R E S E A R C H @ H K U S T
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Sewage sludge is a growing worldwide
problem, as established cities deal with
expanding populations and new
urban areas spring up in developing
economies requiring efficient treatment
for sanitation. Conventional plants
utilize biological processes that convert
around 60% of the organic carbon
in sewage to carbon dioxide and the
remainder to sewage sludge. Such
sludge is then disposed of in landfills or
incinerated, contributing to greenhouse
gas emissions and using up energy.
Seawater Change
Prof Guanghao Chen and his team have
been working on the problem since
2004,studyingtheconnectionsbetween
seawater, sulfate and sludge, leading to
the transformational SANI municipal
wastewater treatment process that is
generating opportunities for a cleaner
environment through innovative ways to
deal with “dirty water”.
resources); and Prof Chen’s investigations
into the potential of sulfate to reduce
the sewage sludge produced from
conventional wastewater treatments.
Three-wheel Cycle
The traditional two-wheel organic
oxidation and nitrification biochemical
reaction using the integrated carbon
and nitrogen cycle employs microbes to
convert organic pollutants into carbon
dioxide and clean up sewage. However,
such microbes grow rapidly through
this process, creating large amounts
of unwanted sludge as a by-product.
The novel three-wheel integrated cycle
proposed by Prof Chen employed slow-
growing sulfate-reducing bacteria and
sulfate in seawater together with
nitrification to oxidize and eliminate
pollutants. The method proved highly
viable in lab and pilot testing, reducing
oxygen needed for organic matter
removal and minimizing sludge
generation. From 2007 to 2010, a pilot
test plant at Tung Chung Sewage
Pumping Station in Hong Kong showed
a 90% sludge reduction at a capacity of
10 cubic meters of sewage per day.
In 2013, with the assistance of
Hong Kong government departments,
SANI launched a full-scale trial at Hong Kong's Shatin
Sewage Treatment Works in the summer of 2014.
Fluid Mechanics Meets
Signal Processing
Conventional pipeline diagnostic systems
possess certain limitations, with
good reason – pipes are buried deep
underground, out of sight and difficult
to access. Current technology only
covers a short range (200 meters or less),
produces low-resolution data, targets
specific faults, and is unable to forecast
problems. These critical limitations
call for a new diagnostic paradigm for
water supply network monitoring and
fault detection. However, establishing
a proactive "wave" diagnostic platform
is no simple feat. It will involve complex
physics and mathematics, a highly
dynamic environment encompassing a
“web of pipes”, numerous active devices
and flow controls, noise from turbulence,
traffic, construction activities, and
random flow demands.
Overcoming these issues is now
the focus of a groundbreaking inter-
disciplinary Theme-based Research
project, led by Prof Ghidaoui and
supported by Hong Kong Research
Grants Council. The Smart Urban
Water Supply Systems initiative is
a pioneering undertaking involving
an international group of leading
researchers from Hong Kong, Mainland
China, North America, Europe, and
New Zealand, together with the Hong
Kong government’s Water Supplies
Department. The team brings together
engineering experts in hydraulics and
fluid mechanics, signal processing and
wireless communications and structural
mechanics as well as mathematicians.
The researchers are currently
studying sensing of actively generated
fluid waves traveling at high speed in
pipelines and how to use the electronically
captured wave echoes to “image” and
diagnose the pipes. Theories are being
evaluated in the lab at HKUST and in
SANI stands for Sulfate reduction
Autotrophic denitrification and Nitri-
fication Integrated process, or “sludge
killer” in Chinese. The original platform
stems from a happy confluence: Hong
Kong’s use of seawater for flushing as
an alternative to fresh water (it is one of
the few places in the world to do so
and is the result of a historical initiative
to mitigate the city’s lack of water
FROM SLUDGE TO SANI
field studies in Hong Kong’s urban area.
A pilot-scale demonstration experimental
test bed has also been developed in
Beacon Hill, Kowloon, Hong Kong.
Findings can crucially contribute to the
sustainable development of Hong Kong
through water conservation and locally
developed innovation and technology.
However, the focus is not solely on Hong
Kong but on a system that will work
anywhere in the world.
Prof Ghidaoui has published in
leading journals such as the
Journal of
Hydraulic Engineering
,
Journal of Fluid
Mechanics
, and
Journal of Hydraulic
Research
. In 2007, he received the
Arthur Thomas Ippen Award, the
highest honor presented by the
International Association for Hydro-
Environment Engineering and Research
(IAHR). He now serves as Editor-in-
Chief for the
Journal of Hydraulic
Research
, IAHR.
Urban sustainability to me
means the three Rs:
reduce, recover, and reuse
PROF GUANGHAO CHEN
Chair Professor of Civil and
Environmental Engineering
