DE2753401A1 - METHOD FOR TREATMENT OF WASTEWATER CONTAINING CYANIDIONS - Google Patents

Description

HOFFMANN · EITLE & PARTNER

PAT E N TAN W AI.TE

2753A01

DR. ING. E. HOFFMANN (1930-1976) DIPL-ING. W.EITLE DR. RER. NAT. K. HOFFMANN DIPL.-ING. W. IEHN

DIPL.-ING. K. FDCHSLE DR. RER. NAT. B. HANSEN ARABELLASTRASSE 4 (STERNHAUS) D-8000 MÖNCHEN 81 TELEPHONE (089) 911087. TELEX 05-29619 (PATHE)

30 007 o / wa

NIIGATA ENGINEERING CO. LTD., TOKYO / JAPAN

Method of treating cyanide ions
containing wastewater

The invention relates to a method for removing cyanide ions from a wastewater containing cyanide ions. In particular, it relates to a method for removing cyanide ions from wastewater containing cyanide ions in low concentrations, such as water that has been biologically oxidized using activated sludge.

It is known that the gas water that is produced during the production of coke contains large amounts of harmful substances such as
Phenols, thiocyanate compounds, ammonia, hydrogen sulfide and cyanide compounds. The content of cyanide compounds in the gas water is, for example, about 15 to

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100 ppm. Gas water was previously through a biological oxidation process worked up. But the treated gas water still contains cyanide ions in amounts higher than the standard value allowed for a sewage, and therefore such sewage is problematic to the environment submit.

A waste water containing cyanide ions from a metal plating plant usually represents a waste water with a concentration of 20 to 100 mg / 1 cyanions. Many of the CN ions form cyano complex ions with heavy metals such as Zn or Cd. On the other hand, the concentrated wastewater that is given off has to renew the plating bath, a CN concentration of 10,000 to 50,000 mg / l.

A waste water containing cyanide ions from factories for the hot processing of iron and steel is used in cementing and washing processes and usually contains 100 to 500 mg / l cyanide ions (as CN) and sometimes up to 1,500 mg / l 2,000 mg / 1 of cyanide ions (as CN). In this process, most of the cyanide compounds are oxidatively degraded and are then contained as complex ions (iron cyanocomplex ions).

Other effluents containing cyanide ions fall, for example in metal processing plants in concentrations of 100 to 500 mg / 1 (as CN) and waste water from petroleum refineries generally have a concentration of 5 to 30 mg / l (as CN).

Known processes for removing cyanide ions are the alkali chlorination process and the Prussian blue process * However, the alkali chlorination process has the disadvantage that

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the cost of the chemicals are high and that a cyano complex salt is not removed. The Prussian blue process can remove cyanide ions at a relatively low cost, but the usual procedures of this type (Procedures I and III as described below) are quite problematic.

(I) Method of removing cyanide ions by a ferric compound.

In this process, ferric ions (Fe) are treated with a ferrous

- -s4-
cyanidion (^ Fe (CN) - /) implemented with the formation of the insoluble Prussian blue. If the cyanide ion concentration in the waste water is high, the ferric salt must be added in large amounts in order to obtain a satisfactory effect in terms of removing the cyanide ions. A sludge is produced in large quantities and the operating costs increase.

(II) Method of removing cyanide ions by a ferrous compound.

In this process, an iron (II) ion (Fe) is combined with a

Ferric cyanide ion (/ Fe (CN) _c 7 ³ ~) with formation of the insoluble

^G ~ _ -4-

Turnbull's blue implemented and ^ Fe (CN), / that implemented by a small amount of free cyanide ions, which

0J I _β mm A M

water is present, is formed with Fe and ^ Fe (CN) _g _ / which is present in the wastewater, with Fe ^ + a precipitate of iron (II) ferrocyanide is formed, with removal of the cyanide ions. This procedure is very effective for removal

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of the cyanide ions, but Fe remains in the supernatant liquid (treated water) caused by coagulation and separation is won back. Leaving the treated water

2 +
stand, Fe will form a precipitate

made of ferric hydroxide / Fe (OH) _3- / oxidized. In order ^{to remove Fe +} in the treated water, the reaction must be carried out at a high pH. However, with the addition of alkali / in order to maintain the pH, the precipitate of the insoluble Turnbull's blue dissolves and the effectiveness in terms of removing the cyanide ions is reduced. In addition, the ferrous hydroxide / Fe (OH) _2- / flakes formed in this process are difficult to coagulate and separate because of poor coagulability.

(III) Method of removing cyanide ions by an iron (II) compound and an iron (III) compound.

In this process, one adds an iron (II) compound to the Wastewater with the formation of a precipitate of insoluble Turnbull's blue and iron (II) ferrocyanide. Then you give one Iron (III) compound is added with the formation of a precipitate of insoluble Prussian blue, and finally it is added Add alkali to form Fe (OH) - and Fe (OH) ", and then coagulate and the precipitates obtained are separated from one another.

