Many of those living in rural areas of South Africa, and even more of those beyond our borders, are faced with a shortage of potable water, often requiring them to carry supplies from sources many kilometres from their homes. In parallel, millions of litres of this precious commodity are consumed daily for use in a wide range of industrial applications. Without the support of the suppliers who provide the chemicals and equipment that are necessary for water treatment, the future of both industry and the consumer would be, to say the least, uncertain.
There are few events that could have exposed the vulnerability of our semi-arid nation as effectively as the recent severe drought conditions faced by businesses and residents in the Western Cape. It was an event that could have been disastrous without the temporary relief offered by a hastily installed temporary desalination plant. However, not only will this measure be unable to provide Capetonians with a long-term solution, such drought conditions are not confined to the nation’s southern regions and thus the need for the only viable alternative – that provided by the suppliers of water treatment chemicals – extends beyond the Mother City and to all nine provinces and their inhabitants. Furthermore, if we are to ensure the long-term sustainability of future supplies, both the nation’s industries and its households will need to become far more conservative in their use of this life-giving liquid.
In devising an effective approach to conserving this vital resource, it will be necessary to look at the various ways in which we may reduce any unnecessary water usage, while also addressing strategies to reclaim much of that which has already been used, to purify it to varying degrees and, wherever possible, re-use it. In short, we must either seek some help from the suppliers of water treatment chemicals or simply accept the possibility that punitive usage restrictions could be imposed, on a regular basis, in addition to the current trend of frequent increases in the monthly municipal tariffs. The range of substances employed for this purpose might come as a surprise to most consumers. Whereas most consumers are likely to be familiar with the use of chlorine to maintain the sterility of domestic supplies during distribution, there is far less awareness regarding the identity of and the roles played by most of the other water treatment chemicals available from specialist suppliers. In practice, the use of chlorine gas has been largely discontinued, to be replaced by its dioxide, which presents no health threats.
The substances chosen tend to be determined by the degree of purity required which, in turn, will depend upon whatever use may be planned for the treated effluent. Should the intention be to produce a potable supply, it will require treating the contaminated source with a number of different agents in a planned sequence. While physical means such as straining and sedimentation are necessary preliminaries for the removal of debris and large particles to remove colloidal materials, coagulants such as polyamines or iron salts are used to neutralise the charges that maintain colloidal suspensions. To remove low-density uncharged particles, the suppliers of water treatment chemicals offer flocculants such as acrylic acid polymers to form aggregates which are then sufficiently dense to sediment out.
In other applications such as treating the water that will be used to feed industrial boilers, potability is not the concern but the presence of insoluble calcium salts that may precipitate to cause scaling and, over time, severe damage to the boilers. Especially troublesome in hard-water areas, chemical suppliers advocate treatment of boiler feedwater with anti-scaling chemicals such as phosphoric acid, phosphate esters, and polyacrylic acid. Sometimes, exceptionally high levels of purity are required, as in the preparation of pharmaceuticals, for example. In this context, ion-exchange resins offer a highly effective means to eliminate all traces of dissolved minerals, replacing them with hydrogen and hydroxyl ions, which then combine to form more water and, in combination with heat sterilisation, provides a solvent of exceptional purity. In fact, ion exchange technology is highly scalable and is now being applied to the desalination of seawater and brackish sources, offering new hope in the battle to relieve the pressure on traditional reserves. With plants already operating in the Cape and on the KwaZulu-Natal coast, South Africans have good reason to thank local suppliers of ion-exchange resins and other water treatment chemicals.