Hitachi Metals Develops Ceramics Adsorption Filter for Pretreatment of the SWRO (Sea Water Reverse Osmosis) Desalination System

Hitachi Metals, Ltd. (TOKYO:5486) has developed a ceramics adsorption
filter (CAF) as a pre-treatment technology for the seawater reverse
osmosis (SWRO) desalination process in order to minimize fouling of RO
membranes^*1. A joint research study conducted
by Hitachi Metals Ltd, Japan and the Nanyang Environment & Water
Research Institute (NEWRI) at Nanyang Technological University,
Singapore (NTU Singapore) have shown that with the addition of CAF in
the pre-treatment stage prior to the RO stage, the rate of RO fouling
was slower and hence the membrane cleaning frequency can be reduced. The
findings have shown that the amount of biofilm attached on the RO
membrane was significantly reduced. This is expected to reduce water
production cost. Hitachi Metals will accelerate efforts toward
commercial applications, and will expand the business in Singapore,
which is the center of research of the water treatment technologies.

1. Background

Due to the population growth, economic growth, and climate change, water
shortage has become a global issue. One of the Sustainable Development
Goals (SDGs) promoted by the United Nations is to ensure the
accessibility to clean water and improve in water quality and price.^*2
Seawater
desalination is one of the approaches to access to clean water.
Currently, most seawater desalination systems use RO membranes. When
seawater is desalinated using RO membranes, organic matter and other
contaminants in the seawater may adhere to the membrane surface, a
phenomenon known as fouling. The consequences of fouling include
decrease in productivity, increase energy use, compromised water quality
and shorten membrane life. All of these translate to higher water
production cost. One of the key factors determining the degree of
fouling on RO membrane is the RO feed water quality. As such, an
effective pretreatment process is necessary prior to the RO system to
ensure the fouling of RO membranes is minimized.

2. Overview

Against this backdrop, Hitachi Metals has developed a pre-treatment
filter that aims to minimize fouling of RO membranes, known as the CAF.
The CAF is a filter which has porous partition walls coated with an
adsorbent material. Unlike the conventional filtration method which
based on size exclusion to physically remove substances larger than the
size of the pores, CAF utilizes a chemical action, namely adsorption, to
selectively remove dissolved organic matter that is likely to be
negatively charged, regardless of its size.

Hitachi Metals and NEWRI conducted parallel comparison on RO
performances for seawater treated with UF^*3 alone and the
other seawater treated with UF followed by CAF system. The comparison
studies have shown that the fouling rate of RO membranes can be reduced.
The slower in fouling rate indicates that the RO cleaning frequency can
be potentially reduced by half or more if CAF is used in between the UF
membrane and RO membrane. This will likely cut down the operating cost
of seawater desalination plants and improve the capacity utilization,
resulting in lower water production cost.

Comment from Assistant Professor Chong Tzyy Haur, School of Civil and
Environmental Engineering and Deputy Director, Singapore Membrane
Technology Centre, Nanyang Environment and Water Research Institute,
Nanyang Technological University
“Desalinated water is an
important source of water. NEWRI is pleased to collaborate with Hitachi
Metals to explore technologies that can improve the process efficiency
which ultimately lead to lower cost of water production. We are excited
about the commitment from HM to expand its business in Singapore.”

Comment from Mr. Koji Sato, Vice President and Executive Officer and
CTO of Hitachi Metals
“The global community faces a major issue
in coping with environmental, energy, and resource problems to achieve
sustainable growth. I am very pleased that we have made a step forward
to solve the social issue of water shortage in collaboration with NEWRI.
We remain committed to contributing to the future development of society
by unleashing the potential of materials.”

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