Achieving Sustainable Nutrient Removal for Tailored Water Treatment: A Novel Application of the MBR Technology

The secondary effluent from the activated sludge plants that are operated at low solids retention times to achieve BOD and TSS removal are currently considering the need to either upgrade the main treatment facility or to add tertiary facilities to achieve a more complete nutrient removal for various end use driven reasons. Especially in the cases where a high quality product water is needed in addition to the nutrient removal, membrane technologies are being considered. However, due to the lack of accumulated knowledge in tertiary application of biological and membrane processes, in most cases the facilities are facing a scenario where large capital investments in upgrading existing facilities to generate feed water suitable for tertiary filtration technologies are being considered. In most cases this means that the main facility will have to be derated, unless the original design conditions are amenable to direct conversion to nitrogen removal configuration and operation at longer solids retention time.In the case of tertiary membrane bioreactor (T-MBR) implementation, the main facility continues to operate at low solids retention time conditions providing BOD and TSS removal, and the effluent is then treated in a membrane bioreactor system operated at a sufficient solids retention time to permit year round nitrification. The process can generally be described as two-stage activated sludge with the second stage employing a membrane bioreactor. Considering the limitations on the knowledge base on the design and operation criteria related to separate sludge systems, pilot testing is conducted to obtain proof of concept and establish the design and operating parameters for particular feed water quality and the end point drivers.