Cyanuric acid

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 306 (Biodegradability in Seawater)

GLP compliance:

no

Radiolabelling:

no

Inoculum or test system:

natural water

Details on source and properties of surface water:

- Details on collection: Source: Huttoft on the East Coast of the UK; Depth of sampling: 30 cm
- Storage conditions: Continuous aeration in a temperature controlled room at 21°C
- Storage length: 9 days
- Temperature at time of collection: 11.4°C
- Dissolved organic carbon: 5.89 mg/l
- Water filtered: yes

Details on source and properties of sediment:

Not applicable

Details on inoculum:

Not applicable

Duration of test (contact time):

60 d

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment: 1 L
- Composition of medium: Refer to table 1
- Test temperature: 14 ± 1°C
- pH: 7.4
- Continuous darkness: yes
- Other: Culture vessels were constantly shaken at 100 rpm


TEST SYSTEM
- Culturing apparatus: Erlenmeyer flasks (2 L)
- Number of culture flasks/concentration: 2
- Measuring equipment: The pH and dissolved oxygen concentration of each vessel was determined using a WTW pH/Oxi 340I pH and dissolved oxygen meter. Samples were analyzed for DOC using a Shimadzu TOC-5050A TOC analyzer.



SAMPLING
- Sampling frequency: Samples were taken for DOC analysis from each vessel on days 0, 3, 7, 14, 21, 28, 35, 42, 49, 56 and 60
- Sample storage before analysis: The samples taken on day 14 were stored at approximately - 20°C prior to analysis
- Other: All samples were filtered through a Gelman 0.45 µm Acrocap filter, the first approximate 5 ml being discarded, prior to analysis


CONTROL
- Inoculum blank consisiting of test medium
- Abiotic sterile control: 94 mg test material/L plus 100 mg sodium azide/L, equivalent to 20 mg carbon/L
- Toxicity control: 94 mg test material/L plus 34 mg sodium benzoate/L, equivalent to 40 mg carbon/L

Reference substance:

benzoic acid, sodium salt

% Degr.:

4

Parameter:

DOC removal

Sampling time:

60 d

Dissolved organic carbon (DOC) values for the test material, standard material, toxicity control, abiotic test, abiotic control and control vessels on each sampling occasion are given in table 2. The percentage degradation values are given in table 3.

Table 2: Dissolved organic carbon (DOC) values on each sampling occasion

Vessel		DOC (mg C/L)
		Day
		0	3	7	14	21	28	35	42	49	56	60
Control	R1	4.27	7.11	4.93	3.26	3.59	2.89	2.81	2.17	2.60	3.08	3.00
	R2	3.35	6.14	4.02	2.13	2.77	2.82	2.77	2.25	2.05	2.87	2.79
	Mean	3.81	6.63	4.48	2.70	3.18	2.86	2.79	2.21	2.33	2.98	2.90
(= 20 mg C/L)	R1	23.44	10.50	4.99	3.08	3.90	4.00	3.24	2.84	3.08	3.33	3.74
	R2	23.20	10.36	5.24	6.69	3.57	3.78	3.28	2.64	2.77	3.33	3.40
	Mean	23.32	10.43	5.12	4.89	3.74	3.89	3.26	2.74	2.93	3.33	3.57
Test Material(= 40 mg C/L)	R1	25.47	28.36	26.05	20.26	23.95	24.18	23.19	23.04	22.85	23.68	23.25
	R2	25.06	28.72	25.95	32.27	24.03	24.56	23.42	23.34	23.13	23.55	23.72
	Mean	25.27	28.54	26.00	26.27	23.99	24.37	23.31	23.19	22.99	23.62	23.49
Toxicity Control(= 40 mg C/L)	R1	45.99	34.47	29.87	29.99	25.29	25.97	24.57	24.24	23.84	24.63	23.75
	R2	45.93	33.70	29.05	33.30	25.32	25.83	25.04	24.05	24.36	24.71	24.40
	Mean	45.96	34.09	29.46	31.65	25.31	25.90	24.81	24.15	24.10	24.67	24.08
Abiotic Control	R1	3.63	5.97	3.91	3.20	3.44	3.50	3.46	3.17	3.07	3.67	3.61
	R2	3.60	5.93	3.96	3.86	4.16	3.70	3.68	2.84	3.34	3.72	3.88
	Mean	3.62	5.95	3.94	3.53	3.80	3.60	3.57	3.01	3.21	3.70	3.75
Abiotic Test(= 20 mg C/L)	R1	24.92	28.66	26.16	26.01	25.21	25.37	24.58	24.60	25.05	24.95	25.19
	R2	26.03	28.44	26.71	37.85	25.17	25.60	24.56	25.03	24.37	24.40	24.95
	Mean	25.48	28.55	26.44	31.93	25.19	25.49	24.57	24.82	24.71	24.68	25.07
R1– R2= Replicates 1 and 2

 

