PRE-THICKENED AEROBIC DIGESTION WITH MEMBRANE THICKENERS
Bailey, E.1 and Mendez, E.2
1Eimco Water Technologies, USA, 2MBR Enviroquip, a Division of Eimco Water Technologies
(free)
In 2005 Enviroquip, a division of Eimco Water Technologies (EWT) began operation of two
historic Membrane Bioreactor (MBR) plants; the Village of Dundee Wastewater Treatment Plant
(WWTP) located in Dundee, Michigan and McFarland Creek Wastewater Treatment Plant
(WWTP) located in Bainbridge Township, Ohio. The Village of Dundee and McFarland WWTP
were existing conventional plants with the need to expand in order to meet future flows and
demands due to the overall growth and development in their respective areas.
In the year 2003, the Village of Dundee began work in upgrading their wastewater treatment
plant. The decision to go forth with the expansion was made based on the modifications enforced
by the Michigan Department of Environmental Quality (MDEQ) mandating that they lower the
plant discharge limits due to water in the receiving stream not meeting federal quality standards.
The McFarland Creek WWTP also faced the matter of expanding its existing plant capacity by
fifty percent due to continued growth of the region. Both of the facilities engineering firms
reviewed available technologies to determine the best approach and the most suitable equipment
to utilize in the expansion project, and concluded that the MBR technology was the best option for
this application.
The technology proposed for both plants was an MBR system for the Biological Process and the
PAD-K system (Pre-thickened Aerobic Digestion with Membrane Thickener) for the sludge
treatment process. The PAD-K system provides integrated operation of a Kubota flat-plate
membrane thickener and two or more aerobic digesters. By operating these units as a combined
system, improved treatment is achieved. The different drivers that led to this option for McFarland
WWTP were to retrofit existing digesters and reduce sludge disposal cost by a minimum of 20%.
For the Village of Dundee the main driver was to reduce sludge production by 30% and increase
the sludge storage capacity from 120 days to 180 days. The upgrade from Sequencing Batch
Reactors (SBR) to MBR in combination with the PAD-K process was targeted to meet both
stringer effluent limits and handle a higher solids load without the need of additional storage
tanks.