2 +

In this method too, Fe remains in the waste water at a low pH as in the method (II). As a result, the picture a precipitate forms in the treated water on standing. Unless the treatment is carried out at a high pH In order to avoid this disadvantage, it is necessary to increase the amounts of the alkali added and consequently also increase

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the operating costs. At the same time, however, the precipitate dissolves again. This causes difficulties, especially when the cyanide ion concentration in the waste water is high and the amount of ferrous compound added increases.

An object of the invention is to provide a method for removing of cyanide ions from wastewater containing cyanide ions, which proceeds safely and at low cost. A Another object of the invention is to provide a method for removing cyanide ions from waste water containing cyanide ions to show in which in the last treatment stage the precipitate is not redissolved and in which one only a small amount of alkali is required for pH control, which gives precipitates with good coagulability and in which no precipitates form in the treated water after completion of the entire process.

According to the invention, the aforementioned objectives can be achieved by a method for the treatment of wastewater containing cyanide ions can be dissolved by adding (1) an iron (II) salt to the wastewater gives the conversion of the cyanide ions into a precipitate of iron (II) ferrocyanide and insoluble Turnbull's blue,

(2) adding an alkaline agent to the wastewater to convert the remaining ferrous ions to Fe (OH) ₂ , and

(3) Adding an iron (III) salt to this waste water in order to precipitate as a precipitate ^ Fe (CN) _ß _7) which is formed by the addition of the alkali in the form of insoluble Prussian blue.

The drawing represents a flow diagram of an embodiment of the method according to the invention.

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2753Λ01

The cyano complexes as used according to the invention

_ _ -4- - -3 - mean CN, ^ Fe (CN) - /, ^ Fe (CN), _ / ■ and cyanide complex ions of Cd, Zn, Cu and the like. In general, they are contained in the wastewater as M (CN) ₁ , ", where MH, K, Na, Cu, Zn, Cd and the like, or in the form of XCN, where X is F, Cl, J or Br, or in Form of RCN, in which R is an alkyl group with 1 to 17 carbon atoms or an aryl group with 6 to 10 carbon atoms, which if desired can be substituted by alkyl, or in the form of alkali salts (Na, K, Ca and the like) of ^ Fe (CN ) _g _ / ~ and ^ Fe (CN), _ 7; and in the form of metal cyanocomplexes of Cu, Cd, Zn and the like.

Included in wastewater containing cyanide ions are, for example Gas water that occurs when washing coke oven gas in coking plants or from coke oven gas manufacturers, a product obtained by biological oxidative treatment of gas water and the waste water obtained from metal plating plants, Iron and steel heat treatment plants, metal refining plants and petroleum refineries. With the inventive Method, treatment is possible regardless of the materials contained in the wastewater.

With the inventive method, wastewater can with all Concentrations of cyanide ions are treated. However, the method is particularly effective in the treatment of wastewater, with a cyanide ion concentration of less than 1000 ppm, as is generally found in conventional factory wastewater.

In the first stage of the process according to the invention, one gives a predetermined amount of a ferrous compound depending on the

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Concentration of the cyanide ions in the waste water and the mixture is stirred, if desired. Here, the cyanide ion ₍₂ ^ Fe (CN) ₆ _7 Fe) and insoluble Turnbull's Blue put in the waste water with iron (II) compound to form a precipitate of iron (II) ferrocyanide to.

An example of the ionic equation indicating the formation of Turnbull's Blue is shown in (a) below.

4Fe ²⁺ + K ⁺ + 3 ^ Fe (CN) ₆ _ / ³ ~

> KFe ¹¹ ^ Fe ¹¹¹ Fe ¹¹ (CN) ₆ J ₃ (a)

If the cyanide ion in the sewage is in the form of a cyano complex ion of copper, cadmium, Zn and the like is present, the pH of the waste water is previously adjusted to 3 or less and the complex ion is split to form CN, followed by the aforementioned treatment with the ferrous salt he follows.

Any water-soluble ferrous salt can be used in step (1). These salts include, for example, FeCl- , FeCl ₂ -4H ₂ O, FeSO ₄ ^ nH ₂ O (n = O, 1, 4, 5, 7) and (NH ₄ ^ SO ₄ -FeSO ₄ -6H ₂ O. Im however, iron (II) chloride or iron (II) sulfate is generally used, and the appropriate amount of iron (II) salt to be added is so high that the amount of iron (II) is within the range of x ¹ , which is calculated according to the following equation:

y = 0.213x - 3.8
χ ¹ = χ + 25 (mg / 1)

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where y is the concentration (mg / 1) of the cyanide ions in the inflowing Wastewater measured by the method shown in Table 1 and χ is the iron content (mg / 1) of iron (II) salt.

