Waste treatment effluent

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

Tailored copolymer resins are not the only exchangers to exhibit specific affinities towards selected ions. Many types of inorganic materials such as clays, zeolites, amphoteric oxides, heteropolyacid salts, and phosphates exhibit useful specificity towards selected monovalent and polyvalent ions. In the laboratory such media are often the basis of chromatographic separations, whilst industrially many such materials offer benefits in radioactive waste effluent treatment for removing nucleides such as caesium ( Cs) and strontium ( °Sr). 

Additional separation and recycling. Once the possibilities for recycling streams directly, feed purification, and eliminating the use of extraneous materials for separation that cannot be recycled efiiciently have been exhausted, attention is turned to the fourth option, the degree of material recovery from the waste streams that are left. One very important point which should not be forgotten is that once the waste stream is rejected, any valuable material turns into a liability as an effluent material. The level of recovery in such situations needs careful consideration. It may be economical to carry out additional separation of the valuable material with a view to recycling that additional recovered material, particularly when the cost of downstream effluent treatment is taken into consideration. 

The process is designed from a knowledge of physical concentrations, whereas aqueous effluent treatment systems are designed from a knowledge of BOD and COD. Thus we need to somehow establish the relationship between BOD, COD, and the concentration of waste streams leaving the process. Without measurements, relationships can only be established approximately. The relationship between BOD and COD is not easy to establish, since different materials will oxidize at different rates. To compound the problem, many wastes contain complex mixtures of oxidizable materials, perhaps together with chemicals that inhibit the oxidation reactions. 

The capital cost of most aqueous waste treatment operations is proportional to the total flow of wastewater, and the operating cost increases with decreasing concentration for a given mass of contaminant to be removed. Thus, if two streams require different treatment operations, it makes no sense to mix them and treat both streams in both treatment operations. This will increase both capital and operating costs. Rather, the streams should be segregated and treated separately in a distributed effluent treatment system. Indeed, effective primary treatment might mean that some streams do not need biological treatment at all. 

When viewing effluent treatment methods, it is clear that the basic problem of disposing of waste material safety is, in many cases, not so much solved but moved from one place to another. The fundamental problem is that once waste has been created, it cannot be destroyed. The waste can be concentrated or diluted, its physical or chemical form can be changed, but it cannot be destroyed. 

The depressed prices of most metals in world markets in the 1980s and early 1990s have slowed the development of new metal extraction processes, although the search for improved extractants continues. There is a growing interest in the use of extraction for recovery of metals from effluent streams, for example the wastes from pickling plants and electroplating (qv) plants (276). Recovery of metals from Hquid effluent has been reviewed (277), and an AM-MAR concept for metal waste recovery has recentiy been reported (278). Possible appHcations exist in this area for Hquid membrane extraction (88) as weU as conventional extraction. Other schemes proposed for effluent treatment are a wetted fiber extraction process (279) and the use of two-phase aqueous extraction (280). 

Fig. 4. Schematic of a leather tanning faciUty fitted with a wastewater treatment plant. Treatment of the combined wastes using sulfide oxidation and waste effluent pH adjustment greatiy decreases the suspended soHds and BOD loading (3). Courtesy of Krieger Publishing Co.

Industrial Wastewater Treatment. Industrial wastewaters require different treatments depending on their sources. Plating waste contains toxic metals that are precipitated and insolubiHzed with lime (see Electroplating). Iron and other heavy metals are also precipitated from waste-pidde Hquor, which requires acid neutralization. Akin to pickle Hquor is the concentrated sulfuric acid waste, high in iron, that accumulates in smokeless powder ordinance and chemical plants. Lime is also useful in clarifying wastes from textile dyeworks and paper pulp mills and a wide variety of other wastes. Effluents from active and abandoned coal mines also have a high sulfuric acid and iron oxide content because of the presence of pyrite in coal. 

Groundwater is vulnerable to pollution by chemicals carried by rainwater, leaching from waste sites or from waste water carrying industrial or agricultural effluent. Treatment of drinking water may remove some, but not all, of these contaminants. Some polycarbonate or metal water pipes that are lined with epoxy resin lacquers may release bisphenol A. 

The wash water and the spent acid from all the pre-treatment tanks is also transferred to the effluent treatment plant for further treatment. Spent passivation liquor from the passivation tank is a strong waste and it may be provided with a separate pipeline to the effluent treatment plant, as shown in Figure A13.12. 

The best solution to effluent problems is to not produce the waste in the first place through clean process technology. If waste can be minimized at source, not only are effluent treatment costs reduced but also raw materials costs. 

The environmental fate of chemicals describes the processes by which chemicals move and are transformed into the environment. Environmental fate processes that should be addressed include persistence in air, water and soil reactivity and degradation migration in groundwater removal from effluents by standard waste-water treatment methods and bioaccumulation in aquatic or terrestrial organisms. 

The most widespread biological application of three-phase fluidization at a commercial scale is in wastewater treatment. Several large scale applications exist for fermentation processes, as well, and, recently, applications in cell culture have been developed. Each of these areas have particular features that make three-phase fluidization particularly well-suited for them Wastewater Treatment. As can be seen in Tables 14a to 14d, numerous examples of the application of three-phase fluidization to waste-water treatment exist. Laboratory studies in the 1970 s were followed by large scale commercial units in the early 1980 s, with aerobic applications preceding anaerobic systems (Heijnen et al., 1989). The technique is well accepted as a viable tool for wastewater treatment for municipal sewage, food process waste streams, and other industrial effluents. Though pure cultures known to degrade a particular waste component are occasionally used (Sreekrishnan et al., 1991 Austermann-Haun et al., 1994 Lazarova et al., 1994), most applications use a mixed culture enriched from a similar waste stream or treatment facility or no inoculation at all (Sanz and Fdez-Polanco, 1990). 

The high amounts in which these substances are consumed and produced have conferred illicit drugs and their human metabolites a pseudo-persistent character in the environment. Like over-the-counter and prescribed pharmaceuticals, illicit drugs are metabolized after consumption and different proportions of the parent compound and metabolic by-products are excreted via urine or feces and flushed into the sewage system toward wastewater treatment facilities, if existing. However, these substances are poorly or incompletely removed by conventional waste-water treatment processes [2, 3]. As a consequence, illicit drugs and metabolites are continuously introduced via wastewater treatment plant (WWTP) effluents into the aquatic media. In fact, this constitutes the main route of entry of this type of compounds into the environment as direct disposal is unlikely. 

Vitanov, T., Budevski, E., Nikolov, I., Petrov, V., Naidenov, V., and Christov, Ch., in Effluent Treatment and Waste Disposal, Institution of Chemical Engineers, Rugby, England, 1990, 251. 

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