Theme 2: Developing a Sustainable Environment
Project Title: Enhanced Separation and Sludge Refinery for Wastewater Treatment – Solving the Nexus of Pollution Control and Resource Recovery in Mega Cities
Project Coordinator: Prof. Xiao-yan Li, Department of Civil Engineering, HKU
Funding Amount: HK$35.556M
Abstract
Many forms of development erode the environment, causing serious water pollution in Hong Kong, China and many other regions of the world. Most core wastewater treatment technologies were developed about half a century ago that are no longer capable of accommodating the fast population growth, industrialization and urbanization. A city like Hong Kong discharges more than 2 million tons of municipal wastewater every day. Removal of the pollutants in wastewater treatment is not only difficult and costly (~HK$3/ton) but also produces a large amount of sludge (~1 ton dewatered sludge per 1000 ton wastewater). Disposal of the sludge, and the food waste as well, is one of the most challenging and expensive environmental problems for large cities.
On the other hand, major pollutants (organics and nutrients) in wastewater are valuable resources that should be recovered instead of being degraded or wasted with the sludge. As a mega city with over 7 million people, Hong Kong is a typical urban environment needing such technological breakthroughs for its planned wastewater treatment upgrading from the current primary level to the secondary level. In this project, novel technologies, namely Enhanced Separation and Sludge Refinery (ESSR), will be developed for advanced wastewater treatment and food waste processing. The theme-based research includes the following programs.
(a) Chemically-enhanced Membrane Filtration (CeMF) replacing the conventional primary sedimentation, together with the side-stream Acidogenic sludge and food waste Co-Fermentation (sACF), for phosphate recovery and organic hydrolysis for use in production of organic acids and bio-plastics and in nitrogen removal by denitrification;
(b) Treatment of the waste sludge by thermal Sludge Hydrolysis followed by fungal Fermentation and Refinery (SHFR) for waste minimization and production of ethanol and bio-fibres, with the subsequent recovery of ethanol and ammonia from the solution;
(c) Integration and pilot demonstration of the novel CeMF-sACF and SHFR modules for advanced wastewater treatment with improved nutrient removal, energy saving, resource recovery and sludge reduction, together with the assessment of the effluent quality and its impact on the receiving aquatic ecosystem.
The proposed technological development will fundamentally transform wastewater treatment from an end-of-the-pipe purification to a resource-mining practice. Besides the design of new treatment plants, the novel processes can also be used as add-on modules to retrofit existing treatment facilities, achieving more sustainable water pollution control, resource recovery and sludge minimization for Hong Kong, China and elsewhere.
Objectives
(a) To develop a new wastewater treatment process aiming for effective and energy-saving treatment, sufficient nutrient removal and high-quality effluent;
(b) To create the capabilities of recovering resources and energy from municipal wastewater, achieving sludge minimization together with the production of value-added products; and
(c) To present an advanced urban water pollution control system with a sound integration of wastewater treatment, resource recovery and minimization of sludge and food wastes.
Deliverables
(a) Development of an innovative chemical-biological process, namely Chemically-enhanced Membrane Filtration (CeMF) by ceramic membranes with side-stream Acidogenic sludge & food waste Co-Fermentation (sACF), that can greatly advance wastewater treatment to fulfil the demands of high nutrient removal, small footprint, energy-saving, and phosphate and organic recovery;
(b) Development of a novel sludge treatment system, namely thermally-enhanced Sludge Hydrolysis followed by fungal Fermentation and Refinery (SHFR), that can greatly reduce the waste sludge and recover energy and resources for valuable products, including ethanol, organic acids, bio-plastics, phosphorus, ammonia and bio-fibrous materials; and
(c) Pilot trials and demonstration of the novel CeMF-sACF and SHFR scheme for both new and existing wastewater treatment systems, together with the assessment of the effluent quality and system performance, in particular the ecological impact of the effluent from the proposed treatment system.
Project team members (left to right): Dr. Kaimin SHIH, Prof. X.Y. LI, Prof. Tong ZHANG and Dr. May CHUI
Investigators are checking the materials (P-fertilizer and hyphae-fibre) recovered from the wastewater and sludge.