Sharjah Phase 6

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ACWA Services Ltd designed, installed and commissioned the electromechanical & control works for the Phase 6 extension to Sharjah Sewage Treatment Works in the United Arab Emirates. The contract forms part of an £18 million project being carried out by CCIC for the Sharjah Municipality, with Halcrow International Partnership acting as the Client's Engineer.

The project incorporates the following treatment stages:-

A new inlet works, activated sludge aeration lanes, final effluent clarification, rapid gravity sand filtration complete with air scouring and backwashing, final effluent pumping station with ultra violet disinfection and all pipe-work, sludge thickening, sludge dewatering, odour control, ancillary services and controls. The Phase 6 extension has increased the capacity of the works to process an additional 37,400 m3/day of sewage from the projected increase in population.

Plant Description

To ensure that loads and flows to the treatment works are proportionally balanced between the phases, and to reduce the effect of peaking from any of the pumping stations feeding the existing plant, all incoming streams of sewage are combined in a new pressure sump at the inlet works.

The incoming sewage is split between the existing phases and the new Phase 6 inlet works. The inlet works consists of fine screens, compaction of screenings, grit removal and flow monitoring. Modifications to the tanker unloading station include a new odour collection & scrubbing system.

The screened sewage is combined with the return activated sludge in a premixing tank prior to splitting the flow to the aeration lanes. Four aeration lanes, each 58 m x 11.6 m x 4.5 m working depth and equipped with a fine bubble diffused aeration system, provide the biological treatment process for the sewage. The aeration lanes are split into five sections with the first section as an anoxic zone to allow de-nitrification and to improve the sludge settlement. The remaining four sections have progressively reduced aeration capacity so as to optimise process control. The mixed liquor from the aeration lanes gravitates to a distribution chamber to be evenly split to feed four 25m-diameter settlement tanks, each fitted with tri-arm scrapers. The return activated sludge from the settlement tanks gravitates via actuated bellmouths to a return sludge wet well. Four pumps, operating as duty/assist/standby control the return of the activated sludge to the pre-mixing chamber. Surplus sludge and scum removal are included within the wet well design.

To ensure excellent final effluent quality there are 10 rapid gravity sand filters. A screw pump lift station provide flow to the filters which have air scour and backwash facilities. The treated effluent from the plant is disinfected with ultra violet radiation and pumped for storage prior to distribution for irrigation.

A new SCADA system is installed to incorporate the whole of the Sharjah STW, connecting the various PLCÕs from phases II-V and the new Phase 6, via Ethernet links, to the main control room. The SCADA system provides the operators with monitoring and set point control for each area of the plant.

The sludge treatment capacity of the works has been extended by the installation of three belt thickeners and two additional filter belt presses to ensure the additional sludge produced can be dewatered. This ensures that ideal operating conditions are maintained for the aeration system.

Project Details

Client: Sharjah Phase 6

Industry: Sewage Treatment Works

Application: Inlet Works, Aeration, Settlement and sand filtration