Hello, experts in water quality control fields.
I am eager to know something about ammonia toxicity.
How much ammonia would do harm to fish, microbial, and algae?
Are there some reference you could provide?
Thanks alot.
Ammonia is toxic to fish if allowed to accumulate in fish production systems. When ammonia accumulates to toxic levels, fish cannot extract energy from feed efficiently. If the ammonia concentration gets high enough, the fish will become lethargic and eventually fall into a coma and die. Ammonia in water is either unionized ammonia (NH3) or the ammonium ion (NH4 +). The techniques used to measure ammonia provide a value that is the sum of both forms. Un-ionized ammonia is the toxic form and predominates when pH is high. Ammonium ion is relatively nontoxic and predominates when pH is low. In general, less than 10% of ammonia is in the toxic form when pH is less than 8.0. However, this proportion increases dramatically as pH increases. The proportion of toxic, un-ionized ammonia increases as a function of pH and temperature.
USEPA (2013) recommends an acute criterion magnitude of 17 mg Total Ammonia Nitrogen (TAN) per liter at pH 7 and 20°C for a one-hour average duration, not to be exceeded more than once every three years on average. For chronic criterion, it recommends magnitude of 1.9 mg TAN (total ammonia nitrogen)/L at pH 7 and 20°C for a 30-day average duration, not to be exceeded more than once every three years on average. In addition, the highest four-day average within a 30-day period should not exceed 2.5 times the chronic criterion magnitude (e.g. 1.9 mg TAN/L x 2.5 = 4.8 mg TAN/L at pH 7 and 20°C) more than once in three years on average.
You should also go through the EPA 2013 report on Aquatic Life Ambient Water Quality Criteria for Ammonia, for further details.
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