Water & Wastewater Asia September/October 2019

54 | TECH ROUND UP
The Kuraray team at INDOWATER
2019, with Motosugu Yoshihara
(bottom right), Senior Manager of GEL
and Carrier Production Technology
Development
“A high-rise apartment
for bacteria”:
How KURAGEL’s
revolutionising
the market
A gel that reduces excess sludge
simply by being added into
activated sludge might sound
a little too good to be true,
but Japanese manufacturing
company Kuraray assures us that
this isn’t so. Water & Wastewater Asia
finds out more.
Developed by Japanese company
Kuraray, KURAGEL is a polyvinyl
alcohol (PVA) hydrogel which features
higher bacterial retention as compared
to ordinary carriers, and enables more
efficient wastewater treatment.
According to Mototsugu Yoshihara, senior
manager of the gel and carrier production
technology development department,
KURAGEL has three main points that set it
apart from the competition, “Firstly, the main
material of KURAGEL is polyvinyl alcohol and
gel, so it includes much more water, about
90 per cent – it’s very hydrophilic, and has a
very high affinity with biomass like bacteria.
This accelerates the retention of
bacteria on the surface of and
inside the KURAGEL. Secondly,
the shape is spherical and the
KURAGEL’s specific gravity is
slightly higher than water – it’s
slightly heavier than water – so
it flows easily inside the tank.
The third point is the most
important: The KURAGEL has
a co-continuous structure with
pores that are less than 20
micrometres in size. Activated
sludge is usually composed of
bacteria, metazoa and protozoa,
with metazoa and protozoa
making up 95 per cent of the
material, and these are larger than bacteria
so these microorganisms cannot enter the
KURAGEL. So, the surface area of KURAGEL
makes it much more effective in retaining only
bacteria, which can then be treated.”
Due to its porous structure, each KURAGEL
sphere is able to retain one billion bacterial
cells, and can dramatically increase the
capacity of wastewater treatment plants.
This is aided by the properties of PVA gel,
which has a very high water content due
to its extensive porosity and allows for
the favourable permeability of oxygen and
nutrients to the bacteria colonised inside
the beads.
Mototsugu laughed, “The bacteria are
very happy to live here, it’s like a high-rise
apartment for them!”
USING KURAGEL
KURAGEL is well suited for use in biotreatment
processes such as the treatment of sewage
and polluted river water, and in industrial
wastewater treatment systems. It is also
suitable for the removal of nitrogen, and the
strength to withstand mechanical agitation
for efficient denitrification.
Another of KURAGEL’s strengths lies in how
easy it is to retrofit. Mototsugu explained,
“KURAGEL has a very high performance
rate, so we can make treatment systems
very compact, and the footprint becomes
very small. In a typical wastewater treatment
plant, you don’t have space to add more
equipment. In this case, we can simply add
KURAGEL into the existing aeration tank to
increase performance and without the need
to put in a new tank.”
Depending on the characteristics of the
wastewater to be treated, the plant’s
treatment ability can be enhanced up to five
times over that of conventional activated
sludge by using the KURAGEL system,
allowing for the potential upgrading of
existing overloaded systems or for design
of new process units with greatly reduced
footprints.