Aerobic Biodegradation of Surfactants

Abstract

Surfactants are a wide group of chemical compounds which have a large number of applications due to their solubility properties, detergency, endurance of water hardness, as well as emulsifying, dispersing, and wetting properties. Surfactants have a characteristic structure, with one or several hydrocarbon chains that form the lipophilic part of the molecule (or the hydrophobic part of the molecule) and one or several polar groups that form the hydrophilic part. These compounds, also called surface-active agents, can have different lengths and degrees of unsaturation in the hydrocarbon chains, as well as in the polar groups, giving rise to a wide variety of surfactants with different properties. Surfactants can be classified as ionic or non-ionic, depending on the nature of the hydrophilic group. The ionic surfactants are disassociated in water, forming ions. Notable within this group are organic acids, and their salts are anionic surfactants, while bases-amines of different degrees of replacement-and their salts are cationic surfactants. Some surfactants contain both acid and basic groups. These surfactants may be anionic or cationic and are therefore called amphoteric, or ampholytic. Surfactants constitute a group of substances in which the main characteristic is their accumulation in the interfaces, solid-liquid or liquid-gas, weakening the surface tension of the liquid. This property enables the formation of foams and the penetration of solids as a wetting agent, leading to wide and varied applications of these compounds [1]. These substances are widely used in household cleaning detergents, personal-care products, textiles, paints, polymers, pesticides, pharmaceuticals, mining, oil recovery, and the pulp and paper industries. Detergents and cosmetics involve the mayor use of these compounds. After use, residual surfactants and their degradation products are discharged to sewage-treatment plants or directly to surface waters. Several of these compounds are not biologically degradable

Surfactant selection for a liquid foam‐bed photobioreactor

“…The second characteristic for surfactant selection is the biodegradation rate of the surfactant. Many surfactants can be biologically degraded, which means that the surfactants can be used as carbon and energy source by bacteria. However, biodegradation is directly related to the molecule's structure.…”

Potential Impact of Biodegradable Surfactants on Foam-Based Microalgal Cultures

“…This resulted in a marked increase in the bacteria-to-microalgae ratio during the first day of cultivation in the presence of Saponin. Microorganisms usually show a latency time to acclimate themselves to the new substrate [25,26], which is the surfactants in this case. Bacteria started growing earlier in Saponin-enriched cultures than in cultures with BSA and Tween 20.…”

“…This indicates that beyond the biodegradation of Saponin, this surfactant supports the growth of S. obliquus-associated bacteria. In this sense, it has been stated that microorganisms can either utilize surfactants as substrates to obtain energy and nutrients, or co-metabolize surfactants by microbial metabolic reactions [25]. Moreover, the fact that the cultures with Saponin grew faster than those without the surfactant suggests that either S. obliquus-associated bacteria consumed Saponin and nutrients from LB/20 medium simultaneously, or that Saponin is a more efficient substrate to promote bacterial growth compared to other nutrients present in the culture media.…”

Ecotoxicological Behaviour of Poorly Water Soluble Fatty Alcohol Ethoxylates in Freshwater Environment

“…According to Jurado et al (2013), the biodegradation of ether carboxylic surfactants with shorter alkyl chains was higher than surfactants with longer alkyl chains. For surfactants with similar chain length, biodegradability was higher for those with higher degree of ethoxylation as observed in this study.…”