Experimental Study on the Hydraulic Performance of the Horizontal Main Drain of Building Drainage Systems Affected by Surfactants Sodium Dodecyl Benzene Sulfonate and Alkyl Ethoxylate-9

Surfactants play a pivotal role in daily life owing to their commendable performance. The outbreak of the COVID-19 pandemic notably escalated surfactant usage. Upon entering building drainage systems with wastewater, surfactants profoundly influence hydraulic performance, an aspect that has garnered limited scholarly attention. This study employs an equally proportioned drainage test device to meticulously examine the variances in physical properties between surfactants, such as sodium dodecyl benzene sulfonate (SDBS) and alkyl ethoxylate-9 (AEO-9), and their repercussions on the hydraulic dynamics of building drainage horizontal main drains. Our findings reveal that the introduction of surfactants leads to the following: (1) an augmentation in water velocity and deposition distances of the solid simulant in the building drainage horizontal main drain with concentrations exacerbating this effect. The deposition distance of the solid simulation surged by up to 527% under experimental conditions compared to no surfactant; (2) there was a suppression of hydraulic jump and full degree of the horizontal main drain, with the concentration amplifying this suppression; and (3) an exacerbation of positive pressure in the horizontal main drain was found with increasing concentration, reaching a staggering 235.3% elevation compared to no surfactant. Moreover, SBDS foam outperformed AEO-9, demonstrating a 17.70-36.04% higher positive pressure in the horizontal main pipes. SBDS exhibits lower starting and ultimate viscosity, along with smaller colloid particle sizes, resulting in a 0.9-2.0% reduction in hydraulic jump and full degree. However, its inferior drag-reduction capability leads to a 17.48-36.44% decrease in the final deposition distances of solid simulant in the building drainage horizontal main drain compared to AEO-9.