This study
was completed for the Water Corporation during 1991-92. The following
factors were considered for reuse of effluent from the sewage lagoons
(oxidation ponds):
(1) The final
effluent will have coliform organisms in excess of the guideline for
reuse (1000 organism/100ml). So there should be facilities to chlorinate
the water if the reuse involves any spray irrigation or the use involves
any human contact with the water.
(2) The effluent
will have algae as it comes from the oxidation
pond. Chlorination will kill most of the algae, but the water has to
be stored in a closed container which does not allow sunlight promoting
any algal growth. As per guidelines there should not be any visible
algae in the water. Moreover algae will clog the reticulation, spray,
drip or other irrigation system.
(3) The storage
tank should be preferably at an elevation and convenient location depending
on the type of use. So a pumping facility will also be necessary.
(4) As the
oxidation pond system loses water by infiltration and evaporation,
on-site reuse systems (eg. Biomax, Aquarius or Dowmus) may be advantageous
to make water available for lawn and vegetable garden.
(5) For transport
of water from the storage tank to the place of use either connection
by pipe or truck with water tank may have to be provided.
(6) Final
effluent can also be stored underground by recharging the groundwater
aquifer. There will not be any evaporation loss or algae problem and
the effluent gets purified by infiltration through the soil. The pumping
from the underground aquifier needs be done only when water is required.
(7) A vegetable
garden or orchard close to the ponds is a possibility if land is available
and the community is prepared to work in the garden. An enclosed area
for growing vegetables will be of great value to the community. This
needs fencing of the area and preparing the soil. Subsurface evapotranspiration
trenches can be used.
The study
found that in each community there may not be enough effluent produced
that would be necessary to provide year-round irrigation of a football
oval.