2+ In stage (2) the Fe remaining in the wastewater is converted into Fe (OH) ₂ , which is then removed as Fe (OH) ₃ by air oxidation. Examples of the alkali reagents that can be used in this stage are NaOH, KOH, CaCO- and Ca (OH) ₂ . CaCO ₃ and Ca (OH) ₂ are not preferred over the others because they form scale (scale). The pH of the waste water after the addition of the alkali reagent is adjusted to 7.5 to 9.5, preferably 8 to 9. Included

2+ the Fe remaining in the wastewater is converted into Fe (OH), and the insoluble precipitate of Turnbull's blue decomposes into Fe (OH) ₃ , Fe (OH) ₃ and ^ Fe (CN) ₆ _7 ⁴ ~ · The decomposition of the Turnbull's insoluble blue is given by equation (b), for example

KFe ¹¹ ^ Fe ¹¹¹ Fe ¹¹¹ (CN) ₆ _ / ₃ + 11OH ~

»K ⁺ + Fe (OH) ₂ + 3Fe (OH) ₃ + 3 ^ Fe (CN) ₆ _ / ⁴ ~ (b)

Step (2) can also be carried out after separation and removal of the precipitate formed in step (1). If one chooses this procedure, an additional step is required, but one can reduce the amount of alkali reagent. In this case, the remaining precipitate becomes complete removed in stage (2) and subsequent stages. Thus, in the step of removing the precipitate, it is not necessary to to completely remove the precipitate.

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In step (3) a ferric compound is in a predetermined Amount is added to the wastewater and the mixture becomes

- —4 -
touched. Thereby, ^ Fe (CN) _β / becomes due to the addition of alkali

3+

dissolved and reacts with Fe to form the insoluble Berlin blue, as shown in equations (c) and (d) will be shown.

Fe ^Xi (CN), ._ 7 (C)

Fe ³⁺ + ^ Fe ¹¹¹ Fe ¹¹ (CN) ₆ _7 "

> Fe ¹¹¹ ^ Fe ¹¹¹ Fe ¹¹ (CN) ₆ _? ₃ (d)

(insoluble Berlin blue)

Any water-soluble ferric salt can be used in step (3). These salts include, for example, FeCl ₃ , FeCl ₃ -OH ₃ O, Fe (NO ₃ J ₃ -9H ₂ O, Fe ₂ (SO ₄ ) ₃ * nH ₂ O (n - 0, 3, 6, 7, 7, 5, 9, 10, 12), KFe (SO ₄ ) ₂ * 12H ₂ O and NH ₄ Fe (SO ₄ J ₂ - ^ H ₂ O. In general, iron (III) chloride or iron (III) sulfate is used The amount of iron (III) salt is generally in

III such a range that the Fe / Fe is 0.5 to 3, preferably 1 to 2.

such a range that the Fe / Fe weight ratio

In general, steps (1) to (3) are carried out at 15 to 25 ° C carried out.

The resulting precipitates from Berlin blue, Turnbull ¹ s blue Fe (OH) ₃ and Fe (OH) ₂ are coagulated together and

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severed. The separated precipitates (sludge) are treated in a suitable manner and the supernatant liquid (treated water) which remains after the separation of the precipitates is subjected to further treatment and then given to rivers.

Since in the process according to the invention an iron (II) compound is first added to the wastewater containing cyanide ions, then an alkali is added and finally an iron (III) compound is added, it is possible to use the cyanide ions

2+
and to completely remove the remaining Fe ions. With higher concentrations of cyanide ions in the wastewater, the amount of ferrous compound added also increases. As a result, of course, the amount of

2+

residual Fe in the waste water to and consequently added alkali takes the re-dissolving of the insoluble Turnbull Blue formed by the addition of ferrous compounds had been, too. In the process of the invention, the ferric compound is used added in the last stage and as a result, cyanide compounds, which are dissolved with the addition of a lot of alkali were certainly removed as Berlin blue. According to the present invention, sufficient removal of the

2+
Cyanide ions and Fe achieved. The cyanide ions can be safely removed below the values that can be tolerated in the case of water pollution, and Fe does not remain. As a result, if the treated wastewater is left to stand after the precipitates have been separated, no further precipitation takes place and the purity of the wastewater is excellent. The amount of ferric compound can be drastically reduced compared to the methods for removing cyanide ions in which ferric compounds are used alone. In addition, the amount of the needed to adjust the pH

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used alkalis low. As a result, the cost of the chemicals is low and the wastewater treatment is low can be done at low cost. Even if you as previously stated, the ferrous compound with

2+ used with a good removal effect, Fe does not remain back in the treated wastewater. In addition, since the ferric compound is used in the last stage, the coagulability of the precipitate becomes good and the precipitate can be easily sedimented and separated. That means that wastewater treatment is greatly simplified as a result.

In a common method of treating gas water, the gas water is 2 to 4 times more than industrial water (water obtained by treating wastewater with activated sludge, spring water or river water) or sea water diluted and the diluted gas water is subjected to an activated sludge process and a post-treatment (coagulation and sedimentation of cyanide ions and an absorption treatment using granular activated carbon) (see FIG Gousins, W.G. and Mindler, A.B., J. Water Pollution Federation, Vol. 44, No. 4, 607 (1972); Paul D. Kostenoader and John W. Flecksteiner, J. Water Pollution Federation, Vol. 41, No. 2, 199 (1969)). This type of treatment varies the treatment effect in the activated sludge device is considerable and stable treatment performance with high efficiency cannot be obtained. As a result, a Such a practice does not meet the strict legal requirements regarding the prevention of environmental pollution correspond. In addition, with this method, one has to dilute the gas water with industrial water and industrial water

809838/05 ^ 1

is scarce itself. Therefore, there is a need to perform a method of treating gas water using works with high effectiveness and does not require a dilution stage.

