Techniques for cleaning up
Two main general approaches to water quality improvement exist: treatment of pollution at its source or occasionally after it has entered a stream, and augmentation of the stream's flow to help it assimilate loads of waste beyond its natural capacity. A third possibility in certain situations is the diversion of wastes out of a stream's drainage entirely. In practice, these methods can be varied and combined in any number of ways to fit a need.
To take the last one first, diversion of whole wastes as received from their sources is a total and dramatic means of coping with a pollution problem stemming from collectable wastes, but it often has disadvantages. One of these, of course, is the possibility that the pollution problem may be simply transplanted elsewhere—that the water in which the wastes eventually end up will suffer. Another is loss of water from the stream system. If, as is usual, a town gets its water out of the local river or a tributary and does not give it back after use—preferably well cleaned up—other users downstream are not going to have as much water available to them, and the essential processes and ecology of the river itself may suffer.
The only place such wholesale diversion of wastes has been seriously considered in the Potomac Basin is at metropolitan Washington, whose sewage could feasibly be piped across Chesapeake Bay and the Delmarva peninsula and well out into the Atlantic—possibly, as has been suggested, in combination with sewage from Baltimore. It would be a permanent means of disposal, but very expensive in terms of both investment and operating costs. Furthermore, though in the estuary no downstream users would suffer a loss of water supply, the water content in metropolitan sewage has at times risen as high as 80 percent of the flow of the river above the upstream intakes. The effects of such a subtraction of fresh water on the estuary itself—changes in flow, and in the penetration of salt water upriver, with an inevitable alteration in valuable fisheries and the whole balance of aquatic life established through millennia—could easily turn out to be disastrous.
Standard treatment of pollution at its source consists of the primary and secondary processes we have glanced at, sometimes adjusted to specific industrial wastes. It has to be brought up to peak efficiency along the Potomac, for this is a "known factor" of great significance. Plants can and must be improved physically where necessary, and qualified operators provided for them. Collection systems have to be improved or enlarged in many places. Diminutive plants, doomed to inefficiency by their size and the financial impossibility of hiring expert workers for them, need to be eliminated in favor of regional waste collection and treatment facilities, which are quite feasible, particularly in the watershed units of the upper Basin.
Even so, it has emerged clearly to view in this Potomac study that standard treatment alone is no longer an answer in areas of concentrated or continuous population and industry, where the leftover wastes and the nutrients in the effluent from even well-run standard plants can often add up to a killing load for water.
Total diversion of treatment plant effluents is sometimes possible, but is subject to the same objections that apply to total diversion of untreated sewage—possible pollution of the receiving water (such as Chesapeake Bay or the lower Potomac estuary, both of which have been suggested and considered for Washington's effluent) and the alteration of hydrological and ecological conditions. Modified forms of effluent diversion, however, may offer more promise.
Effluents from maximum standard treatment processes, for instance, can be injected into underground strata as recharge water for aquifers—a process mentioned earlier as one alternative in the emerging package of water supply techniques—or may be spread over the surface of large areas of rural land where they serve as irrigation water and fertilizer combined, as well as soaking down into underlying aquifers. For large scale, sustained use, both of these practices still offer some technical difficulties—algae buildups that interfere with percolation, odor problems, limited aquifer capacities, the large amounts of land required for spreading, the effect of rain and freezing weather, and such things. And where the aquifers in question do not feed the original source stream system, a big subtraction is again involved. But for certain conditions in certain places these problems are undoubtedly going to be worked out.
A more modest but highly useful modification of effluent diversion is the spacing of treatment plant outfalls at intervals for a long distance downstream from a treatment plant. If nutrient and organic loads are not tremendously heavy in relation to the size of the receiving stream, this procedure can help to assure that no one stretch gets too strong a dose of them. It is likely to find good use in the Potomac and elsewhere, though only as an adjunct to the best available treatment.
"Advanced treatment" and "tertiary treatment" are becoming common terms nowadays. They refer to any of a considerable array of additional or intensified processes aimed at attaining levels of purification that would have cost an impossible price a few years ago. Most of them are still experimental and often still expensive, and they involve everything from filtration through powdered coal to flash distillation, with still others in prospect. Some bypass conventional treatment and deal with whole raw wastes. More build on conventional treatment and are designed to remove nutrients and residual organic material from its effluents. Of these latter approaches, at least one, involving lime precipitation and other processes to remove nearly all phosphorus and most remaining organic material, is nearing a stage of development and economy that may warrant important use. It will be applied first at the new Piscataway treatment plant of the Washington Suburban Sanitary Commission in Prince Georges County, Maryland, which will also incorporate research and demonstration projects in nitrogen stripping and other things.
