Development of a biofilm-MBR for shipboard wastewater treatment: The effect of process configuration

The direct discharge of wastewater from ships is prohibited by the International Maritime Organization, especially discharge of oily bilge water. This study aims to develop a compact onboard integrated wastewater treatment system for all the wastewater streams on ships, including grey water, black water and bilge water, using biofilm-MBR technology. Both dead-end side-stream and recycle side-stream configurations of a biofilm-MBR concept have been investigated. Flat sheet ceramic membranes from KeraNor AS were applied in the membrane filtration unit. A good membrane permeate quality was achieved in each process configuration, with oil concentrations < 5 mg/L. However, the membrane was seriously fouled when the dead-end side-stream configuration was operated with a high filtration unit recovery (93%). A significantly improved membrane performance, and better permeate quality, was achieved by recycling the concentrate solution back to the biofilm reactor due to better bio-flocculation and biodegradation of oil compounds in the process. The effect of process configuration was investigated by comparing oil concentration, SMP, TSS, FCOD, TCOD, PSD of the concentrate solutions around the membrane in filtration unit. The membrane fouling rate was found to be directly related to oil concentration and oily biomass characteristics in the membrane filtration unit.