105
Water or wastewater treatment system comprises of combination of the treatment
unit/process designed to reduce concentration of pollutant to the desired level.
Water treatment comprises of only unit operations and chemical process. While
the wastewater treatment uses wide array of biological processes to remove biodegradable pollutants.
Economics, aesthetics and availability of space/energy determine the choice of
unit operation and process. In practice, consultants and designer may choose costly
operation/process to make more profit.
Wastewater can arise from domestic activity, industry, intensive animal farming,
waste leaching, urban runoff, agricultural runoff or any other activity. But wastewater treatment as the end of pipeline solution is usually adopted where wastewater can
be trapped economically.
Wastewater treatment is done by the same principle and phenomena that are
observed in the nature during natural purification even though there are many technologies available, which demands investment.
Fig. 5.4 Another example
of self-purification by
water-tolerant plants
forming wetland, thereby
absorbing chemicals like
nitrates and phosphates
that provide surplus
nutrients to plants and
affect the health of the
fauna
5.2 Engineering Control