The effects of surfactant dosed water on solid transport in above ground near horizontal drainage systems

Surfactants play an increasing part in the makeup of waste water from building drainage systems. The determination of the concentration of surfactants in drainage flows is complicated by the wide range of actual concentration levels revealed by manufacturers of commercially available cleaning products and soaps and the dilution of this by varying quantities of water in the drainage systems, due to the unsteady flows from appliance discharge. A methodology of determining the relationship between the surfactant concentration and solid velocity is tested, whereby the concentration of surfactant in the water flow was progressively increased and solid velocity measured. This method proved difficult as surfactant levels accumulated in the system made it impossible to determine real concentration levels. An alternative approach of determining surfactant concentration levels as a result of appliance discharge proved more useful. This methodology lead to the determination of realistic concentration levels of surfactants in a drainage line. Solid velocities were found to increase as a result of the presence of surfactants. This modification has a significance in the area of water conservation as it shows that systems perform better, even with reduced water usage appliances, as a result of the presence of surfactants. © 2005 Elsevier Ltd. All rights reserved.