One of the main problems occurring during operation of recycling water systems at oil refinery, petrochemical and chemical enterprises is biofouling of the internal surfaces of supply lines, filters, heat exchange units and other process equipment. Biofouling is an aggregate formation of various microorganism (bacteria, fungus, amoeba, legionella, etc.) that enter the system with make-up water and air when water pases colling towers.
Biofilms are formed in water and represent a protective layer for microorganisms. Such biofilms form ideal conditions for reproduction and other mode of interaction, nutrient metabolism and exchange of genetic materials. 99% of microorganisms live under protection of biofilms in biologically active water systems. Protective mechanisms inside biofilms are very strong and bacteria inside them are highly resistant even to chlorine. Therefore effective disinfection of water is possible only under condition of damage or destitution of biofilm.
Biofouling reduces the efficiency of equipment operation (250 micron thick biofilm can reduce heat exchange by 25%), results in pitting corrosion, reduces the effect of corrosion and sedimentation inhibitors.
Classic approach to prevent biofouling, i.e. disinfection of water using biocides, if effective only in case if biocides can remove and prevent further formation of biofilms. Water disinfection using classic biocides (chlorine, bromine, hypochlorite, etc.) cannot resolve the issue of biofouling.
In 1999, «aqua-mol GmbH» company proposed a technology of industrial waster disinfection called MOL®Clean as an alternative to the classic approaches.
Phospholipids play an important role in the creation of cell membrane. Phospholipids consist of hydrophobic aliphatic residue of hydrocarbon with unsatisfied C=C compounds and hydrophilic groups. Ability of this molecules to create membranes is the most important organic life process. Phospholipids form cell membrane, which services as a «lipid coating» and protects the cell from negative impact, supports its structure and helps to form a certain shape. Cell membrane molecules are joined by hydrogen bonds and Van der Waals force. In the course of interaction phospholipids polarize in electrostatic field of other molecules resulting in slight negative charge on the cell surface.
The idea of MOL®Clean technology is as follows. A mesh with non-expandable metal catalyst (structured Cr-Ni-Fe alloy) is placed in the cooling water flow with MOL®aktiv reagent (30% hydrogen peroxide solution Н202) dozed into the water.
When adding hydrogen peroxide into water (for instance, MOL®aktiv reagent), with the microscope it is possible to observe separate bacteria forming certain structures to protect against the aggressive media. The reason for that consists in a higher dipole moment of hydrogen peroxide molecules in comparison with water molecules. Microorganisms with negative surface charge come into exchange reactions with hydrogen peroxide, not with water, resulting in increased dispersion and thus increasing Van der Waals force between separate bacteria. After complete degradation of hydrogen peroxide, bacteria revert to the initial independent state.
However, interaction runs though a completely different scheme upon introduction of a catalyst into the system. Hydrogen peroxide molecules absorb on the catalyst and start to draw uncoupled electrons. As a result, a positive charge accumulates on the catalyst surface thus drawing free microorganisms. Van der Waals force inside cell membranes become significantly weaker under the influence of a positive charge. Polar phospholipid groups segregate into tenside molecules. Loss of polar groups destabilizes hydrogen bonds. Internal pressure in cells is higher that the ambient pressure. The weakened membrane cannot resist the pressure and bursts.
Cellular debris partially is oxidized forming substances with tenside properties — the so-called «Biotensides». In comparison with the synthetic SSA, biotensides are not toxic and become active only on liquid/solid phase division surface; they show low level activity on liquid/gas phase division surface, i.e. they do not cause foaming and, what is more important, are structurally very similar to cell membranes of microorganisms since they are produced from their partial degradation.
Moving along with the water flow, biotensides remove biosediments from metal surfaces. This help to clean all system elements (irrigation caps, pumping equipment, pipelines, heat-exchange equipment, etc.).
Delivery package includes the following:
- non-expandable catalyst meshes;
- dosing unit;
- MOL®aktiv reagent.
Equipment installation can be carried out by plant staff without shutdown of the process equipment.
Dosing unit includes:
- Metal case with a mounting set for wall fixing, mounting plate for dosing pump, circuit breaker with timer, detailed operating manual.
- Flow-control pump
- Suction system with two-level switch and two 5m hoses (heavy-gauge 5m hose for reagent feed and light-gauge 5m hose for pressure release).
- Downstream line
Please, find more information about MOL®Clean at www.mol-clean.ru