Japanese company designs a new system that integrates seawater desalination and sewage recycling to conserve energy.
Desalination is an innovative process that separates dissolved salts and other minerals from seawater to make fresh water. Notable recent examples include Singapore’s Keppel Marina East Desalination Plant, and a new desalination method that mimics the ion selectivity of organic cell membranes. Nonetheless, desalination demands a considerable amount of energy and the reduction of this energy requirement remains a major concern.
Hitachi has responded by developing a low-cost seawater desalination called RemixWater, located in the Water Plaza Kitakyushu facility. Uniquely, RemixWater uses water reclaimed from sewage recycling processes to dilute the seawater before filtering it through semi-permeable, reverse osmosis (RO) membranes. This method significantly reduces operating costs since lower salt concentrations mean lower RO pressure and electricity consumption. As a result, 40 percent of pumping pressure is reduced compared to conventional RO plants, and brine discharge is diluted by 3.5 percent. The RemixWater system stably produces 1,400 cubic meters of drinkable water per day.
However, filtration over extended periods leads to ‘fouling’ – the clogging and/or degradation of RO membranes – and drives up pumping costs. This prompted Hitachi to apply its proprietary AI technology to analyse operational data to identify factors affecting inlet pressure. These insights form the basis for strategies of fouling control. This technology can be implemented in all types of treatment systems as long as operating history data is available.
Hitachi wishes to expand RemixWater adoption both domestically and internationally. As of 2016, Water Plaza Kitakyushu has attracted over 7,500 visitors among which 1,900 are from overseas. Officials from the eThekwini Municipality in South Africa also visited and expressed interest in installing RemixWater at a local sewage treatment plant. The project period is four years, from 2016 to 2020, and will produce 6,250 cubic meters of water per day.