Author(s): Joseph H W Lee; Q S Qiao; David K W Choi; Henry K M Chau
Keywords: IAHR; Hydrolink; climate change; carbon reduction; wastewater treatment plant; turbulent jet mixing; chlorine disinfection; chlorine demand; energy conservation; Joseph H W Lee; Q S Qiao; David K W Choi; Henry K M Chau
Fluid mechanics can play an important role in carbon reduction in waste-water treatment plants operations.Full scale in-plant experiments in the Hong Kong Harbour Area Treatment Scheme (serving populationof 5.7 million) demonstrated that significant savings in chlorine dosage in CEPT sewage disinfection canbe achieved by optimal jet diffuser design and placement. At nominal applied chlorine dosages of 12mg/L(20 mg/L) in winter (summer) respectively, the chlorine demand can be reduced by up to 30% as comparedto the conventional dosing design. As large quantities of chlorine (300 tonnes of 10% sodium hypochloritesolution) are used every day, the reduction in chlorine dosage translates to a saving in 1.6 million kWh/yearassociated with chlorine production, and around 1200 tonnes per year in CO2 emission reduction. The relatively simple dosing reconfiguration results in significant savings in chlorine and energy, reduces harmfulimpact to the environment, and improves plant operation reliability-thus enhancing the environmentalsustainability of the city as a whole.