HU199096B - Process for treating concentrated and/or toxic industrial waste waters - Google Patents

Abstract

The organic content of toxic, concentrated and neutralised effluents is oxidised at 200-280 deg.C and 50-100 bar pressure optionally in two stages and in the presence of a catalyst. The treated effluent, can be mixed with communal effluents and treated further biologically in its original or diluted form before passing it into a receiver.

Description

The present invention relates to a process for the treatment of concentrated and / or toxic industrial wastewater by wet oxidation at temperatures ranging from 200 to 300 ° C and pressures from 50 to 140 bar.

Industry also often produces wastewater containing relatively high concentrations (COD - 300-300000 mg / l) of various dissolved (possibly dispersed, organic) substances. Because of their high concentration and toxic effect, these wastewater are particularly harmful to the environment but cannot be directly treated. The biological methods used for the removal of dissolved organic matter (activated sludge, drippings, submersible discs, etc.) and the waste water cannot be disposed of by incineration due to the high water and low flammability.

Of the known methods for the treatment of concentrated and toxic industrial wastewater, a high degree of post-dilution biological purification and wet oxidation may be considered, but in practice their use is hindered by various shortcomings of these methods. A disadvantage of the first method is that it requires a dilution (100 to 1000 thousand) which, on the one hand, has a high water requirement and, on the other hand, requires the establishment and operation of a large-capacity biological treatment plant.

Oxidation of organic matter, dissolved or suspended in water, with air or oxygen-containing gases, the so-called. wet oxidation is a process known in the art by which the organic matter content of waste water is oxidized to carbon dioxide and water. The reaction is subjected to relatively high pressures and high temperatures (140 ... 200 bar and 100 psi)

300 to 350 ° C) and e.g. even at 300 ° C, the degree of wet oxidation used to treat cellulosic sulphite slurry and sewage sludge, even under such conditions, is only 90-95%. (Randolf R .: Wasser-Wirtschaft-Wassertechnik 18, 342 (1968)).

For the treatment of toxic and concentrated industrial wastewater, classical wet oxidation is not used at high operating costs due to these reaction conditions.

Solutions to improve the conventional wet oxidation process in various directions have become known. For example, No. 22 47 841; DE and 1 453 59; It is known from GB patent publications that the wet oxidation process is carried out under intense stirring. Stirring increases the reaction rate and, under milder reaction conditions (at lower temperatures and lower pressures), results in similar conversion rates as in the conventional wet process.

Nos. 1,555,176 and 1,534,337. GB patent documents describe a modified version of the conventional process where wet oxidation can be performed at a lower pressure than the conventional process, thereby reducing the investment cost of the pressure equipment. Because of the lower pressure, the greater the amount of evaporated water (which removes heat energy from system I), this process also requires various energy recovery devices that can recycle at least a portion of the energy lost due to the lower pressure into the system.

Finally, U.S. Patent Nos. 4,000,068 and 4,124,505 disclose modifications of the wet oxidation known as the basic process in which the reaction rate is affected in an accelerated manner by various catalysts.

Both the conventional wet oxidation process and all of the other advanced processes listed above, have consistently sought to oxidize the organic matter content of wastewater to the highest possible efficiency (conversion rate) into carbon dioxide and water, thereby obtaining purified water of very low impurity end product .

Although it has been known for hours that organic matter is not oxidised to carbon dioxide and water in one step, but is oxidized in several steps, through the intermediate formation of several intermediates, it has not been known to the art to . the question of the toxicological variation of the remaining organic matter.

It is an object of the present invention to provide a process for treating toxic and / or concentrated industrial wastewater which, when combined with wet oxidation under relatively mild reaction conditions and optionally biological treatment, especially activated sludge, results in a highly economically acceptable, non-toxic, properly purified water.

The present invention is based on the recognition that wet oxidation intermediates, after a certain degree of conversion, are always members of the same group of compounds, in particular low molecular weight partially oxidized open-chain organic compounds, e.g. aldehydes, ketones, organic acids. During our experimental work it has been proved by several toxicity tests (daphnia test, fish test, etc.) that these intermediate reaction products are completely harmless and are well biodegradable. The biodegradability of the intermediate reaction products was demonstrated in a laboratory semi-industrial biological wastewater treatment plant.

Accordingly, the object of the present invention is achieved by the development and use of a process for the wet oxidation of organic compounds in the starting wastewater according to the invention.

