Biodegradation primary degradation

Linear primary alcohol sulfates often need only one day for 95 % primary biodegradation and degrade faster than other anionic surfactants, which usually need several days. This difference has been confirmed by Ruschenberg [412, 413]. 

The conversion rates of individual components in a commercial LAS mixture are dependent on the molecular structure. For example, the length of the alkyl chain is positively correlated with the primary degradation rate, and as such, isomers with the phenyl substituted at central positions are degraded more slowly than other isomers [79,80]. Both effects are a direct consequence of the enzymatic attack on the hydrophobic moiety. The relation between surfactant structure and the biodegradation has been termed as Swisher s distance principle which, in summary, describes that an increased distance between... 

Static die-away tests were performed by Potter et al. with an A9PEO7 24 mixture in water from a vertically well-mixed estuary in Florida [36]. Lag times of 0—12 days were observed, and after 4—24 days, primary degradation was complete. These rates are similar to those reported by Kvestak and Ahel [6]. It is likely that the microorganisms in these experiments were pre-acclimated to biodegrade nonionic surfactants, as a municipal sewage treatment plant discharge is present a few kilometres upstream. 

Aerobic degradation of diethyl phthalate by acclimated soil and activated sewage sludge microbes was studied using an acclimated shake flask CO2 evolution test. After 28 d, loss of diethyl phthalate (primary degradation) was >99%, with a lag phase of 2.3 d, and ultimate biodegradation (CO2 evolution) was 95%. The half-life was 2.21 d (Sugatt et al., 1984). 

Biodegradation, hydrolysis, and sorption influence the environmental fate of LAS, AS, and AES. Primary degradation of surfactants is important because this process usually results in loss of surfactancy and reduced toxicity (5, 6). Complete mineralization ensures that persistent intermediates will not be formed and that biodegradation will be an effective mass-removal mechanism in the environment. Sorption and association of surfactants with particles or dissolved organic substances are processes that decrease bioavailability and can be correlated with decreased surfactant toxicity (7). 

Biodegradation complete primary degradation in 10-21 d for river die-away smdies when exposed to the natural microbial population of the water t,/, < 28 d for primary biodegradation rate from semicontinuous activated sludge studies (Saeger et al. 1979). 

---