Apr 06, 2007

Black & Veatch Awarded Patent for Innovative Digester Cover

Black & Veatch announced today that it has received a patent for an anaerobic digester cover that solves a significant wastewater treatment operations problem.

The invention enables operations staff to maintain constant digester levels and prevent foam from entering gas lines. Black & Veatch engineers Jeff Wells and Mark D. Wilson designed the new system to prevent accidental spillage and downstream equipment failures at the Pelham Wastewater Treatment Plant in Greenville, S.C., during its expansion.

“Our leadership and advancements within the water industry typically revolve around treatment processes and technology applications,” said Dan McCarthy, president and CEO of Black & Veatch’s water business. “In this case, the project team delivered a unique solution to a common problem through the invention of new equipment, as well as through process design.”

Lauren Hildebrand, engineering manager for Western Carolina Regional Sewer Authority, explained the impact of the solution: “The challenges in the Pelham WWTP expansion extended beyond process design to system redesign. The Black & Veatch team went the extra mile to help us solve a pervasive wastewater treatment problem. The expanded facilities, including the new digesters, have met our high expectations for water quality and operations.”

Anaerobic digesters biologically reduce the volume of organic wastes by mixing microorganisms with wastewater residuals in an oxygen-free environment. This process produces biogas, a byproduct primarily composed of carbon dioxide and methane gases. While biogas can be used to power operations, it often creates foam within the digester that can negatively impact treatment plant operations. To solve this problem, Black & Veatch applied innovative thinking to a well-established treatment technology.

The patented cover utilizes a fixed (as opposed to floating) cover that is in direct contact with the digester contents over a large surface area. Its shape and orientation direct foam toward a central tower, where a series of liquid sprays direct the foam into an overflow weir for discharge under a small-diameter biosolids dome. A gas-collection dome at the top of the tower collects the gas produced during anaerobic digestion. Its position above the residuals and foam overflow weir minimizes the likelihood that foam will enter the gas lines and damage the digester gas handling equipment.