RU2283815C1 - Process of neutralizing sulfuric acid-containing waste waters - Google Patents

Abstract

FIELD: waste water treatment.

SUBSTANCE: invention relates to cleaning acid waste waters and can be used in various industry fields wherein detoxification of sulfuric acid-containing waste waters is required. Neutralization process involving averaging and neutralization by filtration through the bed of dicalcium silicates-containing filter material is characterized by that neutralization is preceded by preliminary averaging of waste water and. As filter material containing dicalcium silicates, common-curing foamed concrete with density 500-800 kg/m³ is used and neutralization is carried out to pH 11-13.

EFFECT: speeded-up neutralization process due to performed one-step neutralization of effluents and extended post-neutralization pH value range.

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Description

The invention relates to the field of acidic wastewater treatment and can be used in various industries where it is necessary to neutralize acidic wastewater.

A known method of purification of acidic iron-containing wastewater, including averaging, neutralization of wastewater with lime milk, sedimentation and mechanical dewatering of the formed sludge (Smirnov D.N., Genkin V.E. Wastewater treatment in metal processing. - M .: Metallurgy, 1980 , 195 p.). However, this method has significant disadvantages: high consumption of lime, plastering of pipelines, the difficulty of precipitating finely dispersed flakes of iron hydroxide, the large amount of sludge formed and the difficulty of dehydrating it.

A known method of two-stage neutralization of wastewater, including averaging, neutralization, sedimentation and mechanical dehydration of the formed sludge (Shabalin A.Yu. Treatment and use of wastewater at the enterprises of ferrous metallurgy, Moscow, Metallurgy, 1968, p.257-278), while neutralization Wastewater is divided sequentially into two stages: ferrochrome slag and lime milk.

The disadvantages of this method are: high consumption of ferrochrome slag; difficulties associated with sediment removal from sedimentation tanks.

The closest in technical essence to the claimed technical solution is the wastewater neutralization method selected for the prototype, including averaging, neutralization, settling and mechanical dewatering, in which the wastewater neutralization process is divided sequentially into two stages - to a pH of 6-7 by filtration under vacuum 0 , 4-0.6 kgf / cm ² through a thin layer of finely dispersed neutralizing reagent - ferrochrome slag with a thickness of 0.5-2.0 mm for 1 min at the first stage and up to pH 8.5-9.5 neutralization milk of lime in the second stage (RF Patent No. 2207324, C 02 F 1/66, 06/27/2003).

The disadvantages of this method are the large amount of sludge formed in the second stage of neutralization during processing with milk of lime, the difficulty of dehydration and the duration of the neutralization process.

The task to which the invention is directed is to accelerate the process of neutralization by switching to a single-stage neutralization of effluents and expanding the pH range after neutralization.

The problem in the proposed solution is achieved by the fact that in the method of neutralizing acidic wastewater, including averaging and neutralization by filtering through a layer of filter material, the neutralization is carried out in one step to a pH of 11-13, and foam concrete of conventional hardening with a density of 500-800 kg / m ³ .

EXAMPLE OF SPECIFIC PERFORMANCE

The proposed method is as follows. As a neutralizing filtering material, foam concrete of ordinary hardening is used (GOST 25485-89 "Cellular concrete. Technical conditions"). The neutralizing ability of foam concrete is determined by the content in its composition of dicalcium silicates capable of entering into neutralization reactions.

Filtration was carried out in a column with a diameter of 30 mm and a height of 400 mm. For neutralization, a fraction with grain sizes of 0.316-0.65 mm was used, which corresponds to the requirements for neutralizing materials.

Wastewater containing sulfuric acid (pH 1-3) was filtered. The thickness of the foam concrete layer was 70 mm, the density of the foam concrete was 500 kg / m ³ , 700 kg / m ³ , 800 kg / m ³ .

The filtration rate was taken equal to 6 m / h, which corresponds to the filtration rate in real filters at wastewater treatment plants. Sampling was carried out at the end of the filtration time. The change in pH was monitored on an ionometric converter I-500 TU 4215-002-18294344-02, in accordance with the current rules for working with chemical reagents according to GOST 12.4.21 and measurement procedures.

The table shows the results of the neutralization of acidic wastewater

After passing the samples through the filter material, the pH varies from 11 to 13.

Foam concrete with a density of less than 500 kg / m ^{3 is} not used, because leads to a decrease in the strength of the filter material, which leads to deterioration of the filter material, and foam concrete with a density above 800 kg / m is not advisable to use due to a decrease in its filtering properties.

Claims (1)

A method of neutralizing wastewater containing sulfuric acid, comprising neutralizing by filtering through a layer of filter material containing dicalcium silicates, characterized in that prior to neutralization, pre-averaging of the initial wastewater is carried out and foam concrete of conventional hardening with a density of 500 is used as filter material containing dicalcium silicates -800 kg / m ³ and neutralization lead to pH 11-13.