Organic Waste Recycling

Land treatment of wastewater 441

U.S. EPA (1973) Wastewater Treatment and Reuse by Land Application Vol. I and II,
EPA-660/2-73-006 a&b, Washington, D.C.
U.S. EPA (1976) Land Treatment of Municipal Wastewater Effluents. Design Factors-1,
EPA-625/4-76-010, U.S. Environmental Protection Agency, Washington, D.C.
U.S. EPA (1981) Process Design Manual for Land Treatment of Municipal Wastewater,
EPA-625/1-81-013, U.S. Environmental Protection Agency, Cincinnati, Ohio.
Witherow, J.L. and Bledsoe, B.E. (1986) "Design model for the overland flow process",
J. Water Pollut. Control Fed., 58 , 381-386.

8.9 Exercises

8.1 Discuss the functions of vegetation in the land treatment process. Give

the criteria to be used in selecting a type of vegetation (or crop) for a land

treatment process.

8.2 a) You are to find out the indigenous types of soil and crops in your city.

Based on this information, suggest a suitable process of land treatment of

wastewater you would select for the city.

In practice, what are the other information needed for the selection of the

type of land treatment process?

b) If the city agrees to employ the land treatment process recommended

in a), you are to determine the following:

• Land area requirement for wastewater treatment


• Method of wastewater application


• Wastewater application rate (hydraulic and organic loading rates),
  and the periods of wastewater application and resting


• expected characteristics of the treated wastewater


• harvesting frequency of the crop


• lay-out (or schematic diagram) of the land treatment system,
  including the pre-treatment units.

8.3 Among the three processes of land treatment, i.e. slow-rate, rapid

infiltration and overland flow, discuss which process is most effective in

treating wastewaters containing the following constituents:

a) Nitrogen (in organic and ammonium forms)

b) Phosphorus

c) Heavy metals

d) Fecal coliform bacteria