2. CONTENTS ► Drinking water cycle ► Contamination and water quality ► Microorganisms in drinking water systems ► Biofilms and origins ► Types of biofilms ► Biofilm formation 1) Surface conditioning 4) Secondary colonization 2) Colonization and adhesion 5)Maturation 3) Growth and excretion ► Effects of biofilms ► Treatment ► Biocide resistance ► Main facts ► Bibliography
3. DRINKING WATER CYCLE Water source Water Treatment Systems Distribution Testing Drinking water Source: Drinking Water Source Protection
4. CONTAMINATION AND WATER QUALITY ► Pollution types Chemical Biological •Inorganic compounds (nitrate, ammonium, etc.) • Organic solvents • Metals (Pb, Cr, Cd, etc.) • Toxic compounds and pesticides •Bacteria • Viruses • Protozoa ► Effects Public health (patogens) Water quality (organoleptic properties)
5. MICROORGANISMS IN DRINKING WATER SYSTEMS ►In drinking water there are microorganisms although the low nutrient concentration and the disinfection treatments. ►Origin: • Body washing • Urban discharges • Wastewater pollution • Failure of disinfection protocols and • Biofilm formation and erosion
6. MICROORGANISMS IN DRINKING WATER SYSTEMS • Rotavirus, Astrovirus, Calicivirus, Enterovirus • Norovirus • Hepatitis A virus ►Viruses ►Bacteria ►Protozoa and parasites • Enterobacteriaceae: Salmonella, Shigella, E. coli, etc. • Aquatic bacteria: Pseudomonas, Legionella, etc. • Giardia, Cryptosporidium, Microsporidum, Isospora • Ascaris • Taenia
7. BIOFILMS AND ORIGIN "More properly known as biofilm, slime cities thrive wherever there is water - in the kitchen, on contact lenses, in the gut linings of animals. When the urban sprawl is extensive, biofilms can be seen with the naked eye, coating the inside of water pipes or dangling slippery and green from plumbing." (Coghlan 1996)
8. BIOFILMS AND ORIGIN ► Accumulations of microorganisms surrounded by a polysaccharide matrix excreted by themselves and attached to living or inert surfaces. ► They only need to grow: microorganisms, moisture, nutrients and surfaces. ► In any water distribution system, 99% of total bacteria are associated with biofilms. ► The presence of biofilms in water distribution systems cause problems in both the functioning and the water quality.
10. BIOFILM FORMATION ► Complex, highly structured and composed by different type of bacteria with complementary metabolisms. ► Parameters: Temperature, water flow rate, nutrients, surface characteristics, pH. ►Phases: 1) Surface conditioning 2) Colonization and adhesion 3) Growth and excretion 4) Secondary colonization 5) Maturation Source: Battling BiofilmsScientific American, July 2001
11. 1) SURFACE CONDITIONING ► Trace organics adsorption to the clean pipe surface when this one comes into contact with water. ► The organics form a ‘conditioning layer’ which neutralizes excessive surface charge and then the surface is ready for bacterial colonization. ► The adsorbed organic molecules serve as a nutrient source for bacteria. Source: Edstrom
12. 2) COLONIZATION AND ADHESION ► Some planktonic bacteria attach to the pre-conditioned surface when water velocity falls to cero and dominated by electrostatic and physical forces. ► The first step is called reversible adsorption as some of these cells desorb. ► Attached cells begin to forming structures which may permanently adhere the cell to the surface irreversibly. Source: Edstrom
13. 3) GROWTH AND EXCRETION ► Massive excretion of polymeric extracellular material. ► Formation of the structural matrix called glycocalyx. ► Glycocalyx functions: • Structural • Adhesion • Nutrient trap • Water supply • Protective against biocides, antibiotics, etc.
14. 4) SECONDARY COLONIZATION ► The glycocalyx net traps other planktonic microbial cells called secondary colonizers. ► These ones use waste products from the primary colonizers to grow and produce their own waste which other cells will use. ► The metabolic cooperation established allows a rapid grow of the biofilm. Source: Center forBiofilmEngineering.
15. 5) MATURATION ► Cooperation between species. ► Once matured, the water current may allows migration of biofilm particles to other pipe’s areas. ► When migration occurs then new biofilms start to form.
19. BIOCIDE RESISTANCE ► Bacteria associated with biofilms are much more difficult to remove from surfaces than planktonic organisms. ► Bacteria in a biofilm can resist biocides because they are shielded in slime even though biocides have a multitude of potential target sites. ► Incomplete removal of the biofilm will allow it to quickly return to its equilibrium state. Source: Edstrom
20. BIOCIDE RESISTANCE “Piping material that microorganisms cannot adhere to has yet to be discovered. Studies have shown that microbes will adhere to stainless steel, Teflon, PVC and PVDF (Kynar) with nearly equal enthusiasm.“ Mayette(1992)
21. MAIN FACTS ►Biofilms only need microorganisms, nutrients, moisture and surfaces in order to grow. ►Biofilms can be found in artificial systems like pipes, bioreactors, etc. ►The presence of biofilms in water distribution systems cause problems in both the functioning and the water quality. ►Their structure and complexity gives them resistance to cleaners and sanitizers. ►It’s better to use physical and chemical methods together to obtain good results in biofilm treatment.
22. BIBLIOGRAPHY Biofilm research & education relevant to industry, health and the environment. Montana State University. MSU Center for biofilm Engineering (1999-2010). http://www.erc.montana.edu/ Camper, A. (2003). The slimy truth about biofilm. Center for Biofilm Engineering (CBE). Edstrom Industries. [en línia] http://www.edstrom.com/Update.cfm?doc_id=333#1 Dreeszen, P. H. (2003). Introduction to Biofilm. Edstrom Industries. http://www.edstrom.com/Resources.cfm?doc_id=23 Dreeszen, P. H. (2003). Biofilm. The key to understanding and controlling bacterial growth in Automated DrinkingWater Systems. Edstrom Industries. Potera, C. (1996). Biofilms Invade Microbiology.Science, 273 : 1795-1797.
