Biodegradability Ultimate biodegradation

The methacrylates ate slightly to essentially nontoxic to fish and other aquatic species. Hydrolysis data suggest rapid breakdown at alkaline conditions, and studies show that MMA is ultimately biodegradable ia sewage sludge samples. Based on this information, the methacrylates ate not considered to be a significant environmental hazard. 

Most uses of chloroisocyanurates are regulated by the EPA under EIERA. Cyanuric acid (or cyanurate) is ultimately the end product of use of chloroisocyanurates in bleaching, sanitizing, and disinfection appHcations. Since the N-chloro derivatives are biocidal, biodegradation studies have centered on the residual CA. Biodegradation occurs (128). 

In a continuous model river test system it can be shown that after passage through a sewage treatment plant ester sulfonates have no significant influence on the qualitative and quantitative composition of the biocenosis of a receiving water [113]. All the investigations into the environmental fate of a-sulfo fatty acid esters demonstrate that aquatic toxicity is alleviated by their fast ultimate biodegradability, which allows them to be classified as environmentally compatible. 

In the following sections, an attempt is made to provide a critical outline of experimental aspects of investigations directed to biodegradation and biotransformation, with particular emphasis on outstanding issues to which sufficient attention has not always been paid, and which have not therefore received ultimate resolution. Before proceeding further, it is desirable to define clearly some operational terms ... 

Ultimate biodegradability (OECD 301) <60% within 28 days >60% within 28 days >50% within 10 days window... 

Staples CA, Naylor CG, Williams JB, Gledhill WE (2001) Ultimate biodegradation of alkylphenol ethoxylates surfactants and their biodegradation intermediates. Environ Toxicol Chem 20 2450-2455... 

The ultimate fate of those PAHs that accumulate in sediments is believed to be biotransformation and biodegradation by benthic organisms (USEPA 1980). PAHs in aquatic sediments, however, degrade very slowly in the absence of penetrating radiation and oxygen (Suess 1976), and may... 

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... 

Support for this hypothesis on iso-LAS is given through the findings of Nielsen et al. [100] in a degradation study carried out with radiolabelled substrate, in which it was reported that most of the iso-LAS isomers underwent ultimate biodegradation (79-90%), although some of their carbon (10-20%) was released as water-soluble intermediates. Furthermore, Kolbener et al. [90] could identify structures... 

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]. 

While 02 serves as the electron acceptor in aerobic biodegradation processes forming H20 as the final product, degradation in anaerobic systems depends on alternative electron acceptors such as sulfate, nitrate or carbonate, which yield, ultimately, hydrogen sulfide (H2S), molecular nitrogen (N2) and/or ammonia (NH3) and methane (CH4), respectively. 

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