(From left) Professor Kaimin Shih, Professor Li Xiao-yan, Dr May Chui and Professor Zhang Tong are among the forerunners in global research in water science and technology.
In a high density, highly urbanised city like Hong Kong, wastewater treatment is of the prime importance to ensure public health. In recent years local research in the area has been stepped up, resulting in advanced technology that yields diverse benefits.
Researchers from Department of Civil Engineering of The University of Hong Kong have focused on resource recovery and sustainability of wastewater treatment, says Professor Li Xiao-yan, who has been carrying out research in the field for 20 years. In contrary to traditional treatment technology developed decades ago, Professor Li and his fellow researchers have addressed the water pollution issue from the key perspectives of environmental protection, conservation of resources, and due to the unique context of Hong Kong, safe water supply.
Generation of useful resources
“We promote recovery of resources from wastewater and sludge,” said Professor Li. “It is estimated that 15% to 20 % of food consumption end up in sewage, not utilised but discharged as pollutants; if we are able to recover them, we save the environment while saving the resources. We no longer focus on removal but on separation and recovery of materials.” His team also promotes water reclamation or wastewater reuse.
Comparing their endeavour to the conventional process of oxidation and degradation, Professor Li said his HKU team is at the forefront in global research on the recovery of materials. One recent advancement is the recovering of energy and materials from thermally hydrolysed sewage sludge. Professor Li’s team succeeded in generating fibrous materials that can be used for making papers from fungal hyphae grown through fungal fermentation
Tackling challenges of a unique city
Another HKU Civil Engineering Professor, Kaimin Shih, has developed a catalytic membrane technology which will change the whole process of water purification and wastewater treatment. He found it particularly challenging to do the research in a compact city like Hong Kong. “Compared to other renowned universities in the world, an important task we face here at HKU is to tackle the challenges of an urban environment.” It is an environment in which the wastewater generated is not the same as that generated half a century ago, containing a greater variety of chemicals than before. Many are hard to be biodegraded, or of different kinds of characteristic, which demand different kinds of physical and chemical treatment. “These chemicals may not exist in other developed cities, we are in a unique situation how they end up in the system,” Professor Shih said.
There is much room for research because of the additional challenge of a huge population in a single city. “We have to treat discharged water quickly with a small footprint, and that calls for new methods and along with that more chances of resources recovery.”
Unlike other advanced cities in the world, Hong Kong’s wastewater is treated only at the primary level at the moment. “To ensure public safety, we should do more to enhance water environment protection. We are working on upgrading it to secondary treatment through advanced technology, and exploring possibilities to enhance it to tertiary treatment.” Professor Shih said.
In other developed cities, it is not as common for people to live in high rises with the more complicated piping systems for distributing drinking water. But in Hong Kong, after being treated at treatment plants, drinking water is delivered to residential estates with a variety of piping systems, leading to a challenge of finding potential contamination sources.
At the invitation of the Water Supplies Department, Professor Shih started a project a few years ago to identify a robust, convenient and reliable water sampling protocols - in the wake of the Lead in Drinking Water Incidents in 2015 in which some household tap water samples were found to contain amounts of lead exceeding World Health Organisation standards. After periods of testing, analysing and designing, he developed a water sampling protocol which has then been well-implemented and proven to be highly effective for the purposes.
Professor Shih has also won commendation from the Drainage Services Department for his hydrothermal carbonization technology for improving sludge dewaterability at Shek Wu Hui Sewage Treatment Works. An advanced technology to turn biomass into high quality “brown coal”, it opens the door for the next generation of sludge treatment options.
Curbing the rise of antibiotic resistance genes
Professor Zhang Tong, also from the Department of Civil Engineering, emphasises the importance of water and wastewater treatment especially in today’s world when more antibiotics than ever have been found in water environment. For the past decade he has carried out research on an emerging pollutant, antibiotic resistance genes, whose dissemination through antibiotic-resistant bacteria poses a threat to public health. He and his co-investigators have produced a number of highly-cited publications in the frontier area of research.
It is an area that has attracted much international attention. The past years have seen increased antibiotics discharged from animal farms, hospitals, pharmaceutical wastewater plants in addition to human bodies, Professor Zhang noted. “If we treat sewage in a good way, we can minimise the residue antibiotic in the effluent and remove the bacteria.” In this regard, Hong Kong lags behind Europe and to some extent places like Beijing in that it lacks mandatory rules for hospitals in relation to wastewater treatment,” he said.
“By controlling the environmental pollution, we can help improve the health of human beings and animals. If we do not do good things on the environment, then human and animal health could face the threat of new viruses or bacteria,” he said. “By spending money on the critical control point, it helps reduce future problems and the costs on the human society.”
His team has developed a system of measurement for antibiotic resistance genes –widely used by researchers elsewhere - through DNA sequencing, which requires mathematical analysis to dig out resistant genes from a vast amount of data. Their long-term goal is to develop a novel integrative risk assessment and management framework for antibiotic-resistant bacteria and harmful micro-pollutants in wastewater effluent and reclaimed water.
Saving Rainwater
Dr May Chui is another researcher from HKU’s Department of Civil Engineering with a passion for water resources. For a decade she has focused on environmentally friendly, sustainable stormwater management. Hong Kong usually experiences typhoons and much rainfall during the summer, and Dr Chui is committed to retaining the water rather than simply getting them out into the sea. “We will lose water as a resource if we simply stop the potential floods through the drains. There can be more natural ways to hold the water so as to support the plants in the city while solving the flooding issue,” she noted.
Her work has won recognition from the Drainage Services Department for her application of porous pavement that can save rainwater for planting and other purposes. Rainwater can be stored underground through the porous pavement, which in turn is utilised by roadside trees and planters. Such endeavour requires special designs that fit the road situation and the level of groundwater in the city.
Her trial of porous pavement, conducted for the Drainage Services Department, covered an area of 30 metres by 3 metres. Its performance was monitored under natural rainfall as well as artificial rain. “It could work in Hong Kong but maintenance is an issue, and porous pavements are better to be used in areas with less traffic. In addition to the pavement, there is a need for an overall strategy to implement other measures to make it happen across the city.”
Dr Chui’s other project covers the wetlands in Mai Po Nature Reserve in the north of Hong Kong, in efforts to study the potential impact of both human activities and climate change on the ecology of the wetlands.
Certainly, engineers and researchers like her and the others above are paying attention to burning environmental issues. In 2018, the Faculty of Engineering took a further step of establishing the Centre for Water Technology and Policy with the Faculty of Social Sciences of HKU to take on a more proactive role in ensuring their research can bring forth social benefits. The interdisciplinary centre seeks to offer cutting-edge research findings to help the government formulate effective policies.
“Traditionally engineering is about technology alone but we have realised the importance of policy,” said Professor Li. “Technological development is one thing, while application and implementation of our findings is another. We want to be more impactful with our research output, and being able to influence policy is important.”
The engineers are open to collaborations with academics from other disciplines within the university, as well as working on more government projects.
“Our work is not limited to water reuse or treatment technology. It has started to have policy elements. Our work has become softer,” said Professor Li.
The Centre for Water Technology and Policy, a collaboration between Faculties of Engineering and Social Sciences at HKU, aspires to becoming the focal point on water technology and water policy research that has direct policy relevance for Hong Kong.
The team nurtures a large group of young researchers who have passion for water science and technology.