INFLUENCE OF NITROGEN LOADING RATE (NLR) ON NUTRIENTS REMOVAL IN ATTACHED GROWTH-MEMBRANE BIOREACTOR (AG-MBR)

Abstract

Water remains a critical resource for sustained well being of a country. Sustainable development is the possible solution, of which wastewater reuse is an essential part. Membrane bioreactors (MBRs) are ready to maintain water sustainability which combines aerobic degradation with a direct solid-liquid separation of activated sludge using either microfiltration or ultrafiltration. Introduction of media into MBR, in addition to providing high biomass concentration, also supports denitrifying bacteria and as a result the total nitrogen removal can be enhanced. Moreover, the nitrogen loading rate (NLR) in influent is one of the most critical parameters for wastewater nitrogen removal process, because it directly effects functional microorganism population. In this study, nutrients removal, fouling phenomenon and sludge characteristics were evaluated and discussed in an AG-MBR containing sponge as a moving media, operated at different NLR of 0.15 Kg/m3/d (condition I) and 0.3 Kg/m3/d (condition Il) corresponding to COD/N ratio of 20 and 10, respectively. Sponge with a density of 28-30 Kg/m3 and fill volume of 15% was used in AG-MBR during both conditions. Results showed that NLR had little influence on COD and NI-14+-N removal efficiencies and it was maintained above 98% and 90%, respectively during the two stages of operation. Whereas, TN removal was reduced from 88% to 69% due to increase in NLR in condition Il as compared to that in condition I. Also, phosphorous removal was relatively reduced. Particle size and SOUR also decreased in condition Il but it was more related to sludge age rather than NLR. It was observed that NLR has no profound effect on membrane fouling however, fouling behavior was changed possibly due to change in particle size distribution and microbial community. Overall, it can be concluded that higher NLR influences microbial population, denitrification rate as well as phosphorous removal in AG-MBR.