Water. Desalination + reuse
Issue link: https://fhpublishing.uberflip.com/i/724419
water.desalination+reuse September 2016 SPONSORED ARTICLE P erformance of reverse osmosis (RO) systems is sensitive to seawater qual- ity, meaning that it might struggle if the seawater quality changes due to algal bloom, or "red tide," which leads to bio-fouling issues. Therefore the intake system has an important role in the RO process, especially in a harsh environment such as The Gulf. In this article, we introduce the High-Speed Seabed Infiltration System (HiSIS) which is an innovative technology to solve these prob- lems developed by Hitachi Zosen together with Nagaoka International. Put simply, HiSIS is an open concrete box with infiltration sand, gravels and intake pipes, installed on the seabed or submerged into the seabed. When seawater passes through the filtration sand layer, marine organisms and colloids are filtered naturally leaving the intake seawater highly clear. By adopting a backwash system to keep the sand layer clean, it is possible to draw sea- water at a high infiltration velocity of up to 100 m/day, which is 20 times higher than conventional infiltration intake systems. - Preventing the adhesion of marine organisms: When using HiSIS, anti-fouling systems and periodical pipe cleaning work are not required. By filtering all marine tower, intake pipe, bar screen, band screen, intake pump, DAF, Dual Media Filter and RO membrane. It is also equipped with an elec- trochlorination system to prevent the adhe- sion of marine organisms to the intake pipe, and a sludge treatment system to treat sludge generated from DAF. More importantly, it consumes a lot of energy and chemicals dur- ing the process resulting in increased opera- tional costs as well as environmental loads. On the other hand, RO desalination plants adopting HiSIS complete the pretreatment without screens, DAF, or sludge treatment systems, resulting in a reduced footprint hence saving capital (CAPEX) and opera- tional spend. Therefore, our best estimate of CAPEX for 100,000 m3/d intake capacity indicates HiSIS can help to save as much as 15 to 20 per cent for intake and pretreatment systems. - Environmentally friendly: Using HiSIS can minimise the use of chemicals and does not generate any sludge leading to less envi- ronmental load. Pilot results Our two-year successful operation of a pilot plant in Abu Dhabi, UAE, in coopera- tion with Abu Dhabi Water and Electricity Authority proved the efficiency, robustness and reliability of HiSIS. For two years, it has been continuously and stably operated as an intake and pretreatment system without any chemical use or maintenance. Various indi- ces such as TOC, DOC, ATP, TEP, and biopoly- mer, show that HiSIS reduces organic matter in raw seawater and prevents RO membrane bio-fouling. HiSIS is the hybrid system of a seawater intake and high grade pretreatment sys- tem, with a highly reliable and cost-saving solution. Innovative seawater intake system by Hitz Hitachi Zosen presents its high speed seabed infiltration system for economical and environmentally friendly seawater intake for reverse osmosis desalination plants THE BIG IDEA SPONSORED ARTICLE By Katsu NaKaBayasHI organisms with filtration sand neither sodium hypochlorite (NaOCl) dosing at the intake tower, nor piping maintenance is nec- essary to prevent fouling. - Reliable operation: In a conventional intake system, if seawater quality is worse than the design limits of the dissolved air flo- tation (DAF) system, the deterioration of the quality of seawater severely affects the desal- ination plant, resulting in a load down or shutdown. With HiSIS, it can be stably oper- ated even during red tide without a DAF sys- tem since the filtration sand layer removes phytoplankton from seawater. - Dramatic cost reduction: Generally, a conventional RO plant is composed of intake 1 2 3 1. HiSIS 2. UF Units 3. RO Units