Chemical characteristics
Inorganic chemicals
The principal chemical tests include free ammonia,
organic nitrogen, nitrites, nitrates, organic phosphorus
and inorganic phosphorus. Nitrogen and phosphorus
are important because these two nutrients are
responsible for the growth of aquatic plants.
Other tests, such as chloride, sulphate, pH and
alkalinity, are performed to assess the suitability of
reusing treated wastewater and in controlling the
various treatment processes.
Trace elements, which include some heavy metals,
are not determined routinely, but trace elements
may be a factor in the biological treatment of
wastewater. All living organisms require varying
amounts of some trace elements, such as iron, copper,
zinc and cobalt, for proper growth. Heavy metals can
also produce toxic effects; therefore, determination of
the amounts of heavy metals is especially important
where the further use of treated effluent or sludge is
to be evaluated. Many of the metals are also classified
as priority pollutants (see below).