Scientists from Masdar Institute of Science and Technology, Abu Dhabi devise a promising waste water treatment system to harness fertilizer from bio-solids in sewage.
A team led by Shadi Wajih Hasan from Water & Environmental Engineering labs at Masdar made a unique three step technology to harness eco-friendly fertilizer.
Currently, livestock waste is used to make soil more fertile and urban sewage sludge has the same potential. But it was costly before this innovation as it contains high level of heavy metals needs more energy and resources to remove. For instance, in the US, it sucks up the equivalent energy output of four of the country’s biggest power plants every year.
The promising Three-in-One treatment system removes over 90 per cent of Zinc and 60 per cent of Copper from sewage sludge, creating good fertilizer for UAE farming industry. The removal limit is much low from the standards set by regulatory agencies.
A three-step technology
The three-step process combines chemical conditioning, electrokinetic method and post-treatment washing.
In beginning the team conditioned the sludge with aqua regia – a mixture of concentrated nitric and hydrochloric acids – to reduce the sludge particles size. This step also disrupts Zinc and Copper trapped in waste sludge
Then, the team applied an electrokinetic method by running the current between two electrodes to break to bonds between metallic ions.
Later Hasan’s team introduced a third step for even higher metal removal rates. They used an organic product called Pectin, extracted from citrus fruit peel. Pectin can absorb heavy metals at higher degree after EK treatment. The engineers used Pectin as post treatment of the sewage sludge and the remaining residue can be used as fertilizer.
Towards a pilot plant
To determine the commercial aspect of the method, the researchers also tested a pilot plant showed excellent results towards scale up production of the plant at industrial level.
This low-cost and less energy efficient system could be a solution for the ever growing urban sewage problem across the world by turning the waste into excellent fertilizer. Masdar’s team estimated that by using this method, Abu Dhabi could earn two million dollars annually from the fertilizer.
The bio-solids from sewage currently buried in landfills which are harmful for the environment due to their heavy metal contamination.