The method according to the invention is particularly useful for treatment suitable for gas water. For example, this method can be used to produce low-concentration cyanide ions (generally below 30 ppm) in connection with a treatment process using microorganisms, such as an activated sludge process or a charcoal process, or both. An example of the combination of the treatment of Gas-liquid with the method of the present invention comprises:

(A) A pre-treatment stage in which this is done when washing gas water produced by coke oven gas, containing ammonia, phenols, thiocyanide compounds, cyanide compounds, suspended solids and oils are treated in such a way that the ammonia content is increased 1000 ppm or less is decreased.

(B) A biological treatment step or a treatment of the gas water treated according to step (A) with Microorganisms or

(B ¹ ) a stage in which the gas water is treated with activated carbon.

(C) A biological treatment stage in which the in (B) or (B ') treated gas water in an aeration tank in which in the liquid mixture

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suspended pesticides from powdered activated charcoal and activated sludge are present, is treated.

A cyanide ion removal step according to the invention , and

if desired, a step for treating the treated gas water with pulverized activated carbon.

The gas from the coke oven is supplied by a coke and coke oven gas Factory is washed in a first cooling system, with steam, tarry substances and ammonia and the like in condense the gas. These are drawn off as a condensed liquid. The condensed liquid turns into raw tar and gas water divided in a tar separator. The gas water contains large amounts of harmful and impure compounds, as can be seen from Table 1.

Table 1

PH 8.5 - 9.5 Analysis method 1. ^C0D Mn 2500 - 7500 ppm JIS KO1O2-1974 8 2. COD _Cr 3300 - 9500 ppm JIS KO1O2-1974 14 3. BOD ₅ 1500 - 4000 ppm ASTM D 1252-1974 4th Phenols 700 - 1700 ppm JIS KO1O2-1974 16 5. Thiocyanate compound
fertilize 150 - 800 ppm JIS KO1O2-1974 20.1 + 20.2 6th Nitric acid decomposition

Settlement method (as SCN)

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7. Cyanide compounds

8. NH.

9. Suspended solids

10. oils

15-1OO ppm 3000-4000 ppm

50-100 ppm 100-200 ppm

JIS KO1O2-1974 29.1.2 (as CN)

JIS KO1O2-1974 17.1.3 (as N)

JIS KO1O2-1974 10.2.1 JIS KO1O2-1974 18.2

In Table 1, COD .. means the chemical oxygen demand

Mn

of the pollutants in a gas water. This is measured using potassium permanganate COD_ is the chemical oxygen demand of pollutants measured using potassium dichromate and BODc is the biological oxygen demand of the polluting substances in a gas water for a period of 5 days at 20 C. The nitric acid decomposition method is as follows shown.

The pH of an aqueous liquid containing thiocyanate compounds is adjusted to 1 to 2 with sulfuric acid. Cyanide ions in the liquid are removed from the liquid thus obtained by flowing gas or distillation. Then the thiocyanate compounds in the liquid will be with ENT. decomposed into cyanide ions and the amount of cyanide ions is determined, for example according to the method according to JIS KO1O2-1974 29.1.2. (This procedure is for example described by H. Weisg in "Mikrochim Acta", 1956, p. 1225).

The phenols present include, for example, phenol, o-, m- and p-cresols, 2,5-xylene, alpha and ß-naphthol, oxine,

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Pyrocatechol, pyrogallol, metal salts (for example Na, K, Ca, Ba or Al salts) of these phenols, phenol carboxylic acids such as salicylic acid and benzoic acid (m- and p-) and the esters and ethers of 1-, 2- and 3-valent phenols .

The present thiocyanate compounds include thiocyanic acid (including isothiocyanic acid), ammonium salts thereof Acids, metal salts (for example Na or Fe salts of these Acids) and phenyl thiocyanate.

The cyanide compounds present include M (CN). _{o <} j _er 2 (where MH, K, Na, Cu, Zn, Cd and the like), XCN (where X is F, Cl, J, Br), RCN (where R is alkyl or aryl) and cyano complexes containing Ni , Fe, Cr, Mn, Cu, Hg, Cd and the like (see, for example, Encyclopädia Chimica, Vol. 7, p. 727, 19th edition, published September 10, 1976).

The suspended solids present are insoluble inorganic or organic compounds such as carbon, corrosion products from the plant (e.g. Fe ₂ O ₃ ), naphthalene and sulfur. The oily components include coal pitch and pyridine.

In step (A), ammonia is removed, which is the most disturbing factor in the decomposition or oxidation reaction of contaminating substances by microorganisms. In steps (B) and (B ¹ ), phenols, suspended solids and oils are removed and thereby the BOD and COD mainly attributable to the phenols are reduced. In stage (C) the phenols, thiocyanate compounds, are suspended

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Solids and oils diminished with further reduction of the COD and BOD. In the step (D), cyanide compounds, suspended solids and oils are removed and thereby become the COD and BOD values in the gas water are reduced to extremely low values.

