The contniuing growth in the population of Sharjah has led to a need to provide additional treatment capacity at the existing wastewater treatment plant. The existing plant has been previously expanded under Phases 1-6 and will now be additionally expanded by Phase 7, to provide an additional 75 000 m3/day capacity to the existing 156 400 m3/day capacity.

The process adopted comprises preliminary treatment, biological treatment (activated sludge) and final settlement. Alternative processes were considered, but the client required process uniformity across the entire site. The design will provide much greater flexibility than the way the plant has been previously operated and will help ensure consistent compliance with the treated effluent quality parameters. All incoming flow from the various catchment pumping will now be combined and distributed from a single distribution point, enabling the operator to adjust the flow split ratios to suit inlet the individual treatment stream performances or capacities.

A three-dimensional computational fluid dynamics (CFD) model was used to assess the design of the aeration tanks, with particular emphasis on the hydraulic residence time in the anoxic zones. The model allowed the designers to refine the arrangement of the aeration tanks to achieve a three fold increase in residence time and to also optimise the effect of recirculation within the tanks.