Patent ID: 7744755

Claim:
A biological treatment and filtration system equipment for raw water, which comprises 1) a water treating vessel provided with a raw water inlet and a treated water outlet; 2) a filter sand layer provided between the inlet and the outlet in the vessel for filtering and biologically treating the raw water using a sand layer containing at least minute sintered sand particles carrying microorganisms; 3) a filtering net provided on the top of said filter sand layer, comprising a net body carrying absorbent for absorbing arsenic components contained in the raw water and a frame fixed to the periphery of the net body, wherein a tube ring is engaged on the periphery of the frame of filtering net in a manner to bulge out by a pressure fluid supplied thereto until contacting to a inner surface of the vessel to make a sealing off between the frame and the inner surface, and wherein the raw water inlet is disposed above the filtering net and the treated water outlet is disposed below the filter sand layer.