Most innovative environmental strategy award, runner-up: AECI
Industrial waste does not disappear on its own. The containment and management of waste generated by chemical manufacturing has always been a challenge.
But the South African chemicals giant, the AECI Group, has tried to counter the waste problem scientifically. Its Vumbuka project in KwaZulu-Natal is an example of the kind of positive action that can be taken to remedy past impact on the environment.
In 1995 AECI identified its Umbogintwini industrial complex (UIC) outside Amanzimtoti on the KwaZulu-Natal South Coast as requiring attention.
The Vumbuka project was launched to address the contamination of the land and groundwater caused by the long-term manufacture, storage and distribution of chemicals, agrochemicals and fertilisers on the site.
According to AECI’s Fulvia Putero, Umbogintwini had mainly used settling precipitation dams (or slimes dams) to contain and treat its liquid and semi-solid waste. But the decision was made to close that system and to replace it with a proper effluent chemical treatment plant.
The unlined slimes dams, based on outdated construction methods, were seeping toxic chemicals — mostly solvents in the form of chlorinated hydrocarbons — into the surrounding soil and groundwater, she said. The challenge led AECI, with the cooperation of the relevant local and national authorities, to formulate a plan to clean and seal the area.
AECI’s solution had two-phases. The first was to prevent further underground contamination from sludge in and around the dams to the adjacent land by sinking boreholes.
‘These are abstraction wells drilled down to a depth of between 35m and 50m below ground level along the boundary of the contaminant source,” said Bill Oliver, the original project manager. ‘The wells are designed to create a hydraulic curtain that intercepts and abstracts contaminated groundwater.”
The abstracted water was processed in the UIC’s treatment plant to decrease the chlorinated solvent component and then went through a flocculation/settlement period to remove inorganic chemicals before being safely pumped though a pipeline to the sea.
‘The treated solid waste itself is sent to a certified off-site disposal storage facility,” he said.
Emptying the dams has reduced the pressure that was driving groundwater beyond the boundaries of the UIC.
Agricultural drains were installed to capture seepage around the dams and in the neighbouring residential area of Ezimbokdweni and the ‘drums area”, where the chlorinated hydrocarbon waste containers were buried, was capped with a conventional certified engineered geosynthetic liner.
But all this was a precursor to the second phase and key objective of the project — to avoid the infiltration of rainwater to the emptied dams. While options on how to cap the dams were being evaluated, it became apparent that vegetation was reestablishing itself naturally.
Extensive research followed to determine whether this could be augmented and if it would benefit the long-term cleanup. This led to the choice of ‘evapo-transpiration” covers for the dam area. These were achieved by revegetating the area with indigenous plants.
The evapo-transpiration cover replaces the need for a geosynthetic liner and allows, through naturally occurring microbial activity, the progressive reduction of source concentration levels in the contaminant area beneath the root zone.
‘The cover was rigorously tested over a five-year period to verify its ability to perform in the Vumbuka environment as well as a conventional cap would,” Oliver said.
Clearly, it is succeeding — about 77ha, or 30% of the UIC’s developed land, is now a thriving green belt and much of the fencing alongside the Umbongavango Reserve has been removed to allow the free movement of fauna between the two. The entire green belt area is open to visitors by appointment.