Wastewater-treatment technologies, types

Conventional wastewater treatment technologies, often barely adequate for existing waste types, offer even less promise of providing the type and the degree of treatment that will be required in the near future. Therefore, industrial pollution-control technology must be developed to achieve effective and economical control of pollution from... 

A summary of potentially suitable industrial wastewater treatment technologies for various waste types is given in Table 3.9. Additionally, there are three basic approaches to land treatment of nonhazardous industrial effluent wastewater, as depicted in Fig. 3.10. 

Some type of toxic pollutants which at present may be present in the wastewater will be banned out. This makes the composition of the wastewater less complex so that compounds can more easily be recovered for reuse. Taking these aspects into account, together with other specific aspects related to closed water loop systems, it can be expected that future developments in the treatment technology of wastewater will be focused on Anaerobic treatment... 

The application of a certain technology for wastewater treatment is dependent on the type of wastewater, thus different technologies have been proposed and are applied at present. Normally a combination of procedures and equipment are applied and a big variety of concepts have been realized. To facilitate an overview of the different techniques, the most important processes are discussed in this section. Full concepts that are specialized to a distinct situation are given in the references [77-82]. Some of the techniques have already been discussed in Section 8.2. 

Alternate technologies have recently become available to deal with certain types of waste materials. Ion-exchange and bio-recovery offer the attractive potential of recovering metals from waste water for re-use in the primary process, but these techniques are limited to low concentration, aqueous solutions of metal ions, and thus are more suited for "polishing" a wastewater stream before discharging it to city wastewater treatment facilities. In many cases, capital costs for these techniques are prohibitive relative to the value of the metal recovered. 

Membrane technology has been applied to various types of wastewater. The largest number of installations is probably for industrial wastewater applications, however, municipal wastewater is largest in volume treated. The emphasis of wastewater treatment by membranes in this chapter will be for municipal waste-water treatment. 

Membrane technology may become essential if zero-discharge mills become a requirement or legislation on water use becomes very restrictive. The type of membrane fractionation required varies according to the use that is to be made of the treated water. This issue is addressed in Chapter 35, which describes the apphcation of membrane processes in the pulp and paper industry for treatment of the effluent generated. Chapter 36 focuses on the apphcation of membrane bioreactors in wastewater treatment. Chapter 37 describes the apphcations of hollow fiber contactors in membrane-assisted solvent extraction for the recovery of metallic pollutants. The apphcations of membrane contactors in the treatment of gaseous waste streams are presented in Chapter 38. Chapter 39 deals with an important development in the strip dispersion technique for actinide recovery/metal separation. Chapter 40 focuses on electrically enhanced membrane separation and catalysis. Chapter 41 contains important case studies on the treatment of effluent in the leather industry. The case studies cover the work carried out at pilot plant level with membrane bioreactors and reverse osmosis. Development in nanofiltration and a case study on the recovery of impurity-free sodium thiocyanate in the acrylic industry are described in Chapter 42. 

The author discusses application of ELM, SLM, and polymer inclusion membrane techniques in separation of metal ions (precious metals, Cu, Ni, Zn, Pb, Cd, Cr(VI), Pu, Am, etc.) and organic pollutants (phenols and its derivatives, carboxylic acids, antibiotics, etc.) from wastewaters using laboratory, pilot, and industrial scale modules. Effects of experimental variables upon the solute flux for the various types of liquid membranes are analyzed. The author discusses potential and commercial aspects of hquid membrane technology in wastewater treatment. 

In the individual production sections so-called technological wastewaters are produced which have certain typical properties and composition. In addition to these, normal sewage waters occur in the works, and in the rainfall periods the contribution of the rainfall waters must be omitted. Therefore, wastewaters from industrial operations are a mixture of different types of wastewaters. Industrial wastewater treatment is therefore much more complicated and difficult than the treatment of sewage waters. Also, the effect of such water when discharged into a recipient is different and in most of cases also more harmful because the quantity and quality of wastewaters in industry is noted for high variability, and maxima and minima are not necessarily in agreement with the extremes in the changes of municipal wastewaters. 

Depending on the type of wastewaters, treatment plants for municipal, industrial, agricultural and other wastewaters are recognized. In a waste-water treatment plant two technological systems usually operate a system for wastewater disposal and a system for sludge disposal. 

In water technology, various modifications of classical flotation are used depending on the water quality, quantity and type of substances present in these waters, and the size and shape of particles, etc. Apart from the separation of suspended particles, flotation is more and more used for the condensation of activated sludge, particularly in wastewater treatment practice. 

Other studies attest to more applications of these fibers, for example, filtration with palm fibers could be a potential technology for tertiary wastewater treatment as it provides a green engineering solution [30]. Rriker et al. examined four types of palm surface fibers and determined their mechanical and physical properties for application of this raw material in concrete structures [31]. 

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