Page 64 - Studio International - May 1974

which trout feed. Large amounts of algae can be means is practised in Sweden, Switzerland and and in the interests of its public image, has
synthesized from small amounts of nutrients; North America. It adds appreciably to the adopted a more responsible position towards the
one gram of phosphorus, for example, is cost of sewage treatment however, and so far, problem of pollution. Ignorance and
sufficient to synthesize 100 grams of organic such treatment methods have not been justified thoughtlessness account for many sources of
matter in the form of algae. If such nutrient-rich in this country. pollution: in the past, lack of knowledge of the
waters are used for public supply in storage effects of different discharges on rivers was
reservoirs, they produce nuisance-causing algal The changing face of pollution understandable, but today, with the present
growths which may impart taste and odours to One is often asked whether the pollutional publicity, this is no longer an excuse.
the water and add to the cost of water treatment. situation in our rivers is improving or In contrast with causes of pollution which are
For effective control of this nutrient problem deteriorating. Because of the public awakening socially controllable, other essential activities
the sources of the nutrients need to be to the pollutional problem, it is commonly of man have an inevitable effect on his
identified. In most British rivers the major believed that the pollution is progressively environment. Man's effect on the environment
source of nitrogen is from land drainage. The increasing, and the doomwatch attitude is is proportional to his population density and
increased concentration of nitrogen in our prevalent. But surveys have shown that in activity. Since the industrial revolution, which
rivers is commonly attributed to the increased Britain three-quarters of the total river length resulted in the concentration of populations
use of artificial fertilizers on agricultural land. is classified as unpolluted and supports fish. and the development of industry on the banks
Surveys, however, comparing the relative use Furthermore, the length of river so classified of rivers, the problem has been accentuated.
of fertilizers in different countries with the has increased over the past decade. Thus, in As an example of man's inevitable effect on his
increase in concentration in the respective spite of the increased pollutional load from environment let us consider one element —
rivers, showed that there was no general industry and homes, we can claim at least to be phosphorus. As a result of his metabolic
correlation between nitrate concentrations and holding our own. This has been due to the activities man necessarily excretes
fertilizer use. There is, however, an appreciable building of new sewage works and the approximately 1.5 grams of phosphorus per
drainage of nitrogen from natural soils to which renewing of older ones : considerable advances day. A further 1.5 grams per head per day is
artificial fertilizers are not added. Since only have been made in the field of sewage treatment added by the use of detergents. Taking into
5o percent of the added nitrogen is recovered in technology. Although the organisms responsible account the pollution removed at the sewage
the crop, the absence of a corresponding increase for the purification processes are the same as works, it can be calculated that a city the size
in the river water suggests that nitrogen is those active at the beginning of the century, of Birmingham will contribute approximately
probably accumulating in the soil or in ground when their role in the process was not two tons of elemental phosphorus to the river
water. It has been estimated that the nitrate appreciated, research has enabled us to control every day. Apart from the effect on the river,
concentration in the chalk bore-hole water from their activities and greatly improve efficiency. this represents the loss of an enormous
the Lincolnshire wolds increased by 5o to The pollutional problem, however, is a quantity of valuable fertilizer. It appears an
Too percent over the last ten years. In rivers changing one. The recession of the coal mining ironic consequence of sewage treatment that
such as the Trent, for example, which drains industry a decade ago which reduced the amount the nutrient stripped sludge is sold as a
the English industrial Midlands, most of the of coal dust entering some rivers, resulted in fertilizer and the plant nutrients, nitrates and
nitrogen was attributable to sewage effluents. the improvement of certain rivers so that fish phosphates pass away in solution in the
In contrast to nitrogen, phosphorus is not were able to return to them. In some such effluent. As mentioned earlier, these nutrients
readily leeched from the land. Although rivers however, as the mines filled with water can technologically be removed from the
considerable amounts of phosphorus are added and dissolved the iron from the pyrites, the effluent but at appreciable cost. Whether the
to agricultural land as fertilizer, almost all of resultant waters discharged to the rivers were community is willing and able to pay is an
this is recovered in the crop. Losses of acid and contained iron which deposited on the economic and social consideration. It has been
phosphorus which do occur, result from water river bed as ochre. Other rivers, previously estimated that under British conditions it is
and wind erosion of fertile top soils. This type polluted organically, now suffer nutrient probably cheaper to pay for increased water-
of erosion of sandy soils in the Eastern enrichment; sewage fungus growths have given treatment costs resulting from the adverse
counties in the spring removes appreciable rise to the more colourful but equally conditions than to remove nutrients at source,
amounts of phosphorus, much of which finds its troublesome growths of cladophora. but this does not remedy the position in the
way to water courses and reservoirs. Sewage Our present understanding of the nature of river itself. A more advanced approach to the
effluents are easily the most common source of pollution and water pollution control technology problems of water pollution control would be
nutrients entering rivers. Agricultural could enable us to effectively control river the positive one of conservation; that is,
effluents however, as opposed to land drainage, pollution. The main problems are sociological conservation by recovery of valuable materials
are becoming a more important source of and economic. Although, for sake of which would result in the conservation of the
nutrients with changing agricultural practices. presentation, I have classified pollution natural freshwater habitats. In some countries
Whereas in the days of mixed farming, animal scientifically, the causes of pollution can be enjoying longer hours of sunshine, algae
wastes were recycled to fertilize the land, with classified quite differently sociologically. These grown on the nutrients of sewage effluents has
factory farming they are discharged to the rivers range from the inexcusable to the inevitable, been used as poultry feed.
and adversely increase their fertility. being associated with human vices, failings, and The problem of river pollution, at least, is
Unlike carbon, which is oxidized by bacteria man's essential activities both physical and not an insoluble one. Indeed, because of
in the sewage treatment processes, much of the metabolic. Of the inexcusable causes of nature's inbuilt purification process involving
nitrogen and phosphorus is not utilized and is pollution, malicious forms are rare. The more evaporation and precipitation in the form of
still present in the effluent. Although the common form in this category is selfishness. the hydrologic cycle, we are given another
bacteria require some nitrogen and phosphorus At management level it is realized that it is less chance of improving our rivers each time it
as well as carbon in a well-balanced diet, the costly to discharge effluents to water courses rains. Generally, by virtue of the developed
relative proportions of nitrogen and phosphorus than to install treatment plants. At the operator technology, society can have the environment
in relation to carbon present in sewage is in level, the easiest way of emptying a tank is often it is able and willing to pay for. Man's
excess of the organisms' needs. Technical into the nearby water course. With the general technology has produced for him both
processes have been developed for the removal realization of the pollutional problem these affluence and effluents. For him to continue to
of nitrogen and phosphorus from the sewage attitudes and practices are largely things of the enjoy the former he must use some of it to
effluents. The removal of phosphorus by such past. Certainly industry, in its own interest, control the latter. q

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