Project Title: Water Conservation through Enhanced Biological Wastewater Treatment and UV Disinfection

Applicant : The University of Hong Kong

Project Proponent : Dr. Josie Close

Total Approved Grant : $129,867.22

Duration : 1 June 2005 to 31 January 2006

Project Status/Remarks : Completed

Scope :
This project explores the biological treatment of sewage to meet the standards and criteria for irrigation purposes as well as discharge into a Marine Reserve. The study uses the existing waste treatment process at the Swire Institute of Marine Science (biological filtration plus chlorination) and compares its effectiveness with an enhanced biological treatment using aquatic plants and UV disinfection. A comparison of the process costs will be made.

Summary of the Findings/Outcomes :
The enhanced biological system plus UV disinfection (referred as the 'Bio-UV' system hereafter) successfully demonstrated that it was an effective and economical means of sewage treatment.  Compared with the existing chlorination pathway, the Bio-UV system performed comparably well in disinfection and performed even better in improving effluent quality by effective removal of suspended solids, BOD (biochemical oxygen demand), ammonia nitrogen and phosphate content from the sewage.  The whole effluent eco-toxicity test also showed that the Bio-UV system produced effluent that was less toxic to marine micro-algae, suggesting that this advanced system can generate a more environmentally friendly effluent, rather than the chlorinated effluent which is highly toxic to the micro-algae.  In addition, the operation cost of the Bio-UV system is more economical than that of the existing chlorination system at the Swire Institute of Marine Science.