Experiences From the Start-up Phase of a Retrofitted Membrane Bioreactor

A conventional activated sludge plant for municipal wastewater treatment is retrofitted by using membrane bioreactor technology. The bioreactor and other parts of the infrastructure are incorporated into the new process design. The plant capacity is increased. Stringent discharge criteria are met. After several steps of start-up the plant is in full operation since spring 2008. The efficiency of the treatment process is optimised. In this case study retrofitting the existing CAS as an MBR was beneficial in several ways:
(a) Technologically the membrane filters replace the secondary clarifier and, by increasing the biosolids concentration, the plant capacity was increased significantly without building a new bioreactor.
(b) Economically the cost of building a new second WWTP could be saved.
(c) Ecologically a substantial increase in the nutrient removal and the hygienic effluent quality was achieved. This is an important precautionary measure in the water protection area.                                                                                                                                                                        It can be said, that MBRs can offer a viable and efficient option for the retrofitting of existing CAS. Source: WEFTEC 2009 Proceedings