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Biodegradation in water: screening tests

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Description of key information

Substance is not readily biodegradable and has not ultimate biodegradability potential.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable, not fulfilling specific criteria

Additional information

The determination of the ready biodegradability was performed according to the OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test) test method. The biodegradation after 28 days was 45.8 %. No inhibitory effect on the inoculum bacteria at the tested concentration (2 mg/l) was observed. The average COD value was 0.36 mg O2/mg of test substance and the BOD on days 7, 14, 21 was 0 and on day 28 was 0.165 mg/O2 mg. Thus, DG HF/2000 resulted as non readily biodegradable. 

In the cases of complex substances, there are some factors that may affect the biodegradation rate: firstly, the rate of biodegradation is limited by the rate of dissolution and solubility of individual UVCB components. Secondly, substances containing a complex mixture of constituents results in a stepwise, sequential adaptation of the microorganisms, again resulting in deviation from ‘typical’ kinetics.

During the test, a biodegradation rate of 0 % was recorded up to the 21th day. Between the day 21 and the day 28 the biodegradation increases up to 45 %; unfortunately there is no data available about the biodegradation rate after 28 days.

The fact that no biodegradation was observed up to the 21th day and then a great increase was observed, may be explained by two possible scenarios:

- substance may be toxic for microorganisms: in this case may be that substance killed all of the inoculum organisms, except those who are able to degrade it. Thus, degradation “starts” after 21 days; or

- substance may be not bioavailable in the first 21 days.

The first possibility can be disregarded since the biodegradation in the two series of bottles containing 2 mg/ml of sodium acetate plus 2 mg/l of the test item on day 14 was 75.64 % (i.e. greater than 25 % of the ThOD), showing that the test article had no significant inhibitory effect on the bacteria inoculum (on the basis that organisms degraded the sodium acetate).

Furthermore, a test to evaluate the toxicity of the test item to the activated sludge respiration activity gave no evidence of any sign of toxicity.

The second hypothesis seems more probable considering the type and the chemical characteristics of the substance to be registered: DG HF/2000 is an UVCB and the precise UVCB structure is unknown and variable. It is probable that bonds between portions of phosphates occurred, forming a reticule of polyphosphate of varying length, containing melamine and piperazine; thus the possible structures which will be formed may be the piperazine phosphate and melamine phosphate.


Experimental results showed that the substance components are characterized by opposite properties, when placed in water: the piperazine phosphate showed quite high water solubility (about 10000 mg/l) when analyzed alone; on the contrary, the other component not detectable under the analytical conditions adopted in the water solubility assay (refer to IUCLID section 4.8) resulted as practically insoluble and its water solubility being estimated to < 9 mg/l. The solubility of this complex UVCB substance could not be determined as the core substance is not soluble. The percentage weight soluble at pH 7 is 20.18 %. The soluble fraction of phosphate in water is 2.31 % and the soluble fraction of piperazine is 18.60 %.

This means that in water there is a large portion of the substance in the undissolved phase and hence, not fully available to the degrading organisms.

The results from the biodegradation studies indicate that piperazine is not readily biodegradable under aerobic conditions, but it is inherently biodegradable [European Chemicals Bureau, 2005]. Because no relevant persistence data for melamine polyphosphate were identified, melamine polyphosphate was assigned as score of Moderate for persistence based on analogous data suggesting melamine polyphosphate will not biodegrade rapidly [EPA, 2014].

In conclusion, DG HF/2000 is not readily biodegradable.

About inherent biodegradability potential, in general substances that are degraded more than 70 % in tests for inherent biodegradability have the potential for ultimate biodegradation; biodegradation above 20 % of theoretical (measured as BOD, DOC removal or COD) may be regarded as evidence of inherent, primary biodegradability. Data available suggest that the substance has not the potential for ultimate biodegradation, whereas there are no sufficient information to judge the primary biodegradability potential. Thus, according to a conservative approach, the substance is regarded and treated as if it would not even be inherent biodegradable.


Environmental Protection Agency (EPA) United States. An Alternatives Assessment for the Flame Retardant Decabromodiphenyl Ether (DecaBDE). Final report. January 2014.

European Chemicals Bureau. European Union Risk Assessment Report. Piperazine CAS No: 110-85-0 EINECS No: 203-808-3. 3rdpriority list, Volume 56. Risk assessment. European Commission Joint research centre. EUR 21642 EN. Institute for Health and Consumer Protection. 2005.