Surfactants in sludge-amended agricultural soils: a review

Abstract

Surfactants are included in different detergent formulations and are one of the most ubiquitous and important families of organic compounds. The possible contamination of the environment by surfactants is due to their remarkable capacity to modify the surface tension of water and solubilize xenobiotic subtances. Detergents are a common component of domestic wastewater, which may be disposed in water bodies without treatment, with possible health risks through drinking water. Although the generic term “surfactants” is applied to a great number of products, 80% of their demand is covered by only 10 types of compounds. The global surfactant market volume size is more than 18 million tons per year. Large quantities of surfactants are continuously released to the environment, accumulating in sediments and soils, where they can or cannot be degraded depending on their structure. Linear alkylbenzenesulfonate (LAS) is the most widely used surfactant. LAS can be degraded under aerobic conditions, but is persistent in the environment under anaerobic conditions. Surfactants may enter the terrestrial environment through several routes, by far the most important being the use of sewage sludge as fertilizer on agricultural land. High concentrations of surfactants and their degradation products may affect the biota. On the other hand, due to their amphiphilic nature, surfactants may interact both with inorganic as well as organic contaminants affecting their bioavailability. Sections of this review article include: uses, types, and consumption of surfactants, analysis of surfactants in environmental matrices, surfactants in sludge-amended soils, biodegradation of surfactants, transport and fate of surfactants in wastewater treatment plants, fate of surfactants in waters and soils, and interaction of surfactants with soil contaminants.