Biofilms and Environmental Protection

Abstract

Biofilms are the result of adhesion and growth of microorganisms at interfaces. They consist mainly of water (70-95 % wet weight), held by the highly hydrated extracellular polymers (EPS, 70-95 % dry weight) in which the microorganisms are embedded. Adhering cells differ from their suspended counterparts in both activity and resistance to toxic substances. The cells are immobilized next to each other and form well organized consortia, capable of performing sequential degradation processes. Biofilms are ubiquitous and the majority of microorganisms on earth is living in biofilms. The particular properties of biofilms are utilized for environmental protection in bioreactor technology, applied to sewage water and waste air purification, soil remediation and solid waste decomposition. Biofilms can have detrimental effects, inducing metal corrosion and microbially induced weathering of mineral materials such as stone or cement. Resulting damage, e.g., to oil tanks and pipelines and to concrete sewers, has lead to substantial pollution of soil, groundwater and surface water. Biofilm development on heat exchangers, filter materials and separation membranes leads to the application of large amounts of biocides. These cause waste water problems after use. A deeper understanding of the particular properties and dynamics of biofilm development and processes could help to optimize the application of desired biofilms and to minimize the detrimental effects of undesired biofilms and of countermeasures.

Rainwater Harvesting Systems in Australia

“…It is expected that these biofilms exist on the air/liquid interface of the rainwater tank and the solid/liquid interface within the rainwater tank, pipes and in bioretention systems (Blanchard & Syzdek, 1970;Characklis & Marschall, 1990;Flemming, 1993;Hermansson & Dahlbäck, 1983;Sawyer et al, 2010;Spiers et al, 2003;Spinks et al, 2003). The velocity of flow within the rainwater tank itself is slow, even when it is raining and when the tank is utilised.…”

Effect of glutaraldehyde biocide on laboratory-scale rotating biological contactors and biocide efficacy

“…The increase in the thickness was probably due to cross-linking between glutaraldehyde and the amine group of proteins or enzymes found on bacterial cell walls (Simons et al 2000). Moreover, glutaraldehyde may also react with protein which is the one of the predominant constituents of biofilm extracellular polymeric substances (EPS) apart from polysaccharide (Christensen and Characklis, 1990;Flemming, 1993;Norwood and Gilmour, 2000). Figure 2 shows that COD removal of the control unit (without glutaraldehyde) was 71.73 ± S.D.…”

“…Microbial biofilms play an essential role in engineered processes especially in biological treatment and energy production (Flemming, 1993;Bryers, 2000). They have been reported to have higher resistant to toxic compounds than free cell systems (Sofer et al 1990;Lazarova and Manem, 2000).…”

Biofouling control of reverse osmosis membranes using free nitrous acid

“…there was more than 88% of organic material deposited in all fouling matrixes. It has been reported that membranes are likely biofouled if the fouling layers contain a large quantity of microorganisms and more than 70% of organics substances [57,137]. Hence, the LOI results, along with the ATP measurement, confirmed the presence of large amount of organic matters on the surface of membranes, suggesting these membranes (RO1-5) were covered by a mixture of organic and biological fouling.…”

“…Biofilm is mainly made up of 70-95% water. Within 5-30% of dry weight, 70-95% of EPS hold microbial cells [57]. Beside the embedded microorganisms, EPS consist 40-95% of polysaccharides, up to 60 % of proteins and small amount of nucleic acids, lipids and other biopolymers [58].…”