Accurate and Reliable Non-Contacting Open Channel Flow Measurement for Sewage Treatment Works in Hong Kong.

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The Sai Kung Sewage Treatment Works in Hong Kong is a secondary sewage treatment works that supplies sewage treatment services to a population of 20,000 in the Sai Jung District. The plant includes two primary sedimentation tanks, two aeration tanks, two final settlement tanks, an ultra-violet disinfection system, and sludge treatment facilities.

Engineers at the treatment works were having issues with a low flow velocity of 0.05-0.1 m/s in their UV channel. Accurately knowing the amount of water that is flowing is crucial in this stage of the treatment process as it helps control the UV intensity on the effluent flow over the exit flumes.

The end-user approached CHI Instrumentation, a Pulsar Measurement partner in Hong Kong, for help. After reviewing the application, engineers at CHI Instrumentation decided that a non-contacting flow solution would be best. A non-contacting open channel flow solution does not come into contact with the measurement medium, therefore cannot contaminate already treated water, and does not require maintenance due to wear and tear. Additionally, there were no system shutdown costs or complications as the sensors are installed above the measurement medium.

dBMACH3, MicroFlow, & FlowCERT

CHI Instrumentation suggested Pulsar Measurement’s dBMACH3, MicroFlow, and the FlowCERT system. This system is a complete non-contacting, area-velocity solution. The dBMACH3 measures the level of the channel, and the MicroFlow measures the surface velocity of the flowing liquid. Both readings return to the FlowCERT controller, which performs a calculation to supply a localized reading of flow.

To get the right results, CHI Instrumentation conducted a trial at the treatment works to make sure that everything was working as it should be. Because of the success of the trial, the end-user bought a system and had it installed.

First Class Support

To get the desired result, engineers at CHI Instrumentation worked to fine-tune the MicroFlow velocity sensor with Pulsar Measurement’s PC Suite software and got the end-user a more accurate flow reading of 0.07 m/s in their UV Channel. CHI Instrumentation left the customer extremely happy with the results, who are now considering adding more open channel flow solutions around the site.