Innovations in wastewater treatment: –the moving bed biofilm process

This paper describes the moving bed biofilm reactor (MBBR) and presents applications of wastewater treatment processes in which this reactor is used. The MBBR processes have been extensively used for BOD/COD-removal, as well as for nitrification and denitrification in municipal and industrial wastewater treatment. This paper focuses on the municipal applications. The most frequent process combinations are presented and discussed. Basic design data obtained through research, as well as data from practical operation of various plants, are presented. It is demonstrated that the MBBR may be used in an extremely compact high-rate process (<1 h total HRT) for secondary treatment. Most European plants require P-removal and performance data from plants combining MBBR and chemical precipitation is presented. Likewise, data from plants in Italy and Switzerland that are implementing nitrification in addition to secondary treatment are presented. The results from three Norwegian plants that are using the so-called combined denitrification MBBR process are discussed. Nitrification rates as high as 1.2 g NH₄-N/m² d at complete nitrification were demonstrated in practical operation at low temperatures (11 °C), while denitrification rates were as high as 3.5 g NO₃-N_equiv./m².d. Depending on the extent of pretreatment, the total HRT of the MBBR for N-removal will be in the range of 3 to 5 h.