Influence of physicochemical and hydrodynamic growth conditions on biofilm adhesion in a moving bed biofilm reactor

Moving bed biofilm reactors have proven to be a good alternative for conventional biological wastewater treatment systems due to their ability to carry out simultaneous removal of carbon and nitrogen (nitrification and denitrification processes). However, optimization of physicochemical growth conditions and operational parameters in a moving bed biofilm reactor system is very crucial to ensure minimized biofilm sloughing and consistent treatment performance. This study investigates the possible ways to enhance biofilm attachment for wastewater treatment. To improve bacterial adhesion, strategies were devised based on enhancing the van der Waal’s forces of attraction by varying the operating and chemical growth parameters. Environmental and operating conditions, namely salinity, temperature and rate of aeration, were optimized to further understand biofilm adhesion and to enhance it. The study involving the variation of physicochemical parameters showed that a combination of an aeration rate of 1.5 L per minute, salinity of 6000 mg/L and a temperature of 37 °C was found to be optimum for both bacterial adhesion and chemical oxygen demand reduction. The extracellular polysaccharide secretion enabled excellent adhesion. In addition, the biomass adhesion and chemical oxygen demand reduction efficiency were found to be positively correlated which reinforces that with greater active biomass in the attached phase, better would be the chemical oxygen demand reduction efficiency. Further, owing to the innate resistance of biofilms to toxins, the mechanism developed here, to enhance biofilm adherence can be deployed to treat emerging contaminants such as antibiotics and other pharmaceuticals which are otherwise not easily combatable by conventional suspended growth biological systems. Graphical Abstract: [Figure not available: see fulltext.].