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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

DHTDMAC was not biodegraded in the closed bottle test after 28 days (3%).

Secondary activated sludge was obtained from a plant treating predominately domestic wastewater. The sludge was pre-conditioned to reduce the endogenous respiration rates. To precondition, the sludge (200 mg Dry Weight (DW) /Litre) was aerated for a period of one week. The sludge was diluted to a concentration in the BOD bottles of 2 mg DW/Litre. Ammonium chloride was omitted from the medium to prevent nitrification. Due to omission the pH of the medium decreased slightly.

However, in the prolonged closed bottle test DHTDMAC is biodegraded 68 % at Day 287. The pH of the medium at day 28 is 6.9.

In 1974, Guidry assessed the substance which was added to a bacterial culture and kept mixed and aerated. The concentration of the quaternary was 10 mg/Litre in test solution. Changes in the concentration of the quaternary ammonia compound were measured as a function of time. The presence and concentration of quaternary material was measured colorimetrically, using standard procedures. DHTDMAC5 was found to be biodegradable at concentrations equal to or less than 10 mg/L (p. p. m.) when tested at ambient temperatures. DHTDMAC was found to be 78.8 % biodegraded in the 48 hour test period. Nevertheless this information cannot be considered as relevant based on the poor level of reporting information.