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Seamless Coagulation Control

Challenge Statement

How might we determine the required coagulant dosage in water treatment processes using new means that are faster, connected, and automatic?

Background & Current Practice

Due to fluctuating quality in the source water, the required coagulant dosage for removing suspended, colloidal and dissolved matter in the water treatment process needs to be adjusted accordingly. However, the optimum coagulant dosage is presently determined using jar testing, a laboratory procedure where the effect of varying dosages of coagulants on the coagulation and flocculation processes are tested in a series of jars under identical conditions. Jar testing is manually conducted in batches outside of the treatment process and each test takes about one to two hours to complete. As such, there is a time delay between testing and actual coagulant dosage, and this needs to be repeated whenever there are changes in the source water quality.

Opportunities Areas & Key Considerations

We are looking for solutions that can determine the optimum coagulant dosage in view of potential fluctuating source water quality in near real-time. This would allow automatic coagulation control and prevent underdosing of coagulant which will affect water quality, and overdosing which will result in wastage of chemicals and additional sludge handling. We are open to solutions that make use of the zeta potential principle.

Key Challenges
  • Scoring the jar test result requires a fair degree of skill and experience on the part of the operator and may be difficult to replicate using sensors or machines.
  • Given the time lag involved in the jar test method, the proposed solution would need to significantly reduce the time taken to measure the appropriate coagulant dose providing near real-time information of required coagulant dosage to the operator.
  • The proposed solution should also be able to correlate the information with data from the jar test to validate the system.
  • The proposed solution should be integrated into the treatment system to allow for real-time adjustment of coagulant dosages.
  • The proposed solution must support PUB’s practice of enhanced coagulation for the removal of dissolved organics in addition to colloidal particles.
Resources

After Selection

  • PUB water treatment plants as test sites
  • Jar test results from the chosen test site
Challenge Owners

Water Supply (Plants) Department

Funding

Eligible to pilot funding of up to SG$250,000

Expected Timeline for Deployment

Total project period - less than 18 months Data analysis and solution development - 9 months Testing and review of the solution - 6 months

Expected Project Outcomes

A prototype system validated at a test site within one of PUB’s facilities to be able to provide real-time continuous predictions of optimal coagulant dose with at least 85% correlation with manual coagulant dosing estimates (i.e. jar test results). The proposed solution should target a reduction of 20% in coagulation costs while maintaining water quality under fluctuating raw water quality conditions