Requirements for a Sewage Pond


Sewage ponds are very simple to construct.  A bulldozer is used to remove soil from the ground and create a basin in which water can collect.  However, the pond and surrounding area must be planned in such a way that the human and natural environments surrounding the pond are not damaged.      



The first requirement of a sewage pond is that it must be surrounded by a berm (a mound or wall of earth) or an embankment (a raised structure to hold back the water.)  The berm or embankment prevents storm water from running into the pond.  Without a berm, a heavy storm could cause the sewage pond to overflow and send untreated sewage out into the surrounding area.  

The soil in which a pond is built must be impermeable.  This will prevent the sewage from being absorbed into the ground and from leaking pollutants into the area.

A pond must be completely fenced to keep unwanted visitors out.  In addition, the area around the fence must be mowed to keep out vermin which could dig holes into the sides of the pond.  Tree growth must be restricted near the pond since roots could enter the pond and provide a way for sewage to escape if the trees died.  

Sewage ponds must be encircled by a windbreak, which usually consists of a row of pine trees.  The windbreak will prevent the pond's odors from disturbing the nearby residents and will also make the area aesthetically pleasing.  

The depth of the pond is another important factor.  The pond must be greater than two feet deep at all parts to exclude plant growth.  Plants growing at the edge of a pond will create areas of still water in which mosquitoes will lay their eggs.  But at depths of over six feet, anaerobic conditions occur, so regulations stipulate that the depth of a sewage pond can be no more than 5 feet.  



Health of the Surrounding Environment

The final requirement which must be met when constructing sewage ponds is to be sensitive to any streams or rivers into which the effluent from the pond will be released.  This entails knowing the classification of the stream, whether the stream contains any endangered species, and whether there are any existing contaminants in the stream.  

One way of protecting the surrounding environment is by adding a finishing pond.  A finishing pond, also known as a polishing pond, is like a finishing school - it prepares the water to go out into the world.  The finishing pond is installed between the sewage pond and the stream as shown below.  




One of the largest problems when water is released directly from a sewage pond into a stream is algae.  Sewage ponds are perfect environments for these one-celled plants.  Food is readily available, as is moisture and sunlight, so algae grow quickly and become quite numerous.  

When water from a sewage pond, rich in algae, is released directly into a stream the stream can be harmed.  The large quantities of algae use up the water's oxygen at night or during an algal bloom (when the algae reproduce very quickly).  Without the oxygen they need to survive, the fish in the stream die.  

A finishing pond can eliminate this problem.  Finishing ponds are usually stocked with fish, such as carp, which eat the algae in the water.  Finishing ponds also allow the quality of the effluent to be monitored before it is released into the stream.  As a result, streams being fed by finishing ponds tend to be healthier than those fed directly from sewage ponds.