Commentary Article

Afriwaste

C o m m e n t a r y Article

Afriwaste The Fixation and Stabilisation of Hazardous Waste - Rendering Waste into a Product Safe for Landfills Ian Hammond, K. Robert Mfiller Waste Resources (Pty) Ltd., 265 Oxford Road, Illovo 2196, South Africa

Abstract The disposal of hazardous and toxic wastes is an area where utmost care and responsibility needs to be exercised. A certain (and mostly acceptable) level of care and responsibility has been legislated and is in place in most developed economies (UK, USA, Canada, Europe, etc.). This is, however, generally not the case in under-developed or developing economies, South Africa being no exception. This paper reflects on various disposal methods and describes a potentially economic alternative to existing methods of the disposal of toxic and hazardous wastes. These existing methods are: Disposal in Class I landfill sites and destruction via incineration. Although incineration (which entails the total destruction of toxic compounds) is the preferred method of disposal, an alternative solution is the fixation of these wastes using specially formulated cementitious agents. The Fixation Solution can be economically feasible, especially in developing economies.

Radioactive wastes were for a long time indiscriminately dumped at high sea without bothering about the effects. Today, the D & D principle is no longer accepted in the developed world. "Dissolution is no solution" to any problem, but is C & C really the viable alternative? Love Canal, Times Beach, Lekkerkerk, Georgswerder and T h o r Chemicals are just a few names out of m a n y to serve as failed examples to contain toxic substances on industrial or landfill sites. Something went wrong at these places and we have to ask what to do about it and h o w to avoid similar cases in the future. When landfill sites are studied, two disposal methods are evident: 1.3

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domestic wastes are dumped together on one site. This system was practicised all over the world until two decades ago. It is still used to some extent in the UK. As a matter of fact, it has worked in many cases, as aerobic or anaerobic degradation processes, known to occur in domestic landfill sites, were able to decompose some types of industrial waste, too. This was accomplished either by biodegradation in case of organic waste, or by forming insoluble waste from inorganic

Developments Towards Fixation

When the disposal of hazardous waste is considered, there are two philosophies how to approach the problem. The first one is the "disperse and dilute" (D & D) principle, the other the "contain and concentrate" (C & C) principle. Both systems have advantages and disadvantages to consider. For most of our history, people favoured the D & D system. Its advantage is that it is a final solution to the problem and, if it is performed with consideration, a safe solution. The disadvantages are: 1.1

It is not reversible. Once diluted, it seems impossible to retrieve the toxic constituent.

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In some cases it seems difficult to calculate acceptable levels of dilution.

Consider two examples: D D T and radioactive wastes. D D T was the most widely used insecticide in history. It was applied on large areas, nobody cared to recollect it after use and it was allowed to disperse and dilute. T o d a y we find traces of D D T all over the world, even in deserts or in the ice layers of Greenland. Nobody studied the bio-degradation potential of D D T and nobody knew about acceptable levels of dilution until Rachel CARSON'S novel "The Silent Spring" was published in 1962.

ESPR-Environ. Sci. & Pollut. Res. 2 (3) 175-178 (1995) 9 ecomed publishers, D-86899 Landsberg, Germany

Co-disposal System: This is where industrial and

waste.

Since it is difficult to predict the fate of industrial (or toxic or hazardous) wastes in a plethora of other wastes, legislation in most parts of the world has ruled out co-disposal in favour of separate disposal systems.

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Separate Disposal Systems: These demand that domestic and industrial waste be kept apart. In SA, e.g. Class I and Class II landfill sites are required for the separate disposal of certain waste categories. Similar regulations prevail in most industrial countries.

Separate disposal systems apply to well developed economies where all other means of waste treatment are available (incineration, liquid treatment, composting, waste exchange etc). The situation is very different in developing countries, where in most cases none of the aforementioned facilities is available.

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Afriwaste

Commentary Article

Incineration is specifically important, as it is the only method to safely decompose most organic compounds. A proper incineration plant which meets all modern requirements is extremely expensive and can only be economically erected amid highly industrialised environments. In many regions of the world such amenities are not affordable and sustainable, and alternatives therefore have to be sought.

Table 2:

Criterion

Critical Value

Criterion

Critical Value

pH

>__7

Zn 2+

Afriwaste The fixation and stabilisation of hazardous waste : Rendering waste into a product safe for landfills.

The disposal of hazardous and toxic wastes is an area where utmost care and responsibility needs to be exercised. A certain (and mostly acceptable) le...
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