This protective blanket (Biofilm) is made up from sugars, proteins and nucleic acids and is one of the main nutritional sources (together with scale encrustations) enabling the bacterial spores to thrive in safety – especially pseudomonas spp. which are notable for their ability to rapidly form biofilm. Biofilm can be microscopically seen as a sponge-like material with thicknesses ranging from a few microns up to a few centimetres in extreme cases, and its porosity allows ingress of nutrients from the surrounding medium and supporting the mobility of bacterial cells within the colony as well as providing ideal conditions for accelerated cell division (proliferation) and mutually beneficial co-operation between different species – or possible mutations!.
One of the important properties of biofilm and the produced EPS is the ability to react with metal ions. The initial protected colony is able to alter the electrostatic charges and wetability of the metal surface, facilitating its further colonisation by bacteria. For example, in a marine environment the presence of a biofilm can accelerate corrosion rates of carbon steel by several orders of magnitude. After colonisation and formation of biofilms, maintenance and operational problems arise, including a reduction in flow, heat transfer rates, fouling, corrosion, and scale.
Biofilm is a live, evolving community offering ideal conditions for growth with inter-specie co-operative relationships. As the bacterial density of the community increase via absorption of bacteria cells previously free floating from outside the biofilms protective environment as well as new cells from the already protected community, new bacteria will be released to continue the cycle of growth and layers of the biofilm mass will slough off becoming a free floating floc with a concentrated bacterial concentration to either reattach itself further downstream, or washout of an outlet such as a water saving showerhead or ceramic disc mixer or faucet with an aerator – extremely dangerous if there are pathogenic bacteria contained such as pseudomonas Legionella (when the biofilm floc comes to rest at the physical restrictor of either a water saving shower outlet, or an aerator on a mixer, it colonises around the apertures of the flow restrictors, but when flow resumes as valve is opened, the accelerated water flows “smashes” the biofilm masses against the physical barrier, shattering the floc and releasing the bacteria/water mixture which upon release becomes vaporised and this bacteria saturated vapour can then be easily absorbed into the mucus membranes of the nose and throat directly into our bodies. The first scientifically proven incident of this was the 1976 outbreak of Legionaries disease (caused by the Legionella bacteria) in Philadelphia, Pennsylvania.)
However as the bacterial density in the biofilm increases layer on layer, the lower layers begin to become staved of nutrient and oxygen and need to slow down their metabolism acting as though they are hibernating. This creates huge problems for health professional as not only does the biofilm matrix create a barrier to deflect antibiotics, but many antibiotics only work on actively multiplying bacterial cells and cannot act when the cells are in a hibernation mode (referred to as a tolerance to antibiotics). It is estimated that 1000 times the quantity of antibiotics are required to kill bacteria protected in a biofilm matrix than in planktonic bacterial cultures (living as free floating organisms in their respective environments)
Essentially, biofilm can form anywhere – either where it can secure itself onto a surface or as a free-floating floc in the water flow providing the conditions are favourable. Biofilm encased bacteria colonies prefer to establish themselves on surfaces with a high microscopic area, which can either be a relatively rough surface, in bends or crevices such as joints and valves or on a surface which is already contaminated with lime-scale or other deposits. Another favourite environment for bacterial biofilms to colonise is in the sediment on the floors of storage tanks which provides even greater protection for the bacteria.
Biofilm colonies can be found in both high and low flow velocity environments (but recent testing seem to prove that high flow velocity environments accelerates growth over more stagnant environments) and as oxygen is an integral constituent of water is comfortable in either a submerged location or at air-water interfaces.
Biofilm colonies will grow on most surfaces, however certain materials such as copper (Copper ions released from surfaces lead to RNA degradation and membrane disruption of enveloped viruses – but is prone to lime-scale encrustations which once attached provide favourable hosting sites) delays formation better than many synthetic materials that are constructed with hydrocarbons such as plastics, fibres, EPDM rubbers, solvents and industrial chemicals as many species of bacteria utilise hydrocarbons as nutrients.
Prevention is always better than reactive treatment, so what are the best ways to stop bacterial infestation and the resultant problem of biofilm? Logically, if you can stop the initial colonisation of bacteria then the individual bacterium would just be carried away in the water flow, but how to do this effectively?
- One of the first steps would be to make it more difficult for the bacteria to attach itself to the surface, which could be attained by minimising the build-up of scale encrustations (as these are microscopically honeycombed in structure and enable bacteria to quickly establish themselves while also providing nutrients to feed the bacteria.)
- Another pro-active step would be to remove as many “dead-legs” from the water reticulation system as possible (by maybe installing a ring main design, or ensuring that all points of use {such as mixers showerheads, fixtures and appliances are flushed regularly)
- Regularly cleaning of any water storage tanks and ensuring constant turnover of the water volume held.
- By keeping a reasonable level of residual chlorine as provided in mains water to counter free floating bacterium cells (however this in itself is not desirable as chlorine is thought by many to be carcinogenic)
However, once a biofilm protected colony exists, not only does it nurture bacterial growth, it also protects its residents such as Legionella. Bacteria within biofilm are typically circa 1000 times more resistant to chlorine oxidation than when free floating in the water flow. There are certain other complications to be addressed
- Some oxidising agents (such as chlorine) are thought to be too large to pass through the microscopic waterways of the biofilm protective blanket to contact the target bacteria,
- Possible insulation of the bacteria cells by the EPS matrix
- Biofilms provide a rehabilitive environment for any damaged bacteria (individual cells that would die in open water will restore themselves within the protection of the biofilm matrix)
- Sterilization procedures such as UVC treatments (Ultra-violet lamps) will only be effective against free flowing bacterial cells that are down stream and have passed through the treatment sector, however
- Scale encrustations are attracted to heat and tend to form on the crystal sleeve of the UVC lamp. These encrustations will not only reflect the beams of light radiation, but also encourage the growth of biofilm colonies on their surface
- Any sloughed off free-floating biofilm floc moving past the UVC lamp will protect all the bacteria within it from the UV radiation
So why wait? Why risk you and your family’s health to water borne bacteria and diseases? Why not invest in a maintenance free solution and at the same time as protection your family, also protect one of the greatest investments, your home, fixtures, fittings and appliances
Scale protection for your water supply without removing essential minerals and while protecting your piping network, fixtures, fitting and appliances and returning the original pressure and flow rate in your piping network we offer a full range of Electronic Impulse Technology anti-scale systems to effectively combat scale encrustations on a three tier approach
- stop new scale encrustations forming
- safely break down existing encrustations in the system
- protect metallic surface the pipework and fittings by laying a protective carbonate coating to counter corrosion
These systems can be retro fitted on a DIY installation on a install and forget basis, requiring only access to an open run of pipe and a normal South African electrical connection (230volt/50Hz)
To find more information of the new technology of electrical impulse anti-scale systems and electrophoresis we suggest that you visit the website www.amanzirms.co.za, or either contact us via e-mail at mwchrisd@mweb.co.za or on the mobile +27 84 690 2644
