High salinity slops treatment through a biofilm-MBR inoculated with halophilic bacteria

Oily wastewater generated, in amounts of millions of tons per year, by ships mainly in engine-rooms (bilge waters) and by washing oil tanks (slops) create a major disposal problem throughout the world because of the persistence and accumulation of xenobiotic compounds in the environment. The high salinity levels (up to 25.000 p.p.m.) and the pollutants concentration limit the chances of discharge into the sewer systems and address the disposal to the sea. This situation severely lowers the discharge limits for most of the “sensible” parameters, such both COD and hydrocarbons. Slops are usually treated by ASP with pretreatment of oil/water separation. There are limited investigations on the treatment of these wastewaters using MBR technology. However tightening effluent regulations has generated interest in the treatment of wastewater of petrochemical origin with the advanced MBR process. The objective of this study were to evaluate the feasibility of treating slops to meet the applicable discharge limits consistently using BF-MBR technology. With this aim in mind, a BF-MBR pilot plant has been realized, characterized by an hybrid MBBR compartment followed by a membrane unit. The obtained results showed good removal performances, although the biofilm compartment seemed not to give a crucial contribution to the performances.