Heritage Cases

Feed water to the desalination plant is currently sourced from the surface of the sea on the south side of the island and pumped to an existing 250 kℓ ground reservoir located at the Desalination Plant. Table 1 provides information on the feed water quality and the design values specified for design of the new desalination plant. Please note that no historical results were available and that only limited samples were taken and tested for purposes of this tender. “Upwelling” and associated algal blooms and elevated Total Organic Carbon (TOC) and Dissolved Organic Carbon (DOC) may be common occurrences in the surrounding waters. The seawater may therefore both nutrient rich and of very variable quality. Pre-treatment processes to provide water suitable as feed to RO membranes must be designed to accommodate the full range of physical and biological quality expected, while retaining the capability of producing consistent high quality feedwater to the seawater RO system. The pre-treatment systems therefore need to be reliable and robust. reverse osmosis permeate shall be produced at an instantaneous flow rate of 12.22m³/h during normal operation (equivalent to a daily production capacity of 220m3/day. The quality of product water from the desalination plant (before stabilisation) shall always comply with SANS 241:2006 Class 1 specifications (ignoring pH, Ca and Alkalinity that will be adjusted during subsequent stabilisation).