Foulants organic

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). 

A colloidal dispersion of oil-in-water. In BW systems where oil contamination has occurred, emulsifying agents from the oil can produce an emulsion which further adds to the total foulant load and impedes heat-transfer. Specific organic emulsifiers have both hydrophilic (water loving) and lipophilic (oil loving) groups in the same molecule. 

Any sedimentary deposit or foulant that fails to form a crystalline scale. Often the result of supersaturation or the binding of biological or other organic material with dust, sand, or other mineral deposits. Also, sludge is not always deposited at point of origin and can additionally bake onto heat transfer surfaces. 

Lack of exposure data for most organotins together with limited toxicity information for marine organisms preclude the calculation of risk factors for the marine environment. For dibutyltin, measured concentrations in seawater reflect the use of tributyltin as a marine anti-foulant rather than the use of dibutyltin in plastics. It is therefore not possible to conduct a reliable risk assessment for the current uses of the compormd. 

Sulfates are also involved in depassivation, especially with deposits or foulants. Sulfates can be reduced by selective microbial actions (sulfate-reducing organisms) that are almost always present in biofilms, producing deep pits of corroded steel. 

It may also be difficult to distinguish between passive and active forms of biocorrosion, as they may occur at the same time biofilm accumulations on metal surfaces will naturally contain live organisms (including slime producers, sulfate reducers, and acid producers), as well as dead bacteria, excretion products, trapped particles, and perhaps oil and grease or other foulants. 

The source of most sludges and other foulants, however, is from the surrounding environment. Air-blown leaves, sand, dust, and dirt, the infiltration of microbiological organisms, the air scrubbing effects of the cooling... 

Marine Crustacea, which include barnacles and crabs and the marine molluscs, which include mussels, can cause severe fouling problems when coastal seawater is used for once-through cooling of power plant turbine condensers. Various species of marine barnacles, mussels, and their spat quickly establish in warm waters and become extremely troublesome. (The problems are exacerbated by seaweed, sponges, various other marine organisms, and SRBs.) The marine acorn (or rock) barnacle, of group Cirripedia, is a common marine foulant, as are the mussels of family Mytillidae. 

Dalvi, A. G. I., Al-Rasheed, R., and Javeed, M. A. (2000) Studies on organic foulants in the seawater feed of reverse osmosis plants of SWCC. Desalination 132,217-232. 

Pretreatment. Most feed streams are mixtures with varying characteristics. In many cases there are foulants present that can be minimized by pretreatment. For example, seawater fed to RO desalination plant usually contains turbidity and micro-organisms, which can be partially mitigated by prefiltration (media or membranes) and... 

Attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy can provide insight into the chemical nature of deposits on membranes [46]. The spectra of the foulants can be easily distinguished from the spectra of the membrane material. ATR/FTIR can also indicate the presence of inorganic foulants as well as the ratio of inorganic-organic foulants. 

Puro L, Tanninen J, and Nystrom M. Analyses of organic foulants in membranes fouled by pulp and paper mill effluent using solid-liquid extraction. Desalination 2002 143 1-9. 

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