Comparison between two MBR pilot plants treating synthetic shipboard slops: effect of salinity increase on biological performance, biomass activity and fouling tendency

The paper reports the main results of an experimental campaign carried out on two bench scale pilotplants for treatment of synthetic shipboard slops. In particular, two membrane bioreactors (MBRs)with submerged configuration were analyzed. One MBR pilot plant (namely, Line A) was fed withsynthetic shipboard slop and was subjected to a gradual increase of salinity. Conversely, the secondMBR pilot plant (namely, Line B) was fed with the same synthetic shipboard slop but without saltaddition, therefore operating as a “control” unit. Organic carbon, hydrocarbons and ammoniumremoval, kinetic constants, extracellular polymeric substances (EPSs) production and membranesfouling rates have been assessed. The observed results highlighted a stress effect exerted by salinityon the biological performances, with lower removal efficiencies in the Line A compared to Line B.Significant releases of soluble EPS in Line A promoted an increase of the resistance related toparticle deposition into membrane pores (pore fouling tendency), likely due to a worsening of themixed liquor features. Such a condition enhanced the reduction of the “pre-filter” effect of the cakelayer.