PROJECT: PROCESS CONTROL INSTRUMENTATION, INSTALLATION, AND SETUP
Online Water Quality Monitoring
In South Africa, drinking water must comply with the SANS 241 standard, which defines the minimum numerical limits and risk management requirements for safe drinking water, including the correct pH, turbidity (cloudiness or haziness), bacteria, etc. Raw water sources from dams and rivers contain solids and unwanted minerals, which have to be removed, or partially removed, in order to comply with the SANS standard.
Operations teams regularly take water samples for laboratory testing to ensure compliance. Evidence of compliance is based on these manual actions.
To assist with quality control at a municipal water plant, instruments were installed in the clearwell to measure the final pH and turbidity of the water going into the reservoir and then into the network. These instruments are connected to a PLC and logged in a trend on a 24 hour basis to ensure safe levels. In the event that the water is too acidic or alcaline, the PLC triggers an alarm to alert operators to the incorrect pH levels. The turbidity in the water must be very close to zero and an alarm is triggered when this is out of specification.
Although operations teams are still required to verify quality levels by means of taking and testing water samples, they now have an online system to monitor the levels in real time, and they can act immediately when deviation occurs.
