Surfactants biological degradation

Liquid scrubbing is also known as one of the most efficient methods for very fine-particle collection, but they are gathered in the form of a suspension that can be rather used for nasal, pulmonary, or parenteral delivery. The suspension stability is often a delicate issue because no chemical or biological degradation shall occur, nor particle decantation, which requires the use of complex mixtures, including a buffer (especially for biomolecules), preservatives (antimicrobial, antioxidant, etc.), and surfactants. Several systems have been described (37,86-88) ... 

Most products are stabilized against biological degradation by preservatives. Despite the antibacterial activity of cationic surfactants, there is some risk of bacterial contamination of fabric softeners. 

Quats are usually less easily biodegraded than anionic or nonionic surfactants, or esterquats, as they are less prone to be attacked by bacteria. Nevertheless softeners are not detrimental to the environment, since, besides their elimination by biological degradation, their concentration in effluents remains very low [15],... 

As there are other less sophisticated and less expensive techniques available, surfactant-enhanced aquifer remediation will only be useful for decontamination of LNAPL sites in special cases. However, applicable techniques are still needed for DNAPL sites and microemulsion techniques are really promising. Therefore, most research has concentrated on this type of contaminant in recent years. Integrated concepts have been developed including aspects of soil properties [47, 48, 62, 63], density control [47, 48, 62-64], recovery and reuse of microemulsion components [47], biological degradation of residues of contaminants and injected compounds [48, 65] and costs [47, 48, 64, 65]. Two main approaches have been followed for developing effective surfactant systems which form microemulsions with DNAPL, but do not mobilise the liquid contaminant into deeper... 

A knowledge of chronic and sub-acute toxic effects is the basis of a risk-assessment procedure which is closer to natural conditions. It is decisive to know what concentration of surfactant causes no observable effects any more. For the quantitative description of a chronic exposure situation, the NOEC value is used. By the eventual use of additional safety factors a so-called PNEC (predicted no effect concentration) value can be derived. The latter describes a situation where in the environment no deleterious effects should be expected any more. Aquatic toxicity and biological degradation are closely connected with each other insofar as a... 

Quantitative data on the biological degradation of anionic surfactants can be found in Table 22.8. Pilot studies carried out with LASs in the Netherlands, Germany, Italy, Spain and the UK show mean removals of 99.2% in activated sludge plants in these countries where a high standard in waste-water treatment exists. 

Choice of surfactant(s) for the preparation of multiple emulsions can, in principle, be made from any of the four classes of surfactants discussed in Chapter 3, although nonionics tend to be materials of choice because they are more easily tailored to meet the needs of the system. The choice will be determined by the characteristics of the final emulsion type desired, such as the natures of the various phases, additives, and solubilities. In many applications (e.g., foods, drugs, cosmetics), the choice may be further influenced by such questions as toxicity, interaction with other addenda, and biological degradation. In a given system, several different surfactants may perform adequately in terms of stability, but produce different types of multiple emulsions (A, B, or C in Figure 11.15), so that the choice will depend on application as well as function. 

Schneider, E., K. Levsen, Monitoring the biological degradation of surfactants with field desorption MS (in German), Fresenius Z. Anal. Chem., 1987,326,43-48. 

Some surfactants were found to be hardly degradable in the biological wastewater treatment process. Therefore, non-ionic surfactants are observed not only in wastewater and surface water but also in drinking water [7,8] and other environmental samples. In addition, they could be... 

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