The First Egg-Shaped Digester Treatment System in Pennsylvania
Planning, engineering design, and construction management of 1.5 mgd wastewater treatment system for the Borough of Kutztown. The project utilized an innovative treatment technology called the egg-shaped digester system. The digester has a unique egg-like shape, which accounts for many of the benefits claimed by its supporters. Sludge in an egg-shaped digester (ESD) can be mixed more completely and with less energy than can a conventional cylindrical-shaped digester. There are no "corners" or dead spots in the tank where mixing does not occur or where solids can settle out. This results in a more efficient and more complete digestion process with higher gas production. The steep sloping sidewalls at the bottom of the egg keep grit and heavy solids moving until they reach the bottom of the tank where they can be removed or resuspended. The converging sidewalls at the top of the egg concentrate the scum making removal relatively easy. The major benefits of this type of system were a high rate of gas production, a sludge heating system that utilized digester gas rather than fuel oil as previously used to heat the sludge, and a 2% increase in digested sludge solids. The social implication of this is that a more highly processed sludge will be produced and it is intended that the excess renewable gas will be used for on-site power generation for some plant needs and thus reduce commercial power usage.
The ESD was the first such unit in Pennsylvania. It received an Engineering Excellence Award from the Pennsylvania Consulting Engineers Council.
BIRDSBORO MUNICIPAL AUTHORITY WASTEWATER TREATMENT PLANT
SSM designed the Wastewater Treatment Plant upgrade for the Birdsboro Municipal Authority to meet the NPDES permit limits and be in compliance with a PADEP consent order. The innovative design of the vertical loop reactor (an oxidation ditch turned on its side) allows for the mixing and aeration to be provided by disc rotors supplemented with coarse bubble air diffusers for aeration. The WWTP is capable of handling high peak flow and provide nitrification and denitrification within the same tank providing a small footprint on the limited space on the WWTP site. A slurry wall utilizing high clay content material installed below grade shaped the barrier walls that surround the WWTP. The wall was constructed to prevent water from percolating through the ground under a dike and allowing the WWTP to be protected during potential flooding events.