Purification of waste water

Activated sludge Material containing a very large active microbial population used in the purification of waste water. 

Etienne F. Vansant is presently Professor in Inorganic Chemistry at the University of Antwerp (UIA), Belgium. He has served as Visiting Professor, Research Associate and Invited Consultant in several universities and companies in the field of material science. Professor Vansant s research interests include the optimalization of gas separation and purification techniques for both industrial and ecological purposes, the conditioning and purification of waste waters and soils, and the development of new materials. 

Biochemical purification of waste waters in silicone production... 

The technological process of the biochemical purification of waste waters in silicone production comprises the following stages the neutralisation of acid waste waters the averaging and mechanical purification of waste waters the biochemical purification of waste waters and the dehydration of the sediment (Fig. 82). 

Fig. 21. Diagram of the biochemical purification of waste waters 1 - slushers 2 -slaking apparatuses 3 - heat exchanger 4, 28, 29 - transporters 5 - screw trap 6, 10, 17, 23 - reservoirs 7 - bin 8, 11, 12, 18, 21, 24, 26 - pumps 9 - neutraliser 13, 16, 22, 25 - settling boxes 14 - damping chamber 15 - averager 19 - aero-tank 20 - biogenic tank 27 - pressure filter...

G. D. Hitchens, O. J. Murphy, L. Kaba and C. E. Verotsko, 20th Int. Conference, Environmental Systems (1991). Electrochemical purification of waste water. 

Removal and purification of waste waters, especially in densely populated and industrial areas, has become a serious problem. Waste waters are very different. They generally contain a complex mixture of solids and dissolved components of different... 

Recently supercritical carbon dioxide has been used as a solvent in dyeing textiles and fibers. In comparison with conventional techniques, this method has the advantage of complete separation of the remaining dyestuff from the solvent. Furthermore, there is no need in purification of waste water or in drying textiles [1-5]. 

Mynin, V.N. and Terpugov, G.V., Purification of waste water from heavy metals by using ceramic membranes and natural polyelectrolytes, Desalination, 119, 361, 1998. 

Horacek, J., Soukupova, L., Puncochar, M., and SlezakJ. (1994). Purification of waste waters containing low concentrations of heavy metals. J. Hazard. Mater., 37, 69-76. 

Stahov, E.A., Purification of Waste Water from Oil, Nedra, Leningrad, (1983), (in Russian)... 

The technological system of wastewater disposal (purification of waste-waters themselves) includes equipment for mechanical, biological, chemical and physico-chemical treatment [11-13]. The sludge technology involves equipment and systems appropriate for sludge disposal (see Section 3.11) [14-18]. 

The question arises, as to how the decomposition of water humus in the ocean proceeds. The method of estimation of oxygen decrease in water, incubated in the dark at specific temperature, is commonly applied as a qualitative index of OM decomposition. The biochemical oxygen demand (BOD) method was suggested to estimate the degree of purification of waste waters... 

The purification of waste waters must always be carried out to such a degree that the corresponding lawful norms be satisfied only then the purified water can be discharged into the surroundings. Eventual differences between the lawful norms of various industrially developed countries are not significant. These norms indicate the permissible concentrations of contaminants besides other parameters (colour, odour, content of microorganisms, salinity, etc.) and they are currently supplemented to include further substances, whose toxicity has been determined in recent years. 

Moreover, in acidic medium some metal powders can react directly with hydrogen ions. Therefore, the formation of powdered metals should be avoided in purification of waste waters, except for some special cases. 

Electrolysers with graphite felt or fiber cathodes were used in Czechoslovakia already in the seventies for purification of waste waters containing platinum and gold. The metal concentrations were thus decreased from less than 1 mg/1 below 10 ng/1 the rate of flow in the "flow-across" mode was very low. 

Activated carbon is one of the most commonly used meda for dye removal [95]. It very effectively adsorbs cationic, mordant, and acid dyes while the adsorption of dispersed, direct, pigment, and reactive dyes is lower. Because the effectiveness of axdivated carbon in adsorption of dyes depends on the cliaracteristics of the waste water, in certain cases carbon adsorption can be ineffective [5]. Other examples of carbon filtration in waste water treatments include an effective controlling of perfluorocarbons (PFCs) emissions from the semiconductor manufecturing processes, purification of waste waters in the paper industry, etc [96-97]. 

To purify water, use of clay pots is a very well known old process. With time, variation of filtering materials and methods have been developed as needed. This purification process of water varies according to the scale of purification and also the amoimt and type of contaminants present e.g. the water purification for household need is quite different from the waste water purification processes or removal of oils and fat or colour contaminants. The purification of waste water from various industries is an acute problem. To tackle such widely varied problems, clays with a combination of suitable oiganic compounds were synthetically developed to alter the filtering properties and processes as needed. 

SUvo, O. E. J. 1972. Some Experiments on Purifications of Waste Waters from Slaughterhouses with Sphagnum Peat-Peat Chemistry and Physics, Proceedings Fourth International Peat Congress, Otan-iemi, Finland, vol. 4, pp. 311-318. 

Extra purification of waste water of health care institutions... 

Polymerizations and polycondensations can be carried out in bulk, in solutions or in various forms of dispersions. The selection of one of these process configurations is not only determined by the polymer chemistry, but also by the possibilities of polymer recovery. The costs of separation of unconverted monomer and solvents, and of purification of waste water, if any, are also important factors in this respect. 

In contrast to the cleaning of natural water by ozonation, which is experimentally confirmed as the most appropriate, the purification of waste water by ozone is still an area of intensive future research. This could be explained by the great diversity of pollutants in the used water and the necessity of specific approach for each definite case. 

Purification of waste water containing CICH COOH and PhOH is carried out by ozone treatment and UV-radiation in the presence of immobilized photocatalyst. Thus the rate of decomposition is higher than the rate obtained only in the presence of ozone and UV-radiation [26]. 

The purification of waste water from paper manufacture characterized by enhanced biodegradability, as well as the removal of COD and halo-genated compounds is carried out by a method based on ozonation and biofiltration [29]. 

Ozonation is very economical and highly efficient metiiod for decomposing cancerogenic substances such as 3,4-benzopyrene, etc., particularly after the biological purification of waste water. 

Ozone is also successfully applied for the complete purification of waste water form dyes manufacture. Their color decreases about 10,000 times at exposure to 0.22 g/1 ozone and the biological activity of the reaction products is reduced almost to zero. The semi-industrial experiments in CP Kistenetz were carried out on the dyes manufactured in the plant ... 

The purification of waste water from phenol compounds is one of the most essential tasks of green chemistry considering the hazardousness of phenols. Although numerous methods are known for the elimination of phenols from water, the majority of them are physical methods that preserve the phenol mass balance, i.e., lead to the pollutant redistribution/concentration without its transformation to non-hazardous substances. The ideal purification is a complete oxidation of phenols to CO2 and H2O. Catalytic conversion is considered to be the best solution to this problem. 

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