Water treatment solutions company Veolia Water Technologies South Africa has been awarded a contract to design, build and operate South Africa’s first Biobulk wastewater treatment facility, which will be ready for commissioning in March 2016.
The facility, owned by wine and spirit producer Distell, which is headquartered in Stellenbosch, in the Western Cape, has over the last four years developed its Green Plan to install a common anaerobic water treatment facility that will lower the chemical oxygen demand (COD) load in the municipality outfall, harvest the energy in the wastewater and lower the overall cost of effluent treatment.
Owing to this, Distell selected the Veolia Biobulk Continuous Stirred Tank Reactor technology, which is a green technology that is a robust and proven process that treats industrial effluents with significant amounts of suspended solids. It is the anaerobic equivalent of the conventional activated sludge digestion system.
Following an anaerobic suspended bacteria treatment process, the bulk of the soluble and solid organic content, measured in COD, is converted into biogas.
The Biobulk can be operated as a once-through system or the biomass can be returned after the clarification stage. The key to the Biobulk system design is the manner in which the reactor vessel is mixed and the design of the degassing stage prior to clarification. The biogas is a source of renewable energy converted into steam for the Distell site.
“The Biobulk system represents a long-term capital savings investment. It brings with it an operating cost saving whereby solids in the effluent need not be removed; they can be converted into biogas in the reactor,” says Veolia Water Technologies industrial technical manager Jaco Oosthuizen.
He adds that the effluent in the plant will be treated by clarifiers, the centrifuge, the boiler and biogas flare, where, firstly, the digester reduces the effluent COD content by 94.1% and then a clarifier removes suspended solids, followed, in turn, by the Veolia Hydrotech drum filtering for tertiary treatment. This ensures that the total suspended solid concentration is less than 150 mg/ℓ.
With Distell and Veolia having agreed on a ten-year build, operate, transfer (BOT) contract, it will enable Veolia to assume full ownership of the plant’s functions for the agreed period. This will also ensure an appropriate transition from Veolia’s commissioning teams to its operations team.
Following the commissioning, the plant will be handed over to Veolia’s Western Cape operations and maintenance division, which will perform all operations and maintenance functions for ten years.
Oosthuizen notes that, owing to the ten-year BOT contract, Distell will pay a set monthly fee for the water treatment, while Veolia will finance the plant, which means that it retains its interest in the plant. Also, this ensures the plant remains in peak condition.
Veolia is mandated to deliver the specified quality for water, carry out ongoing maintenance and ensure the plant’s operating performance is in accordance with set objectives.
For this project, Veolia will treat 1 000 m3 of effluent a day with an organic load of 8.6 t of COD a day. The treated water will be discharged to the municipal wastewater works. During the process of anaerobic digestion, COD is converted into biogas, which will be transferred from the Biobulk system directly to the biogas boiler. The final effluent discharged to the municipality will contain less than 500 kg COD and fat and the suspended solids concentration will be less than 150 mg/ℓ.
Veolia’s operation and maintenance personnel, along with Veolia engineers from water treatment specialist Biothane Netherlands, which developed the Biobulk solution, will form part of the commissioning team. Veolia’s operational personnel will be trained, through on-the-job coaching and theoretical training modules, to take over full plant responsibility.
Oosthuizen believes that Veolia’s pricing structure, the operating cost benefits accrued by the client, the income from the additional biogas produced, and the fact that Biothane Netherlands has extensive experience in anaerobic treatment – having been the leader in this technology for over 35 years – are the drivers for being awarded the BOT contract.
“Distell took careful consideration of offers on the table and, with this bold step into green technologies, we feel really proud to be part of such a dominant player in the marketplace,” he concludes.