Removal of nutrients and micropollutants treating low loaded wastewaters in a membrane bioreactor operating the automatic alternate-cycles process

The necessity to produce treated wastewaters with high quality standards for both discharge or reusing, implies the adoption of very effective processes in the field of biological wastewater treatment. The Membrane Biological Reactor (MBR) has showed the capacity to remove COD, BOD, N, P and suspended solids as well as heavy metals and organic micropollutants so to obtain reusable water. In this study the automatically controlled alternate cycles process have been applied to a MBR, the process allows for the reuse purpose with a remarkable reduction of the operational costs. This paper regards the treatment of a real low loaded domestic wastewater (TSS = 136 mg/l, COD = 113 mg/l; TKN = 22 mg/l; P-tot = 2.4 mg/l) with low attitude to biological treatment. Despite the lack of necessary readily biodegradable organic carbon (RBCOD), the nitrogen removal was good (Edenitrification = 67%) thanks to the flexibility of the alternate cycles process to the low loading fluctuation. Moreover, the perfect retention capacity of the ultrafiltration membranes permits an high removal of heavy metals and polycyclic aromatic hydrocarbon (PAH). The effluent quality was suitable to reuse purpose according to the Italian law.