Biodegradation ultimate degradation

Taking into consideration its physico-chemical properties, removal efficiencies, low biodegradability, predicted environmental levels, toxicity, and the need to provide sufficient safety margins for aquatic organisms, the demand for alternative cationic surfactants arose. Since 1991, DTDMAC has been replaced in some European countries due to producer s voluntary initiatives with new quaternary ammonium compounds, the esterquats. These contain an ester function in the hydrophobic chain (Table 1.3) that can be easily cleaved, releasing intermediates that are susceptible to ultimate degradation [24-26]. The effects of the phasing-out and replacement of DTDMAC can be demonstrated by the results of a Swiss study, where the surfactant... 

Alcohol ether sulfates. Ready aerobic biodegradation of AESs has been described [113], with co/(3-oxidation and cleavage of the sulfate and ether bonds attributed to the process [10]. However, molecular oxygen is not necessary for the two latter steps, and primary and ultimate degradation has been described under both aerobic and anaerobic conditions [114]. 

The ultimate degradation product is glyoxylic acid hydrate which is a Krebs cycle metabolite and allows us to think that PEtG is biodegradable. 

In many inherent biodegradability tests only the disappearance of the test substance is measured. Such a result only demonstrates a primary biodegradability and not a total mineralization. Thus, more or less persistent degradation products may have been formed. Primary biodegradation of a substance is no indication of ultimate degradability in the environment. 

Biodegradation is degradation catalysed by biological activity, ultimately leading to mineralisation and/or biomass. 

The important group of fatty alcohol ethoxylates is readily biodegradable (Table 22.16). The ultimate degradation measured by Coupled Units Tests ranges between 93 and 96%. The mineralization determined in a... 

Two mechanisms for the first step of biodegradation of alkylmethylammonium salts are described. The first of these is oxidation of the methyl groups at the far end of the alkyl chain end a stepwise shortening of the latter. The second is a fission of the bond between the nitrogen atom and the alkyl chain, followed by the oxidation of the alkyl chain to the carbon acid which is further metabolized through 0-oxidation. It was proven in laboratory tests that alkylmethylammonium compounds are subjected to a primary degradation with an approximate half-life of 2.5 h. The ultimate degradation requires 28-40 h half-life. 

Ready Biodegradability Aerobic degradation of concentrated solution measured by change in dissolved organic carbon, biochemical oxygen demand, or carbon dioxide. "Pass/fail" test if substance meets criteria for success, it is expected to undergo rapid and ultimate biodegradation in the environment. 

With regard to these pass levels, it is important to note that such requirements practically represent complete and ultimate degradation of the test substance, since the remaining 30-40% is assumed to be assimilated as biomass [36]. Moreover, whenever a substance satisfies the ready biodegradability test requirements, it can be assumed it will undergo rapid and ultimate biodegradation in any biologically active environment [36]. 

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