Biodegradability and toxicity of dodecyl trimethyl ammonium chloride in sea water

Studies were conducted to assess the biodegradability and toxicity of the cationic surfactant dodecyl trimethyl ammonium chloride (DTMAC) in sea water samples collected from the Gulf of Cadiz (Spain). Ultimate biodegradation was studied following the guideline proposed by the United States Environmental Protection Agency (USEPA). Growth inhibition tests on five marine microalgae species and mortality tests on a marine crustacean (Artemia franciscana) were carried out. Biodegradation process was modelled according to a logistic kinetic model. Lag time and half-life were 15.17 and 26.95 days, respectively. Depending on the microalgae, 96-h EC50 values ranged from 0.69 to 6.34 mg L^-1 DTMAC, respectively. 48-h and 72-h LC50 to A. franciscana were 46.74 and 34.19 mg L^-1 DTMAC, respectively. The results indicate that DTMAC can be mineralised in sea water. Marine crustacean was more resistant than the microalgae. Surfactant tolerance on microalgae followed this order: T. chuii > N. gaditana > C. gracilis ≈ I. galbana ≈ D. salina, being the Green microalgae T. chuii the most tolerant.