Wastewater contains significant sources of pollutants and contaminants. often the failure of a pipe, inadequate sealing or corrupt pipe-connections cause the loss of raw sewage, which percolates into the nearby soil. As a consequence, a colmation layer in conjunction with soil clogging is developing, which regulates the exfiltration rate. Recently, literature has emerged that offers findings about the effects of wastewater surfactants on the change of physical properties of the soil. A survey of published literature in this field provides information highlighting the influential mechanisms of surfactants in soil clogging through physical, chemical and biological processes. Therefore, to provide a comprehensive approach, this review describes the adsorption mechanisms of surfactants on organic and inorganic particles, at gas-bubbles and at biomass. We also provided our own input to the description of the adsorption of surfactants at fluid/fluid and fluid/solid interfaces in porous media associated with the clogging process.
The municipal wastewater collection system is recognized as an initial point of interaction between microplastics (MPs) and the urban wastewater matrix. The raw wastewater contains a wide variety of organic and inorganic substances including chemicals and heavy metals. However, the fate of MPs in urban sewer systems is not yet well understood. In this work two types of virgin polypropylene (PP) samples, isotactic (iPP) and atactic (aPP), were exposed to two synthetic wastewater solutions in order to study their effects on the physical properties of the hydrophobic polymer surfaces. Particular attention was paid to the pollution adhesion at the air-liquid-solid interfaces of the surface air pockets entrapped on the polymer surfaces. The first wastewater solution consists of mixed fat, oil and grease (FOG) -surfactant and another which is an exclusively contained wastewater surfactant. The interaction experiment over a period of 10 min between the polymer's air pocket and solutions indicated that the size of the bubble in the mixed FOG-surfactant solution increased more pronouncedly for iPP (%152) in contrast to aPP (%31) and was also compared with the greater surface roughness of the polymers. The size variation of the spherical cap on the immersed polymer surfaces were measured between 17 µm and 85 µm using image processing techniques while the data was analyzed by the Young-Laplace equation. The corresponding technical surface roughness of the polymers, the surface tension of the liquids and their air/water contact angle on the flat polymer surfaces were also measured. The results of this study indicated that surface air pockets influence the adsorption capacity of MPs and thus their buoyancy and contamination potential.
Leakage of wastewater from sewer lines may result in contamination of soil and groundwater. Our investigation dealt with the effects of surfactant as one of the constituents of wastewater on the infiltration process of wastewater through soil. To that aim, in a laboratory experiment, a column was uniformly packed with glass beads of 0.25-0.50 mm diameter and equipped with sensors to measure local fluid pressure at three observation points along the direction of flow. The artificial laboratory wastewater was created by adding a commercially available detergent to degassed tap water producing surfactant concentrations between 8 and 16 mg l -1 . The displacement process of degassed tap water by such a particle-free artificial wastewater was studied by loading the surfactant solution into the saturated glass beads column. Short-term pressure changes were observed while the interface between water and surfactant solution passed the observation points within the column. The pressure peaks increased for higher surfactant concentrations. The theory of growing interface between surfactant solution and clean water by aggregation of monomers to a double layer could be supported by the column experiments.
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