Long term operation of an anaerobic membrane bioreactor (AnMBR) treating municipal wastewater was investigated in a real seawater intrusion spot in Falconara Marittima (Central Italy) on the Adriatic coastline. Changes in biological conversion and system stability were determined with respect to varying organic loading rate (OLR) and high salinity conditions. At an OLR of 1 kgCOD.m3-1d-1, biogas production was around 0.39 ± 0.2 L.d-1. The increase of the OLR to 2 kgCOD.m3-1d-1 resulted in the increase of biogas production to 2.8 ± 1.5 L.d-1 (with 33.6% ± 10.5% of CH4) with methanol addition and to 4.11 ± 3.1 L.d-1 (with 29.7% ± 11.8% of CH4) with fermented cellulosic sludge addition. COD removal by the AnMBR was 83% ± 1% when the effluent COD concentration was below 100 mg O2.L-1. The addition of the fermented sludge affected the membrane operation; significant fouling occurred after long-term filtration, where the trans-membrane pressure (TMP) reached up to 500 mbar. Citric acid solution was applied to remove scalants and the TMP reached the initial value. High saline conditions of 1500 mgCl-.L-1 adversely affected the biogas production without deteriorating the membrane operation. The treated effluent met the EU quality standards of the D.M. 185/2003 and the new European Commission Resolution for reuse in agriculture.

This study was carried out within the framework of the "SMART-Plant" Innovation Action which has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 690323. This study was carried out within "Safe and Sustainable Solutions for the Integrated Use of Non-Conventional Water Resources in the Mediterranean Agricultural Sector (FIT4REUSE)" which has received funding from the Partnership on Research and Innovation in the Mediterranean Area (PRIMA) under grant agreement number 1823 (Call 2018 Section 1 Water). The authors kindly acknowledge Diego Cingolani, Gianluigi Buttiglieri and VivaServizi.