GREEN: Green Project Reduces Brine Effluent for Power Station
Recent Gauteng Business News
Veolia Water Solutions and Technologies South Africa (VWS South Africa) is driving a R60 million green project aimed at reducing the amount of unexploited brine water produced at the Eskom Tutuka Power Station in Mpumalanga. The Actiflo® ballast clarification solution will be used as the main cog in the brine treatment process for the first time in South African industrial water treatment.
Currently, 3 mega litres of effluent, generated by Eskom Tutuka and New Denmark Colliery, also including some acid mine water, are disposed of using unsustainable methods. The new treatment plant will reduce this quantity pumped into lined evaporation ponds to 0.60 mega litres per day.
Brine water is high in total dissolved solids (TDS) -organics, calcium, and sulphates, making it prone to scaling and fouling membrane systems downstream. To prevent this, the following range of wastewater treatment processes will be employed:
The flocculated solids in the brine will be coagulated inside the Actiflo® maturation tank with the addition of Actisand® for ballasted floc formation. The next step involves the Actiflo® where water, flowing under gravity into the clarification section, is allowed to settle; separating and collecting heavier particles. The addition of Actisand® into the clarification process enables the Actiflo® to operate at a rise rate in excess of 50 m/hr.
Characteristics of the Green Project
Julius Pistorius, Project Manager at VWS South Africa explains: The patented Actiflo® system, designed by VWS South Africa and its sister company, Opalium, demonstrates unique settling characteristics, high up-flow velocities, and short retention times. These characteristics allow for a clarifier design with footprints five times smaller than classic lamella clarifiers or dissolved air flotation units, and up to twenty times smaller than conventional clarifiers.
The sludge collected by the Actiflo®, will be processed in a vertical thickening unit to ensure that solids are reasonably dry, while still fluid enough to be pumped.
The clarified water, exiting the Actiflo®, flows under gravity to the Multiflo® unit where it will be coagulated again. The addition of lime, soda ash, magnesium chloride, and sludge recycle streams will reduce the scaling potential of the water. The softened water from the Multiflo® is then passed through three carbon filters, further reducing the waters organic content.
Following this, water will be treated using ultrafiltration (UF) with non-oxidising biocide, after which, reverse osmosis (RO) units will complete final polishing.
The brine produced by the RO plant is the final effluent to be disposed of in lined evaporation ponds. The permeate (cleaned water), generated by this plant, will be used in the Tutuka power stations cooling towers, ensuring minimal waste generation.
Green Project Reduces Power Station Costs
Pistorius says: The result is that overall recovery of water is greater than 75%. This will reduce expenses associated with evaporation pond brine treatment and the power stations raw water intake.
The contract awarded by Eskom also requires that people from previously disadvantaged communities are trained in various fields of plant construction, including project management, site management, pipe welding, etc. This project makes for ideal training opportunities, as the site has very specific challenges relating to available space, environmental conditions, and other challenges typical to construction on brownfield sites, concludes Pistorius.
Construction began for the VWS Green Project in July 2011, and should be completed within four months.
Business News Sector Tags: Environment|