Iron-rich waters, treatment

In practice, the most frequently applied method for the treatment of iron-rich waters is oxidation of ferrous iron to ferric iron and simultaneous pH adjustment and hydroxide precipitation. Typical process configurations for hydroxide precipitation comprise a neutralization-precipitation stage, and a settling or clarification stage. 

Drinking water treatment residuals (iron rich) Laboratory solutions 23 2 6.0 0.3 As(lll)... 

Solidification/stabilization Refers to reducing the mobility of a contaminant in soils, other solids, or even liquid wastes by mixing them with Portland cement, lime, cement kiln dust, clays, slags, polymers, water treatment sludges, iron-rich gypsum, fly ash, and/or other binders. The process decreases the mobility of contaminants through physical encapsulation (solidification) and chemical bonding between the contaminants and the binders (stabilization). 

Rich, G. (1963). Unit Process of Sanitary Engineering. John Wiley Sons, New York. Robinson, R. B. (1990). Sequestering Methods of Iron and Manganese Treatment. Am. Water Works Assoc. Denver. 

Continuous ferrous sulphate addition has been used for many years to reduce water side corrosive attack of steam condenser tubes. It is usually applied to once through cooling water systems because of its low cost, to provide an iron-rich protective film on the tube surface. For recirculation systems other more expensive, corrosion inhibitors are generally employed. Two phases of the ferrous sulphate treatment programme may be recognised. The first phase involves the initial laying down of the protective film. The second phase involves the maintenance of the film, which would be otherwise destroyed by the shear effects of flow. 

In austenized samples, the morphology and flie ehemical composition of the phases produced depend on the transformation temperature and flie stress-strain response of flie material depends strongly on the austemper-ing treatment [1994Lue]. The heat treatment is also a craeial factor on the morphologies of the iron rich powders. When flie substrate is not water cooled, flie deposit layer done by spray plasma teehnique is composed of ferrite and eementite. In flie ease of water-eooled substrates, the main constituents are retained austenite and the metastable phase Fe2C(ro) on the free surface side [1989Mur]. 

While it is arguable that iron could form temporary, weak, ionic complexes...so that when analyzed by the TCLP test the lead appears to have been stabihzed, the Agency believes that this stabiUzation is temporary, based upon the nature of the complexing. In fact, a report prepared by the EPA on Iron Chemistry in Lead-Contaminated Materials (Feb. 22 1994), which specifically addressed this issue, found that iron-lead bonds are weak, adsorptive surface bonds, and therefore not likely to be permanent. Furthermore, as this iron-rich mixture is exposed to moisture and oxidative conditions over time, interstitial water would likely acidify, which could potentially reverse any temporary stabilization, as well as increase the leachabihty of the lead. Therefore, the addition of iron dust or filings to...waste...does not appear to provide long-term treatment. 

Speth et al. (1996) investigated foulants on NF membranes after conventional treatment. Foulants had a specific fingetprint, different to the organics in the feedwater. The deposit was also rich in aluminium, calcium, iron, magnesium, sodium, and silica. MalleviaUe et al. (1989) analysed membrane deposits and found a higher ash content in the deposits compared to the raw water. 

Four process streams closely link the zinc and lead operations. Iron and lead residues produced in Ae zinc operation are treated in the lead operation, and comprise nearly half of the total feed to the lead operation. Zinc-rich smelter fume makes up about 15% of the total feed to the zinc operation. Lead smelter sulphur dioxide off-gases are fed to the sulphur gas handling plants in the zinc operation, and waste water streams from both lead and zinc operations are treated in the effluent treatment plant. 

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