Water problems in the future will become more intense and more complex. Our increasing population will tremendously increase urban wastes, primarily sewage. On the other hand, increasing demands for water will decrease substantially the amount of water available for diluting wastes. Rapidly expanding industries which involve more and more complex chemical processes will produce larger volumes of liquid .wastes, and many of these will contain chemicals which are noxious. To feed our rapidly expanding population, agriculture will have to be intensified. This will involve ever-increasing quantities of agricultural chemicals. From this, it is apparent that drastic steps must be taken immediately to develop corrective measures for the pollution problem. There are two ways by which this pollution problem can be dwindled. The first relates to the treatment of wastes to decrease their pollution hazard. This involves the processing of solid wastes 'prior to' disposal and the treatment of liquid wastes, or effluents, tn permit the reuse of the water or minimize pollution upon final disposal. A second approach is to develop an economic use for all or a part of the wastes. Farm manure is spread in fields as a nutrient or organic supplement. Effluents from sewage disposal plants are used in some areas both for irrigation and for the nutrients contained. Effluents from other processing plants may also be used as a supplemental source of water. Many industries, such as meat and poultry processing plants, are currently converting former waste products into marketable by products. Other industries are exploring potential economic uses for their waste products. The purpose of this passage is ______.