External MBR system launched by Aquatech
Aquatech International has launched a membrane bioreactor (MBR) system in which the ultrafiltration (UF) membrane is positioned outside the bioreactor rather than submerged in it or in a downstream membrane tank.Aquatech says its new Aqua-EMBR offers several benefits over submerged MBR systems, which already have advantages over conventional activated-sludge systems.
Because the Aqua-EMBR system has no membrane tank, it can be built more quickly. Installed as one or more skids on a flat concrete slab, the system eliminates the need for complex civil engineering and lowers the risk for contractors due to construction delays caused by weather conditions, environmental or other local uncertainties.
The UF membrane modules are arranged vertically and aerated continuously at the bottom. Mixed liquor is transported via "air lift pump" action through the module, while the membrane feed/recirculation pump is only used to overcome the hydraulic losses and maintain a relatively constant flow of mixed liquor through the membrane.
This innovative design reduces much of the feed-pumping energy requirement needed to maintain high crossflow velocity. Permeate flow, which is inside-out from the membrane modules, is collected by a permeate pump.
Because no membrane components are submerged in the biological mixed liquor, the biological and membrane systems can be operated and optimized independently. The membrane operation is automatically controlled.
With its tight membrane pore size (nominal/maximum 30 nm/50 nm), Aqua‑EMBR produces high effluent quality - an important factor for reuse purposes and future regulations. Applications for Aqua-EMBR include wastewater treatment or reclamation in new industrial and municipal wastewater treatment plants (WWTP) or in existing plants undergoing upgrades.
Importantly, the Aqua-EMBR system offers an operator-friendly working environment. Operators do not see, smell or come in contact with the biosludge, nor do they work on top of open membrane tanks where the air could contain harmful aerosols. Should maintenance be required, Aqua-EMBR's membrane modules can be removed or replaced without any contact with the biosludge.
Another significant benefit is the Aqua-EMBR's higher operating flux - approximately 50% higher than submerged systems. Because 50% less surface area of membrane is needed per unit volume of permeate production, the low membrane cost per unit volume filtrate means savings in capital and operating costs. Maintenance costs, such as labor and chemicals, are also reduced.
One of the first applications for Aqua-EMBR was treatment of effluent generated from a chemical manufacturing plant, where Aquatech successfully commissioned a 50 m³/d capacity plant. After proper sludge acclimatization, it was possible to reduce chemical oxygen demand by 85% and consistently achieve a reduction of more than 95% of biochemical oxygen demand.