News

11 May 2011

MURRAY & ROBERTS CONSTRUCTION POWER JV PUT UNIQUE SPIN ON ZEEKOEGAT WWTW UPGRADE

The Murray & Roberts Construction Power Construction joint venture (M&R Construction Power JV) is making excellent headway on a R190-million contract to execute Stage 1 of the upgrade and expansion of the Zeekoegat wastewater treatment works (WWTW) near Pretoria, on the Pienaars River.

The contract was awarded by City of Tshwane in October 2010 and calls for the construction of a new 40 Mℓ/day BNRAS (Biological Nutrient Removal Activated Sludge) module to boost the existing capacity of the WWTW. Completion is scheduled for early 2013.

Detailed design and supervision of the extensions was awarded to the BAKV3 joint venture, comprising BIGEN Africa Services and KV3 Engineers.

Anton Botha, contracts director at Concor, a subsidiary of Murray & Roberts, says this contract has taken a unique turn in that, in addition to the civil work, the M&R Construction Power JV has been given responsibility for project managing the mechanical, electrical and instrumentation components of the work including dry and wet testing, commissioning and final handover of the plant to the client. Lektratek Water Technology is the mechanical partner and EDSE Projects, the electrical partner on this project.

“This ‘single source’ approach is unique in the civil industry,” Botha says. “We have established excellent relationships with the mechanical and electrical contractors and we are proving that we can successfully co-ordinate the implementation of these disciplines in a project of this nature. Based on this track record, we are already tendering for other similar projects offering the same ‘package deal’ approach.”

The JV will supply 15 000 m3 of concrete, 47 000 m2 of formwork and 1 600 tons of reinforcement for Stage 1 of the Zeekoegat WWTW upgrade and expansion.

The modifications to the existing works include supply and installation of a third 8 mm screen at the existing screenings chamber; construction of three additional vortex degritters and a new division box to split the flow between the existing and the new module and construction of a new finescreen structure.

The contract includes three new conventional 25 metre diameter primary settling tanks, equipped with rotating bridges and scrapers. Primary sludge will be drawn off to a new primary sludge pump station that will transfer it to a sludge handling facility that will be constructed in Stage 2.

A new 10 000 m3 balancing tank will allow a six hour retention period and will be equipped with 16 vertical shaft stirrers to prevent the organic matter from settling.

Two identical new biological reactors, each capable of handling 20 Mℓ/d, are being constructed and configured to incorporate several process configurations. Diffused aeration has been chosen as the method of aeration based on its energy efficiency and the fact that the existing plant already operates on diffused air. The unaerated zones will be equipped with 40 vertical shaft stirrers and 20 axial flow pumps will be installed for internal recycling purposes.

Included in Stage 1 are four new 35 metre diameter secondary settling tanks, equipped with rotating bridges and scrapers. Return activated sludge (RAS) will be withdrawn and pumped to the biological reactors

A new chlorination contact tank has been sized to handle the eventual total flow of 85 Mℓ/day. The tank has been split into two separate units to allow for disinfection to take place when one unit is taken out of operation for cleaning and maintenance.

An additional estimated electrical load of 4 MVA will be required for the extensions to the plant. The bulk power on site will be distributed to various 11 000/400 V substations and mini substations.

The Murray & Roberts Construction Power JV is responsible for the mechanical, electrical and instrumentation components of the work at the Zeekoegat WWTW.

Some 15 000 cubic metres of concrete was used on this contract for modifications and new structures.