MICROBIAL BIOFILMS AND

WATER SUPPLY

M PILAR VALVERDE GRANADOS

MCTA 2009-2010

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

DRINKING WATER CYCLE

Source: Drinking Water Source Protection

Water source

Water Treatment Systems

Distribution

Testing

Drinking water

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)

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

MICROORGANISMS IN DRINKING WATER SYSTEMS

► Viruses

► Bacteria

► Protozoa and parasites

• Rotavirus, Astrovirus, Calicivirus, Enterovirus• Norovirus • Hepatitis A virus

• Enterobacteriaceae: Salmonella, Shigella, E. coli, etc.• Aquatic bacteria: Pseudomonas, Legionella, etc.

• Giardia, Cryptosporidium, Microsporidum, Isospora• Ascaris• Taenia

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)

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.

TYPES OF BIOFILMS

► Environmental biofilms ► Infectious biofilms• Leguminous modules• Ruminant and termite gut• Wastewater bioreactors• Water transport systems

• Dental plaque• Endocarditis• Cystic fibrosis• Otitis• Urinary catheters• Implants• Contact lenses• Surgical instruments

► Artificial systems ► Natural systems

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:

Source: Battling Biofilms Scientific American, July 2001

1) Surface conditioning2) Colonization and adhesion3) Growth and excretion4) Secondary colonization5) Maturation

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

2) COLONIZATION AND ADHESION

Source: Edstrom

► 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.

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.

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 for Biofilm Engineering.

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.

EFFECTS OF BIOFILMS

Effects Specific Process Concerns

Heat transfer reduction

• Biofilm formation on condenser tubes and cooling tower fill material.• Energy losses.

• Power industry• Chemical process industry

Increase in fluid frictional resistance

• Biofilm formation in water and waste water conduits. Causes increased power consumption for pumped systems or reduced capacity in gravity systems. • Energy losses

• Municipal utilities • Power industry • Chemical process industry

Mass transfer and chemical

transformations (I)

• Accelerated corrosion caused by processes in the lower layers of the biofilm. Material deterioration. • Biofilm formation causing reduced effectiveness.

• Municipal utilities• Water quality data collection• Power industry• Chemical process industry

EFFECTS OF BIOFILMS

Effects Specific Process Concerns

Mass transfer and chemical

transformations (II)

• Detachment of microorganisms from biofilms. Releases pathogenic organisms.• Biofilm formation and detachment in drinking water distribution systems.• Changes water quality in distribution systems.• Extraction and oxidation of organic and inorganic compounds from water and wastewater.• Biofilm formation in industrial production processes reduces product quality.

• Public health• Municipal utilities • Water treatment• Wastewater treatment• Stream analysis

Source: Adapted from Trulear and Characklis (1982).

TREATMENT

► Chemical methods

Oxidizing biocides

Nonoxidizing biocides

• Chlorine• Chlorine dioxide• Ozone• Hydrogen peroxide

• Quaternary ammonium compounds• Formaldehyde• Anionic and Nonionic surface-active agents

► Physical methods

Mechanical scrubbing

Hot water

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

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)

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.

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.