The Arabian Sugar Company refinery in Bahrain was commissioned towards the end of 2013. It is a carbonatation / ion exchange refinery designed to process VHP sugar. As with most refineries in the region, water availability is an issue and therefore it was designed with indirect condensing to optimise water consumption. As a consequence, it is also a refinery with low effluent discharge, most of the environmental loading coming from the ion exchange regeneration. The specialist ion exchange subcontractor designed a system with a stated 90% brine recovery using nanofiltration and brine evaporation. It incorporates various holding tanks to optimise the use of water while sweetening off and on. The operating manual, issued during commissioning, reported that the effluent would be 44.8 m~3/d at full capacity with 15 kg of chemical oxygen demand [COD] content, equivalent to 307 ppm of COD and therefore comfortably within the required limit of 600 ppm for permitted discharge to the municipal sewer. In the event, the local treatment plant could not cope with the refinery effluent discharge which was both puzzling and worrying. It turned out that the effluent was nothing like that claimed with both higher volumes and much higher COD loadings. This paper describes the investigations and solutions developed for the issues found so that others can learn from the experience.
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