Sludge to build homes
doi:10.1038/nindia.2010.45 Published online 13 April 2010
Indian scientists have found an innovative way to utilise sludge generated in oil fields, whose disposal is a problem since it usually contains more hydrocarbons than permissible in landfills.
Scientists at the North East Institute of Science and Technology (NEIST), formerly Regional Research laboratory, in Jorhat, Assam hit upon an alternative. They have developed a process to convert the sludge into masonry bricks for building construction.
The sludge accumulating in effluent treatment plants (ETP) in petroleum oil fields contains hydrocarbons, water and inorganic material. The NEIST process utilises all the components for making bricks: the water in the sludge serves as the process water, the hydrocarbons burn and provide partial fuel requirement (cutting down coal requirement), and the inorganic materials are fixed as constituents of the bricks.
This not only eliminates environmental problem associated with disposal of hazardous hydrocarbon bearing sludge but also replaces upto 30% of raw material (sand and clay) and to reduces fuel and process water requirement, says Balagopalan Unni, a senior scientist at NEIST. Scientists Pinaki Sen Gupta from the Material science division and Neelima Saikia from the biotechnology division headed by Unni worked together in the project. The technology consumes less coal than traditional clay brick kilns — thereby releasing less carbon dioxide, one of the gases responsible for global warming.
The NEIST technology for "green bricks" — so called because of the climate-friendly process used — has been utilised in commercial brickfields near Lakwa in Assam. The effluent treatment plant of Lakwa oil field — largest oil bearing structure in northeast India — generates 12 cubic meters of sludge per day. The sludge contains 7-10% hydrocarbon (very high in comparison to the permissible limit of 3% for safe disposal by land filling) and is environmentally hazardous.
The process has been utilised in successful field trials for making 150,000 bricks, says Unni. The NEIST work was carried out with funding from federal environment ministry and participation of Assam state pollution control board and brick kiln owners. Large scale production of "green bricks" is expected to begin once the Ministry of Petroleum gives permission to transport sludge from their installations across the country, he says.
Apart from the technology to utilize effluent sludge, NEIST has found a solution to reclaim land contaminated by oil due to drilling and other operations. Degraded lands that have remained barren for years are now lush with vegetation thanks to NEIST technology that consists of treating the wasteland with a mixed culture of certain organisms isolated from local soils (bioremediation), followed by introduction of vegetation (phytoremediation), says Unni.