In step (A) the reduction of the ammonia, ie the stripping of the ammonia, is generally achieved by bubbling air or steam through the gas water. The amount of ammonia removed at this stage should be as large as possible, but it is preferable to leave some of the ammonia in the microbiological treatment as a nitrogen source. The optimal amount of ammonia left for this purpose is from about 50 to about 200 ppm. In this case, after adjusting the pH of the gas water to about 10 to 11, the stripping can be carried out by adding an alkali such as sodium hydroxide (usually in the form of a concentrated aqueous solution of the alkali). In general, however, it is sufficient that the ammonia is removed up to a residual amount of ammonia of about 800 to 1000 ppm. At this level there is no need to add alkali. KOH, CaCO- and Ca (OH) - can be used as alkali. CaCO ₃ or Ca (OH) - is less preferred because of the deposition of limestone.

The ammonia stripping is generally carried out at atmospheric pressure carried out. Furthermore, the effectiveness stripping better at high temperatures. In general, the ammonia stripping temperatures are around about 60 to 100 ° C, preferably 90 to 100 ° C.

The pH of the gas water increases after the ammonia is removed

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adjusted to a pH suitable for microbiological treatment, for example to a pH of about 5 to about 8, preferably 5.5 to 7.5. This pH adjustment is generally carried out by, for example Sulfuric acid in a concentration of 10 to 80% by weight is added. Hydrochloric acid can also be used to neutralize Use nitric acid and phosphoric acid, but sulfuric acid is most preferred.

The pH-adjusted gas water is then subjected to a first biological treatment stage (B) using microorganisms, i.e., subjected to an activated sludge process such as in the Japanese patent application (OPI) 5949/69. This step can be carried out using a suspension process such as the activated sludge process perform or by a fixed bed process (for example "rotating disc method"), a contact oxidation process (or a submerged filter procedure). Since the concentration are organic substances in the incoming gas water is high, the Application of a contact oxidation process using an aeration tank in which a synthetic resin is present as a filler, that is resistant to changes in stress is preferred.

The filler material in the aeration tank used in the contact oxidation process can be a non-woven fabric with a three-dimensional Network structure made of irregularly intertwined fibers, as obtained, for example, from Crimping synthetic fibers such as nylon, polyvinylidene chloride or polyvinyl chloride, a heat treatment,

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Aligning the crimped fibers into a mat and bonding these fibers together to form a sheet and using a binder or by melt-gluing the fibers together by heat treatment. The filler can also consist of a foamed synthetic resin sheet, which is produced when foaming a synthetic resin such as polyurethane or polystyrene.

In general, such filler materials of a thickness of about 20 to about 40 mm are spaced parallel to one another aligned from about 20 to about 50 mm, and a large number of aerobic and optionally anaerobic microorganisms are held on the surface of the fillers and in the spaces inside them and grow there.

The pH in the aeration tank at the first biological treatment stage is usually set from about 6.0 to about 7.5. Depending on the type of gas water, you can adjust the pH of the Adjust the gas water to the most suitable value. The pH treatment can be performed before the gas water is introduced into the aeration tank take place. Alternatively, the pH of the gas water can also be roughly adjusted before it is introduced into the tank, whereby the exact setting is then carried out in the tank by an automatic device.

In the suspension process, the activated sludge concentration is in the aeration tank generally 2000 to about 5000 ppm, preferably 3000 to 4000 ppm. The temperature is generally about 20 to about 40 ° C, preferably 25 to 35 ° C. Air is introduced into the tank in such quantities that the amount of dissolved oxygen is about 1 to about

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5 ppm, preferably 3 to 4 ppm.

In the fixed bed contact oxidation process, the treatment is carried out at a volume loading of about 4 to about

3 3

8 kg COD _M / m per day, preferably 5 to 7 kg COD _M / m / day and a surface loading of about 200 to about 400 g

COD "/ m ^ / day, preferably 250 to 400 g COD" / m / day through Mn fui

leads. The temperature and the pH can be the same as in the suspension process. The amount of dissolved Oxygen is generally from 2 to about 7 ppm, preferably from 4 to 6 ppm.

In step (B), phenols and others become contaminants Materials removed due to the action of the microorganisms. Preferably the contaminating substances this stage removed to such a mass that the

COD "is reduced to about 30% and thereby the Be-Mn

charge in the subsequent treatment with activated charcoal and Activated sludge reduced. In this way, stable treatment can be achieved very effectively. A removal of the contaminating Substances that reduce the COD .. by more than about 90% are not preferred in this procedure. If the amounts of contaminating substances to be removed are low and the BOD and COD .. are high, take the amount of sludge formed in the second biological treatment stage increases and this is undesirable from the point of view the cost of equipment, treatment effectiveness and treatment effect. On the other hand, if the The degree of removal of the contaminating substances is high and the COD “is reduced by more than about 90%, then the amount of sludge formed in the second biological treatment stage is too low. That means that the crowd