EN 199096 only partially) up to a conversion rate of 60 to 70%, and the resulting purified organic effluent containing the opened organic compounds, in particular aldehydes, ketones and organic acids, is optionally diluted and / or mixed with municipal waste water, especially after biological treatment with activated sludge, it is discharged to a recipient. The combined purification efficiency of the two sequential process steps always achieves a conversion efficiency of about 90% with conventional wet oxidation.)

The process of the present invention results in less concentrated wastewater under milder reaction conditions (lower pressure and lower temperature) and shorter residence time, which can be deposited directly in the soil or any desired recipient, directly or after desired biological purification. Further reduction of the reaction temperature and pressure to the desired extent can advantageously be achieved using a catalyst known in the art.

In preferred and targeted embodiments of the process of the invention, the concentrated and / or toxic industrial waste water to be treated is neutralized prior to partial wet oxidation. For the treatment of toxic chemical wastewater with a chemical oxygen demand (COD) of 3000 to 30000 mg / l, we have found it particularly advantageous to use partial wet oxidation

At a temperature of 250 to 280 ° C and a pressure of 60 to 80 bar, the oxygen demand of the air is 0.3 to 0.4 times that of the initial chemical oxygen demand (COD) of the concentrated toxic waste water , to reach a non-toxic water quality, and lead the treated waste water to the biological grade of municipal sewage treatment. .

The process according to the invention will now be described in more detail by way of example only with reference to the flowchart of Figure 1.

The circuit shown in Figure 1 comprises a reactor 1, a heat exchanger 2, a preheater 3, a compressor 4 and a feed pump 5. The reactor 1 may optionally consist of separate parts 1a and 1b and in such an embodiment the part 1b is filled with catalyst

The concentrated and toxic industrial wastewater to be treated is fed by the feed pump 5 at a sufficiently high temperature through a pre-heater 3 formed as a heat exchanger, which provides heat exchange between the treated wastewater and the treated water, and heats it to the desired reaction temperature; else into reactor 1. From here, the hand waste water is led through a temperature-reducing 3 live lawn to an inlet or outlet. Biological Purifier The oxidation air is supplied to the wastewater to be treated by the 4 concentrator.

The process of the present invention is further illustrated by the following examples:

Example 1

A batch reactor (2 L, ale cluster with magnetic stirrer) was treated with 1 L of neutralized industrial waste: (COD = 7900 mg / L) at 250 ° C and 60 bar! Air from p lack was introduced into the kiss capillary of the needle valve at the bottom of the reactor (124 1/30 min). After the reaction was completed, the device was turned off and the mixer was stopped and the COD value of the hands (3200 mg / l) was measured.

Partially oxidized wastewater was tested in a 1: 10 mixture of rock urinary wastewater in a ground suspension: the treated wastewater was found to be non-toxic when compared to control and blank.

Example 2

In the apparatus of Example 1, the same industrial waste water was treated under the same conditions, but 20 g of Ct catalyst were also charged into the reactor. After 190 1/60 min 1 <of air injection, the treated water COD decreased to 2000 mg / l.

The treated wastewater is non-toxic and can be mixed with municipal sewage in a biological way (activated sludge method).

The process according to the invention has the advantage that the organic matter content of extremely hazardous activities and toxic industrial wastewater is carried out at relatively low levels. partial sap oxidation significantly reduces the amount of tubing that also eliminates the toxicity of the wastewater, so that the treated wastewater

a) in itself, in a much less hazardous environment, where it is appropriate! can be placed between, and

(b) any further treatment may be carried out by mixing with municipal waste water.

Claims (3)

PATENT CLAIMS A process for the treatment of concentrated and / or toxic industrial wastewater by wet oxidation at a temperature of 200 to 300 ° C and a pressure of 50 to 140 bar, characterized in that the wet oxidation of organic compounds in the wastewater is limited to 60 To about 70% conversion, and the resulting purified effluent containing the open-chain organic compounds, in particular aldehydes, ketones and organic acids as reaction products, is optionally preferably diluted with municipal sewage and / or known, especially activated sludge. after biological purification, to the recipient. Process according to claim 1, characterized in that the concentrated and / or toxic industrial waste water to be treated is neutralized prior to wet oxidation. 3. A process according to claim 1 or 2, wherein wet oxidation is used in the treatment of toxic chemical wastewater with a chemical oxygen demand (COD) of 3000 to 300000 mg / l. At 250-280 ° C and 60-80 bar pressure, air oxygen, pure oxygen or hydrogen peroxide is 0.3 to 0.4 times the initial chemical oxygen demand (COD) of the concentrated toxic waste water at any given time. and is treated to a biological grade of municipal sewage treatment plant.