Assessing the Impacts of Pulp Loading from Non-Dispersible Materials on Downstream Sewer Systems

This study subjected wipes from five different manufacturers to a variety of tests to determine if changes to their physical characteristics occur when introduced into a sewer system and what effect the shredded material (pulp) has on the downstream sewer. Shredded and non-shredded, wipes were used in the study utilizing specialized bench-scale testing and live sewer testing.

Results from the benchmark testing and live sewer testing, within both local and regional sewer systems, indicate that the wipes used in the study were significantly reduced in size through shredding and the resulting pulp, while increasing in weight due to water absorption, does not appear to cause clogging in the downstream sewer lines or exhibit noticeable odors. The pulp recovered during live sewer testing was found to consist of individual pieces less than two square inches in size. A small amount of pulp was observed binding with other background material in the sewer when grease and hair were present. The results suggest that shredding of the wipes by a mechanical grinder can minimize impacts to the downstream sewer lines by reducing the size of the material. Recommended actions include: educating the public on what to flush down the toilet, implementing an effective fats, oils, and grease (FOG) program and employing mechanical grinders ahead of pumps, when clogging due to non-dispersible material becomes a problem.