ADVANTAGES WITH UPGRADING FOR NUTRIENT REMOVAL WITH HYBAS™ BIOLOGICAL PROCESS COMPARED WITH ACTIVATED SLUDGE OR BIOFILM
Marius Haegh and Vibeke Rasmussen, AnoxKaldnes AS, Norway
(free)
Since the late 90s Integrated Fixed Film Activated Sludge (IFAS) systems have gained new interest from owners of wastewater treatment plants all over the world, because of their unique ability for upgrading of existing activated sludge plants for nitrification or nutrient removal.
The Hybas™ biological process is an IFAS process which utilizes plastic suspended carriers for biofilm growth within the activated sludge aeration basins. The system is hence a combination of an activated sludge and a Moving Bed Biofilm Reactor (MBBR) system. In this approach, the activated sludge favors microorganisms with high growth rates e.g. for denitrification and BOD5 removal, while the biofilm carriers provides a very high specific surface area which enhances growth of slow growing microorganisms like nitrifiers. This way the Hybas™ biological process can provide complete nitrification at suspended sludge ages significantly shorter than the nitrifiers wash out rate in normal activated sludge systems.
Over the last 7 years AnoxKaldnes have designed, pilot tested and installed several full scale Hybas™ biological treatment systems. The results from these pilot tests and full scale plants show that the system have many advantages over traditional activated sludge or biofilm systems on its own. The combination of activated sludge and biofilm carriers in the same reactor has an advantage on the overall treatment efficiency. The processes influence each other and the design has to encompass the effect the processes have on each other.
This paper will present the benefits of the Hybas™ biological process and compare with pure activated sludge and biofilm systems. It will also give examples of different configurations of the Hybas™ biological treatment process depending on what effluent standards you need to reach.
KEY WORDS Integrated Fixed-Film Activated Sludge (IFAS, IFFAS), Moving Bed Biofilm Reactors (MBBR), Suspended Carrier Media, Hybrid Activated Sludge, Biological Nutrient Removal
