Abstract: A biological treatment apparatus comprising: (a) a vessel; (b) an inlet conduit for providing feed water to an inlet region; (c) an outlet conduit for removal of treated water from an outlet region; (d) an inlet distributor comprising inlet ducts, each in fluid communication with both the inlet region and a porous surface section of the inlet duct wall; (e) an outlet distributor comprising a plurality of outlet ducts, each in fluid communication with both the outlet region and a porous surface section of the outlet duct wall; and (f) a media bed comprising particles in fluid communication with porous surface sections of both the inlet and outlet duct walls; wherein a ratio of the length of an inlet duct to a minimum distance between an inlet duct and an outlet duct is from 15:1 to 2:1.

Abstract: Provided is a method of treating feed water comprising the step of passing the feed water through a biostratum that comprises resin beads and living microorganisms to produce biostratum-treated water, wherein (a) the area-normalized free void volume in the biostratum is 0.018 m3/m2 or less; (b) the packing density in the biostratum is 0.68 to 0.96; (c) the ratio of the exterior surface area of the resin beads to the total free void volume in the biostratum is less than 2.0 to 50 m2/L; (d) the velocity of the water through the biostratum is 1 to 1,500 biostratum volumes per hour; and (e) the Reynolds number of the flow through the biostratum is 0.10 to 3.0.

Abstract: Provided is a method of treating feed water comprising the step of passing the feed water through a biostratum that comprises resin beads and living microorganisms to produce biostratum-treated water, wherein (a) the area-normalized free void volume in the biostratum is 0.018 m3/m2 or less; (b) the packing density in the biostratum is 0.68 to 0.96; (c) the ratio of the exterior surface area of the resin beads to the total free void volume in the biostratum is less than 2.0 to 50 m2/L; (d) the velocity of the water through the biostratum is 1 to 1,500 biostratum volumes per hour; and (e) the Reynolds number of the flow through the biostratum is 0.10 to 3.0.