Desk Calculator Model for Wastewater Planning

by Donald T. Lauria, (M.ASCE), Prof. of Environmental Engrg.; Dept. of Environmental Sci. and Engrg., School of Public Health, Univ. of North Carolina, Chapel Hill, N.C.,

Serial Information: Journal of the Environmental Engineering Division, 1979, Vol. 105, Issue 1, Pg. 113-120

Document Type: Journal Paper


This paper presents simple equations to: (1)Assist hand calculations for screening; and (2)indicate whether a computer model might be called for. Assuming only two adjacent polluters, two alternatives are considered: separate treatment plants for each or an enlarged treatment plant plus a connecting sewer. Treatment plant costs depend primarily on flows, which are assumed to be known. Sewer cost, however, is primarily a function of its length and diameter. Diameter in turn depends on length and elevation difference between the polluters. Writing total present value cost expressions for the two alternatives and setting them equal, it is possible to solve for either the length or the elevation difference for which the planner is indifferent between the alternatives. If the actual length is shorter or the elevation difference is larger than that obtained from the equations, then a regional plant should be built. Sequential use of the equations for a real region with eight towns is illustrated.

Subject Headings: Wastewater management | Computer models | Sewers | Writing skills

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