Wastewater treatment plant based on membrane bioreactors (MBR) in a touristic locality

This paper is focused on a wastewater treatment plant based on MBR in an Italian touristic locality. The plant is designed for 5000 person equivalent (p.e.) in winter and 8200 p.e. in summer; it is made of primary treatments (screen, sand and grit removal, buffer tank, rotary drum screen), predenitrification (220 m3), oxidation (370 m3) with ferric chloride dosage, membrane tank (250 m3) equipped with Kubota plane membrane (total filtration area 3600 m2), deoxygenation tank (115 m3), disinfection with sodium hypochlorite, sludge thickening and dewatering by centrifugation. In 2012, on average basis the plant treated 733 m3d-1 wastewater with 442 mgL-1 COD, 253 mgL-1 BOD, 38.1 mgL-1 TKN; removal efficiencies were 86% for COD, 96% for BOD, 93% for TKN and 74% for total nitrogen. Permeate flux varied in the range 4 – 24 Lm-2h-1 and negative pressure in the range 85 – 300 mbar; membranes were backwashed with sodium hypochlorite once a month.