TM 5-814-8
restricted from drinking water supplies because it
bicarbonate and hydroxide components of natural
inhibits oxygen transfer in blood. Maximum
water supplies. Industrial wastes often contain
N O 3-N concentrations of 10 mg/L are allowed in
these species in addition to mineral and organic
drinking water under National Interim Primary
acids. Alkalinity determinations are useful in
Drinking Water Regulations.
determining wastewater neutralization require-
ments.
monly found in treated wastewaters or natural
streams at very low concentrations (0.5 mg/L).
or proton concentration in waters or wastewaters.
Nitrite is a metabolic intermediate in the nitrifica-
pH is an extremely important wastewater param-
tion process. It is rapidly converted to NO 3-N by
eter as it affects the solubilities of metals, salts
nitrifying organisms. Nitrite is an inhibitor to the
and organic chemicals, the oxidation-reduction
growth of most microorganisms and for this
tendency and direction of wastewater compo-
reason is widely used as a food preservative.
nents, and the rate of chemical activity in
(5) Phosphorus. Phosphorus occurs naturally
wastewater solutions. Gross wastewater charac-
in rivers and streams as compounds of phosphate.
teristics affected by pH include toxicity, corrosiv-
Elemental phosphorus does not persist naturally
ity, taste, odor, and color. Th pH of pure water is
in aquatic systems as it is quickly oxidized by
given the value of 7. Acid solutions have a pH
molecular oxygen to phosphate. Phosphates are
below 7 and alkaline or basic solutions have a pH
commonly found in industrial and domestic
above 7.
wastestreams from sources including corrosion
(4) Nitrogen. In wastewater treatment, the
inhibitors, detergents, process chemical reagents,
nitrogen forms of primary concern are:
Total Kjeldahl nitrogen (TKN),
and sanitary wastes. Phosphorus is an essential
Ammonia nitrogen (NH3-N),
nutrient in biochemical mechanisms. A residual of
0.5 to 1.0 mg/L total phosphorus is usually
Nitrate nitrogen (NO3-N), and
Nitrite nitrogen (NO2-N).
required in biological waste treatment systems to
ensure efficient waste treatment. Excessive phos-
(a) Total Kjeldahl nitrogen represents the
phorus in natural waterways, however, can be
organic nitrogen plus ammonia nitrogen indicated
very harmful resulting in algal blooms and
in the Kjeldahl test procedure. Following mea-
eutrophication.
surement and removal of the ammonia nitrogen,
(6) Sulfur. Sulfur occurs naturally in rivers
the organic nitrogen in the wastewater sample is
and streams as compounds of sulfur. Elemental
converted to ammonia nitrogen by catalyzed acid
digestion o f the wastewater. The resulting
sulfur does not persist naturally in aquatic sys-
tems as it is oxidized by molecular oxygen to
N H3-N is then analyzed and reported as the
sulfate. Due to the cathartic effect of sulfate upon
organic nitrogen fraction. Not all organic nitrogen
humans, the drinking water limit for sulfate has
compounds, however, will yield ammonia nitrogen
been placed at 250 mg/L in waters intended for
under catalyzed acid digestion. Acrylonitrile and
human consumption.
cyanuric acid are examples of compounds that are
(a) In some industrial waste streams sul-
only partially hydrolyzed by the Kjeldahl test
fate and sulfur compounds are present in high
procedure.
concentrations and may be a major component of
(b) Ammonia nitrogen (NH3-N) as well as
TDS and conductivity. Sulfates can cause odor
organic nitrogen is present in most natural waters
and corrosion of sewer pipes under the proper
in relatively low concentrations. Concentrations
conditions. The malodorous gas, hydrogen sulfide,
as low as 0.5 mg/L have been reported to be toxic
is produced by the anaerobic biological reduction
to some fish and concentrations as high as 1,600
of sulfate to hydrogen sulfide. As pH is increased,
mg/L have proved to be inhibitive to biological
the chemical equilibrium favors the ionization of
waste treatment plant microorganisms. The toxic-
ity of ammonia is a function of pH, being highly
sulfur and prevents the formation of hydrogen
sulfate (H2S). As pH is decreased, the formation
toxic at an alkaline pH and less toxic at an acidic
of H2S is favored.
pH. Ammonia nitrogen is also an essential nutri-
(b) Crown corrosion of sewers occurs when
ent in biological waste treatment systems and a
the H2S gas is released and rises to the crown of
slight residual (0.5 to 1.0 mg/L) is recommended
the sewer. At the crown, condensed water and
for optimum biological activity.
H 2S form sulfuric acid which dissolves concrete.
(c) Nitrate nitrogen (NO3-N) may appear in
(7) Chlorine. Chlorine is widely used as a
wastewaters as dissociated nitric acid, HNO3, or
disinfectant for drinking water supplies and for
may result from the biological vitrification of
treated sanitary discharges. Chlorine is toxic to
ammonia to nitrate. Nitrate nitrogen should be
3-3
Previous Page
