The ICI Olefines plant at Botany, New South Wales, produces hydrocarbons that are primarily used in the manufacture of plastics. The plant was designed by a German company and was commissioned in 1982. The production capacity of the plant is 250,000 tonnes per annum of ethylene.
In the initial design of the plant the wastewater was treated, analysed and directed to the sewer.
Cleaner production initiatives
Motivated by the need to meet increasingly stringent wastewater quality requirements for discharge to the sewer, Olefines' personnel implemented a program of continuous improvement in wastewater quality. This program included:
- recycling wastewater for use in the plant;
- changing operating procedures; and
- reclaiming hydrocarbons into the production process.
In addition to these measures, an effluent stripping column was commissioned in February 1995 as a key part of its effluent improvement strategy.
Advantages of the process
The cost of waste management on the Olefines site has been dramatically reduced by the implementation of the three measures. Based on 1994 costs, the cost of waste (including value of water, value of chemicals in wastewater and the cost of disposal) fell from $2.77 million per annum in 1985 to $325,000 per annum in 1995, a reduction of $2.4 million per annum.
Additionally, the new effluent stripping column has dramatically improved the performance and control of the plant's effluent treatment system. By removing approximately 95 % of petroleum hydrocarbons from one of the plant's major sources of effluent, it has significantly reduced the overall concentration and mass of hydrocarbons going to the sewer. As a result, the plant easily complies with the latest 95 percentile limit (30 mg per litre) set by the Sydney Water Corporation.
The petroleum hydrocarbons concentration has also been reduced by approximately a factor of 10. Long-term environmental compliance will now be achieved without the need for a wastewater treatment plant, which would cost about $4 million to build and $180,000 in operating expenditure.
Cleaner production incentives
The company was faced with having to make a substantial new investment in order to meet the increasingly stringent wastewater quality standards. This could have meant an increase in both operating and capital costs, adding to an already expensive part of the company’s operation. The clear incentive was to both reduce current costs and avoid future expense.