In the long run such advances offer the main hope of clean water for a superpopulated future America, where volumes of wastes are going to be enormous and first-rate off-stream treatment is going to have to be the main way of handling them. Even where wastes can be collected easily for treatment, however, as in industry or in sewered populated areas, it may take a good many years to work out varied forms of advanced treatment adaptable to different sets of circumstances, at prices that communities can afford to pay—and a willingness to pay what can be paid is going to have to be a part of the long clean-up job ahead. Undoubtedly continuing research will work out such forms of treatment, but the research itself may be quite costly and no one can predict its pace.
Where waste sources are too diffuse to be channeled into collection systems—as along many agricultural streams heavily polluted through land runoff and drainage, and also in some urban situation—present tools are extremely limited. Soil conservation practices aimed at cutting down erosion—to be discussed within a few pages—tend to keep not only silt but nutrients and other substances on the land to some extent. Concentrated sources of animal manure such as dairies, poultry operations, and feed lots can be brought under some control by fencing stock off from streams and by techniques of lagooning and later field spreading, which need much wider use in the Potomac Basin. But even if these approaches were applied fully throughout the region within a shorter time than appears likely or even possible, land runoff would still be a heavy source of water degradation.
Hence it is probable that flow augmentation—sometimes called "flow dilution" or included in the broader term "flow regulation"—through the release of stored water, will be an important auxiliary tool in water quality management for a good while to come. This is not a form of flushing wastes downstream from their source and out of sight, as some opponents continue to insist, but a means of helping streams to oxygenate and decompose excess wastes by the same processes they have always used on natural and normal loads. On the other hand, neither is flow augmentation the end-all cure for pollution that enthusiasts of a few years ago claimed it to be. Its effect on slow masses of water is uncertain and probably minimal, and too much dependence on it even for flowing streams would obviously encourage neglect of the practical and moral need to keep filth and troublesome substances from getting into the streams in the first place. Furthermore, such dependence would lead rapidly to a point of diminishing returns, like the flood-plain development and protection cycle examined in the preceding chapter. Increases in populations and pollution would lead to a necessity to provide more and more augmentation of flows, with storage space in reservoirs becoming more and more expensive precisely as flood protection does. Flow augmentation is no substitute for good treatment, but a valuable adjunct.
In the record drought summer of 1966 the South Fork of the Shenandoah, heavily polluted with municipal and industrial wastes near Waynesboro, and with fertilizer, manure, and other substances in drainage from the rich and intensively utilized farm country through which it flows, ran very low for months. In many places it was slimy and unpleasant, and aquatic life suffered to some extent, but the picture was not nearly so dismal as it would have been if the river had not been helped out more or less by accident. The source of this help was some 2000 gallons of water per minute that the Merck plant at Elkton and the Dupont plant near Waynesboro were releasing after having pumped it out of deep aquifers and used it for cooling. If all sources of pollution had been receiving adequate treatment, this minimal dilution might not have been so badly needed to avoid the fish kills and algal stagnation and other results that would have ensured without it. But "all sources" include the problematic agricultural drainage, and for that matter the definition of "adequate treatment" is going to have to go up and up in our expansive future.
The sad situation of the smaller and much less industrialized Monocacy in the same summer underscores the point. The Monocacy flows through similar farming country and passes by a few towns. The largest of these is Frederick, Maryland, for whose approximately 40,000 people the little river furnishes water and a conduit to carry away the effluent from their average-to-good secondary plant. At times during that dry summer practically the entire flow of the river below Frederick consisted of effluent, with effects on stream life, esthetics, and the general surroundings that are not hard to imagine.
Another good example of a place where, under present conditions, augmentation could sometimes be used beneficially is at Great Falls and in the Potomac gorge below. Heavy public expenditure has protected the shore in much of this neighborhood and provided pleasant recreation areas whose main scenic focus is the violent magnificence of the river in its plunge. But the magnificence becomes a rather drab joke in dry summers when metropolitan withdrawals of water above that point shrink the river to a semblance of normal flow.
