Feasibility of the BIOFIX-process for treatment of municipal wastewater

The feasibility of the sc-called BIOFIX-process to treat municipal wastewat er was investigated in a pilot-plant. The innovative element of this proces s is that carrier material to which a biofilm is attached is recirculated b etween a sorption reactor to take up COD from the wastewater and a reactor where this COD is used for (post-) denitrification. In between the sorption and denitrification reactor the wastewater passes two subsequent reactors for removal of the remaining COD and for nitrification, respectively. The r esults showed that COD uptake by the biofilm in the sorption reactor with a maximum of 34% of the influent load was far below expectations and did not meet the COD requirement for denitrification (50-60% uptake). Also, 9-21% of the influent load of ammonia was taken up by the biofilm. In the denitri fication reactor this ammonia was released to the bulk and in this manner d ischarged with the effluent without having passed the nitrification reactor . Nitrification was inhibited by the presence of high concentrations of sus pended solids (50-60 mgl(-1)) discharged from a COD removal reactor. Togeth er these bottle-necks caused effluent concentrations which were well above the effluent demands and it therefore can be concluded that the BIOFIX-proc ess is not a feasible process to treat domestic wastewater.