A new membrane bioreactor system combines suspended growth activated sludge with an immersed membrane to produce effluent ideal for meeting stringent discharge criteria, direct reuse or reverse osmosis feed. The membranes are placed in direct contact with the mixed liquor, replacing conventional filtration and integrating clarification, aeration and sludge digestion into a single process step.
An integral component of the Zenon ZenoGem? Membrane Bioreactor process is the ZeeWeed? Immersed Hollow Fiber Membrane. Unlike other membranes that are housed in shells, pressure-driven and assembled on skids, ZeeWeed membranes are immersed directly in the process tank and are driven by a slight suction. The mixed liquor is drawn toward the fiber surface where the solids are rejected. The permeate passes through the membrane pores into the lumen of the membrane fiber and withdrawn.
The pores of the membrane form a barrier to bacteria and cysts, retaining them in the process tank and allowing for efficient liquid-solid separation.
The immersed membrane effectively eliminates the need for gravity settling of solids, meaning a secondary clarifier is not necessary. This provides control of solids retention times and allows operators to concentrate on optimizing the biological treatment system without the worry of sludge settling problems.
The ZenoGem system is typically operated at an MLSS of 12,000 mg/L - 20,000 mg/L. The high MLSS allows for greater treatment throughput with smaller tank volume and smaller overall facility footprint. The absence of sludge settling allows facilities to raise the sludge age, resulting in less sludge production. Finally, the membrane barrier allows for control of nitrogen and phosphorus removal, whether they are of organic, pin-flocked alum, phosphate or ferric phosphate nature. Effluent typically has a turbidity of <0.1 NTU and meets effluent criteria requirements of all states.
The modular nature of the system allows the membranes to be inserted into an existing process tank, converting it into a single step treatment system or to build small footprint sewage plants. Modularity also offers flexibility in hydraulic capacity, allowing plant expansion in 100,000 gpd phases to meet future capacity demands, and reducing front-end development costs.
The ZenoGem Membrane Bioreactor has been applied in more than 200 installations throughout North America, from large municipal wastewater treatment plants to small-scale treatment plants for land developers. Typical applications are: 1) water reuse 2) California Title 22 direct reuse 3) Floridas 5,5,3,1 discharge plants 4) pre-treatment to reverse osmosis plants and 5) upgrade of existing secondary or tertiary plants.
