We Are Faced With An Increasing Need for Water Treatment
In the wake of news articles describing the damage and loss of life caused by tropical storms, torrential rain, and flooding, it can be hard to believe that our planet is faced with a global water crisis. The reason for the problem, however, is not that the liquid has become scarce but that we are consuming and contaminating it at a rate that is far faster than our existing water-treatment plants are able to convert it back into a potable end-product. To be effective, these plants must maintain substantial reserves but, in recent years, burgeoning consumer demand combined with changing weather patterns have led to a decline in the volume of those reserves.
On a commercial level, one of the most significant advances in the attempt to replenish those dwindling reserves has been the development of water-treatment technology that is able to extract potable water from the sea and the brackish sources often present in coastal areas. The concept first adopted was not new but mimicked nature in that it involved evaporation of seawater followed by condensation to provide a salt-free distillate similar to rainwater. However, the cost of energy for heating was too high to be economical and only with the introduction of reverse osmosis have desalination plants become a viable option.
Conventional water-treatment plants are operated by local municipalities throughout South Africa and rely on a combination of methods to arrive at a potable product. The first of these is straining and is designed to remove coarse materials such as leaves, branches, and stray items of refuse. Straining is followed by sedimentation in which the incoming liquid is allowed to settle out under the action of gravity. This step serves to remove much of the particulate matter that remains after straining but fine solids in colloidal suspension will often fail to separate out. To remove these, a water-treatment plant will add a flocculating agent to the sedimentation tank. This causes the fine particles to clump together to form larger masses that are sufficiently dense to sink to the bottom of the tank. At this stage, the partially treated effluent still contains tiny particles as well as bacteria that will have to be removed by passing it through a sand filter. Like the distillation process first used for desalination, this is a process first utilised by nature. As rainwater passes through the soil, it is filtered in the same fashion before it eventually reaches the bedrock beneath to form an aquifer.
At this stage of the water-treatment process, though it may be crystal clear, the treated effluent still contains bacteria and there are two methods commonly used to ensure they can do no harm to the consumer. One method is to expose the filtered liquid to the bactericidal effect of an ultraviolet light source. However, while this will kills all organisms present, it cannot prevent re-contamination at some later stage. The more effective option is chlorination, using either the gas or one of its soluble compounds. The residual chlorine in the transported product should be sufficient to ensure that it will remain sterile until it is consumed.
As things stand today, it is no longer feasible to leave the responsibility for water treatment to municipalities. Households, farms, and heavy industry all need to participate in a joint effort to conserve, reclaim, and reuse this vital natural resource wherever it may be possible. For the nation’s residents and farmers, the solution is rainwater harvesting, a practice that is both simple and relatively inexpensive. Starting with no more than some modified guttering, a downpipe, and a suitable PVC storage tank, the rainwater collected can, during times of drought and rationing, be safely used for irrigation and cleaning tasks without any further processing. By adding a compact water-treatment plant, the stored rainwater can be made potable and, if desired, it could even be integrated into the main domestic supply. Another option is to use these compact installations to cleanse greywater from sinks, baths, showers, and washing machines.
In many common industrial processes, water is used extensively and invariably becomes contaminated with chemicals. While, in the past, many factories have settled for processing their effluent sufficiently to be safely discharged into the surrounding environment, an industrial-grade water-treatment plant can just as easily be used to render their wastewater suitable for reuse while cutting costs in the process.