Vessel		DOC (mg C/L
	Day	0	3	7	14	21	28	35	42	49	56	60
Control	R1	4.27	7.11	4.93	3.26	3.59	2.89	2.81	2.17	2.60	3.08	3.00
	R2	3.35	6.14	4.02	2.13	2.77	2.82	2.77	2.25	2.05	2.87	2.79
	Mean	3.81	6.63	4.48	2.70	3.18	2.86	2.79	2.21	2.33	2.98	2.90
Test Mat. (= 20 mg C/L)	R1	23.44	10.5	4.99	3.08	3.90	4.00	3.24	2.84	3.08	3.33	3.74
	R2	23.20	10.36	5.24	6.69	3.57	3.78	3.28	2.64	2.77	3.33	3.40
	Mean	23.31	10.43	5.12	4.89	3.74	3.89	3.26	2.74	2.93	3.33	3.57
Test Mat. (= 40 mg C/L)	R1	25.47	28.36	26.05	20.26	23.95	24.18	23.19	23.04	22.85	23.68	23.25
	R2	25.06	28.72	25.95	32.27	24.03	24.56	23.42	23.34	23.13	23.55	23.72
	Mean	25.27	28.54	26.00	26.72	23.99	24.37	23.31	23.19	22.99	23.62	23.49
Tox. Control (= 40 mg C/L)	R1	45.99	34.47	29.87	29.99	25.29	25.97	24.57	24.24	23.84	24.63	23.75
	R2	45.93	33.70	29.05	33.30	25.32	25.83	25.04	24.05	24.36	24.71	24.40
	Mean	45.96	34.09	29.46	31.65	25.31	25.90	24.81	24.15	24.10	24.67	24.08
Abiotic Control	R1	3.63	5.97	3.91	3.20	3.44	3.50	3.46	3.17	3.07	3.67	3.61
	R2	3.60	5.93	3.96	3.86	4.16	3.70	3.68	2.84	3.34	3.72	3.88
	Mean	3.62	5.95	3.94	3.53	3.80	3.60	3.57	3.01	3.21	3.70	3.75
Abiotic Test (= 20 mg C/L)	R1	24.92	28.66	26.16	26.01	25.21	25.37	24.58	24.60	25.05	24.95	25.19
	R2	26.03	28.44	26.71	37.85	25.17	25.60	24.56	25.03	24.37	24.20	24.95
	Mean	25.48	28.55	26.44	31.93	25.19	25.49	24.57	24.82	24.71	24.68	25.07

R1– R2= Replicates 1 and 2

Table 3: Percentage degradation values:

Day	% Degradation
	Sodium Benzoate	Test Material	Test Material plus Sodium Benzoate Toxicity Control	Test Material plus Sodium Azide Abiotic Test
3	81	0	35	0
7	97	0	41	0
14	89	0	32	0
21	97	3	48	2
28	95	0	46	0
35	98	4	48	4
42	97	2	48	0
49	97	4	49	2
56	98	4	49	4
60	97	4	50	2
* Corrected for control DOC values

Conclusions:

Mono sodium salt of cyanuric acid attained 4% degradation after 60 days.

Reference 2

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Data waiving:

other justification

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
Cyanuric acid biodegrades readily under a wide variety of natural conditions, and particularly well in systems of either low or zero dissolved oxygen level, such as anaerobic activated sludge and sewage soils, muds and muddy streams and river waters as well as ordinary activated sludge systems with typically low (1 – 3 ppm) dissolved oxygen levels. CO2 and ammonia are initial hydrolytic breakdown products References: Saldick, J. (1974) Biodegradation of cyanuric acid. Applied Microbiology 28 (6) 1004 – 1008.

Reference 3

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

GLP compliance:

no

Radiolabelling:

yes

Table 1: ¹⁴CO₂ evolution from ¹⁴C-labelled cyanuric acid on muds and in natural waters.

Medium	Days at room temp	^14C added evolved as CO2 (%)
Muds:
Creek bottom	23	105, 116
Creek bottom: 1% suspension	8	1
Lake bottom 5%^d	8	26
Lake bottom 5%	23	41
Lake water control	29	5
Saline mud^e	9	73, 55

Conclusions:

The results in lake and creek water with added mud suggest that biodegradation of cyanuric acid takes places in mud rather than the liquid phase.

Description of key information

Aerobic and anaerobic investigations have been  performed.

Additional information

CYA was shown to preferentially biodegrade in solid phase as opposed to liquid phase when tested with creek water and mud.

Cyanuric acid biodegrades readily under a wide variety of natural conditions, and particularly well in systems of either low or zero dissolved oxygen level, such as anaerobic activated sludge and sewage soils, muds and muddy streams and river waters as well as ordinary activated sludge systems with typically low (1 – 3 ppm) dissolved oxygen levels.

In highly aerobic media cyanuric acid resists biodegradation. The ability to degrade cyanuric acid is rapidly gained and lost by bacteria in aerated medium when dissolved oxygen was lowered and raised.

The biodegradation of the monosodium salt of cyanuric acid was investigated in seawater. 4% biodegradation was attained in 60 days.