Start-up of decentralised MBRs Part II: the use of additives as initial inoculum

Abstract

Abstract This paper corresponds to the second part of a study aiming to establish the best conditions to start-up decentralised membrane bioreactors. The first part focused on the impact of different operational parameters on the start-up, whereas this second part aims to find a substitute for activated sludge to serve as initial inoculum. Both low powdered activated carbon addition and Alumin 7 (alkaline coagulant) demonstrated a low performance in terms of filterability and operation. In turn, ferrous chloride (FeCl2), due to its ability to coagulate soluble and colloidal matter, was able to create a cake layer composed of large coagulated particles acting as a prefilter. Additionally, the combination of wastewater plus FeCl2 allowing sufficient contact time before the filtration starts has demonstrated to be the best way to start-up decentralised membrane bioreactor using this additive. Eventhough some drawbacks are associated with its high acidity, i.e. low pH, high conductivity and low removal, the e...