THE ELECTROPLATING INDUSTRY
2.1 WASTE MINIMISATION AND WASTE MANAGEMENT
An industrial process can be regarded as the conversion of low cost input/s into more valuable output/s using machinery and/or labour (see Figure 2.1 ).93, 94 These input are of two types, energy and matter.
Chemical Input ^ w PROCESS Desired Output
Waste In process
recycling/ re-use
Figure 2.1 Simple industrial process model93'94,95
Chemical inputs include primary raw materials which end up in the finished product as well as process, ancillary or secondary raw materials that are not found in the final product but are necessary to run the process.94 The latter includes lubricating oils for plant machinery, catalysts to speed up the process, analytical chemicals for process monitoring and control, any personal protective equipment worn by workers and water used as a chemical (raw material), solvent (or carrier) or as a rinse. Output can also be of two types: desirable and undesirable. The desired output is obviously the final product which meets those specifications laid down by the customer or by trade law. Undesired outputs are waste. There are very few industrial plants that do not produce waste when preparing their desired products. Waste is defined as any matter, whether gaseous, liquid or solid or any combination thereof, which is deemed as undesirable or superfluous by-product, emission, residue or remainder of any process or activity.96 This means that it exists in material and energy forms, which can be interconverted. Material waste streams include wastewater or liquid effluent discharge, particulate and gaseous atmospheric emissions
and solid waste. These can be conscious and/or accidental emissions. For example the release of chromic acid mist from an electroplating solution into the atmosphere would be an established process waste whereas a vapour leak from a solvent degreaser would be an accidental or fugitive emission. Chemical wastes are often referred to as pollutants and contaminants in the literature.35 In both these cases, the chemicals are present in higher concentration than that found in the natural or ambient environment. This increase is man made through, for example, industrial or agricultural activities. Such waste only becomes a pollutant at these elevated concentrations if it damages the environment whereas it is termed a contaminant if it has no adverse effect on the environment. These wastes are all covered by the National Environmental Management Act No. 107 of 1998 and include the waste produced from metal finishing processes like electroplating and powder coating of workpieces.
Once waste is formed it can be handled in many different ways depending on the amount or volume, its physical form (solid, liquid or gas), its toxicity and its suitability for re-processing.
These approaches to handling waste are listed in order of decreasing sustainability in the waste management hierarchy (see Figure 2.2).
/ \ Best
Worst
Figure 2.2 The waste management hierarchy*7- **•w-10°
Waste management looks at using waste minimisation approaches at the upper end of the hierarchy to deal with industrial waste. The ideal approach therefore is to reduce waste at source; that is decrease (minimise) or eliminate (waste avoidance or zero-waste) any waste produced in the process.96' • ,02 This means using less raw materials (which end up in the finished product) and less process chemicals at the start of the process. By not forming waste in
the first place, it means there will be no storage, handling, treatment, disposal or recovery problems of waste. This approach to waste management is termed start of pipe treatment.94'I03 The alternative to waste minimisation is the treatment of waste once it has already been produced. This uses waste management approaches from the lower end of the hierarchy to deal with the waste. This means having to re-use or recycle the waste and, where this is not possible, having to treat the waste so that it can be disposed of safely. Re-use and recycling104'l05 is concerned with used raw materials (which have been through the process), processed and rejected workpieces and waste. Re-use sends used materials or workpieces through the same process again (in-process recycling which takes place on-site). Recycling looks at re-processing used raw materials etc. in order to make different products or in energy production (waste recycling). Recycling can take place on- or off-site and the selling of waste for recycling can generate income. Such an approach is referred to as end of pipe treatment.106107
The hierarchy also defines the order of preference for ranking potential waste minimisation efforts that can be implemented in an industrial process. This is based on achieving the maximum conversion of input to output and the minimum conversion of input and output to waste in a sustainable way. It aims to make high environmental savings or benefits by preventing damage to the environment caused by the creation and disposal of waste. The former involves producing less waste by not using excessive amounts of non-renewable or scarce resources as input to the process.94' 96 This avoids depleting raw material stocks by conserving mineral and other non-farmed or cultivated resources. The latter means not placing toxic waste output into the land, water courses or the atmosphere where they can cause damage by migrating, (bio)accumulating or persisting in the environment.105'108 However the hierarchy does not always offer a practical means for enabling industry to prioritise its waste minimisation efforts. The fact that waste minimisation can be expressed in monetary terms as well as by volume or amount of waste can be used to overcome this problem.104 The cost of producing waste based on raw material consumption has been widely used as a means for selecting suitable waste minimisation options from a range of potential options in order to achieve sustainable waste minimisation.102 Producing less waste can reduce the economic expenditure on purchasing raw materials (pay for then use), on waste treatment and disposal
and on collecting and transporting both raw and waste material. It also reduces the cost of utilities including water and electricity which, unlike the other raw materials, are used first and paid for later. The waste minimisation audit takes this into account by seeking to identify the most cost effective and viable ways to achieve waste minimisation using established waste minimisation analysis techniques. Other benefits arising from practising waste minimisation include reduced immediate and future criminal risk and liabilities and a better, greener public image.109 However the financial savings and reduced operating costs which a company can make have been found to be the most significant incentive for the adoption of a waste minimisation approach in industry.110