Treatment of Dye-Containing Wastewater

Within the EU the chemical control directives are based on three steps (1) Hazard assessment, (2) Risk assessment, and (3) Risk management. 

because they are intensely colored, present special problems in wastewater even a very small amount is noticeable. However, the effect is more aesthetically displeasing rather than hazardous, e.g., red dyes discharged into rivers and oceans. Of more concern is the discharge of toxic heavy metals such as mercury and chromium. 

Wastewaters from both dye manufacturing plants and dyehouses are treated before leaving the plant, e.g., by neutralization of acidic and alkaline liquors and removal of heavy metals, and in municipal sewage works. Various treatments are used [39], 

Biological treatment is the most common and most widespread technique used in effluent treatment, having been employed for over 150 years. There are two types of treatment, aerobic and anaerobic. The aerobic system needs air (oxygen) for the bacteria to perform the degradation process on the activated sludge, whereas anaerobic bacteria operate in the absence of air. Activated sludge usually removes only a moderate amount (10-20%) of the color. 

Removal of color by adsorption on activated carbon is also employed. Activated carbon is very effective in removing low concentrations of soluble chemicals, including dyes. Its main drawback is its limited capacity. Consequently, activated carbon is best for removing color from dilute effluent. 

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Various physical, chemical, and biological methods have been used for the treatment of dye-containing wastewater. However, these conventional technologies have disadvantages like poor removal efficiency and high running cost. Therefore, low-cost sorbents which can bind dye molecules and be easily regenerated have been extensively searched and tested [3-7]. 

Keharia H, Madamvar D (2003) Bioremediation concept for treatment of dye containing wastewater a review. Indian J Exp Biol 41 1068-1075... 

Azo dye-containing wastewaters seems to be one of the most polluted wastewaters, which require efficient decolorization and subsequent aromatic amine metabolism. On the basis of the available literature, it can be concluded that anaerobic-aerobic SBR operations are quite convenient for the complete biodegradation of both azo dyes and their breakdown products. Nevertheless, like the other methods used for biological treatment, SBRs treating colored wastewaters have some limitations. Presence of forceful alternative electron acceptors such as nitrate and oxygen, availability of an electron donor, microorganisms, and cycle times of anaerobic and aerobic reaction phases can be evaluated as quite significant. 

Though treatment of azo dye-containing wastewaters needs combined anaerobic-aerobic phases, microorganisms are subjected to continually alternating anaerobic and aerobic conditions. Thus, it is presumable that anaerobic enzymes involved in the azo dye reduction may be adversely affected by aerobic conditions, as well as aerobic enzymes involved in the aromatic amine mineralization may be adversely affected by anaerobic conditions. Since little is known about the regulations of the enzymes involved in complete biodegradation of colored wastewaters, this approach seems to need advanced investigation to improve color removal and aromatic amine mineralization. 

Treatment of Azo Dye-Containing Wastewater Using Integrated Processes... 

As stated earlier, the biodegradation of azo dyes requires an anaerobic and aerobic phase for the complete mineralization. The required condition can be implemented either by spatial separation of the two sludge using a sequential anaerobic-aerobic reactor system or in one reactor in the so-called integrated anaerobic-aerobic reactor system. In recent years, combined anaerobic-aerobic treatment technologies are extensively applied in the treatment of azo dye-containing wastewaters. Table 1 lists the systems based on combined anaerobic-aerobic treatment in separate reactors. Table 2 lists SBR based on temporal separation of the anaerobic and the aerobic phase. Table 3 lists the other systems, either hybrids with aerated zones or micro-aerobic systems based on the principle of limited oxygen diffuse in microbial biofilms [91]. 

Table 1 Treatment of azo dye-containing wastewater using sequential anaerobic-aerobic reactor systems... 

The state of the art in the field of integrated processes for treatment of azo dye-containing wastewater was reviewed in this paper, based on a substantial number of relevant references published recently, and the following conclusions were reached ... 

The above work indicated that the combined processes for the treatment of azo dye-containing wastewater have become promising alternatives to replace conventional technologies used for the purposes of decolorization. These processes are efficient in azo dyes removal with advantages of being cheap, nontoxic, and biocompatible. 

Y. Xiong, P.J. Strunk, H. Xia, X. Zhu and H.T. Karlsson, Treatment of dye wastewater containing acid orange II using a cell with three-phase three-dimensional electrode. Wat. Res., 35 (2001) 4226 1230. 

With this technology, a wide variety of compounds at low concentrations can be destroyed. It can be used for discoloration of dye-containing waters and for the treatment of other wastewaters. For improved effectiveness, waters should have alow absorbance. So far, there are no legislated discharge requirements for iodine compounds, from which I2 and I" are the... 

Wojnarovits L., Takacs E., Irradiation treatment of azo dye containing wastewater An overview. Rad. Phys. Chem., 2008,77,225-244. 

I hereby declare that this thesis entided Advanced Chemical Oxidation Treatment of Dye Wastewater and Remediation of Chlorinated Aromatic Dyes (CADs) Polluted Soil by Surfactant Micellar/UV System has not been, either in whole or in part, previously submitted to any other institution for a degree or other qualification, and contains no material previously published or written by another person, except where due reference is made in the text. 

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