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sedimentation is basically similar to primary sedimentation except thus low or slow decomposition of organic matter resulting into
that the sludge contains bacterial cells rather than fecal solids. The reducing efficacy of treatment plant.
biological removal of organic matter from settled wastewater is
conducted by microorganisms, mainly heterotrophic bacteria Thus to treat these water oxygen incorporation is necessary.
but also occasionally fungi. The microorganisms are able to According to the amount of organic matter and requirement of
decompose the organic matter through two different biological effluence, wastewater treatment might involve different processes
processes: biological oxidation and biosynthesis. The biological and different types of microbes required to decompose organic
oxidation forms some end-products, such as minerals that matter. They also require particular operational procedures that
remain in the solution and are discharged with the effluent. will differ that are subject to the environment norms needed to
The biosynthesis transforms the colloidal and dissolved organic keep biomass growth rates optimal for the specific microbial
matter into new cells that form in turn the dense biomass that can populations. It is also required to monitor aeration process to
be then removed by sedimentation. maintain a consistent dissolved oxygen level to keep the system’s
bacteria multiplying at the appropriate rate to meet discharge
Oxidation:

requirements. Not only Dissolved oxygen but other parameters
Biosynthesis:
like pH, nutrients temperature and ratio of organic matter
to microbes are also important to monitor as they affect the
treatment process rate of decomposition.

Following are examples of some common types of aerobic
High levels of BOD indicate an elevated concentration of biological wastewater treatment systems, including a brief
biodegradable material present in the wastewater and low levels description of how they function within an industrial wastewater
of dissolved oxygen and can be caused by the introduction of treatment procedure to give you an idea of the types of
pollutants such as industrial discharges, domestic fecal wastes technologies and systems that might benefit your industrial facility.
or fertilizer runoff. High BOD levels means low oxygen levels

Water Today - The Magazine l March 2020 53