On the Issue of Treating Industrial Enterprise Wastewater from Organic Substances
Abstract Generated abstract
This paper addresses the removal of dissolved organic pollutants from industrial wastewater, focusing on wastes from Tomsk enterprises containing solvents, oils, resins, and related substances. It argues that activated carbon sorption is costly and inefficient without prior removal of suspended matter, and examines the use of metal hydroxides formed during neutralization of spent etching solutions and wash waters as alternative sorbents. The study identifies conditions under which hydroxides of metals such as iron, aluminum, copper, and chromium can sorb organic contaminants, and recommends a treatment scheme combining reduction of hexavalent chromium, lime neutralization, hydroxide precipitation, contact with organically contaminated wash water, and settling. The proposed process reportedly removes organic substances from wash water containing 10 to 15 mg/l of contaminants while keeping residual metal ions within permissible limits.
Full Text
ON THE ISSUE OF TREATING WASTEWATER FROM INDUSTRIAL ENTERPRISES FOR ORGANIC SUBSTANCES
S. A. Babenko, O. I. Popova
(Presented by the scientific seminar of the Department of Processes, Apparatuses, and Cybernetics of Chemical Production)
The most harmful pollutants of the wastewater of industrial enterprises in the city of Tomsk are various organic substances: solvents, varnishes, resins, oils, lignin-like substances, etc. Since most of these organic substances are dissolved in water, their removal to sanitary standards \((0.1—0.03\ \mathrm{mg/l})\) is an extremely difficult task. The sorption used for this purpose on activated carbons without preliminary purification of wastewater from suspended substances is irrational, since it leads to a rapid decrease in the sorption capacity of the carbons. Taking into account their high cost, the expenses for treating wastewater from organic substances will be considerable.
Under the conditions of industrial enterprises in the city of Tomsk, which have electroplating and etching installations, the most accessible and effective method for treating wastewater from organic substances may prove to be a sorption method using metal hydroxides as sorbents. Spent etching solutions and wash waters contain sulfuric-acid or hydrochloric-acid salts of divalent and trivalent iron, copper, chromium, aluminum, and other metals. Their separation is carried out by neutralization with lime milk or caustic soda. The hydroxides of the above-mentioned metals formed in this process may be regarded as sorbents of organic substances.
At present, iron and aluminum salts are used to extract from water oil, grease, and other insoluble and soluble organic substances \[1—7\].
Taking into account that etching solutions and wash waters are harmful production wastes, it is necessary to carry out their separation in such a way that, simultaneously with conversion into hydroxide, their maximum sorption capacity toward organic substances is ensured.
In this connection, the sorption of a number of organic substances polluting the wastewater of one of the Tomsk plants by metal hydroxides was studied. The optimal conditions for the sorption process of organic substances on hydroxides of various metals were found.
As a result of the investigations carried out, a technological scheme was recommended for treating wastewater both from metal ions and from organic substances, providing for the reduction of hexavalent chromium by ferrous chloride, which is part of the etching solution, followed by neutralization of the wastewater with lime milk, which
leads to the formation of metal hydroxides, which precipitate. When such a precipitate is brought into contact with wash water containing organic substances (10–15 mg/l): xylenol, benzene, acetone, gasoline, machine oils, and after subsequent settling, the wastewater is completely purified of organic substances. The content of metal ions in the purified water is within permissible standards.
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