Low Flow Augmentation
The North Branch and some smaller Basin streams also need this same kind of help and most will continue to need it even when the best economically feasible treatment of all collectable wastes entering them is ensured. It can be provided out of reservoirs, large or small, whose need for other purposes as well will keep the cost of dilution within reason. A future possibility, if research presently going on in the Basin verifies it and shows ways of putting it to use, is to employ ground water in the same way. There can be no doubt that if the flowing waters of the Basin are to be put back in good condition and kept that way under population pressures that are in prospect, flow augmentation in some places is going to be an important tool.
In the upper estuary, however, its usefulness appears to be far more limited. The plan proposed in the Army Report of 1963, in line with a Public Health Service approach emphasized in the 1961 Water Pollution Control Act, was designed to provide an eventual minimum flow into the upper estuary of 3100 cubic feet per second, or around two billion gallons per day, for the purpose of dealing with treatment-plant effluents and miscellaneous pollution. But more recent investigations have raised strong doubt as to whether such augmentation could do the job in the estuary with its huge volume of water, and its slow, tide-baffled currents that greatly lessen its assimilative capacity.
In terms of dissolved oxygen, dilution of such a body of water for quality improvement appears to decrease in unit effectiveness as the volume of dilution is stepped up, which means that past a certain minimal point of improvement it gets expensive and requires unreasonable amounts of storage. In terms of nutrients, one authority has calculated that about 20,000 cubic feet per second would be required to reduce the nutrient level in the upper estuary to a point where it would be only twice that of a normal and healthily "rich" section of the upper Chesapeake Bay. Some augmentation below the point of diminishing returns will undoubtedly be needed, not only for the estuary but to keep the river alive in its gorge above Washington during periods of low flow. But as a main tool for the metropolitan river, it will not substitute for achievement of the best possible standard treatment followed by advanced treatment and other techniques.
Obviously, just as in water supply, an ultimate cure for water quality ills is going to consist of a "mix" of solutions, different techniques being applied to the situations they are best suited to deal with, and combinations of them being worked out where combinations are what is indicated. Already the same kind of sophisticated mathematical models of given bodies of water—including the Potomac—that are being used to study solutions for water supply problems are being put to use on water quality as well, weighing the benefits and drawbacks of various combinations of means. And, just as in water supply, ultimate "hard" technology is undoubtedly going to make better solutions possible, while a strong and meaningful start is possible with the technology that is on hand.
Silt is a truly Basinwide problem. The individual tiny grains of soil that mass to sully and choke the estuary may have originated anywhere in the thousands of square miles of drainage above. They constitute an economic loss at their points of origin as well as a trouble all along their downstream course of migration.
The basic-physical ways of preventing silt are twofold and easily defined: first, the maintenance of proper land cover—vegetation or humus or mulch which blankets and anchors the soil particles and prevents falling or flowing water from dislodging them—and second, structural approaches that control the flow of water and can also serve to trap eroded material. These latter can be anything from good contour plowing practices to a major reservoir with a certain silt capacity built into it.
Such techniques are the basis of existing programs of the Soil Conservation Service and the Forest Service that have proved their effectiveness over many years of rural application. Watershed planning with small reservoirs, check dams, and terraces backed up by good land treatment and use, soil surveys, wise forestry practices, and such things are stimulated and bolstered in these programs by technical and financial assistance given to private landowners, States, and local organizations. They have already had important local effects in the Potomac States as throughout the country, but for maximum value in relieving sedimentation they are going to need much wider and more intensive application.
In modified form, they can be effective against newer and more concentrated sources of silt, while sometimes accomplishing other purposes as well. As we noted in discussing metropolitan pollution, urban land undergoing development can enormously benefit from good watershed planning. Preservation of critically erosive and flood-prone land in grass and forest, insistence on prompt re-vegetation of bared land and the use of such things as sediment detention basins by developers, the construction of small headwater reservoirs when they are needed to trap silt and reduce flooding—all these elements of watershed planning are effective not only against silt but against standard urban and suburban ugliness. The translation of rural techniques to city use cannot be literal, for both urban hydrology and urban land use are distinctive, and a good deal remains to be learned about making the techniques work better there. But their basic principles are obviously a main hope.
Other modifications of them, if put into wide practice, can cut down on the heavy production of silt by strip mines in the upper Basin; these involve both the reclamation of abandoned mines and the use of more care in scraping new ones. And application of the same principles—protective cover and detention of runoff—to new highway and road construction, as well as to the reclamation of banks and shoulders on old secondary roads, has to be achieved.
