Paint Shop Effluent Plant – 22m3/hr Settling and Filtration Plant
Nissan South Africa is a Rosslyn, Pretoria based motor manufacturing plant. Nissan South-Africa produce among others the Nissan Duke, Almera, Micra and GT-R vehicle models. Nissan has a global footprint with its headquarters in Yokohama city and, manufacturing facilities in over 20 countries. It offers products and services to over 160 countries and areas worldwide.
The design of an Effluent Plant for the Paint Shop was needed to take the water produced from the paint-shop sump and produce water with a quality good enough to feed the Reverse Osmosis System. The required flow rate of the plant was specified at a rate of 22 m3/hour to run over an 8 hour day.
It was proposed to design a system which would provide a flowrate of 22 m3/hour to run over an 8 hour day. This system consisted of flocculent mixing columns, chemical mixing & dosing tanks, settlers, Break tanks, media filters as well as water softeners, pH correction, coagulant and anti- scalent were also added to the water. A filter press was also suggested as an option for treatment of the settler paint solids.
The Effluent plant consisted of the following:
- pH correction of the feed water
- Flocculent & Coagulant dosing.
- Media filtration
Raw water is fed at a rate of 22 m3/hour from the existing effluent sump via a submersible pump installed in the sump. The effluent water is dosed with a chemical for pH correction to raise the pH and initiate the coagulation process. The water then passes through the mixing columns in order to further advance the coagulation reaction.
Once the water exits the mixing columns, it is dosed with flocculent. This process is then followed by settling. The supernatant liquid flows off the settlers into a break tank and the precipitated floccs are removed via the de-sludge process. An option for a filter press to further process the sludge was been offered here.
Water is then pumped from the break tank through the two sets of media filters to further polish the effluent as well as reduce the COD level to within an acceptable range. The water is then passed through a water softening process, after the softening process, the water goes through pH correction. It is then sent to the second break tank, from there the water is pumped through to the existing RO pre-treatment system and where it is filtered and dosed with anti-scalent, biocide etc.