Patent ID: 7074338
Filing Date: 2006-07-11
Classification: B01D

Abstract:
1. A filtering method comprising the steps of: pre-coating a filter with an auxiliary agent by flowing a filter auxiliary agent liquid accommodated in a pre-coat tank and containing a filter auxiliary agent in a forward direction through a filter element to circulate the filter auxiliary agent liquid to the pre-coat tank and for attaching and stacking the filter auxiliary agent on the filter element to form a filter auxiliary agent layer; filtering a filter treatment liquid accommodated in a main tank independent of said pre-coat tank, by flowing said filter treatment liquid in the forward direction through the filter element to circulate the filter treatment liquid back to the main tank, and for removing sludge contained in the liquid by the filter auxiliary agent layer of the filter element; backwashing said filter by flowing the filter auxiliary agent liquid contained in said pre-coat tank in a direction opposite to said forward direction to separate both said filter auxiliary agent layer and a sludge layer from said filter element; and circulating said separated filter auxiliary agent layer and sludge layer to the pre-coat tank when the filter auxiliary agent layer of the filter element is clogged by the sludge layer, wherein the filter auxiliary agent pre-coat step, the filtering step and the backwashing step are repeated a plurality of times.