The silt already in the upper estuary, and likely to continue to be deposited there even after the best available controls may have been put into operation above, will need radical treatment. The tens of millions of tons already choking the metropolitan river, the stockpile of centuries, will have to be dredged out if the river is going to be as pleasant and useful at the capital as it ought to be, and so will the yearly additions that can inevitably be expected. This can be done if the money is available, though a considerable unsolved problem, under research at present, is where to put the silt after it has been taken out of the river, for appropriate fill sites are growing scarce.
Turbidity in the sluggish upper estuary will continue to be a problem too, for the fine particles of silt that cause it are the least affected by standard land treatment and sediment control measures. Polyelectrolytes—chemicals which when applied in quite small amounts can coagulate such suspended silt and settle it out—offer some promise as tools against turbidity and are being tried out experimentally above one of the reservoirs on upper Rock Creek, with good results thus far. Very possibly they may prove to be useful for clearing up the estuary after it has been roiled by storm runoff, and for achieving some control of murky waters around sand and gravel dredging operations. However, ironically, it has also been pointed out that until the excess of nutrients in the upper estuary is eliminated, such clearing of the water could very possibly cause a great increase in the already disastrous algae blooms, by allowing sunlight to penetrate to greater depths and foster more production of this undelightful greenery. Cleanup of pollution as complex as that evolved in the 20th century has to be across the board.
Barring a general philosophical revolution on the part of the American people, the problem of junk and debris in our waters is likely to continue and even to increase as people and their consumption of the products of the economy maintain their geometric growth. Clean rivers in themselves might deter a good many people from cluttering them thus, and so might public education, stiff fines, and the provision of better municipal pickup and dumping facilities. But mainly getting rid of such detritus is probably going to be a matter of fairly continuous gathering and disposal. On navigable waters like those of the upper Potomac estuary, ingenious collection craft under the command of Army Engineers are in prospect; elsewhere the job is likely to be more old-fashioned and laborious.
For certain remaining pollution problems, no definite full technological answers exist at present and the main hope must be to alleviate them as much as possible while pressing a search for long-run answers. Some are relatively restricted in their effects in the Potomac Basin so far, though they have some drastic local effects and some long-run implications. Certain industrial wastes not amenable to any presently known form of treatment, such as tannery discharges at Petersburg, West Virginia, and Williamsport, Maryland, are one example. So are the noxious exudations of raw sewage and garbage from ships and pleasure craft. Marinas themselves and the boats docked there can and must be connected to waste collection systems. Laws can and should prohibit discharges from watercraft in harbors and rivers. But until better means of on-board waste treatment or retention than exist at present are evolved and made mandatory, the multitudes of boats with standard toilet facilities are going to keep on causing trouble.
Other sources of trouble without clear-cut present solutions are big ones. Surface runoff from both cities and rural areas, as we have seen, causes much pollution. In the country, soil conservation measures can slow it somewhat and strain out some pollutants, and augmentation of streams' flow can enhance their capacity to oxidize the wastes. But neither of these seem likely to do much to ease the longrun buildup and diffusion of persistent pollutants like pesticides, or to avert the possibility of disastrous spills. Public education and wiser restrictive legislation may help, but the only real hope in terms of these poisons appears to be that more selective and less indestructible substitutes will be found, and all promising means of biological pest control explored. Continuing programs are focused on the problem, but it continues to be serious.
Pollutive runoff from urban areas merges with the whole question of urban sewer systems, for most of it gets to the river through storm sewers. We have seen that the old-style combined sewers of the District of Columbia and Alexandria cause gross pollution when storms force open their overflow gates, and we have seen too why the approach to this problem that formerly prevailed—the arduous, hugely expensive digging up of sewers and their replacement with dual pipes to carry storm runoff and sewage separately—is no longer considered satisfactory. For the more modern dual systems also contribute much trouble through the filthy rainwater that pours out into streams from the storm system and through the accidental or illegal channeling of sanitary wastes into storm sewers.
A wholly satisfactory answer would allow runoff water as well as all sanitary wastes to be held for full treatment at a standard plant. But when we consider that at the Washington metropolis the dirty local runoff from a single storm may amount to billions of gallons, the question of where to hold it grows a bit complex, and is leading toward experimentation with such ideas as vast subterranean networks of tunnels for storage. Partial answers might come from subjecting storm and mixed flows to different and lesser kinds of treatment by micro-screens at sewer outfalls, detention and settling tanks, and filtration beds. These possibilities and others need much investigation and testing.
