What is wastewater treatment? What are the different
processes of wastewater treatment?
Wastewater treatment is a process to convert wastewater –
which is water no longer needed or suitable for its most recent use – into an
effluent that can be either returned to the water cycle with minimal
environmental issued. The latter is called waste reclamation and implies
avoidance of disposal by use treated wastewater effluent for various purposes.
The following is a step process of how wastewater is
treated:
Wastewater
Collection:
This is the 1st step
in the wastewater treatment process. Collection systems are put in place by
municipal administration, homeowners as well as business owners to ensure that
all the wastewater is collected and directed to a central point. This water is
then directed to a treatment plant using underground drainage systems or by
exhauster tracks owned and operated by business people. The pipes or tracks
should be leak-proof and the people offering the exhausting services should
wear protective clothing.
Odor Control:
At the treatment plant, odor
control is very important. Wastewater contains a lot of dirty substances that
cause a foul smell over time. To ensure that the surrounding areas are free of
foul smell, odor treatment processes are initiated at the treatment plant. All
odor sources are contained and treated using chemicals to neutralize the foul
smell producing elements. It is the first wastewater treatment plant process
and it’s very important.
Screening:
This is the next step in
the wastewater treatment process. Screening involves the removal of large objects
for example nappies, cotton buds, plastics, diapers, rags, sanitary items,
nappies, face wipes, broken bottles or bottle tops that in one way or another
may damage the equipment. Failure to observe this step results in constant
machine and equipment problems. Specially designed equipment is used to get rid
of grit that is usually washed down into the sewer lines by rainwater. The
solid wastes removed from the wastewater are then transported and disposed of
in landfills.
Primary Treatment:
This process involves the
separation of macrobiotic solid matter from the wastewater, primary treatment
is done by pouring the wastewater into big tanks for the solid matter to settle
at the surface of the tanks. The sludge, the solid waste that settles at the
the surface of the tanks is removed by large scrappers and is pushed to the center
of the cylindrical tanks and later pumped out of the tanks for further
treatment. The remaining water is then pumped for secondary treatment.
Secondary Treatment:
Also known as the active sludge
process, the secondary treatment stage involves adding seed sludge to the wastewater to ensure that is broken down further. Air is first pumped into huge
aeration tanks that mix the wastewater with the seed sludge which is
basically a small account of sludge, which fuels the growth of bacteria that uses
oxygen and the growth of other small microorganisms that consume the remaining
organic matter. This process leads to the production of large particles that
settle down at the bottom of the huge tanks. The wastewater passes through the
large tanks for a period of 3-6 hours.
Bio-solids handing:
The solids matter that settles out
after the primary and secondary treatment stages are directed to digesters are
heated at room temperature. The solid wastes are then treated for a month where
they undergo anaerobic digestion. During this process, methane gases are
produced and there is a formation of nutrient-rich bio-solids that are
recycled and dewatered into local firms. The methane gas formed is usually used
as a source of energy at the treatment plants. It can be used to produce
electricity in engines or to simply drive plant equipment. This gas can be used
in boilers to generate heat for digesters.
Tertiary Treatment:
This stage is similar to the one
used by drinking water treatment plants which clean raw water for drinking
purposes. The tertiary stage has the ability to remove up to 99 percent of the
impurities from the wastewater. This produces effluent water that is close to
drinking water quality. Unfortunately, this process tends to be a bit expensive
as it requires special equipment, well trained and highly skilled equipment
operators, chemicals and steady energy supply. All these are not readily
available.
Disinfection:
After the primary treatment stage
and the secondary treatment process, there are still some diseases causing
organisms in the remaining treated wastewater. To eliminate them, the
wastewater must be disinfected for at least 20-25 minutes in tanks that contain
a mixture of chlorine and sodium hypochlorite. The disinfection process is an
integral part of the treatment process because it guards the local people who
use the water for other purposes. The effluent (treated wastewater) is later
released into the environment through the local waterways.
Sludge Treatment:
The sludge that is produced and
collected during the primary and secondary treatment processes requires
concentration and thickening to enable further processing. It is put into thickening
tanks that allow it to settle down and later separates from the water. This
process can take up to 24 hours. The remaining water is collected and sent back
to the huge aeration tanks for further treatment. The sludge is treated and
sent back into the environment and can be used for agricultural use.
Wastewater treatment has a number
of benefits. For example, the waste treatment ensures that the environment is kept
clean, there is no water pollution, makes use of the most important natural
resource; water, the treated water can be waterborne diseases and most importantly,
it ensures that there is adequate water for other purposes like irrigation.
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