o 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.