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the added activated carbon is limited, depending on the absolute amount of excess sludge (activated sludge / activated carbon weight ratio) . This therefore does not represent a preferred procedure according to the invention Add the amount of activated carbon and set the concentration of activated carbon in the aeration tank to a fixed value To maintain, the amount of excess sludge formed should also be within certain fixed ranges. If If the amount of excess sludge is too large, large amounts of activated sludge must be removed from the system in order to to keep the concentration of the activated sludge in the aeration tank at the desired value. As a result, the crowd will of activated carbon in the excess sludge is withdrawn in a larger amount than desired and by the concentration To keep the activated carbon in the ventilation tank at the desired level, you then have to add more activated carbon. If on the other hand the amount of excess sludge formed is too small, only a small amount of activated sludge can be withdrawn, to keep the activated sludge concentration in the aeration tank constant. If in such a situation constant Amounts of activated carbon are added, then the amount of activated carbon in the aeration tank increases. To the amount of activated carbon To maintain a fixed value in the aeration tank, the amount of activated carbon added should be reduced. A decrease with regard to the added amount of activated carbon, however, means a deterioration in the properties of the liquid to be treated.

In step (C) the excess sludge is removed with a device treated to regenerate the activated carbon, for example by an oxidation method with moist air. (This method

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is described in US Pat. No. 3,442,798.) The sludge is oxidized and burned and the activated carbon is activated and regenerated for reuse. Fresh activated charcoal is added in such an amount that the during regeneration occurring losses, which make up about 4 to about 7%, are compensated.

To add a predetermined amount of activated carbon, and the composition of the activated carbon / activated sludge mixture To maintain a constant weight ratio, the degree of decrease in COD .. in step (B) is preferably about 30 to

Mn

about 90% and especially 50 to 80%.

The residence time of the liquid to be treated in the treatment tank is generally from about 10 to about 15 hours when the amount of recycled sludge is 100% by volume, based on the volume of the starting liquid.

Step (B ¹ ) can be carried out instead of step (B). This step includes treating the gas water from which ammonia has been removed with powdered activated carbon. The activated carbon used has a particle size of generally 0.105 mm to 0.037 mm, preferably 0.074 to 0.063 mm. It is added in an amount of generally 3000 to 10000 ppm, preferably 5000 to 8000 ppm and the mixture is stirred for about 0.5 to 2 hours to remove the phenols, suspended solids and oils in the gas water and to remove the CODj. by 20 to 80%, preferably 30 to 70%. This can reduce the burden in the subsequent biological treatment stage.

The gas water treated in the steps (B) or (B ^{1) is a}

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Solid-liquid separation process subjected and the supernatant Liquid is fed to stage (C). In the step (C), phenols and thiocyanate compounds and the like are used from the gas water by decomposition, oxidation or decomposition-oxidation action of the microorganisms in the Activated sludge is removed and through the adsorption effect of the activated carbon. As a result, the BOD and COD are decreased. At this stage, the activated sludge and the activated carbon equal the losses of solids in the aeration tank in the Mixed liquid.

The activated carbon used in the present invention has a particle size of generally about 0.105 to about 0.037 mm, preferably 0.074 to 0.063 mm. Activated carbon a particle size that is too small is difficult to separate in the solid-liquid separation process and activated carbon with too large a size Particle has poor adsorption properties and is difficult to circulate well in the tank.

The concentration of activated sludge in the aeration tank is generally from about 2500 to about 5000 mg / l, preferably from 3000 to 4000 mg / l. The concentration of activated carbon is generally from about 10,000 to about 50,000 mg / l, preferably from 20,000 to 40,000 mg / l. The weight ratio from activated sludge to activated carbon is about 1: 2 to about 1:30, preferably 1: 5 to 1:14. If the amount of activated carbon is less than about 10,000 mg / l, the amount will increase of the polluting substances to be absorbed, decomposition products and oxidation products. In case the amount of activated carbon is larger than about 50,000 mg / l, it is difficult to effectively separate it by a solid-liquid separation process.

609838/0541

The treatment in this stage is generally carried out at about 20 to about 40.degree. C., preferably 25 to 35.degree. The amount of air introduced into the tank is adjusted so that the amount of dissolved oxygen in the tank Tank is about 2 to about 6 ppm, preferably 3 to 4 ppm. The pH inside the aeration tank is generally set to 6 to 7 by an automatic adjustment. The pH can be adjusted to the particularly desired range set experimentally, this desired range depending on the type of gas water. The pH of the gas water can be adjusted with inorganic acids, which have been mentioned before, for example with sulfuric acid will. In order to keep the weight ratio of activated sludge and activated carbon constant, the activated carbon is added to the Aeration tank was added in an amount of about 500 to 2000 mg / l, based on the amount of liquid introduced. Regenerated activated carbon can be used for this purpose. The loss of activated carbon during regeneration, which makes up about 4 to 7%, is balanced by fresh activated charcoal. The residence time of the liquid in the aeration tank is generally about 8 to 15 hours.

