Environmental Master Plan - Iron and Steel Production (South Africa)

The site from the North

Within South Africa, we were commissioned by a large coal gasification, iron ore processing, steel production, rolling and finishing facility to critically review tender proposals for a treatment plant for organic effluents (COD, ammonia and dissolved salts removal). The intended plant, a biological nitrification and denitrification system following by reverse osmosis (RO), evaporator and salts crystallisation facilities had an intended capacity to treat 8000 cubic metres per day. Refractory COD issues necessitated the inclusion of activated carbon to ensure compliance against very restrictive discharge criteria. There were also potential issues associated with biocidal components which could be present in variable quantities within the raw effluents.

We reported on the technical and economic efficiencies of the different tender proposals and also on their overall appropriateness relative to the real needs of the site.

As a result, RPA were commissioned as part of a multi-disciplinary team of specialist consultancies to develop the most cost effective overall holistic Master Plan strategy for the site as a whole so as to deal with all:

• Production wastes – both for historic on site deposits and for ongoing production;
• Production effluents;
• Spillages – including appropriate remediation and future containment;
• Atmospheric emissions and the handling of the resultant residue streams;
• Rainfall runoff – both contaminated and clean;
• Ground water contamination;
• Existing landfill deposits and their remediation;
• Contamination from raw materials.

Iron and Steel Production from the South West

This work included both the development of the optimum long term strategy and the selection and design of interim measures to arrest or mitigate the more significant impacts from the ongoing operations whilst the long term measures are developed, approved, designed, built and brought into operation.

The production facilities at this site occupy about 1500 hectares within a total site area (production, raw materials storage, product handling waste deposits and other working areas) of about 4000 hectares.

A natural water shed line divides the site into two almost equal areas. As a result of the above referred interim measures, all contaminated discharges to surface water from the one half of the site were stopped. This was achieved by a combination of containment, reduction at source and redirection to appropriate treatment and re-use.

As a result of specific RPA proposals:-

• A series of carefully integrated containment and spillage/leakage prevention measures were implemented. This achieved the stopping of all net process inputs and storm water overflows to the large on-site storage and evaporation lakes. Arguably the most environmentally sensitive lake was emptied and the inventory of the remainder is reducing rapidly.

Lagoons and Residues (as they were)

• The pipework, the operating concepts and the controls for the on-site treatment facility for the more concentrated process effluents were rearranged. This enabled almost half of the processing stages to be shut down, reagent usage was more than halved, residues production was reduced to <25% and all treatment quality criteria were brought into compliance.
• Using adaptations to existing infrastructure and pipework, a scheme was successfully implemented whereby weaker (but none the less environmentally sensitive) inorganic discharges were directed without additional treatment to other site uses, thereby simplifying and greatly reducing the overall site effluent treatment requirements and reducing the raw water needs of the site.
• A second similar strategy was developed whereby the site’s principal source of organically contaminated effluents is being more than halved and then the remainder will be used, without additional treatment, for other site uses as a replacement for raw water. This scheme has removed the need for a biological effluent treatment facility at the site.
• An overall holistic strategy for handling, re-using and recovering all the remaining site produced effluents (a total of over 1000 m³/hr) and contaminated run-offs (including landfill leachates and contaminated ground waters) was developed whereby the total site will be able to become a zero effluent facility. This scheme is currently going through its tender adjudication stages prior to implementation.
• In conjunction with site staff and others, RPA took the technical lead in developing a new technology for the quenching of hot off-gasses and the wet scrubbing of sub micron sized dust from those off-gases. This technology is undergoing the latter stages of pilot plant development prior to implementation on a 60 Nm3/s demonstration plant. This technology is expected to be very commercially and functionally attractive relative to the only alternative, namely wet electrostatic precipitators. The technology is also able to utilise a heavily contaminated waste water as its only source of make up water.
• Following initial exploratory testwork, RPA has been commissioned to develop and demonstrate a suitable waste stabilisation process whereby all non-recycled/non re-used production residues, silt from the former storage and evaporation lakes and all effluent treatment and desalination plant residues are converted into a sufficiently stable and low risk product to make it suitable for long term on-site disposal.

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