AWWA ACE56317

The Water Corporation of Western Australia has over a number of years been investigating various water treatment technologies aimed at dissolved organic carbon (DOC) removal. Research was prompted by intermittent outbreaks of Dimethyl Trisulphide (DMTS) in the clearwater distribution system. With elevated levels of DOC linked to the formation of DMTS, the MIEX(R) Process was trialed at Wanneroo Groundwater Treatment Plant (GWTP), a currently used source of DMTS affected water. In 2000, after two years of pilot plant and laboratory work, the Water Corporation of Western Australia initiated the design and construction of the world's first large scale MIEX(R) plant. The general layout of the Wanneroo MIEX(R) plant consists of two mixed contactor tanks feeding 6 hopper bottomed settlers. The regeneration facility uses two regeneration vessels with one regenerant tank. Two salt saturating systems are used to prepare and deliver the brine solution for the regenerant tank. Hydrochloric acid and sodium hydroxide dosing facilities are provided for regenerant preparation. The hydraulics of the existing Wanneroo plant dictated that a low lift Pump Station be used, to lift the treated water for gravity flow into the existing clarifiers. The MIEX(R) plant was constructed on the existing Wanneroo GWTP site as a retrofit. Located at the head of the works after the aerator, the plant treats raw water prior to alum coagulation, clarification and filtration in the existing plant. The main driver for DOC removal is the control of DMTS outbreaks. Another benefit is the reduction in chlorine demand during water treatment, and resulting in chlorine residuals extending further into the water distribution network, without supplementary chlorine dosing. A lower overall chlorine dose is therefore required to achieve the desired chlorine residual. The reduced DOC and chlorine levels also contribute to lower levels of disinfection byproducts. Includes 6 references, tables, figures.