Rotating biological contactors for wastewater treatment – A review

Abstract

Rotating biological contactors (RBCs) for wastewater treatment began in the 1970's. Removal of organic matter has been targeted within organic loading rates of up to 120 g.m -2 d -1 with an optimum at around 15 g.m -2 d -1 for combined BOD and ammonia removal. Full nitrification is achievable under appropriate process conditions with oxidation rates of up to 6 g.m -2 d -1 reported for municipal wastewater. The RBC process has been adapted for denitrification with reported removal rates of up to 14 g.m -2 d -1 with nitrogen rich wastewaters. Different media types can be used to improve organic/nitrogen loading rates through selecting for different bacterial groups. The RBC has been applied with only limited success for enhanced biological phosphorus removal and attained up to 70% total phosphorus removal. Compared to other biofilm processes, RBCs had 35% lower energy costs than trickling filters but higher demand than wetland systems. However, the land footprint for the same treatment is lower than these alternatives. The RBC process has been used for removal of priority pollutants such as pharmaceuticals and personal care products. The RBC system has been shown to eliminate 99% of faecal coliforms and the majority of other wastewater pathogens. Novel RBC reactors include systems for energy generation such as algae, methane production and microbial fuel cells for direct current generation. Issues such as scale up remain challenging for the future application of RBC technology and topics such as phosphorus removal and denitrification still require further research. High volumetric removal rate, solids retention, low footprint, hydraulic residence times are characteristics of RBCs. The RBC is therefore an ideal candidate for hybrid processes for upgrading works maximising efficiency of existing infrastructure and minimising energy consumption for nutrient removal. This review will provide a link between disciplines and discuss recent developments in RBC research and comparison of recent process designs are provided (section 2). The microbial features of the RBC biofilm are highlighted (section 3) and topics such as biological nitrogen removal and priority pollutant remediation are discussed (section 4 & 5). Developments in kinetics and modelling are highlighted (section 6) and future research themes are mentioned

Enrichment of anaerobic ammonium oxidation (anammox) bacteria for short start-up of the anammox process: a review

“…The RBC system is an alternative to the activated sludge process that has been called a disc, surface, media and biofilm reactor [100]. RBCs consist of parallel packs of rotating discs with attached microorganisms on their surfaces in the form of biofilms.…”

Performance and Microbial Diversity in a Low-Energy ANF-WDSRBC System for the Post-Treatment of Decentralized Domestic Wastewater

“…Rotating biological contactors (RBCs) are cost-effective and flexible attached growth bioreactors, which are widely used to treat various wastewater including domestic wastewater [14][15][16][17], dye wastewater [18], and landfill leachate [19]. The RBCs are fascinating options to decentralized wastewater treatment due to high specific surface area, high biomass content, low footprint, and easy operation [20]. Even though RBCs are mostly reliable, they still have some shortcomings in terms of costs and stable nitrogen removal efficiency.…”

Removal Effect of CODcr Ammonia Nitrogen and Total Nitrogen of Rural Domestic Wastewater in Southern China by A2/O2 Process

“…Jia Yanping [9] study found that higher COD load not only increases the cost of adding carbon source, but also inhibit the autotrophic nitrification bacteria growth, and reduce the removal efficiency of NH4 + -N. When the inlet velocity is constant, the reflux ratio is determined by the circulation speed. And the change of the circulation rate has great influence on the dissolved oxygen in the wastewater and the thickness and shear stress of the liquid phase layer when the wastewater flows through the biological membrane, which further affects the operation efficiency of the reactor [10][11] . If continue to increase the return ratio, not only increased the thickness and the influence of mass transfer of liquid layer, the hydraulic shear stress increases greatly, resulting in the biofilm is large and scattered off, directly influence the operation efficiency, and high reflux ratio to consume more capacity, mechanical damage probability will increase [11][12] .…”

“…And the change of the circulation rate has great influence on the dissolved oxygen in the wastewater and the thickness and shear stress of the liquid phase layer when the wastewater flows through the biological membrane, which further affects the operation efficiency of the reactor [10][11] . If continue to increase the return ratio, not only increased the thickness and the influence of mass transfer of liquid layer, the hydraulic shear stress increases greatly, resulting in the biofilm is large and scattered off, directly influence the operation efficiency, and high reflux ratio to consume more capacity, mechanical damage probability will increase [11][12] . Based on the existing biological treatment process, designed a set of A 2 /O 2 technology of biological membrane reactor to rural sewage treatment in Southern China area, which is characterized by small footprint, low energy consumption, pollutant removal efficiency, high nitrogen removal function, simple management, the effluent can meet the discharge standard.…”