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10.9 Systems Planning Management and Costs 353
(c) recycling of process waters, and (d) treatment of the waste. Recovery is most successful
when the substances recovered are either very valuable or otherwise not so unlike the pri-
mary products of manufacture that a separate management organization must be devel-
oped. Improvement in manufacturing processes may permit discharge of remaining waste
matter into public sewers.
Satisfactory treatment processes are available for a wide variety of industrial wastes.
Most of them are not unlike established wastewater treatment methods, but some chemical
wastes require quite a different disposal approach. For example, cyanides from plating in-
dustries are most conveniently oxidized to cyanates, chromates from the same source are
most conveniently reduced to chromic compounds, and acids and alkalis from many indus-
tries are most conveniently neutralized.

10.9 SYSTEMS PLANNING MANAGEMENT AND COSTS
The planning, design, and construction of water and wastewater systems for metropolitan
areas usually bring together sizable groups of engineering practitioners and their consult-
ants, for months and even for years. Under proper leadership, task forces perpetuate them-
selves in order to attack new problems or deal with old ones in new ways. For publicly
owned wastewater systems, studies, plans, specifications, and construction contracts are
prepared by engineers normally engaged by the cities and towns or by the wastewater dis-
tricts to be served. Wastewater engineers may belong to the professional staff of municipal
or metropolitan governmental agencies responsible for designing and managing public
works, or they may be attached to private works or to firms of consulting engineers. To
accomplish large new tasks, permanent staffs may be temporarily expanded. For smaller
works, consultant groups may be given most and possibly all of the responsibility.
Engineers for manufacturers of wastewater equipment also play a part in systems develop-
ment. The engineers of construction companies bring the designs into being.
Construction of new wastewater systems, or the upgrading and extension of existing
ones, progresses from preliminary investigations or planning through financing, design,
and construction to operation, maintenance, and repair. Political and financial procedures
are involved, as well as engineering.
The first cost of sanitary sewers lies between USD 180 and USD 600 per capita in the
United States. Storm drains and combined sewers, depending on local conditions, cost
about three times as much.. The first cost of wastewater treatment works varies with the
degree of treatment provided. Depending on plant size, which, for wastewater, is more
clearly a function of the population load than the volume of water treated, the per capita
cost of conventional wastewater treatment works as of 2008 was as follows:
1. Mechanized settling and heated sludge digestion tanks USD 195, varying approxi-
4 1>3
mately as 1>(P l0 )
2. Activated sludge units as well as primary treatment USD 282, also varying approx-
4 1>4
imately as 1>(P 10 )
3. Trickling filters as well as primary treatment USD 270, varying approximately as
4 2>7
l>(P 10 )
4 1>4
4. Stabilization ponds USD 5.40, varying approximately as 1>(P 10 ) .
The approximate annual per capita operating and maintenance cost for the plants
themselves, that is, exclusive of central administrative expenses, is as follows:
5
3
4
1. For primary plants, USD 16.2, 8.4, 5.5, and 4.0 for communities of 10 , l0 , 10 ,
6
and 10 people, respectively