m-Cresol - ipcs inchem

OECD SIDS
m- / p-CRESOL
Table 4:
Standard Tests on Aerobic Biodegradation of Cresols
Method Duration m-Cresol p-Cresol Reference
OECD 301 D 28 d 65 - 90 % Bayer AG (2002c)
OECD 301 C 40 d 80 - 95 % 80 - 95 % Desai et al. (1990)
OECD 302 B 10 d 96 % 100 % Wellens (1990)
5 d 95.5 % 96 % Pitter (1976)
A Closed-Bottle-Test (OECD 301 D) using m-cresol as test substance in two concentrations (0.8
mg/l and 2.4 mg/l) was performed (Bayer AG 2002c). While in two parallel experiments at a m-
cresol concentration of 0.8 mg/l nearly 90 % degradation was determined after 28 days incubation,
at the test concentration 2.4 mg/l about 65 % degradation was achieved in two parallel vessels. At
both concentrations the pass level of 60 % was reached within 28 days. The 10d- window was
fulfilled in all but one parallel tests indicating that m-cresol can be considered as readily
biodegradable.
Desai et al. (1990) determined the Monod kinetics of m- and p-cresol using an electrolytic
respirometry test comparable to OECD guideline 301 C. Activated sludge from a wastewater
treatment plant receiving predominantly domestic sewage was used as inoculum in a concentration
of 30 mg/l. Within an incubation period of 40 days degradation of both cresol isomers (initial
concentration 100 mg/l) was in the range of 80 % to 95 %. The specific oxygen uptake curves of the
cresols are not reported. However, the authors state that all test compounds revealed the same
pattern: the lag phase, biodegradation phase and the plateau region within a period of 10 days.
Therefore, it can be concluded from this test that m- and p-cresol are readily biodegradable. The
first order degradation constants ln(k) [h-1] were determined to be –5.77 (m-cresol) and –5.87 (pcresol).
From these values half-lives of 9.3 d resp. 10.3 d can be calculated.
The inherent degradability of two cresol isomers was studied by Wellens (1990). In a test according
to the OECD guideline 302 B, m-cresol and p-cresol degraded to 95 % resp. 100 % within 10 days
after lag-periods of 2 days. Using a 5 days incubation period, Pitter observed that removal of each
96 % of both compounds occurred with the same initial degradation rate of 55 mg COD g-1 h-1.
Van Veld and Spain (1983) demonstrated that p-cresol is rapidly degraded in different parts of an
aquatic estuary system. From a river estuary, each 3 samples were taken from water, sediment and
intact eco-cores having an aerobic layer of detritus overlying anaerobic sediment. Water and
water/sediment samples were incubated in the laboratory with 14C-labelled p-cresol and shaken in
flasks at 18 °C in the dark. Based on HPLC and 14CO2 measurements, half-lives between 9.4 and
43 h for p-cresol in water and between 5.9 and 11 h in water/sediment systems were determined. In
intact eco-cores, p-cresol degraded with half-lives between 3.0 and 16 h.
The Closed-Bottle-Test (Bayer AG 2002c) reveals that m-cresol is readily biodegradable. As
demanded by the OECD guideline, the oxygen consumption was above 60 % after 10 and 28 days.
Desai et al. (1990) determined the degradation of both m- and p-cresol and found similar rate
constants for both isomers. From this study it can be concluded that both m- and p-cresol are readily
biodegradable.
Anaerobic:
The anaerobic degradation properties of a substance are important for the assessment of the
substance’s fate during secondary digesting of sewage sludge and the fate in anaerobic sediment
layers. A number of investigations on the anaerobic degradability of cresols is available. The most
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