BUG BUSTER: A NEW PRE-DIGESTION PROCESS TECHNOLOGY THAT INCREASES BIOGAS PRODUCTION FROM SEWAGE SLUDGE
Jake Spooner 1, Tom Taylor 2, Fiona Shaw 3, Manocher Asaadi 4, Sam Shepherd1, Clive Rigden 1
1 Yorkshire Water Services, 2 Eco-Solids International, 3 Earth Tech Engineering, 4 AD Technologies
(free)
The continual rise in energy prices and environmental concerns over the past few years have prompted
companies to review and reduce their energy usage or introduce efficiencies of scale on their process lines.
A low-cost, low maintenance process called Bug Buster has been developed to rupture sludge microorganisms prior to entering digesters, allowing more efficient digestion by bacteria. Increases in digestion
efficiency lead to a significant rise in biogas production and proportional reduction in solids load for disposal.
The increased biogas yield can be used to generate electricity, which is eligible for incentive payments
under ROCs (Renewable Obligation Certificates) in the UK, and indicates a pay-back period of well within
two years. The Bug Buster process is a novel way to disrupt sludge cells to aid anaerobic digestion. Biogas
is introduced to the digester feed sludge in a pressurised tank, allowing gas to diffuse across the cell
membrane. Rapid depressurisation follows, causing the micro-organisms to rupture. The sludge is then
transferred to the digesters. Bacteria within the digesters then have immediate access to the cell contents
for digestion, without having to attack the cell wall first, thus improving digestion efficiency. An additional
benefit of the Bug Buster process is that there is a more homogenised sludge mix. A commercial scale
prototype plant has been built at Yorkshire Water’s Old Whittington Waste Water Treatment Works, near
Chesterfield, Derbyshire, to examine the Bug Buster process. This site was selected because suitable
facilities were available to allow easy comparison between a control digester and a digester preceded by the
Bug Buster process. A six month trial is currently underway to investigate plant performance.
This paper is intended to introduce the Bug Buster process, describe commissioning issues and present the
results obtained so far from the ongoing full scale trial. We also present some initial results from a Bug
Buster bench-scale unit.
KEY WORDS
Anaerobic digestion, Bug Buster, disintegration
