Effluent Treatment Applications

Figure Seven (7) depicts a general schematic for membrane processes. In these technologies the implication of increasing the dewatering process is described by the term "recovery", which is defined as the purified water volume divided by the incoming stream volume in other words, percentage of the feed flow which is pumped through the membrane. Typically, for effluent treatment applications, the recovery figure is at least 90%. As recovery is increased (to decrease concentrated solute volume), the concentration of solute and suspended solids in the concentrate stream increases.

Membrane processes, such as reverse osmosis and dialysis, are already used for certain effluent treatment applications and desalination. They can be operated continuously, and they allow recovery of the dissolved values. Membrane processes have benefited enormously from recent advances in membrane materials that can withstand high-pressure gradients and harsh chemical environments. Ultrafiltration of macromolecular complexes of metal ions, which shows more chemical specificity, was more promising for detoxifying effluents, and the work is still ongoing. Particulate matter, which is present in many environmental and processing solutions, can dramatically reduce the permeability of... 

In all its forms, the surface of carbon has oxygenated functional groups and these have been used as the starting point for the covalent bonding of functional groups to the surface. Moreover, in order to enhance the coverage by the functional groups, it has become common to preoxidize the surface by either an anodic treatment or the use of a chemical oxidant. While the properties of these modified surfaces are more suited to sensors, such modifications have been explored for effluent treatment applications. For example, an oxidative treatment of carbon felt was found to enhance the rate of destruction of 4-nitrophenol by an electro-Fenton approach [109] while chemical modification with hydrazine [110] and an anthraquinone polymer [111] has also been reported to increase the efficiency of electro-Fenton treatment. 

Ammonium Ion Removal. A fixed-bed molecular-sieve ion-exchange process has been commercialized for the removal of ammonium ions from secondary wastewater treatment effluents. This application takes advantage of the superior selectivity of molecular-sieve ion exchangers for ammonium ions. The first plants employed clinoptilolite as a potentially low cost material because of its availability in natural deposits. The bed is regenerated with a lime-salt solution that can be reused after the ammonia is removed by pH adjustment and air stripping. The ammonia is subsequentiy removed from the air stream by acid scmbbing. 

Ozone (O3) is a powerful oxidant, and application to effluent treatment has developed slowly because of relatively high capital and energy costs compared to chlorine. Energy requirements for ozone are in the range of 10 to 13 kWh/lb... 

This review article summarizes the broad area of electroorganic synthesis, (selected electroorganic synthetic reactions, with a special emphasis on those that have been commercialized or investigated in pilot plants) and selected applications of electrochemical techniques for waste-water and effluent treatment. There are a number of modern textbooks and updated reviews [4-53] of electroorganic chemistry that include much more detail on organic reactions and their mechanisms than it is appropriate to discuss here. 

Textile bleaching, 4 44-45, 71-73 enzyme applications, 4 66-67 enzymes for effluent treatment, 4 67-69 Textile carding, 17 498-499 Textile (hying, microwave technology in, 16 530... 

Initially the application of this analytical technique to an effluent treatment problem would not appear to be very favorable. In the analytical technique high reagent concentrations relative to the metal salt are employed, and the extraction is dependent upon pH level of the aqueous phase (1,2). Furthermore, organic lead salts in the presence of high concentrations of ions such as Cl will form a series of complexes. As a consequence, any method of extraction must take into account the equilibrium of these species. However, these apparent objections to the use of the analytical technique can be resolved and so the process of combined chemical complexing-solvent extraction does have the potential of successful deployment in the field of the large scale treatment of organic-lead-contaminated waste waters. 

Extraction efficiency is not the only factor to be examined in the choice of solvent or reagent for a particular application. Environmental, as well as economic considerations must be taken into account. Solvents such as benzene and chloroform (which have solubilities of 0.07 and 0.82 parts per 100 parts of water) might be preferred for extractive efficiency, but their use would result in large losses to the aqueous phase. Not only would this be expensive, but it would be undesirable for reasons of health the toxic organo lead salts would be removed, but an equally toxic organic solvent would be added to the effluent. Addition of a solvent recovery unit subsequent to the extraction step might render the technique uneconomic (relative to alternative effluent treatment techniques). 

