DD152528A1 - PROCESS FOR REMOVING NITRATE FROM WASTEWATERS - Google Patents

Abstract

The invention relates to a method for nitrate removal from wastewater by microbiological denitrification. The process is used in sewage treatment plants. The aim of the invention is to provide a method for nitrate reduction from industrial wastewater with high nitrate degradation performance with little effort. The task is solved to develop a continuous process, which is suitable for continuous operation and except wastewater requires no raw materials and auxiliaries. The process is based on nitrate industrial effluents at pH values of 6.5-9, temperature ranges between 20 and 36 degrees C, and residual oxygen concentrations of 0-1 mg / L in continuous reactors with wastewater from a hydrocarbon feedstock production plant be mixed. The mixing is done so that a CSV: NO & ind3! Ratio of 1-10 is set and the proportion of denitrifying bacteria in the total bacterial population is kept at 2-25%.

Description

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Title of the invention

Process for removing nitrate from wastewater

IPK: C02C Field of application of the invention

The invention relates to a method for microbiological denitrification of wastewater and finds its application in wastewater treatment plants.

Characteristic of the known technical solutions

The need to reduce the nitrate content in wastewater is the result of the constant increase in nitrate levels in our rivers and lakes, which are fed with more or less nitrated water. High nitrate levels lead to eutrophication of the waters and to the deterioration of drinking water quality.

It is known that nitrate can be converted into molecular nitrogen with the aid of microorganisms. This denitrification represents a dissimilatory nitrate reduction. It proceeds under anaerobic conditions and presupposes the presence of suitable hydrogen donors.

To simplify matters, the denitrification reaction can be formulated as follows:

2NO ₃ "+ 10 (H) + 2H ⁺ - N ₂ + 6HgO.

This process is used technically to reduce the nitrate content in waste water.

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According to DE-OS 2541676 for nitrogen removal from waste water, the bacterial mass formed at high temperatures (300 ⁰ C) and reacted under pressure and then fed to the medium as a hydrogen donor for the denitrification process. ,

This is an energy consuming operation and therefore unfavorable.

According to US-PS 4039438 a Yerfahren for denitrification of wastewater is known. This method has the disadvantage that only low nitrate concentrations are broken down. Further significant disadvantages are that an addition of cellulose products is necessary and that after the nitrate degradation a complex ozonization must be performed.

A method and an apparatus for removing nitrogen compounds from the water are described in DD-WP 140 031. This process has the disadvantage that straws are used as hydrogen donors to remove the nitrate, with only low nitrate concentrations can be eliminated. According to US Pat. No. 1,430,410, there is known a process for treating waste water by nitrate removal, in which a significant disadvantage is that relatively expensive substances such as starch, glucose or methanol have to be added to the denitrification process. Other methods of wastewater treatment are described in US-PS 1402369 i and DE-OS 2331192, the disadvantage of which]

is that methanol is used as hydrogen donor i, which makes the cleaning process more expensive * j

According to PL PS 64388, the hydrogen donor glycerol [

, used. f

The disadvantage here is that a relatively expensive Hilis- \ substance is required for the denitrification process, {

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According to DD-P 142 177, therephthalsäurehaltige water are used for nitrate degradation. However, this method has the disadvantage that only a discontinuous operation zn noticeable nitrate degradation leads. In continuous continuous operation, no high degradation rates are achieved.

The object of the invention is to provide a method which reduces the nitrate content of industrial wastewater, in particular oil processing and petrochemistry with little effort at high nitrate degradation performance.

Explanation of the essence of the invention;

The invention has for its object to develop a continuous process, which is suitable for lowering high nitrate levels in industrial wastewater, especially petroleum and petrochemicals, for continuous operation and except wastewater requires no additional raw materials and Hi'lfs.

