Even where fine screens are installed in the headworks of wastewater treatment plants, some debris will always end up in the sludge. Plastic parts and fibrous materials can severely disturb the operation of thickeners, digesters and dryers. Such solids impair the operation of pumps, heat exchangers, mixers, dewatering systems, pelletizers, etc. Hair and fibers often lead to the formation of tresses and grease balls. Where biosolids are land applied, plastic parts should be removed.

Such undesired solids should be removed from the sludge before causing problems in downstream processes and machines. Grinders might reduce the issues but they do not remove disturbing solids and are high in maintenance. Only screens can effectively remove debris from sludge in industrial processes. Excellent dewatering and compaction of the removed material is a huge advantage because it ensures a clean and safe environment and volume reduction. Sludge screens should be entirely enclosed for odor control.

It can be argued that the headworks of a plant might be the most critical place in a Waste Water Treatment Plant. What happens there will greatly influence the downstream process of the WWTP. More specifically, it is the operation of screenings and screenings handling which will have a considerable affect on the operation and maintenance requirements of the WWTP. Currently the industry is gravitating towards fine screens, which are typically defined as screens with a bar spacing of 1/4 (6mm) or less. The purpose of the paper is to share Huber?s findings of 30 years with the readers of this paper. These findings consist of our practical experience in terms of design, manufacture, installation, service and operation with a variety of fine screens. It is hoped that this report will prove to be useful for consultants, operations staff, and owners.