Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

OBSH is not readily biodegradable according to OECD Guideline no. 301C. OBSH is considered not biodegradable.

OBSH is not bioaccumulative according to OECD Guideline no. 305E

The hydrolytic half life of OBSH at 25 degrees celcius was:

9.2 h at pH 4

7.9 h at pH 7

5.8 h at pH 9

These data and the result of a stability test suggest that OBSH is hydrolytically unstable over a range of environmentally relevant pH and temperature conditions.

Once released into the water environment, OBSH will readily - due to hydrolysis - be degraded into primarily hydrazine and 4,4’-oxybis(benzenesulfonic acid).

Some retention of the waste water within in the industrial settings can be expected. The travelling time from OBSH is released into waste water until arrival in the STP can vary quite much - in dependence of distance to plant and flow velocity. Typically, the flow velocity in the sewer is about 1 m/s, and with an average distance between the point of discharge and STP of 10 km, a retention time in the sewer of approximately 3 hours is calculated. In the sewer, a pH above 7 is usual (in order to limit the concentration of free H2S and to limit the corrosion due to the presence of sulfuric acid).

The overall retention time in a standard SimpleTreat sewage treatment plant (STP) is approximately 15 hours. Overall, a total retention time of 1 day = 24 hours is assessed to be a reasonable value to apply for the risk assessment. A pH between 7 - 8 is expected in the sewer and the sewage treatment plant.

In conclusion, a total hydrolytic transformation of 90% before final discharge into the environment is assessed to be a reasonable value to use for the environmental risk assessment.