CZ289709B6 - Process for removing polychlorinated biphenyls from aqueous solutions - Google Patents

Abstract

The invented process for removing polychlorinated biphenyls from aqueous solutions by biological way and with addition of organic substrate and nitrogen and phosphorus compounds is characterized in that the solution polychlorinated biphenyls in which auxiliary organic substrate and nitrogen and phosphorus compounds as nutrients have been added is sprayed onto a slag layer. Preferably, compounds containing biphenyl structure may be used as the auxiliary substrate for culturing a microflora. Hexamethylenetetramine is used as a nitrogen nutrient and at the same time as the organic substrate. It is preferred that first the auxiliary substrate and nutrients are sprayed onto slag and only then the addition of water polluted with polychlorinated biphenyls is gradually increased.

Description

The invention relates to a process for removing polychlorinated biphenyls from aqueous solutions.

BACKGROUND OF THE INVENTION

Waters contaminated with polychlorinated biphenyls (PCBs) are freed of them either by chemical methods or biological methods using adapted microorganisms in an aerobic or anaerobic environment, usually with the addition of a carbon substrate and nitrogen and phosphorus compounds as necessary nutrients.

In CZ-A-282 986, the polluted water containing polychlorinated biphenyls is mixed with activated bentonite to form a suspension.

In CZ published application 1994 - 3184 the whole process takes place in tanks, the polluted water is mixed with bentonite, on which the biphenyls are sorbed and subsequently decomposed by selected bacteria.

U.S. Pat. No. 5,635,393 relates to biological dechlorination by granular anaerobic bacteria. The purification process takes place in a reactor having a biologically reactive zone and a sedimentation zone. In the sedimentation zone, organic compounds decompose into methane and CO ₂ , and aid in separation. Again, there is no spraying of the material with contaminated water.

U.S. Pat. No. 4,726,905 describes again the purification of PCB contaminated water. The PCB is adsorbed in suspension to the cyclodextrin polymer.

SUMMARY OF THE INVENTION

A method for removing polychlorinated biphenyls from aqueous solutions biologically with the addition of an organic substrate and nitrogen and phosphorus compounds is to scrape a cinder layer with a solution of polychlorinated biphenyls with the addition of an auxiliary organic substrate and nitrogen and phosphorus compounds as nutrients.

Advantageously, compounds containing a biphenyl structure may be used as the auxiliary substrate to form the microflora. Hexamethylenetetramine is used as the nitrogen nutrient and at the same time as the organic substrate.

Preferably, the slag is first sprayed with an auxiliary substrate and nutrients and then the addition of water contaminated with polychlorinated biphenyls is gradually increased.

The incorporation is carried out by sprinkling the brown coal slag column with a solution of compounds having a biphenyl structure with the addition of nitrogen and phosphorus compounds and after spontaneous formation of the microbial culture, the PCB solution is gradually added, increasing its concentration up to the saturation concentration of the PCB solution.

Brown coal slag has previously proven successful in the treatment of waste water containing phenols, fatty acids, cyanides and other substances, as well as for the capture of air contaminants. It has sorption properties, given by its porous silicate structure and unburned carbon content, catalytic ability, due to the content of various elements, and serves as a good carrier for the spontaneous development of microflora adapted to the supplied organic substances. There is an organic concentration in the pores of the cinder

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Even substances that can lead to anaerobic conditions favorable to PCB dechlorination and their decomposition.

The slag bed incorporation is preferably carried out by first spraying with a solution of compounds having a biphenyl structure, since this creates microflora, adapting well to the degradation of PCBs. Thereafter, the concentration of PCB in the slag feed increases gradually. As with any biological treatment, nitrogen and phosphorus compounds must be added as nutrients.

Hexamethylenetetramine has proven to be a nitrogen compound, which also functions as an organic substrate.

The invention is suitable for the decontamination of waters contaminated with dissolved PCBs, which are decomposed with up to 99% efficiency in this process. The process requires no complex equipment and is energy efficient. It uses waste material - brown coal slag.

The process according to the invention is further described in the following examples.

Examples

Example 1

Cinder layer was incorporated with a solution containing 50 mg.l ¹ on 4,4'-dihydroxybiphenyl, 50 mg.F ^one of hexamethylenetetramine and 20 mg.l ^-1 KH2PO4 and after gradually increasing the concentration of PCB composition up to saturation (about 200 pg. I ¹ ) and the reduction of the auxiliary substrate concentration was operated by feeding a saturated solution of a mixture of PCB with 20 mg.l ^{-1 of} 4,4'-dihydroxybiphenyl, 20 mg.l ^{1 of} hexamethylenetetramine and 10 mg.l ^{-1 of} KH2PO4- PCB content in the effluent dropped to less than 5% of the original PCB content in the inflow.

Example 2

The creamy layer was treated with a solution of 30 mg.l ^{-1 of} 3,3'-dimethyl-4,4'-dihydroxybiphenyl, 30 mg.l ^{-1 of} hexamethylenetetramine and 20 mg.l ^{-1 of} KH2PO4, followed by a gradual increase in PCB concentration. up to the saturation value and after the concentration of the auxiliary substrate has been reduced, run a saturated solution of the PCB mixture with 10 mg.l ^-1 3,3'-dimethyl-4,4'-dihydroxybiphenyl, 10 mg.l ^-1 hexamethylenetetramine and 10 mg.l ^{-1 1} KH2PO ₄ . The PCB content in the effluent decreased to less than 5% of the original PCB content in the effluent.

Example 3

The creamy layer was treated with a solution of 200 mg.l ^{-1 of} 4,4'-diaminobiphenyl and 50 mg.l ^{-1 of} KH2PO4, after complete decomposition of 4,4'-diaminobiphenyl, the concentration of PCB mixture was increased in the inlet until saturation and then reduced the concentration of the auxiliary substrate such that a saturated solution inlet formed PCB composition with 30 mg.l ^-1 4,4'-diaminobiphenyl and 10 mg.1 ^-1 KH 2 PO _fourth The PCB content in the effluent decreased to less than 1% of the original PCB content in the effluent.

Industrial applicability

The invention is applicable to the disposal of industrial waters contaminated with polychlorinated biphenyls.

PATENT CLAIMS

Claims (4)

CLAIMS 1. A process for removing polychlorinated biphenyls from aqueous solutions biologically with the addition of an organic substrate and nitrogen and phosphorus compounds, characterized in that a slag layer is scrubbed with a solution of polychlorinated biphenyls with the addition of an auxiliary organic substrate and nitrogen and phosphorus compounds as nutrients. Method according to claim 1, characterized in that compounds containing a biphenyl structure are used as the auxiliary substrate for the formation of the microflora. Process according to claims 1 and 2, characterized in that hexamethylenetetramine is used as the nitrogen nutrient and at the same time as the organic substrate. Method according to claims 1 to 3, characterized in that the slag is first sprayed with an aqueous solution with an auxiliary substrate and nutrients to form a microflora in the porous material, and then the contaminated water addition is gradually increased.