Abstract: A filtering device uses a filtration unit for filtering raw water, and the filtration unit has a depth filter forming a filtration membrane thereof and a housing accommodating the depth filter. The housing includes a raw water inlet port for supplying the raw water to the depth filter, a filtrate water outlet port, a gas-supplying port for supplying compressed air into the filtration unit to clean the depth filter, and a drain port for discharging the compressed air together with the raw water. A pore diameter of the filtration membrane is designed within a range of 1 to 25 ?m. The filtering device includes a filtrate water supplying passage connected to the filtrate water outlet port, a discharge passage connected to the drain port, a communication passage for communicating filtrate water supplying passage with the discharge passage, and a motor valve for opening and closing the communication passage.

Abstract: A filtering device uses a filtration unit for filtering raw water, and the filtration unit has a depth filter forming a filtration membrane thereof and a housing accommodating the depth filter. The housing includes a raw water inlet port for supplying the raw water to the depth filter, a filtrate water outlet port, a gas-supplying port for supplying compressed air into the filtration unit to clean the depth filter, and a drain port for discharging the compressed air together with the raw water. A pore diameter of the filtration membrane is designed within a range of 1 to 25 ?m. The filtering device includes a filtrate water supplying passage connected to the filtrate water outlet port, a discharge passage connected to the drain port, a communication passage for communicating filtrate water supplying passage with the discharge passage, and a motor valve for opening and closing the communication passage.

Abstract: A method for determining air borne bacteria which includes successive steps of passing a volume of air by a timed suction pump through a membrane filter at a membrane passing velocity of not more than 15 cm/sec and under a constant transmembrane pressure of not more than 100 mmHg to collect the air borne bacteria on the surface of the membrane filter. The membrane filter has a multiplicity of minute holes and is provided on a medium-absorbing pad housed in a holder. A medium is injected into the medium-absorbing pad housed in said holder. The bacteria thus collected are incubated and the number of the colonies developed on the surface of said membrane filter is measured.