Following are descriptions of several specific applications and case histories illustrating where these processes have been utilized in industrial effluent treatment. 

Figure Ten (10) illustrates the application of ultrafiltration to oily waste effluent treatment.

Caro s acid is finding increasing application in hydroiuelalUirgy, pulp bleaching, effluent treatment, and electronics. 

Flocculation. The interaction of the cationic PEIs with anionic substrates leads to substrate flocculation. Applications of this property include the coagulation of latex (434), commercial application in effluent treatments (435—437), and stabilization of highly loaded coal—water mixtures in mining... 

The most important solid-phase separation materials for column-based separations in modern radioanalytical chemistry are extraction chromatographic materials, and these have been particularly important in automated radioanalytical chemistry. Solid-phase extraction materials based on the covalent attachment of ligands to solid supports also exist, and they have found application in large-scale separation processes for waste or effluent treatment.22 25 They have been commercialized as Analig or SuperLig materials by IBC Advanced Technologies (American Fork, UT). However, they are less well characterized or used for small-column analytical separations. 

In conclusion, a greater knowledge of the effect of the key controlling parameters of this powerful separation technique, as well as improvement in membrane life time of the currently available commercial electromembranes and reduction in their costs, would ensure further growth beyond desalination and salt production and foster ED applications in the food sector, as well as in the chemical, pharmaceutical, and municipal effluent treatment areas. This will of course need extensive R D studies and will highly likely result in hybrid processes combining ED to other separation techniques, such as NF, IE, and so on, so as to shorten present downstream and refining procedures. 

Concerns about groundwater contamination and municipal water supply quality have driven much of the growth of various water treatment schemes involving nanofiltration as a stand-alone process or in combination with RO and/or UF in a broad range of water treatment systems delivering precise purity levels and attractive process economics. Other established applications include corn syrup concentration, recycling of water-soluble polymers, effluent treatment for the food and beverage industry, metal... 

It has been demonstrated in the laboratory that both GDEs [105,106] and three-dimensional electrodes [107] may also be used to reduce oxygen to H202 in acid solutions at rates that are appropriate to the needs of synthesis and effluent treatment. As shown below, the application of these cathodes might allow the corresponding processes to be feasible on an industrial scale. 

New starch products might be derived from emulsion copolymerization with synthetic monomers and the replacement of all-synthetic polymers. Potential applications could be in flocculation, sizing, modified rheological characteristics, bonding to a wide range of substrates, film formation and in effluent treatment. A critical requirement will be the removal of hazardous residuals and Food and Drug Administration (FDA) approval for use in specific paper grades. 

Electrochemistry can be used for a number of purposes linked to water and effluent treatment. The most obvious of these involve the removal of ionic components from waters by application of an appropriate potential. This is employed to remove metal ions from process streams and often leads to recovery of the metal, which can be reused. Clearly, cell designs which favour high electrode surface area/catholyte volume ratios are to be recommended. 

Application Inovyl s high temperature chlorination (HTC) is an energy-efficient process to produce ethylene dichloride (EDC) from ethylene and chlorine. Energy is conserved by using the exothermic heat of reaction to vaporize the EDC, thus product purification can be done by fractional distillation. Unlike with the LTC process, waterwashing the product to remove dissolved ferric chloride is not necessary. Therefore, no aqueous effluent treatment is required. 

Recent developments in material science, electrochemical reactor design, and electrocatalysis have led to an increasing number of electrolytic applications in the area of effluent treatment. These developments have allowed electrochemical treatment processes to become competitive with physicochemical and biological processes, in terms of both capital and operating costs. Some cost-competitive cases of electrochemical pollution control have appeared in the literature over the past several years [1-6]. 

To reduce production of chlorinated organics during bleaching, the pulp and paper industry has replaced chlorine with chlorine dioxide. Chlorine dioxide or its primary precursor, sodium chlorate, can be produced by the low-tonnage chlorine industry with the same hardware that is used for synthesis of chlorine and hypochlorite. This simple transition from chlorine to chlorine dioxide synthesis may be the reason for the less-than-anticipated usage of hydrogen peroxide in the pulp and paper industry. Increasing use of chlorine dioxide could also lead to its applications in other effluent treatment areas such as industrial wastewater remediation. 

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