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Phone: 631-242-4249 | Toll-Free: 888-686-3454
Ammonium compounds are present in many surface waters and some groundwaters. Furthermore, they are always present in municipal and often in commercial and industrial wastewaters.
In surface and ground waters, ammonium ions are an indication for the decomposition of animal or vegetable matter. High ammonia concentrations in surface waters can indicate contamination from waste water treatment plants, fertilizer runoff, or industrial effluents. Excess ammonia levels are toxic to aquatic life.
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There are various reasons for the presence of ammonium compounds in different types of water. They
are e.g. products of chemical waste or they are bacterial degradation processes of nitrogen-containing organic
compounds. The latter indicate pollution of the water with feces or other putrefaction and decay processes.
Ammonium compounds enter our waters also with the rain, in the form of fertilizer ingredients being washed
into the water. Almost all volcanic rocks In the mineral kingdom contain small quantities of ammonium salts. The
ammonium content in pure waters is less than 0.1 mg/L; special cases with levels up to 1 mg/L are swamp waters
and special groundwaters with high iron and manganese contents (e.g. in the North German Plain). In polluted
waters, concentrations up to 10 mg/L can be detected.
Toxicity in fish waters is mainly dependent on the pH of the water. Ammonium compounds are
harmless at low pH values. However, with increasing pH an increasingly higher portion of fish-toxic
ammonia is present. This can be explained from the following pH-dependent equilibrium between ammonium
ions and ammonia:
At a pH of 6, the equilibrium is almost entirely on the left side, at a pH value of 8 already
4 % of ammonia, at pH 9 already 25 % and at pH 10 even 78 % of ammonia are present (at a water
temperature of 17 °C). The level of toxicity depends on exposure time, temperature and fish species.
On average, 1 mg/L NH3 is reported as lethal to fish. High ammonium concentrations also strongly
decrease the oxygen concentration in water, since the bacterial oxidation of ammonium to nitrate
(“nitrification”) consumes oxygen O2:
Nitrification is essential for the natural purification process in water. But in case of high ammonium or ammonia content the nitrification leads to increased oxygen consumption and thus kills fish.
The nitrification process is utilized in biological wastewater treatment plants for cleaning. Therefore,
monitoring of the involved parameters ammonium, nitrite and nitrate plays an immense role. The ammonium
concentration in the influent determines the oxygen demand in wastewater treatment plants. Thus the residual
ammonium content in the plant effluent provides information on th effectiveness of the system.
Ammonia is cytotoxic to higher organisms. It is produced as a metabolic intermediate in the brain, the muscles, the liver, the
intestine and the kidney. In the body, ammonia is immediately rendered harmless by the reaction with carbon dioxide to urea and the following
conversion to glutamine. Unlike free ammonia, ammonium salts are non-toxic.
Toxicity in fish waters is mainly dependent on the pH value of the water.
pH < 7 (acidic) | pH > 7 (alkaline)
NH4+ = ammonium ion
OH– = hydroxide ion
NH3 = ammonia
H2O = water
O2 = oxygen
NO3– = nitrate ion
H3O+ = hydronium ion
Ammonium salts are non-toxic, unlike free ammonia.
Colorimetric and photometric determinations are performed in accordance to the Berthelot reaction (underlying reaction in analogy to ISO 7150-1, APHA 4500-NH3-F, EPA 350.1 and DIN 38406-E5).
Ammonium or ammonia reacts with hypochlorite and salicylate in strongly alkaline solution (pH ≈ 12.6), in the presence of sodium nitroprusside (sodium (nitrosopentacyanoferrate(III)) as a catalyst to form a blue indophenol. In the first reaction step, hypochlorite is generated in situ from dichloroisocyanuric acid in alkaline medium.
The hypochlorite reacts with ammonia to form chloramine.
With a catalytic amount of sodium nitroprusside, chloramines react with phenols (here: sodium salicylate) to form quinonimines. The quinonimine reacts with a further equivalent of sodium salicylate, resulting in a blue indophenol.
R-Cl = dichloroisocyanuric acid
R = generic residue
NaOH = sodium hydroxide
NaOCl = sodium hypochlorite
NH3 = ammonia
NH2Cl = chloramine
The sample can be stored for 7 days until the start of analysis, after stabilization of the pH with H2SO4 to pH 1–2 and filtration on site (storage vessel: PE or glass bottle).