Then there are the multitude of nasty mysterious dribbles that help to degrade Rock Creek and can undoubtedly be found in even more profusion along every other metropolitan watercourse. Such of them as issue from storm sewers will be eliminated when a solution turns up for the problem of runoff water. The others, and they are numerous, will not. Even if the bureaucratic and political tangles that help to perpetuate them—which will be mentioned again—are dealt with, the sheer mathematics of possibility in a great city, plus the frequent difficulty of fixing responsibility, make the overall problem of these miscellaneous leaks and dribbles a very tough one, not likely to be resolved with the wave of anyone's hand. Except in visible and well-defended watercourses like Rock Creek, they will probably persist for a long while, even though in reduced quantities, together with some storm runoff and some periodic discharge from combined sewers, not a major component in estuarial pollution but a stubborn one.
A final great contaminant against which weapons are meager is acid mine drainage. Its sources along the North Branch are numerous, as we have seen. They have been and are being minutely studied, but present technology does not furnish any clear and effective means of dealing with each source individually and returning the upper river and its branches to health, and such source rectification would be the only really adequate answer.
Surface strip mines are deservedly notorious for the destruction of the rugged green landscapes that are one of Appalachia's greatest resources. Because of the public disgust they arouse, they have had a lot of attention, and methods for conducting this sort of mining less brutally and for reclaiming old minesites have been worked out. These methods have notable effect on silt and acid production. Because State laws to regulate strip mining have been generally scarce and weak, however, and because the reclamation of old mines is very expensive, such action is mainly more honored in the breach than in the observance.
However, strip mines produce only a tenth to a quarter of acid mine pollution, and if they were all under control the problem would still be huge. The active or abandoned underground mines that give out the great bulk of the acid and other pollutive substances have so far almost totally resisted satisfactory management, despite tremendous efforts. Among techniques that have been tried are neutralization with limestone and other materials, air sealing to cut down on the oxidation that helps form the acid, sealing of mine openings to prevent outflow, mining methods designed to prevent exposure of sulfuritic materials, and chemical inhibition of acid generation. Regardless of the hope that some have aroused, none has worked well and economically, and the search is hindered by a continuing lack of data and scientific knowledge concerning the complex physical and chemical processes by which the pollutants are formed.
A number of agencies are researching this whole problem, among them the Federal Water Pollution Control Administration, the Geological Survey, the Bureau of Mines, the Soil Conservation Service, INCOPOT, and some State government bodies. Sooner or later an answer or a set of answers must come out of these efforts. But nothing presently conduces to a belief that the acid problem on the North Branch or anywhere else is going to find quick and dramatic alleviation at its sources.
Dilution of this acid pollution helps to minimize its effects, not actually neutralizing them but reducing their severity in periods of low river flow. It can be accomplished by impounding mine drainage for release only during periods of high flow, though where sources are many as on the North Branch this would be difficult. Or fresh water can be held in bulk storage for release during low flow. In helping acid conditions along the lower North Branch, therefore, the authorized Bloomington reservoir may play a part, though it will do nothing for the upper reaches of the river and the reservoir water itself will be acidic if nothing is done to neutralize it. Under INCOPOT auspices, a promising inquiry is being conducted into the possibility of instream acid removal above the reservoir, using an energy process possibly powered by electricity generated at the dam. If it works out as well as seems probable, the benefits can be huge.
There is little point, of course, in getting the acid out of the lower North Branch unless the other pollution in that area is dealt with too. This compounded trouble, involving a considerable number of towns and industries with insufficient waste treatment or none at all, is made to order for a pilot application of the regional or sub-basin type of waste management authority mentioned earlier in this chapter. Not only is the problem on the North Branch bad enough to warrant special overall measures, but the area's topography is well suited to collection of wastes and their conveyance to first-rate centralized treatment plants. This approach too is being studied out by INCOPOT, not only for the North Branch but for other well-adapted problem watersheds such as Antietam Creek. Like similar systems in Germany that have long been admired, it would pool the resources of all sub-basin waste producers, get appropriate government funding, and subject all the pollution of a given drainage area to intensive and comprehensive correction.