Using an Innovative Monitoring and Control Method to Ensure Cost Effective and Reliable Scale Control for a Large Brackish Water Desalination Facility in Newark, California

The Alameda County Water District evaluated their scale control program with respect to performance and total cost of operation. Following extensive piloting testing for scale control performance and detailed cost evaluation based on the cost per 1000 gallons of water produced, a decision was made to use a highly concentrated chemical antiscalant at a very low dose rate. The challenge of using a highly active antiscalant to prevent scaling and at the same time ensure the lowest cost of operation possible is to ensure 100% accurate dosing and control of the neat (undiluted) antiscalant. Continuous on-line dose measurement and control allows the minimum amount of antiscalant to be used without the risk of under dosing and subsequent scaling.
An on-line dose measurement and control method using the phenomena of fluorescence was employed by the Newark Desalination Facility to make sure they achieved the cost benefits and
scale control performance expected. A variety of molecules adsorb light at a given frequency then quickly emit light of a different frequency. Incorporating a fluorescent marker in an antiscalant acts, in essence, like a bar code on the antiscalant molecule. The antiscalant dosage to the RO can then be determined in real time and continuously monitored and controlled on line, using a fluorescence detector. The paper details the experiences and challenges in determining and achieving the most cost effective and reliable scale control program.

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