Author(s): Mable Lam; S. K. Wong; Harry Lee

Linked Author(s): Harry Lee

Keywords: Grey Water; Membrane Bioreactor; Water Reclamation & Reuse; Total Water Management

Abstract: Grey water recycling is one of the sustainable, alternative water sources explored under the Total Water Management Strategy promulgated by the Water Supplies Department (WSD) of the Government of the Hong Kong Special Administrative Region (the Government). Being unsusceptible to climate change, the use of recycled grey water aims to enhance water security by recycling grey water from showers/bathtubs, wash basins, washing machines and kitchen sinks, etc. (but excluding discharge from toilet bowls) which could be collected, treated and redistributed for toilet flushing and other non-potable purposes. The Government has identified the opportunity for implementing a grey water recycling system at a district-scale in a new development at the former Anderson Road Quarry (ARQ) site. The ARQ site is located at an altitude above +180mPD in the urban area of Kwun Tong, Kowloon East of Hong Kong and has been planned for residential, commercial and institutional developments with a target population of 30,000. As the ARQ site is located inland and at a relatively high altitude, the conventional approach of using either fresh water or seawater for toilet flushing would require significant amount of pumping energy which is undesirable from economic and environmental points of view. Besides, utilisation of grey water would reduce the sewage to be disposed of in the development, thus cutting down the capacity requirement of the relevant sewerage and sewage treatment facilities. The key components of this district-scale grey water recycling system include a dedicated grey water collection network for separate collection of grey water generated from the developments, a centralized grey water treatment plant with treatment capacity of 3,300 m3/day, and a service reservoir and distribution network of the treated grey water. The grey water treatment plant is designed to accept influent grey water at a wide range of water quality. Its main treatment process is based on membrane bioreactor (MBR) configuration to produce high quality treated effluent. Before being distributed to customers, the treated grey water will be added with a food-grade biodegradable dye for making it visually distinguishable from potable water. Various green and sustainable design features of the grey water treatment plant will also be presented in this paper. Upon its target commissioning by 2023, the district-scale grey water recycling system will showcase and promote its multiple benefits, which include sparing precious fresh water resources, reducing sewage discharge, promoting localized water reuse and minimizing water conveyance energy and cost. Being the first district-based grey water recycling system in Hong Kong, the system is expected to set a precedent case for the water supply arrangement in future new development areas in Hong Kong.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022817

Year: 2022