The amount of water that industry takes from streams or groundwater aquifers is not the governing factor in industrial use of water. Although for the nation as a whole industry withdraws more water than irrigated agriculture, the quantity it uses up is considerably less. Even so, the way in which the water is utilized in production has a significant effect on water supplies, both in terms of the liquid wastes that are returned to the water courses and of the water actually consumed.
Hence, industry's future needs and requirements for water are a central factor in planning and managing water resources. In this connection past trends of water intake per unit of product or per employee can be very misleading as guides to the future. What explains, for example, the fact that production of pulp and paper increased by 26 percent between 1954 and 1959, while the industry's water intake increased by only 8.5 percent? Or that 104 petroleum refineries increased their refining capacity by over 51 percent between 1949 and 1959, while their freshwater intake increased by only 5 percent?
Clearly, there is a host of implicit factors affecting industrial water utilization. Important among these is the impact of technological change. A few examples point up some of the difficulties in planning as industrial water demand presses more heavily on local water supplies.
Petroleum refining
Refineries have increased in size and complexity over the last twenty years. Instead of a relatively simple distillation-cracking operation, today's refineries may have, for example, hydrogen-treating units, catalytic reforming units, alkylation units, and units for the production of the entire range of lubricants. Greater refinery complexity results in a large cooling load and larger amounts of water applied per barrel of crude processed; it also can increase the magnitude and complexity of the waste load per barrel. Thus, refinery complexity is one factor operating to increase the industry's total clean-water needs and its waste loads.
Offsetting this effect, however, are other factors, one of which will illustrate how water per unit can be reduced. In a traditional refinery the different processes are typically separated by intermediate storage. In an integrated refinery, the processes are adjacent to each other and are essentially one big unit. Stock is run directly from one unit as the charge to the next unit. Adoption of integration at the Sohio Toledo refinery saved about 10,000 gallons per minute of cooling water capacity.
Pulp and paper
Higher quality standards for pulp and paper products, together with rising production of colored paper products, account for the continuing increase in total water applied in the production process. Between 1954 and 1959 the total amount of water used to produce a ton of product increased by almost 13 percent. At the same time, the consumptive use of water per unit—water that is actually used up in the production process — apparently decreased. Why this is so is not clear, but it is conceivable that process changes have resulted in the installation of more closed cooling systems with a consequent reduction in evaporative losses.
The quantity of waste in the final effluent per unit of product has also been reduced, sometimes quite dramatically. How much of the reduction results from changes in production processes and how much from waste treatment cannot yet be determined because the available data do not separate the two types of factors. To illustrate the effect of production process: depending on the method of pulping used, the waste load in pounds of biochemical oxygen demand per ton (BOD is one measure of water quality) can vary from less than 50 to more than 500. Efficient heat and recovery systems can reduce pulp losses, a major contributor to BOD load, by as much as 95 percent. One kraft mill reduced its average effluent waste load from 57 pounds of BOD per ton in 1955 to 25 pounds per ton in 1960. This was accomplished through tighter plant operation, reuse of process water, constant observation of waste production, and waste treatment.
Fruit and vegetable canning
Higher standards or more stringent specifications for the quality of canned fruits and vegetables have stimulated the development of new methods for cleaning raw products before they are cooked and canned. As an example, it has been found that if raw tomatoes are dipped in hot lye solution they will be virtually free from fly eggs. Buy large quantities of water must then be applied to wash out the lye. Another process adopted to improve product quality replaces dry conveying belts with water flumes which carry the product through the plant in a wet condition. Improved technology of these kinds results in an increase in the total quantities of water applied per unit.
So far as waste load is concerned, the story is different. Here, more efficient processing equipment is reducing waste load for every ton of raw product processed. The upward trend in case yield attests to this. Over the last twenty years the average cash yield for peaches has increased from forty to about fifty-five cases per ton of raw product processed. As the yield increases, more of the raw product is incorporated in the final output, thereby reducing the waste load. Improved filling operations also favorably affect waste load. Even small amounts of syrup spilled in canning fruit products contribute highly concentrated waste in terms of BOD load. Consequently, any increase in filing efficiency can achieve significant reductions in the waste load per unit of raw product processed.
It is evident from the examples mentioned that most of industry's technological changes have been stimulated by factors unrelated to water problems; more often than not their impact on water utilization has been unanticipated. However, where water is scarce and therefore relatively costly, industry is impelled to conserve it by one means or another.
What measures will best encourage industry to more efficient utilization of water from intake to outlet?
Many advocate providing incentives for industrial plants to construct waste treatment facilities. But this raises some basic questions. Industrial firms analyze water utilization problems in terms of the greatest return per dollar invested. If the cost of constructing waste treatment facilities is reduced by tax incentives, grants, or increased depreciation allowances, these facilities may be adopted more readily than alternative means, such as process changes, by-product recovery, and water recirculation which, by mixing resource inputs, may result in a more efficient pattern of water utilization from society's viewpoint. Another approach to the problem is to impose charges based on the amount of waste load carried by the effluent. Where sewer charges have been levied, they appear to have been effective in stimulating industrial firms to modify either production processes or waste treatment methods, or both. When one company's utilities division levied intake water and waste disposal, charges against each of the company's operating departments at major plant, it stimulated modifications of production processes as well as of water utilization systems within the departments.
However, charges intended to reduce intake and effluent should not be imposed without considering their other possible impacts on water utilization. To illustrate: efficient methods for reducing waste loads in the final effluent can be stabilization ponds, spray irrigatIon systems, and/or underground disposal. One result of such methods, however, is an increase in the consumptive use or net depletion of water, which may be on the order of 50 percent in terms of water per unit of raw product processed per unit of final product. Although small in absolute quantity, increase of this kind may loom large in water-scarce areas. Because the consumptive use of water is the factor limiting the level of economic activity in any area, there can be conflict between the objective of reducing waste loads and that of minimizing consumptive use. Consequently, perhaps what should be considered instead of water intake and/or an effluent charge is a "water utilization" charge which would take into account all aspects of industrial water utilization. Where water is in relatively short supply, such a charge would encourage an industrial plant to reduce its consumptive use. Credits against water utilization charges could be given to those users who achieve this goal. As an example: In the manufacture of tomato products such as paste and catsup, instead of permitting the water extracted from the tomatoes to escape into the atmosphere, facilities could be encouraged that would capture and condense the water for further use. The water utilization charge would, therefore, be based on the four factors: Quantity of water intake, Consumptive use of water, Quantity of effluent, and Waste load in the effluent. Just how such a charge would be formulated in quantitative terms and what relative weights should be given to the various factors remain matters for further investigation.
Adapted from "The Economics of Industrial Water Utilization," by Blair T. Bower.
A version of this article appeared in print in the May 1967 issue of Resources magazine.
