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.
[Illustration]
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.
[Illustration: 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.
[Illustration]
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.
[Illustration]
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.
[Illustration]
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.