms was largely due to volatile and oxidisable components, particularly sulphide and lower aromatic hydrocarbons. This suggests that aeration was likely to be the most cost-effective treatment to achieve acceptable toxicity levels for the final effluent.

Testing of CTW passed through a pilot air stripping plant (again for toxicity and chemical content) confirmed the effectiveness of the process in reducing toxicity. A full scale plant was constructed and is operating satisfactorily. The water after treatment is led to the existing diffuser in Western Port. The volatile toxic chemicals are destroyed in an existing acid gas incinerator operating under an air discharge licence.