Hitachi Metals, Ltd. 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.
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.
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.”