Bacterial slimes

Precipitate formation can occur upon contact of iajection water ions and counterions ia formation fluids. Soflds initially preseat ia the iajectioa fluid, bacterial corrosioa products, and corrosion products from metal surfaces ia the iajectioa system can all reduce near-weUbore permeability. Injectivity may also be reduced by bacterial slime that can grow on polymer deposits left ia the wellbore and adjacent rock. Strong oxidising agents such as hydrogen peroxide, sodium perborate, and occasionally sodium hypochlorite can be used to remove these bacterial deposits (16—18). 

Slime layers are a mixture of bacterial secretions called extracellular polymers, other metabolic products, bacteria, gases, detritus, and water. Commonly, 99% of the slime layer is water, although much silt and debris may also become entrapped in it. 

Sliming is often more severe on inlet tube sheets than on outlets. Bacterial counts are usually quite high, exceeding tens of millions in most slime layers (Table 6.5). Sulfate-reducer counts are also usually high. In waters taken from such systems, bacteria counts are often several orders of magnitude lower. 

Cathodic protection with impressed current, aluminum or magnesium anodes does not lead to any promotion of germs in the water. There is also no multiplication of bacteria and fungi in the anode slime [32,33]. Unhygienic contamination of the water only arises if anaerobic conditions develop in the slurry deposits, giving rise to bacterial reduction of sulfate. If this is the case, HjS can be detected by smell in amounts which cannot be detected analytically or by taste. Remedial measures are dealt with in Section 20.4.2. 

The type of membrane cleaning required depends on both the type and degree of fouling experienced, but typically it is either organic (bacterial slimes, natural organics, or process foulants and nutrients) or inorganic (silica, carbonate, sulfate, or phosphate deposits). 

This formulation is designed as a complete treatment, providing improved atomization and combustion, sludge dispersancy, demulsifi-cation of water from oil, prevention of bacterial slimes at the water-oil interface, reduced cold-end corrosion, and less fuel system deposits. 

Some bacterial species accumulate material as a coating of varying degrees of looseness. If the material is reasonably discrete it is called a capsule, if loosely bound to the surface it is called slime. 

Injectivity can be reduced by bacterial slime which can grow on polysaccharides and other polymer deposits left in the wellbore and adjacent rock. Strong oxidizing agents such as hydrogen... 

In this group we place mainly the neutral bacterial slimes and reserve carbohydrates. They are better defined products than those previously dealt with and as such may of course be regarded as true polysaccharides. Invariably, however, saponification methods are required to rid them of protein residues and to make them water-soluble. The more soluble mold polysaccharides appear to lose their protein constituents by autolytic processes during the longer periods required for mold metabolism. Mold slime production can, however, readily be demonstrated on a solid medium. It is proposed here to give briefly some of the types of structure known in the group. 

Microbes are ubiquitous in the subsurface environment and as such may play an important role in groundwater solute behavior. Microbes in the subsurface can influence pollutants by solubility enhancement, precipitation, or transformation (biodegradation) of the pollutant species. Microbes in the groundwater can act as colloids or participate in the processes of colloid formation. Bacterial attachment to granular media can be reversible or irreversible and it has been suggested that extracellular enzymes are present in the system. Extracellular exudates (slimes) can be sloughed-off and act to transport sorbed materials [122]. The stimulation of bacterial growth in the subsurface maybe considered as in situ formation of colloids. 

In addition to murein, bacterial polysaccharides include dextrans—glucose polymers that are mostly al 6-linked and al 3-branched. In water, dextrans form viscous slimes or gels that are used for chromatographic separation of macromolecules after chemical treatment (see p.78). Dextrans are also used as components of blood plasma substitutes (plasma expanders) and foodstuffs. 

Its chemical makeup is considered in Chapter 8. One of the layers is often referred to as the outer membrane. In some bacteria the wall may be as much as 80 nm thick and may be further surrounded by a thick capsule or glycocalyx (slime layer).13 The main function of the wall seems to be to prevent osmotic swelling and bursting of the bacterial cell when the surrounding medium is hypotonic. 

Other bacterial coats. Archaebacteria not only have unusual plasma membranes that contain phytanyl and diphytanyl groups (Section A,3)608 but also have special surface layers (S-Iayers) that may consist of many copies of a single protein that is anchored in the cell membrane.609 The surface protein of the hypothermic Staphylothermus marius consists of a complex structure formed from a tetramer of 92-kDa rods with an equal number of 85-kDa "arms."610 611 S-layers are often formed not only by archaebacteria but also by eubacteria of several types and with quite varied structures.612 14 While many bacteria carry adhesins on pili, in others these adhesive proteins are also components of surface layers.615 Additional sheaths, capsules, or slime layers, often composed of dextrans (Chapter 4) and other carbohydrates, surround some bacteria. 

Plastic pipes, even when flushed out with the most powerful disinfectants and germicides, have proven to be safe havens for some bacterial strains. Bactena-resistant piping is of major importance in pharmaceutical manufacture, Research is underway to find plastic piping that will reject the adhesion of bacterial slimes. Currently, alloy steels are widely used. The adherence of slimes to plastic pipes permits colonies of bacteria to multiply. A similar problem exists when patients are furnished with plastic implants orprosiheses Hospital water supplies must be continuously monitored. 

Algae and bacterial slime Algae and bacterial control Solubility control... 

Waterside problems that lead to decreases in efficiency and material deterioration can be caused by a variety of mechanisms, such as electrochemical corrosion and deposition of foulants. These problems can be exacerbated by low flow, poor operational practice, process contamination, or specific stresses. It is also important to try to determine cause and effect relationships in order to provide a logical and practical water treatment solution. Such a solution will usually involve some form of cleaning, plus a combined engineering and chemical action plan. Inspection may be made easier by the use of a Boroscope or similar optical/video recording device. The color, texture, and quantity of all deposits should be noted, measurements of pits taken, and microbiological contaminants analyzed. It may be useful to conduct biocide efficiency tests on bacterial slimes. The period when a heat exchanger is open for inspection may be an opportune time for the permanent installation of ports for corrosion-monitoring probes. 

Biofouling involves the formation of biofilm, whereby hydrated algal- or bacterial-based slimes adhere to water-wetted cooling system surfaces and often contain scales, corrosion products, or other debris embedded within a polysaccharide matrix. The role of biofilms in reducing cooling system efficiency and life span is still imperfectly understood. 

Biofilm is commonly found within the labyrinthine waterways of cooling systems and is primarily composed of mixed populations of bacterial cells, immobilized within a fibrous matrix of ionic polymer (slime). 

Hydroxypropyl methanethiosulfonate. Organo-sulfur group. Good bacterial slime controller for cooling systems with pH below 7.5. Limited value as algaecide or fungicide and at alkaline pH. Typical product is 11 to 12% active, with dose rate of 20 to 100 ppm based on volume. 

There has clearly been a gradual decline in the effectiveness of the cooling water treatment program and the cooling system is badly fouled, both from algal/bacterial slimes and from mineral deposits. The process contamination and variability of makeup water quality has exacerbated the situation. 

Poor basic controls and process contamination permitted slime growth. The development of algal and bacterial slimes, SRBs, etc. encouraged various forms of corrosion, especially pitting corrosion. 

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