By mixing activated sludge and activated carbon in the previously described stage, an anaerobic zone is created around the Activated carbon formed around it and an aerobic zone outside the anaerobic zone. Substances that are absorbed on the activated carbon are decomposed by anaerobic microorganisms and oxidized by aerobic microorganisms. As the polluting Substances on the activated carbon can be absorbed, the loadings of the sludge and qualitatively and Quantitative shock loads (resistance to changes in load) are reduced and the treatment effect

809838/0541

is stabilized. In addition, the reactions within the system are accelerated because the biological metabolites are adsorbed in the treatment system.

The activated sludge / activated carbon mixture is separated off and removed from the gas water which is treated in stage (C) and the remainder is subjected to step (D). The precipitate formed in stage (D) is coagulated and separated off. If desired, the supernatant liquid is treated with pulverized activated carbon in step (E). Level (E) can be carried out in practically the same way as stage (B '). The supernatant liquid that occurs during solid-liquid separation after stage (D) or stage (E) obtained can be discharged to watercourses after they if necessary for example was passed through a filter bed of sand.

According to the method described above, the main components by which the biochemical reactions in step (C) are prevented are ^{reduced or removed in step (B) or (B 1} ), and thereby the effectiveness of the biological oxidation reaction in step (C) is increased. Since the biological treatment stage is carried out using activated carbon and activated sludge at a pH of 6 to 7.5, thiocyanate compounds, phenols and other contaminants can be safely removed by a synergistic action of biological oxidation by the activated sludge and adsorption by Activated carbon and thereby BOD and COD are reduced. After the biological treatment stage, the coagulation treatment using iron salts according to the invention and the treatment with

809818/0541

pulverized activated charcoal (if desired) carried out. As a result, the remaining contaminants can Substances and impurities such as cyanide compounds, color components and residues of suspended solids, can be safely removed and the COD “can be reduced

Mn

will. Through the effective combination of the aforementioned pretreatment, the biological treatment and the aftertreatment according to the invention, a gas water, its stable Treatment has hitherto been regarded as very difficult, can be treated stably, whereby one treated water is good Quality is maintained. Through the effective combination of pre-treatment, biological treatment and post-treatment it becomes possible to treat gas water without using it with industrial water or sea water or other wastewater (household wastewater and other effluents) or mixtures thereof, must be diluted. The method is thus very effective for Treatment of gas water.

A preferred embodiment for the inventive The procedure is described below, referring to the flow chart.

The process in the flow chart comprises step (A), which can be viewed as a pretreatment step (an ammonia removal step a ₁ and a neutralization _{step a 2} ), a biological treatment step (B) (treatment with microorganism) or step (B ¹ ) (treatment with activated carbon), a biological treatment stage (C) (treatment with a mixture of activated sludge and activated carbon), an aftertreatment stage (D), a coagulation sedimentation stage d- and a final filtration stage d ~ and a regeneration stage for the activated carbon (F). The flow of gas water is indicated in the drawing by the direction of the arrow.

809838/0541

First, gas water 16 is fed into an ammonia scraper 1 and at the same time air or steam 17 is introduced into the gas water 16 to remove ammonia 18 in the liquid initiated (ammonia bracing stage A-a ..).

Then, the gas water from which the ammonia has been removed is supplied to a pH adjustment tank 2 and the pH of the gas water is adjusted to about 5 to about 8, for example with sulfuric acid (neutralization stage A-a ~).

The gas water whose ammonia has been removed in the pre-treatment step in a predetermined amount and whose pH in at the same stage is then introduced into a first aeration tank 3 for biological treatment. Air 19 is fed into the aeration tank 3. Due to the decomposition and oxidation effects of the microorganisms the contaminating substances in the gas water are partially removed. The pH of the liquid inside the aeration tank 3 is adjusted using an automatic pH adjuster 29. If you have this treatment device Applied in a fixed-bed biological treatment process, the exhausted sludge can be removed from the Put tank 3 back in the tank, but this is generally not required. The gas water from which the polluting Substances have been partially removed, in aeration tank 3 is then passed into a settling tank 4 and the liquid is subjected there to a solid-liquid separation process. The supernatant liquid is introduced into an aeration tank 6. The pH of the liquid in tank 6 is set as in tank 3 using an automatic pH adjuster set. The sludge is placed in an activated charcoal receptacle 14, which will be described below

809838/0541

is given, and then through a thickener 5, and the sludge is in a device for regeneration the activated carbon 15 is treated simultaneously with the regeneration of the activated carbon (first biological treatment stage (B) and regeneration stage (F)).

The supernatant liquid in the aeration tank 6 is introduced from the settling tank 4, is in the aeration tank 6 with activated sludge (including the returned Sludge 20) and activated carbon (regenerated activated carbon 21 plus further activated carbon 22) mixed. Air 23 is in the aeration tank 6 initiated. Due to the biological oxidation effect of the microorganisms in the activated sludge and the adsorption effect the activated carbon, phenols and thiocyanate compounds and the like in the gas water are removed and the BOD and COD is decreased. The regenerated activated carbon 21 may be activated carbon that has been regenerated in the regeneration step (F). The gas water that is in the aeration tank 6 was treated, is passed into a settling tank 7, in which the mixture of activated sludge and activated carbon settles by sedimentation. The supernatant liquid is passed into a coagulation tank 9. Part of the mud (Activated sludge / activated carbon mixture) is fed to the aeration tank 6 as return sludge 20. The rest of the mud is passed to a thickener 8 as excess sludge 24 (biological treatment stage (C)).

