From biofilm ecology to reactors: a focused review

Abstract

Biofilms are complex biostructures that appear on all surfaces that are regularly in contact with water. They are structurally complex, dynamic systems with attributes of primordial multicellular organisms and multifaceted ecosystems. The presence of biofilms may have a negative impact on the performance of various systems, but they can also be used beneficially for the treatment of water (defined herein as potable water, municipal and industrial wastewater, fresh/brackish/salt water bodies, groundwater) as well as in water stream-based biological resource recovery systems. This review addresses the following three topics: (1) biofilm ecology, (2) biofilm reactor technology and design, and (3) biofilm modeling. In so doing, it addresses the processes occurring in the biofilm, and how these affect and are affected by the broader biofilm system. The symphonic application of a suite of biological methods has led to significant advances in the understanding of biofilm ecology. New metabolic pathways, such as anaerobic ammonium oxidation (anammox) or complete ammonium oxidation (comammox) were first observed in biofilm reactors. The functions, properties, and constituents of the biofilm extracellular polymeric substance matrix are somewhat known, but their exact composition and role in the microbial conversion kinetics and biochemical transformations are still to be resolved. Biofilm grown microorganisms may contribute to increased metabolism of micro-pollutants. Several types of biofilm reactors have been used for water treatment, with current focus on moving bed biofilm reactors, integrated fixed-film activated sludge, membrane-supported biofilm reactors, and granular sludge processes. The control and/or beneficial use of biofilms in membrane processes is advancing. Biofilm models have become essential tools for fundamental biofilm research and biofilm reactor engineering and design. At the same time, the divergence between biofilm modeling and biofilm reactor modeling approaches is recognized.

Micropollutants removal in tertiary moving bed biofilm reactors (MBBRs): Contribution of the biofilm and suspended biomass

“…Applying different ratios between the flowrates of the concentrated wastewater and tap water allowed us to operate MBBRs with favorable values of hydraulic retention times (HRTs) and influent's COD. A glance through the literature indicates that MBBRs have been so far operated in a wide range of HRTs (Boltz et al, 2017;McQuarrie and Boltz, 2011;Rusten et al, 2006) and a definitive value has not stablished yet, in particular, for tertiary MBBRs which are in the beginning steps of the attention. However, in the continuous running of the set-up, HRTs and influent's COD values were stepwisely changed from 20 to 4 h and 500 to 100 mg•L −1 , respectively.…”

“…In spite of this fact, recently, moving bed biofilm reactors (MBBRs) are under the sharp-eyed investigation to see their capability in tertiary treatment of wastewater (Tang et al, 2017a(Tang et al, , 2017b. Indeed, the acceptable performance of these versatile reactors have been already proved for carbon oxidation, nitrification, denitrification, and deammonification (Boltz et al, 2017;McQuarrie and Boltz, 2011;Rusten et al, 2006). In addition, Torresi et al (2016) have lately noticed high potential of tertiary nitrifying MBBRs in MPs removal.…”

Effect of Acetic Acid on Denitrification and Dephosphatation Process Efficiencies in Sequencing Batch Biofilm Reactor

“…Unlike the activated sludge, the biofilm is less susceptible to the changes of such technological parameters as: contaminants load, volume of inflowing wastewater or presence of toxic substances in wastewater. This is due to high quantities of extracellular polymeric substances (EPS) which constitute a buffer to microorganisms [Boltz et al 2017, Nicolella et al 2000b. As a result of long period of biomass retention in a reactor, the biofilm is characterized by a higher degree of mineralization and, thus, by a lower volume of excess biomass discharged from the reactor.…”

Quantitative proteomic analysis of Lactobacillus delbrueckii ssp. lactis biofilms

“…Biofilms are self‐assembling, result in high cell concentrations, and can increase the operational lifetime of a reactor by obviating the need to restart the reactor. Numerous applications of biofilm reactors have been successful in wastewater treatment . Several studies have reported improvements in productivity and yield using biofilms for fermentative production of commodity chemicals, including, for example, up to 400% improvement in lactic acid productivity using a repeated batch biofilm system …”