RU2136609C1 - Method of decontamination of sewage containing aromatic amines - Google Patents

Abstract

FIELD: organic synthesis. SUBSTANCE: sewage is treated with sodium nitrite at 15-25 C, nitrated solution is filtered, filtrate is neutralized, diluted with water and subjected to biological purification with activated sludge. Method makes it possible to reduce concentration of aromatic amines in sewage to values significantly lower than permissible concentration values. EFFECT: more efficient decontamination method. 4 ex

Description

 The present invention relates to the neutralization of wastewater production, producing products of basic organic synthesis, as well as dyes. Wastewater of such industries, as a rule, in addition to other compounds contain aromatic amines. The discharge of such wastewater violates the hydrochemical regime of water bodies, changes the number of microorganisms and benthos. In this regard, the task of neutralizing these wastewater is relevant.

 Absorption methods for treating wastewater from nitro- and amino-aromatic compounds are described in the literature and tested in production [1]. As sorbents, brown coal, activated carbon, cation exchangers, polymer sorbents are used. The effectiveness of such cleaning is quite high. However, its use in production is associated with a number of significant difficulties: the deficit of activated carbon, clogging of the column, the difficulty of regeneration, the need to organize the purification of eluates.

 In the 80s, electrochemical methods for treating industrial wastewater became widespread. This direction is promising, however, its main drawback is the high cost of electricity [2].

The most common and cheapest method of biological treatment. So, aniline is relatively easily absorbed by silt [3]. However, when the aniline content in wastewater is higher than 250 mg / dm ³ , microflora of activated sludge is inhibited, and biological treatment facilities fail.

The objective of the invention was the creation of such a method of disposal of wastewater containing aromatic amines, which would ensure the treatment of wastewater containing a significant amount of aromatic amines (500-3000 mg / DM ³ ), and would be available technologically.

To solve this problem, a method of neutralization was proposed, including treatment with sodium nitrite at 15-25 ^o C, neutralizing the diazotized product, diluting it with water and sending it to biological treatment with activated sludge. When carrying out the process of treatment with sodium nitrite at a temperature below 15 ^o C, the diazotization reaction slows down, and at a temperature above 25 ^o C the resulting diazo compound decomposes.

 There is a method of neutralizing wastewater containing aliphatic amino compounds by treatment with alkali metal nitrite [3]. However, since the starting amines are not aromatic, the interaction with alkali metal nitrite occurs by a different mechanism. In addition, it was impossible to predict in advance the effectiveness of biological purification of diazotization products of aromatic amines.

According to the proposed method, the wastewater is treated with sodium nitrite at a temperature of 15-25 ^o C, stirred and incubated for 15-20 minutes, then the diazotization product is neutralized, filtered, the filtrate is diluted with water and subjected to aeration with activated sludge of biological treatment facilities. The described method allows to reduce the content of aromatic amines to concentrations significantly lower than the MPC.

 The proposed method is illustrated by the following examples.

 Example 1

Wastewater (1 l) containing 3000 mg / dm ^{3 of} aniline is acidified to pH 2, a solution of sodium nitrite (235 g in 50 cm ^{3 of} water) is added, stirred at a temperature of 15 ^o C and incubated for 15-20 minutes. After that, the treated wastewater is neutralized to pH 7, filtered off, the filtrate is diluted and sent to aeration with activated sludge (2.0 g / dm ³ on dry matter) of biological treatment facilities. Biooxidation of wastewater, characterized by BODful / COD, is 77% (according to established standards, the substance is biochemically oxidized with a BODful / COD ratio> 50% [5]). The content of aniline in wastewater after treatment with the described method is 0.05-0.08 mg / dm ³ (MAC of aniline is 0.1 mg / dm ³ ).

 Example 2

Wastewater (1 l) containing 2000 mg / dm ^{3 of} 4-toluidine is acidified to a pH of 1.8-2.0, a solution of sodium nitrite (1.35 g in 50 cm ³ H ₂ O) is added, and stirred at a temperature of 20 ^o C and incubated for 15-20 minutes. Then the treated wastewater is neutralized to a pH of 7.2, the precipitate is filtered off, the filtrate is diluted and sent to aeration with activated sludge (2 g / dm ³ on a dry matter basis) of biological treatment facilities. Biooxidation is 67%. The content of 4-toluidine in the treated wastewater is 0.05 mg / dm ³ (MPC of 4-toluidine is 1 mg / dm ³ ).

 Example 3

Wastewater (1 l) containing 2000 mg / dm ^{3 of} 1-naphthylamine is acidified to a pH of 1.8-2.0 and a solution of sodium nitrite (1.01 g in 50 cm ^{3 of} water) is added. It is kept at a temperature of 25 ^o C for 15-20 minutes. Then, the treated wastewater is neutralized to pH 8.3, filtered, the filtrate is diluted and sent to aeration with activated sludge (2.0 g / dm ³ on dry matter) of biological treatment facilities. Biooxidation is 56%. The content of 1-naphthylamine in the treated wastewater is 0.05 mg / dm ³ (MPC for naphthylamine is 0.1 mg / dm ³ ).

 Example 4

Wastewater (1 l) containing 1000 mg / dm ^{3 of} 2-toluidine is acidified to a pH of 1.8-2.0, sodium nitrite solution (0.63 g in 50 cm ³ H ₂ O) is added and kept at a temperature of 22 ^o C for 15-20 minutes. After completion of exposure, the wastewater is neutralized to pH 7.0, filtered, the filtrate is diluted, and then sent for aeration with activated sludge (2 g / dm ³ on dry matter) of biological treatment facilities. The content of 2-toluidine in the treated wastewater is 0.04 mg / dm ³ (MAC for 2-toluidine <1 mg / dm ³ ). Biooxidation is 56%.

 Thus, the proposed method for the disposal of wastewater containing aromatic amines, can reduce their content to concentrations below the MPC.

Claims (1)

A method of neutralizing wastewater containing aromatic amines, comprising a biological treatment stage, characterized in that the wastewater is preliminarily treated with sodium nitrite at a temperature of 15-25 ^° C, followed by filtration, neutralization, dilution of the diazotization product with water and directing it to biological treatment with activated sludge .