Chloramide

Endpoint summary

Additional information

Inorganic chloramines consist of three chemicals that are formed when chlorine and ammonia are combined in water: monochloramine (NH2Cl), dichloramine (NHCl2) and trichloramine (NCl3). The generation of monochloramine depends on the characteristics of water or influent like pH, molar ratio of hypochlorous acid to ammonia, temperature and contact time.

1) For information: naming rules and conversion factors for different types of concentration given for monochloramine / inorganic chloramines

- Free Residual Chlorine (FRC) or free available chlorine (FAC): corresponds to hypochlorous acid [HOCl] and the hypochlorite ion [OCl] concentrations.

- Combined Residual Chlorine (CRC) or Combined Available Chlorine (CAC) : corresponds to the sum of  inorganic chloramines [NH2Cl, NHCl2, and NCl3] or N-chloramides and also organic choramines concentrations.

- Total Residual Chlorine (TRC): corresponds to all species of chlorine in solution i.e.the sum of CRC and FRC.

 - Chlorine Produced Oxidants (CPO): is the sum of all oxidants including non-chlorine species. In water containing bromine, such as seawater, there is displacement of chlorine by bromine resulting in hypobromous acid, hypobromite ions and bromamines. Some authors also mention TRO (Total Residual Oxidant )

 

2) Influence of pH and molar ratio

The experimental pH and molar ratio of hypochlorous acid to ammonia have a great role in the evaluation of aquatic toxicity data as they determine the chemical species present. In water, the monochloramine is in equilibrium with other chloramines (dichloramine (NHCl2 ) and trichloramine (NCl3)). The ratio of each species is highly dependent upon pH, the ratio of chlorine to ammonia-nitrogen and, to a lesser extent, temperature and contact time.

A pH between approximately 7.5 and 9.0 is optimum for the formation of monochloramine; the ideal pH is 8.3. A lower pH favours the formation of dichloramine (pH 4–6) and trichloramine (pH <4.4).

In ambient freshwater, the dominant species is monochloramine.

Therefore due care was taken on test conditions in order to check that test conditions were optimum to predominantly obtain monochloramine.

 

3) Influence of Marine water:

In marine or estuarine water, the presence of bromide ions (Br) causes rapid partial or complete replacement of chlorine by bromine (i.e. bromamines, and bromochloramines). The collection of these reactive chlorine and bromine species is called chlorine-produced oxidants (CPO).

 

Summary of Aquatic toxicity

Valid aquatic toxicity tests (acute and chronic) for fish, aquatic invertebrates and algae and macrophytes are available for monochloramine.

 

Type of test	Species	Effect		Effect conc. (mg/L)	Reference
Acute	Salvelinus fontinalis	Mortality	LC50(96h)	0.064 Measured concentrations	Larson et al 1977
Acute	Ceriodaphnia dubia	Mortality	EC50(48h)	0.0118 Measured concentrations	Farrell et al 2000
Acute	Lemna minor	Inhibition of growth rate	EC50 (7d)	0.33 (total frond area) 0.92 (frond number), 0.57 (dry weight) Measured concentrations	Bellemain et al 2010
Chronic	Lemna minor	Inhibition of growth rate	EC10 (7d)	0.2 (total frond area) 0.18 (frond number), 0.15 (dry weight) Measured concentrations	Bellemain et al 2010
Chronic	Daphnia magna	reproduction	EC10(21d)	0.0117 Measured concentrations)	Egerler et al 2013
Chronic	Danio rerio	Mortality (post-hatching success)	EC10(35d)	0.0098 Measured concentrations	Gilberg et al 2012

 

Based on the available data, monochloramine is considered as rapidly degradable and not potentially bioaccumulable.

For the acute toxicity, invertebrates are the most sensitive trophic level. According to the results of the lowest EC50 (48h-EC50 of 0.0118 mg/L for C. dubia), Monochloramine is considered as very toxic to aquatic life.

For the chronic toxicity, according to the chosen key values, fish is the most sensitive trophic level. According to the results of the lowest EC10 (35d-EC10 of 9.8 µg/L mg for Danio rerio), Monochloramine is considered as very toxic to aquatic life with long lasting effect.