Causes, effects and solutions of operational problems in wastewater systems due to nonwoven wet wipes

Operational problems due to sewer system incompatible nonwoven wipes in wastewater systems affect nearly all wastewater system operators in regions where nonwoven wipes are used as convenience products. They disrupt the operation of the critical infrastructure, cause equipment failures, and large additional expenditures. To date, however, there is no agreement as to which nonwoven wet wipes are the source of the problems (those sold as “flushable” or those designated for a disposal via the household waste). The overall aim of this thesis was to investigate the effects of nonwoven wet wipes in sewer systems, focussing on the sewer system compatibility of different types of nonwoven wet wipes. The distinction between “non-flushable” wet wipes and those marketed as “flushable” was of particular interest. For this reason, a survey among wastewater system operators and among the users of nonwoven wet wipes was conducted, field experiments were performed in a pumping station, and the clogging effect of different nonwoven wipes was investigated in the laboratory. Occurrence, location, type, and financial impacts of the operational problems due to sewer system incompatible nonwoven wipes could be identified. The requirements of the wastewater system operators regarding flushability criteria were also determined. It was shown that wipes are primarily used by young parents and that baby wipes are most frequently wrongly disposed of via the toilet. A general interest of the public for the issue of sewer system compatibility of flushable nonwoven wipes could be determined, as well as a willingness to pay more for truly sewer system safe wipes. The results of the field investigation showed that non-flushable wipes designated for disposal via the household waste were the main cause for the pump blockages. However, a significant amount of nonwoven wipes sold as flushable could also be identified in the clogging material. The results from the laboratory investigations confirmed the clogging behaviour of the non-flushable wipes, which was previously indicated by findings from the field and experiences from wastewater system operators. The results also suggest that flushable nonwoven wipes, which meet the flushability criteria of the industry associations of the nonwovens industry, are compatible with wastewater pumps. In contrast, non-compliant flushable nonwoven wipes were shown to have a clear adverse effect on the pump, even at low concentrations. Overall, the results of this study give an important insight into wipe-related operational problems and can be used to identify suitable solutions.