The Manitowoc Public Utilities (MPU) located in Wisconsin in the United States, treats surface water from Lake Michigan. The existing 31 MGD Water Treatment Plant (WTP) uses a polymeric membrane system to remove all suspended matter including cryptosporidium oocysts (Milwaukee Crypto outbreak in 1993 initiated absolute barriers for crypto).

MPU has expressed interest in evaluating ceramic membranes for treating this source since the main operational challenges for the current plant have been associated with maintaining the design plant capacity over time. Ceramic membranes are of interest due to their durability and ability to operate at a high sustainable flux.

In November 2014, PWN Technologies (PWNT), in partnership with METAWATER and MPU, started a pilot study of ceramic membranes directly on the water from Lake Michigan. This unit includes equipment for pre-coagulation and a ceramic micro filter with a single, full-scale 269 sqft (25 m2) membrane module.

METAWATER USA has provided the pilot equipment and PWN Technologies is responsible for the pilot plant, staffing, operation of the pilot plant, data-acquisition and reporting .  The operation of the pilot started at the beginning of the coldest period with feed waters reaching temperatures around zero degrees Celsius and will continue for a year.

First results are very promising. It seems that a stable operation is possible (CIP frequencies > 1 year) at an operational flux of 175 lmh with an enhanced backwash frequency of once every 10 hours.  It will now be interesting to see the membrane performance evolve in time with fluctuating water quality.