Vissershok Leachate Treatment Success Continues into 4th Year

The operation of the Visserhok Leachate Treatment Plant (a first for South Africa) has now entered its fourth successful year.

Vissershok Landfill near Cape Town receives some 2000 tonnes of the City’s municipal solid wastes and low to medium hazardous wastes every day. The decomposing wastes produce up to 80 cubic metres of highly polluted leachate per day, which since July has been treated to high standards by a state-of-the-art, on-site leachate treatment plant.

Enviros was appointed to work with local consultants Arcus Gibb, to design, construct and commission the full-scale plant. Contractors for the civil, mechanical and electrical engineering works were appointed in August 2002, and biological commissioning to take place during July 2003.

The treatment scheme adopted includes pumping of leachate from the various tipping cells, into a large lined storage lagoon, which provides buffering of flows and quality for treatment by the plant. The main aerobic biological treatment process takes place in a Sequencing Batch Reactor (SBR), which comprises a 6m deep, 16m diameter buried concrete tank, that is aerated and mixed, and automatically settled each day to provide a clarified effluent.

This effluent is then passed through a subsurface flow reed bed, containing Phragmites australis plants, which provide final polishing of water to a quality suitable for use in dust suppression on the roads – replacing potable water previously used for this purpose.

The whole treatment process is controlled automatically by a PLC system, including all operations of the plant, and maintenance of optimum pH-values for treatment. The part-time plant operator is able to programme the PLC, and interrogate all operations of the plant, using a Software Control and Data Acquisition (SCADA) system, on a desktop computer.