Aerobic effluent treatment

Submerged Aerated Filter (SAF) technology was introduced by Veolia over two decades ago, and has been continually developed to include units to treat both municipal and industrial wastewater from 30 population equivalent (PE) upwards.

The BioSAFTM is an upflow Bioreactor which employs a high-efficiency neutral buoyancy plastic media, ideally suited to both BOD5 removal and nitrification of wastewater.

The BioSAFTM consists of a containment vessel made in either GRP, GCS, coated mild steel, stainless steel or concrete with internal dividing walls, internal air and water distribution systems, charge of plastic media and internal support structure.

The media provides a large surface area on which the bacteria attach themselves to grow and live.

Wastewater is introduced into the base of the BioSAFTM unit into the under decking plenum space. Air is introduced into the BioSAFTM through a separate diffuser system also located near the base of the unit. An air blower supplies oxygen to the BioSAFTM environment on a continuous basis. The air and water distribution system design is such that it creates a very effective mixing pattern within the BioSAF. This pattern allows for rapid distribution of the wastewater throughout the packed media bed, which produces a homogeneous solution in full contact with the entire microbial population for the period of time that the wastewater is in the reactor.

The uniform mixing pattern is of key importance in providing a stable environment which has the ability to smooth out fluctuations that may occur in the influent concentrations. The high media voidage eliminates the need for backwashing, thus reducing the costs and ensures minimal disruption of the biological process.

Because of the high media porosity, BioSAFTM is characterised by high retention times, making them ideally suited to both BOD5 removal and nitrification of wastewater. The neutral buoyancy of the media also simplifies reactor construction and maximises active biological volume.