Biological treatment also removes colloidal and dissolved substances from wastewater. Bacteria oxidize organic substance to carbon dioxide, build up (metabolize) biomass and attach (adsorb) matter on their surface. In addition, some bacteria eliminate the nutrients nitrogen and phosphorus under certain process conditions
A particularly efficient process for biological wastewater treatment is performed in membrane bio-reactors (MBR). Large clarifiers, needed in conventional activated sludge processes for removal and recirculation of activated sludge, are replaced by membrane filters. In this way the biomass concentration in activated sludge tanks can be increased by a factor of three to four, and much smaller tanks are sufficient for removal of the same freight. Effluent (permeate) that is drawn through the membranes is free of solids. Ultra-filtration membranes even retain all bacteria and produce a virtually pathogen-free (disinfected) effluent.
Membrane bio-reactors are preferably used where space is insufficient and the plant needs to have a small footprint and/or where effluent of exceptionally good quality is required, e.g. where it is discharged into sensitive water bodies or where it is reused as service water, e.g. for irrigation.
HUBER Vacuum Rotation Membrane VRM® Bioreactor
Our VRM® Bioreactor (Vacuum Rotation Membrane) is a membrane filter for use in membrane bio-reactors. The membranes we use are flat membranes which are placed on both sides of a package of rotating carrier plates. Scouring air is blown in at their horizontal axis. Due to the air bubbles rising in the gaps between the plates biomass is sheared off the membranes so that the water flow through the membranes is not impaired. The rotation of the membranes through the stream of air bubbles leads to several advantages:
A small, but intensive stream of air bubbles is sufficient for reliable cleaning of the membranes' surface
Scouring air is blown in with low pressure at half the water depth
Low power consumption for air scouring
The rotating membranes are exposed to a swelling water pressure and are thus periodically relaxed
Backwashing of the membranes with water is not necessary – continuous filtration without interruptions
HUBER BioMem® Membrane Filter
Our BioMem® Membrane Filter systems are used in small to medium-sized bioreactors. HUBER BioMem® Membrane Filter systems also use flat membranes but these are mounted on a package of stationary rectangular plates. The membrane filters are immersed into the bioreactor. Scouring air is blown in under the plates. HUBER BioMem® Membrane Filter systems offer the following benefits:
They can easily be pulled out to carry out maintenance, e.g. external chemical purification.
Regular replacement with regenerated units ensures always optimum performance.
Scouring air is blown in under the plates sequentially and alternately.
Power consumption for scouring is moderate.
The flow rate can easily be increased by increasing the number of HUBER BioMem® Membrane Filter units.