Roisin Reidy 21 May 2014 More in Water & Wastewater Pall, Mann+Hummel and Ahlstrom: Last week's most-read news stories on filtsep.com News 1. Pall buys Filter Specialists Inc 2. Mann+Hummel takes 50% stake in membrane specialist Microdyn-Nadir 3. Ahlstrom names new president and CEO