Page 50 - March 2020 - WT Site

Reviewing Aerobic Technologies for the

Treatment of Wastewater

There are multitudes of aerobic biological treatment processes and technologies in literature and practice.
Biological treatment using aerobic activated sludge process has been in practice for over a century.

By Mr. Kondiba Metkari

Wastewater treatment has become essential these days, because well as it should be economical. Oxidation means decomposition
it is so interconnected with the other uses of water. This of organic or inorganic matters present in effluent. The
wastewater is treated and then converted to effluent to discharge secondary treatment involves biological oxidation and chemical
it to the natural water streams. If un-treated water discharged in oxidation. Biological oxidation processes can be aerobic and
river streams, leave its effects on the wildlife habitats thriving in anaerobic. Rely on microbial decomposition to treat wastewater,
oceans, rivers and marshes, migratory birds using these areas for the key difference between anaerobic and aerobic treatment is
breeding, resting, and nesting, fisheries which have direct impact that aerobic systems require oxygen, while anaerobic systems do
upon human consumption. Thus this effluent must be treated not. Most people consider bacteria and other microorganisms
before it goes back to the environment to have minimum impact to be undesirable components of wastewater. In fact, only a
on the environment, or can be directly reused. This reclaimed small fraction of the microbes found in wastewater are truly
water can be used for purposes other than consumption. pathogenic. Aerobic wastewater treatment encourages the
As disposal or reuse is the ultimate aim of the treatment of growth of naturally-occurring aerobic microorganisms as a
wastewater, treatment is decided accordingly to create minimum means of renovating wastewater. Such microbes are the engines
impact to the river streams and low sludge for landfills. of wastewater treatment plants. Organic compounds are high-
energy forms of carbon. The oxidation of organic compounds
Wastewater is treated in three stages primary, secondary and to the low-energy form (carbon dioxide) is the fuel that powers
tertiary. Primary treatment includes filtering the insoluble solids, these engines.
grit, suspended matter etc. from water, the sand filter is the most
commonly used filter. The oil and grease found on the surface The biological aerobic treatment uses bacteria or microbes to
of some wastewater can also be removed easily through this clean water systems that degrade the organic matter in presence
method. Next is secondary treatment, the collected filtered water of oxygen. The oxygen required for the decomposition of organic
is then treated to reduce its toxicity, decrease oxygen demand matter by these microbes is often measured in biological oxygen
and disinfect. This treatment includes oxidation and chemical demand or BOD, which refers to the amount of dissolved oxygen
treatment. Oxidation can be aerobic or anaerobic involved in needed by aerobic organisms to break down organic matter into
treatment and the tertiary treatment involves further disinfection smaller molecules. Provided that oxygen and food, in the form
like absorption, advanced oxidation, disinfection depending upon of settled wastewater are supplied to the microorganisms, the
quality of wastewater. biological oxidation process of dissolved organic matter will be
maintained. The bioconversion of dissolved organic matter into
The oxidation is the most important and integral part of the thick bacterial biomass can fundamentally purify the wastewater.
wastewater treatment processes, it defines the efficacy of the Subsequently, it is crucial to separate the microbial biomass from
treatment plant. Thus, secondary treatment should be efficient as the treated wastewater through sedimentation. This secondary

52 Water Today - The Magazine March 2020