SA’s first energy from effluent in anaerobic waste water treatment facility

Over the past four years Distell has been developing a “green plan” to install a common anaerobic
water treatment facility in the Stellenbosch area, Western Cape.
The facility is expected to lower the chemical oxygen demand (COD) load in the outfall to the municipality, harvest the energy in the waste water, and lower the overall cost of effluent treatment.
The Veolia Biobulk® Continuous Stirred Tank Reactor (CSTR)
The contract to design, build and operate SA’s first Biobulk® waste water treatment facility was awarded to Veolia Water Technologies SA. Veolia uses innovative technology and specialised skills to achieve water sustainability for people and industries.
The Distell-owned plant will be ready for commissioning in March 2016.Distell has three operational sites in the Stellenbosch: Adam Tas, Van Ryn and Bergkelder.
The Biobulk CSTR technology is a robust and proven process which treats industrial effluents with significantly high amounts of suspended solids.It is the anaerobic equivalent of the conventional activated sludge digestion system. Blended solid or liquid waste streams enter the reactor and are treated by anaerobic suspended bacteria. The majority of the soluble or solid COD is converted into biogas, significantly reducing the solids concentration in the waste stream. After a retention time of
several days, the treated waste stream leaves the reactor.
The Biobulk can be operated as a once-through system. Alternatively, biomass can be returned after a
clarification stage. The key to the Biobulk design is the manner in which the reactor vessel is mixed and the design of the degassing stage prior to clarification.
Produced biogas is temporarily collected in the headspace of the Biobulk CSTR, which acts as a biogas holder.
Biogas can be used as a source of renewable energy or burned in a biogas flare.
Technology features:
• Tolerance for high concentrations of TSS, fats, oil and grease (FOGs).
• Medium volumetric loading capacity (2-5kg COD/m3/day).
• Energy source from biogas production.
• Economical operation.
• Proven reliability.
The technical manager at Veolia Water Technologies SA, Jaco Oosthuizen, says the system represents a long term capital saving.
“It brings with it an operating cost saving in that solids in the effluent no longer need not be removed. They can be converted to biogas (energy) in the reactor.”
The Biothane Biobulk® Anaerobic Digester is the heart of the plant. “Ancillary equipment includes storage
buffer tanks, clarifiers, the centrifuge, boiler and biogas flare. First, the digester reduces the effluent COD content by 94.1%. Next, a clarifier removes suspended solids, in turn followed by Veolia Hydrotech drum filtering for tertiary treatment. This ensures the total suspended solid (TSS) concentration is less than 150mg/l.”
On commissioning of the facility, a 10-year Build, Operate, and Transfer (BOT)agreement comes into force.
“The 10-year BOT contract will enable Veolia full ownership of the plant’s functions for the agreed period. This will ensure an appropriate transition from Veolia’s commissioning teams to its operations team,” says Oosthuizen.
Veolia’s Operations and Maintenance division in the Western Cape will perform all operations and maintenance functions for 10 years.
Veolia is mandated to deliver:
• The specified quality of water;
• Carry out ongoing maintenance;
• Ensure the plant’s operating performance is in accordance with set objectives.
Veolia will treat 1,000m³ of effluent with an organic load of 8.6 tons COD per day. The water that is treated will be discharged to the municipal wastewater works.
The final effluent discharged to the municipality will contain less than 500kg COD per day and the suspended solids concentration will be less than 150mg/l.
Veolia’s operation and maintenance personnel as well as engineers from Biothane in the Netherlands will form part of the commissioning team. The operational personnel will be trained,via on-the-job coaching and theoretical training modules, to take over full plant responsibility.
Veolia Water Technologies South Africa:

There are 2 major types of systems used for wastewater treatment
They are aerobic and anaerobic systems. This particular piece focuses on anaerobic treatment.
Anaerobic treatment is a process where wastewater or material is broken down by microorganisms without
the aid of dissolved oxygen. However, anaerobic bacteria can and will use oxygen that is found in the oxides introduced into the system or they can obtain it from organic material within the wastewater. Anaerobic systems are used in many industrial systems including food production and municipal sewage treatment systems.
Anaerobic digestion is commonly used to treat sludges in the first areas of a wastewater treatment plant. This process is popular because it is able to stabilize the water with little biomass production.
Anaerobic treatment occurs in many different stages. The key microorganisms are methane formers and acid formers.The acid formers are microorganisms that create various acids from the sludge.
Methane formers convert the acids into methane.
The two main anaerobic systems are batch systems and continuous systems. In a batch system, the biomass
is added into a reactor that is sealed for the rest of the digestion process. This is the simplest form of anaerobic treatment but can have odor issues associated with it. As the most simple, it is also one of
the least expensive ways to achieve treatment.
A continuous system has organic matter constantly added to the treatment system. Since it is continuously being fed, there is a need for the byproduct to continuously be removed. The byproduct can result in a constant source of biogas, which can be used as an alternative source for energy. This system is usually more expensive to operate because of the need for constant monitoring and manpower.
Whether it is aerobic or anaerobic treatment, each treatment system has its place in the world today.
They are very different in the process but both are used to achieve maximum degradation, while meeting
the strict regulations set by the environmental agencies that regulate what is released into the air, ground, or water.