Challenge

An automotive plant had a water treatment system that required further treatment of water supplied by the local municipal water treatment plant.  The raw hardness of the incoming water was 302 mg/L as CaCO₃ but the plant required softened water.  The system the plant had been using since the early 1960s had reached the end of its useful life.  The decision was to remove the old solids contact clarifier and replace it with new technology.  The new technology had to be retrofitted into the basin of the previous system and the plant required purified water during the installation process.

Solution

Siemens Water Technologies developed a solution for both concerns.  A CONTRAFAST® solids contact clarifier was retrofitted into the existing basin.  The system softens the incoming water for potable and process use, similar to the old system.  The clarified water flows through gravity filters where it is polished before use.  A portion of this water is further treated for use as boiler feedwater.  The existing sludge recirculation pumps that draw sludge from the bottom of the unit and recycle it back to the unit inlet were re-used from the previous system.  Sludge is then periodically blown down from the recirculation line and sent to a filter press for dewatering purposes. 

During the installation process, a Mobile Reverse Osmosis (RO) trailer was brought in to ensure the plant had access to purified water.  This self-contained treatment system employs multimedia, carbon, and softening pretreatment, along with reverse osmosis in a single trailer.  The system produces up to 200 GPM of low conductivity product water which was sufficient for the plant to continue its operations while the CONTRAFAST system was being installed.

Result

This system has been in place and working effectively since 2004. 

• The CONTRAFAST system produces the target hardness of 60 mg/L as CaCO₃ for the facility.
• The CONTRAFAST retrofit updated the plant’s existing facility and provided them with a technically efficient and environmentally suitable solution.
• The combination of the CONTRAFAST Clarifier system and the Mobile RO system kept the customer from losing production time while updating technology. 
• The CONTRAFAST unit has the ability to operate at a hydraulic loading rate of over 6 GPM per square foot, but the current flow is around 1.2 GPM per square foot, which allows for future flow increase.