Non-polluting Restaurants in Hong Kong  

Project Title: Non-polluting Restaurants in Hong Kong

Applicant: The Hong Kong University of Science and Technology

Total Approved Grant: $120,000

Duration: 11/97 to 30/04/99

Project Status/Remarks: Completed

Scope: To help restaurants in Hong Kong to clean up the oily, greasy, polluting wastewater with a simple, compact and economical method of wastewater before discharging into the public sewer.

Summary of the Findings/Outcomes:
The objective of this project is to help restaurants in Hong Kong to clean up the oily, greasy, polluting wastewater with a simple, compact and economical method of treatment before discharging into the public sewer. The technology proposed is an efficient electrocoagulation unit consisting of a wastewater container, aluminium electroplates and a safe direct current (DC) power supply. Characterization of the waste contents in the restaurant wastewater shows that oil and grease contents are, as expected, the major pollutants that need to be removed. COD is sometimes a problem depending on the type of restaurants and time of service. A novel unit with the combination of electrocoagulation and separation of sludge is designed and the operational mechanism has been investigated. Electrocoagulation can remove over 95% of oil and grease with the treated wastewater meets all the standards for foul sewer discharge. The fluctuation of flow-rates does not cause significant changes in the performance of the pollutant removal. Electro charge loading was found to be the major influencing factor with its optimal value varying for different restaurants in the range of 4-10 Faradays/m3 wastewater. The consumption of electricity is normally at 1.5 KWH/m3 wastewater. The experiments conducted in a small bench system can be easily scaled up by increasing the electro plates areas.