SOLAR HEATING OF INDUSTRIAL
WASTEWATER STABILIZATION PONDS
Stanley L. Klemetson, Associate Professor
Rebecca Austin, Graduate Assistant
William D. Linfield, Graduate Assistant
Engineering Research Center
Colorado State University
Fort Collins, Colorado 80523
INTRODUCTION
Industrial wastewater treatment and methods of improving the various treatment processes
have been the focus of attention for many years.   One inexpensive method which has
received some consideration is the use of stabilization ponds, both as the primary treatment
process as well as the final step in much more complex processes.   Unfortunately, with the
upgrading of EPA standards in July 1977, and the increasing costs of land, lagoons have
become less attractive economically in certain parts of the country and are having difficulties complying with State standards.
The biological performance of a lagoon is highly dependent on temperature.   The useful
temperature range is from 5 C to 35 C (41 F to 94 F) and the greater the temperature, the
more efficient the system up to 35 C.   Increased biological activity would result in a smaller
detention time which in turn would require less land.   The lower limit is a result of retardation of aerobic bacteria and algal activity.  The upper limit exists as a result of inactivation
of green algal species [ 1 ].
One of the major problems with stabilization ponds, especially in northern climates, is
the winter freeze.   During this time, biological activity is greatly retarded and anaerobic
conditions develop because of the lack of aeration caused by the ice cover.
Organic solids will accumulate under anaerobic conditions. The detention time for facultative ponds is 7 to 20 days and 20 to 50 days for an anaerobic pond [2]. Under the most
extreme condition, it could take an anerobic pond up to seven times as long to treat sewage
as a facultative pond.
Even in properly designed sewage lagoons, there is the problem of accumulated nutrients
in the winter as a result of retarded biological activity.   Spring thaw then brings tremendous
algae blooms as a result of massive nutrient buildup over the winter months.   Subsequent
algae die offs occur resulting in further oxygen demand and further enhance the anaerobic
conditions.   Foul odors are also a problem under anaerobic conditions [3].
As a solution to insufficient biological activity and large land requirements, solar heating
of lagoons has been proposed.   Problems associated with lagoons that hope to be corrected
are: ice cover preventing adequate oxygen, spring thaw resulting in foul odors due to anaerobic conditions, low temperatures that retard biological activity, and large land requirements.
APPLICATIONS OF SOLAR ENERGY
The suns energy is an inexhaustible resource.   During the past several years more and more
uses of this resource have been developed ranging from hot water preheating for private
homes to powering our nations satellites.
One application which has not been explored in depth, to date, is the use of solar energy
to heat wastewater stabilization ponds.   A study of this concept is currently being performed
at Colorado State University.
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