anaerobic digestion process with membrane separation

Membrane bioreactors present the advantage of being compact and obtaining a very good quality effluent, which remains constant even at very high load; membrane separation along with a methanisation reactor such as the Analift for example, as a replacement to the settler, results in a compact and high-performing process. The membrane bioreactor concept can be installed according to an external loop and using a submerged membrane.

The advantages of anerobic bio-reactors are:

• a very good quality of treated water
• a dissociation of the hydraulic residence time and the age of sludge, resulting in the increased retention of matter which it is difficult to degrade and the improvement of its biodegradability
• the compact nature of facilities
• the partial disinfection of treated water

However, if a higher concentration of biomass in the reactor can result in a better treatment capacity, it also leads to an increase in the apparent viscosity of the environment, which can significantly penalise the membrane filtration flow.

Among other things, a study on clogging reveals the importance of compounds from the extracellular bacterial lysis and soluble microbial compounds. The variation in the flow of the permeate linked to membrane clogging over time, can result in significant variations in the load applied to the process, which must be checked and limited.

Within the objective of directly discharging treated water into the surrounding environment following the methanisation stage, the membrane separation process used in conjunction with granular sludge reactors constitutes an interesting prospect. In this case, the structure of granular sludge no longer only qualifies their use for settling but also for the purpose of limiting clogging phenomena.