The liquid is filtered through a membrane. The microorganisms collect on the membrane surface. The filter is incubated on a nutrient medium and the individual colonies can then be evaluated. The method is also suitable for large sample volumes and low microorganism counts. The quality control and product design of our membrane filters are strictly controlled and offer users significant advantages. All membranes used for microbiological quality control are tested systematically in order to ensure the same high quality from batch to batch. Parameters tested are bubble point, flow rate, bacterial retention, recovery rate, and sterility.