The Dorf Design division of Email Kitchen and Bathroom Products Pty Ltd specialises in the production of tapware and bathroom accessories. The majority of tapware is produced on-site from brass and is then given a range of surface treatments to provide the desired finish.
Dorf Design operates two electroplating lines, namely a metal plating line and an acrylonitrile butadiene styrene (ABS) plastic plating line. In both processes a coating of copper is plated onto the workpiece, followed by a coating of bright nickel. A final surface coating of chrome, gold or black nickel is then applied, depending on the particular product range. Approximately 12 million individual components are plated per annum, with approximately 60 per cent being metal components and the remaining 40 per cent being ABS.
Three separate waste water streams are generated by the electroplating operations, namely acid, alkali and chrome. The chrome stream is treated with sodium metabisulphite to reduce chrome VI to the less toxic chrome III, while the acid and alkali streams are neutralised. The three streams are then combined, final pH adjustment made and metal hydroxide sludge settled out. A number of problems were being experienced with the effluent treatment plant, due to constraints on expansion from a lack of available space, ie:
- a high hydraulic flow rate, causing flooding of the final treatment tank and carryover of metal hydroxides to the sewer;
- a perceived difficulty in meeting new chromium trade waste limits being proposed by the sewerage authority; and
- the mass discharge of nickel was approaching the statutory limit.