Application of biofilm reactors to improve ammonia oxidation in low nitrogen loaded wastewater

Current and future trends for biofilm reactors for fermentation processes

Biofilms in the environment can both cause detrimental and beneficial effects. However, their use in bioreactors provides many advantages including lesser tendencies to develop membrane fouling and lower required capital costs, their higher biomass density and operation stability, contribution to resistance of microorganisms, etc. Biofilm formation occurs naturally by the attachment of microbial cells to the support without use of any chemicals agent in biofilm reactors. Biofilm reactors have been studied and commercially used for waste water treatment and bench and pilot-scale production of value-added products in the past decades. It is important to understand the fundamentals of biofilm formation, physical and chemical properties of a biofilm matrix to run the biofilm reactor at optimum conditions. This review includes the principles of biofilm formation; properties of a biofilm matrix and their roles in the biofilm formation; factors that improve the biofilm formation, such as support materials; advantages and disadvantages of biofilm reactors; and industrial applications of biofilm reactors.

Development of biofilm on geotextile in a new multi-zone wastewater treatment system for simultaneous removal of COD, nitrogen and phosphorus

This study investigated the formation and evolution of biofilm on a fixed cylindrical structure wrapped in geotextile, in a multi-zone wastewater treatment system called BioCAST. The organic, nitrogen and phosphorus loading rates of (OLR) 0.95-1.86 g COD/(m(3)d), (NLR) 0.02-0.08 kg N/(m(3)d), and (PLR) 0.014-0.02 kg P/(m(3)d), were applied. The results demonstrated high removal efficiencies of carbon, nitrogen and phosphorus, reaching 98.9%, 98.3% and 94.1%, respectively, after 250 d of operation. The biofilm biomass showed a fast formation (reaching 54.2g/L) and maximum phosphorus content of about 7% (dry basis). Biofilm demonstrated the ability to remove phosphorus, and its characteristics correlated with nitrogen and phosphorus removal rates. The geotextile material with filamentous structure causing rapid attachment and formation of biofilm can solve many problems encountered in conventional attached-growth wastewater treatment systems such as slow start-up, low reactor biomass content and low capacity to handle high organic loading rates.