According to the invention, the If it rat removal from wastewater, especially industrial wastewater of petroleum and petrochemical, by microbiological denitrification at a pH range of 6.5 - 9.0, temperature range of 20 - 36 ° C and dissolved oxygen concentrations of 0-1.0 mg / 1 in continuous-flow reactors, in that the effluent containing the nitrate is treated with waste water from a plant producing putty whites from hydrocarbons, preferably from the primary separation

this plant is mixed. The mixing is carried out so that a CSV: NOo ratio of 1-10 is set and the proportion of denitrifying bacteria in the total bacterial population in the liquid is kept at 2-25 #. With this procedure, it is possible, from waste water with high Mtratgehalten of about 4000 mg / 1 at high Abbsuleistungen of about 100 mg NOo-N / l.h. und.kzen dwell times without additional raw materials and auxiliaries to remove the nitrate nitrogen down to small residual contents of less than 10 mg / 1. "The process was under the conditions of the invention over a long period of time in continuous operation tested and ensures a reproducible almost constant high Mtratabbau. This has a particularly favorable effect if the temperature, pH, the ratio of CSV: N0o and the content of denitrifying bacteria are kept constant in the total bacterial population. However, even with certain variations in parameters within the ranges given, the method allows high levels of nitrate degradation in continuous operation.

Embodiment · · .-

In game 1

In a 150 1 stirred reactor, a partial stream of waste water from a petrochemical combo with a nitrate content of 1920 mg / l was mixed with waste water from a plant producing hydrocarbons with a CSV value of 4400 mg Og / l in the ratio 1: 1 '. Awake setting of dissolved oxygen values 4. 1.0 mg Op / 1, the reactor was discharged with 20 1 active sludge

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Inoculated a denitrification. After the process 20 hours discontinuously e-Inera pH 8.2 and 25-28 ⁰ C -was operated, gas evolution and analytically detectable nitrate removal was recorded. The reactor was switched to continuous operation with a residence time of 11.5 hours with the addition of a mixture of nitrate-containing waste water from a petrochemical combination and waste water from a plant for the production of putty from hydrocarbons, wherein at the inlet of the reactor a CSVtNOo ratio of 2, 1 to 2.5 has been set. The proportion of the denitrifying population in the total bacterial population was adjusted by post-inoculation or sludge removal to a value of 11-19 $. The reactor was operated continuously for several weeks. On average, degradation rates of 19 mg NOo-N / lh were achieved with a final nitrate nitrogen concentration of 1 mg / l.

In a 150 l fixed bed reactor, waste water from an industrial plant for the production of calcium ammonium nitrate with a nitrate content of 3960 mg / l was treated with wastewater from the primary separation of a plant producing putty from hydrocarbons with a CSV value of 7300 mg Og / l in the ratio 1: 1 mixed. After adjusting the dissolved oxygen content in the reactor of , A 1 mg O ₂ A was inoculated with 20 1 active sludge of a denitrification. After the process was operated discontinuously for 48 hours at a pH of · 7.5 and temperatures between 27 and 34 ⁰ C, gas evolution and analytically detectable nitrate degradation was recorded.

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The reactor was switched to continuous operation with a residence time of 1.5 hours with a mixture of ηitrathaltigem waste water of Kalkammonsalpeterherstellung and waste water of the plant for the production of putty from hydrocarbons, wherein at the inlet to the reactor, a CSV: NOo ratio of 8.9 - 9.4 has been set. The reactor was passed from bottom to top and made the mixture of the two wastewater streams before entering the reactor. The proportion of denitrificants in the total bacterial population in the liquid, measured at the outlet of the reactor, was adjusted by inoculation or Schlararnabzug to a value of 2-8 $>. The reactor was run continuously over several weeks in continuous operation. On average, degradation rates of 93 mg NOoK / l.h at a final nitrate nitrogen concentration of less than 10 mg / l were obtained.

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Claims (1)

In troduction to s pruch Process for removing effluent from waste water, in particular industrial waste water from petroleum processing and petrol chemistry, by microbiological denitrification in the pH range of 6.5-9, temperature range of 20-36 ° C and dissolved oxygen concentrations of 0-1.0 mg 0 _? in continuous reactors characterized in that the effluent containing the nitrate is mixed with effluent from an installation for producing waste protein from hydrocarbons, preferably effluent from the primary separation of the plant, so as to have a CSY: NO ratio of 1-10 and the proportion of denitrifying bacteria in the total bacterial population is kept at 2 - 25 $>.