Using submerged membrane bioreactors for biological nutrient removal from municipal wastewater

A pilot submerged membrane bioreactor (SMBR) equipped with ZeeWeed(R) 10 hollow fibre modules was used to remove the nutrients from the primary effluent at a municipal wastewater treatment plant. The pilot plant was operated by varying SRT and HRT and mixed liquor recirculation ratio to obtain the concentration of MLSS up to 16 gMLSS/L. Average operational data collected from these pilot tests were compared for three SMBR configurations achieve post-denitrification, and pre-denitrification, respectively. The collected data were then used to fit to IWA ASM2D model for COD and nitrogen removal in steady-state conditions. The results showed that All configurations could accommodate nitrification-denitrification process. Pilot plant tests showed high COD and ammonia removal (above 90%) but total nitrogen removal was moderate (above 70%). Aerobic conditions in the SMBR enable nitrification thus releasing nitrate in the permeate. Phosphorous removal was above 93% because its precipitation with ferric chloride added in the grit chamber at the wastewater treatment plant. The model was able to predict the COD and nitrogen effluent for the configurations tested. With one exception, stoichiometric and kinetic parameters obtained for the ASM2d model are in agreement with those reported in the literature for typical activated sludge process. Post-denitrifiaction configuration showed better nitrogen removal, but required higher oxygen supply needs.