A water treatment system comprising a pressure vessel, vertically aligned separation elements within the vessel each having at least one porous UF or MF membrane, feed fluid passageways, a permeate fluid passageway, a concentrate removal port, and a biocontactor within the vessel that has biogrowth surfaces surrounding flow paths through the biocontactor. The flow paths have a median ratio of surface area to volume which exceeds 15 cm.sup.1. The pressure vessel also contains a pressure plate with holes which separates the vessel into two chambers, a first chamber containing membrane elements and a second chamber that contains the biocontactor. A sealing means contacting the pressure plate prevents fluid flow between the first chamber and second chamber except through the porous membranes.

A cord for supporting a biofilm has a plurality of yarns. At least one of the yarns comprises a plurality of hollow fiber gas transfer membranes. At least one of the yarns extends along the length of the cord generally in the shape of a spiral. Optionally, one or more of the yarns may comprise one or more reinforcing filaments. In some examples, a reinforcing yarn is wrapped around a core. A module may be made by potting a plurality of the cords in at least one header. A reactor may be made and operated by placing the module in a tank fed with water to be treated and supplying a gas to the module. In use, a biofilm covers the cords to form a membrane biofilm assembly.

A cord for supporting a biofilm has a plurality of yarns. At least one of the yarns comprises a plurality of hollow fiber gas transfer membranes. At least one of the yarns extends along the length of the cord generally in the shape of a spiral. Optionally, one or more of the yarns may comprise one or more reinforcing filaments. In some examples, a reinforcing yarn is wrapped around a core. A module may be made by potting a plurality of the cords in at least one header. A reactor may be made and operated by placing the module in a tank fed with water to be treated and supplying a gas to the module. In use, a biofilm covers the cords to form a membrane biofilm assembly.

A wastewater treatment apparatus has a tank with an access opening, at least one fixed film media pod positioned in the interior of the tank, a diffuser positioned in the interior of the tank, and an air pump connected to the diffuser. The fixed film media pod is formed of a polymeric material and has openings framed by the polymeric material. The diffuser is adapted to aerate liquid in the interior of the tank. The media pod has a tubular structure extending vertically in the interior of the tank and positioned above the bottom of the tank. Floats are attached to the top of the media pod so as to suspend the media pod in the liquid in the tank.

A wastewater treatment apparatus having a tank having an access opening thereon, at least one fixed film media pod positioned in the interior of the tank, and a diffuser positioned in the interior and at a side of the fixed film media pod. The tank has an inlet adapted to allow wastewater to enter the interior of the tank and an outlet adapted to allow an effluent to exit the tank. The fixed film media pod is formed of a mesh material. The diffuser is positioned in the interior of the tank and exterior of the fixed film media pod and adapted to aerate liquid in the interior of the tank without releasing air bubbles through the interior of the fixed film media pod. An air pump is connected to the diffuser.