CS274068B1 - Method of waste waters final treatment from technological processes of leather tanning - Google Patents

Abstract

After mechanical-biological purification of waste water from technological processes of tanning leather, waste water containing ammoniac and increased chromium is cleaned by sorption on granular clinoptilolite. After saturation, washing with a solution of sodium chloride alkalizated by sodium hydroxide, ammoniac is eluated, stripped by air and caught on a foam absorber, which is recycled into the technology of tanning leather. Residual colmation of natural clinoptilolite by chromium is liquidated by final washing of the bed by 0.02 hydrochloric acid. Ammoniac water and the eluate with residual chromium is recycled into the technological process of tanning leather. Ammoniac and residual chromium are removed from waste water with high effectiveness.

Description

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274 06: (11) (13) B 1 (51) LNI. CČ C 02 F 1/28

After mechanical-biological purification of the waste leads from the skin tanning process, the waste water containing ammonia and residual chromium is purified by sorption on granular clinoptilolite. Subsequent to saturation, it is eluted from the natural clinoptilolite by washing with a sodium chloride alkaline sodium hydroxide solution, stripped with air and trapped with ammonia on the foam absorber, which is recycled to the skin tanning technology. The residual collagation of natural clinoptilolite with chromium is eliminated by a final wash of the bed with 0.02 hydrochloric acid. Ammonia water and the residual chromium eluate are recycled to the technological process of tanning leather.

Ammonia and residual chromium are removed from the waste lines with high efficiency.

CS 274068 Bl

The invention relates to a method for purifying waste leads from technological processes of tanning leather in tanneries from ammonia and residual chromium, with the continuous recycling of the removed substances.

Ammonia is used for the coagulation and chemical precipitation of Cr (OH) in the tanning process of the tanning industry, as a suitable agent which can maintain the desired pH = 8 of the regenerative sludge environment.

On the other hand, the consequence of the use of ammonia is that in the waste water from the technological processes of skin tanning, even after their mechanical-biological purification from the point of direct discharge into the recipient, often high ammonia content is inadmissible. The mechanical-biological purification of these waste leaders is also not sufficient to remove residual chromium, which is an inhibitor of biological purification.

It has now been found that ammonia and residual chromium can be advantageously removed from the waste leaders of the tanning process of the tanning industry by purifying them with the recycling of the substances removed according to the invention.

The principle of the invention is that after their mechanical-biological treatment, the waste water is subjected to a sorption treatment on a granular natural clinoptilolite with a grain size of 0.3 to 1 mm, with a specific volume load up to 15 h ^-1 . Following saturation, washing, washing with sodium chloride solution, alkalized sodium hydroxide, elution is carried out from the natural clinoptilolite and stripped with air and absorbed into the water to absorb vented ammonia. The residual colmatation of natural clinoptilolite with chromium is eliminated by a final wash of the bed with 0.02 N hydrochloric acid. The obtained ammonia water and duct with residual chromium are recycled to the technological process of tanning leather.

The process according to the invention removes both ammonia and residual chromium from the high-efficiency waste lines.

Its use is a material-closed system of operation, while the trapped ammonia can be used in addition to direct use in the technological process of tanning leather, for example. in the production of fertilizer.

Natural clinoptilolite is indigenous. Purification of the waste leaders by sorption on the natural clinoptilolite in accordance with the invention is investment and operationally advantageous.

The present invention is illustrated but not limited by the following example.

Tannery waste water was treated, the average values of indicators

the cleanings were as follows: PH 7.4 insoluble matter 33 mg.l ^-1 soluble substances (cel) 1200 mg.l ^-1 bsk ₅ 17 mg 0 ₂ .l COD _Cr 108 mg 02.1 40-60 mg.l Cl 301 mg.l ^-1 Sat ² ' 156 mg.l ^-1 Cr ³⁺ 2.4 mg.l ^-1

CS 274068 Bl *

Purification was carried out in the pilot plant range in the WWTP Experimental Unit.

The sorption was carried out on granular natural clinoptilolite with a particle size of 0.3 to 1 mm placed in two pressure filters with a flow rate of up to 1 m ⁵ h. The eluates were collected in accumulation tanks, subsequently subjected to air stripping and the vented ammonia was collected in water on a foam absorber. The ammonia water obtained was recycled to the tanning technology. Chromium clinoptilolite collation was eliminated by washing the bed in both filters with 0.02 N hydrochloric acid. Residual chromium was also often trapped in the eluate, which was recycled to the technological process of tanning the skin.

Technological characteristics of semi-operational waste water treatment with zeolite in WWTP Otrokovice:

Specific volumetric load of filters zeolite volume in filter (V _Q ) grain size of zeolite used ion exchange capacity to NH1

12, BV / V _Q. h ' ¹ 70 1

0.3 - 1.0 mm ca. 10 rng.g!

working cycle length in hours 20 in I / _{O Q} 260 regeneration fractional in hr. 2.5 volume of purified water per cycle 18 m ⁵ fraction of regenerant for air-stripping 0.75 m ⁵ air consumption for NH3 stripping (T = 20 ° C) ca. 20 m \ l

The utilization of the method of purifying the waste lines from the tanning of the skin enables a material-closed, investment-friendly operation system.

Claims (2)

OBJECT OF THE INVENTION The method of purification of waste leaders from technological processes of tanning of leather in tanneries from ammonia and residual chromium, with continuous recycling of removed substances, characterized in that these waste waters after mechanical-biological treatment are purified by sorption on granular natural clinoptilolite with a grain size of 1 mm at a specific volumetric load of 15 h ^, from which, after saturation, washing with sodium chloride solution, alkalized with sodium hydroxide, elutes, expelled by air and entrained by absorption into the water vented ammonia; 02 N hydrochloric acid, whereby the obtained ammonia water and the eluate with residual chromium are recycled into the technological process of skin tanning.