A predetermined amount of ferrous compound 25, such as ferrous chloride, becomes the supernatant liquid that is introduced from the settling tank 7 into the coagulation tank 9, given and, if desired, the mixture is stirred. then

809838/0541

alkali 26 such as sodium hydroxide or potassium hydroxide is added to adjust the pH of the mixture. Then a predetermined amount of a ferric compound 27 such as ferric chloride is added. The mix will to remove the cyanide components from the gas water and the COD is reduced. The treated liquid is subjected to a solid-liquid separation in the settling tank 10. The supernatant liquid is passed into a sand filter 13 and the sedimented sludge is fed to a thickener 11.

The sedimented sludge is put into a sludge treatment device 12 passed through the thickener 11 and treated there separately (coagulation-sedimentation stage e D-d ..). the Supernatant liquid introduced into the sand filter bed 13 is completely filtered and used as the treated liquid 28 delivered (last filter stage D-d «).

The sludge in the thickener 5 in the first biological treatment stage B and the sludge (the mixture of activated sludge and activated carbon) in the thickener 8 in the second biological treatment stage (C) are each fed to the activated carbon reservoir 14 in the regeneration stage (F) for the activated carbon and mixed in the activated carbon reservoir 14. The mixture is placed in a device 15 for regenerating activated carbon Use of the moist air oxidation method initiated. The used activated carbon is reactivated and regenerated and the excess sludge is burned there. In the activated carbon regeneration stage (F), the regeneration of the powdered activated carbon and the treatment of the excess sludge made at the same time. The activated carbon regenerated in the regeneration device 15 becomes the aeration tank

- 33 -

809838/0541

fed back. In this way the activated carbon will be kept circulating and the cost of the treatment will be reduced reduced (regeneration level (F)).

If step (B ') is used instead of step (B), and the treatment with activated carbon in step (E) is also carried out, then the activated carbon used in step (E) can be used directly in step (B ¹ ) in order to take advantage of the remaining absorption effect. The activated carbon used in step (B ¹ ) is generally concentrated and fed to a regeneration device in which it is regenerated together with the activated carbon used in step (C). The regenerated activated carbon is returned to stage (E). If step (E) is not carried out, the regenerated activated carbon is returned to step (C). In this way, the treatment costs can be reduced when using step (B ¹ ), which steps (A), (C) and (D) are combined therewith, as well as when using step (B).

The following examples describe the invention:

example 1

₇ ppm) was added to gas water containing 5.6 ppm of cyanide ion (CN) and which had been subjected to a biological oxidation treatment. The mixture is rapidly stirred at 150 rpm for 2 minutes. The pH of the mixture is adjusted to 8.4 with sodium hydroxide and the mixture is stirred very quickly for 2 minutes. After 150 ppm FeClj was added, the mixture became 2

809838/0541

Stirred quickly for minutes. Finally, the mixture was slowly stirred at 30 rpm for 10 minutes, coagulated and separated. After coagulation and separation, the supernatant liquid (the treated water) had a pH of 6.5. The analysis showed that it contained 0.7 ppm CN. This means that the cyanide ions were removed very effectively. That treated water did not form any precipitate on prolonged standing.

Comparative experiment 1

FeCl ₂ (100 ppm) was added to the same waste water as in Example 1 and after rapid stirring for 2 minutes, 150 ppm FeCl. Was added. The mixture was stirred rapidly for 2 minutes. The pH of the mixture was adjusted to 6.5 with sodium hydroxide and the mixture was rapidly stirred for 2 minutes. Finally, it was slowly stirred for 10 minutes and then coagulated and separated. Analysis showed that the treated water contained 0.7 ppm CN, but a precipitate of Fe (OH), formed on standing.

If this procedure is with the same conditions as previously set out, except that the amount of sodium hydroxide was increased to adjust the pH of the Bringing the mixture to 7.4, no precipitate formed in the treated water, but the CN concentration in the treated water was 1.1 ppm.

The amount of sodium hydroxide required to bring the pH to 8.4 in Example 1 was the same amount

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Sodium hydroxide which was required in comparative experiment 1, to bring the pH to 6.5.

A comparison of example 1 (the inventive method) with the comparison test 1 shows that in example 1 a smaller amount of alkali is required than in comparison test 1 and that in example 1 the cyanide ions can be effectively removed and that the method is also effective for a Increasing the amount of FeCl ₂ can be operated, as is necessary when the content of cyanide ions increases in the sewage flowing in.

Comparison attempt 2

To the same waste water as used in Example 1, FeCl _{3 was added} in an amount of 500 ppm, 1000 ppm and 1500 ppm, respectively. The mixture was stirred rapidly for 2 minutes and adjusted to pH 7 with sodium hydroxide. It was stirred for a further 2 minutes and finally stirred slowly for 10 minutes, coagulated and separated. The treated water in each case was analyzed for cyanide ions and the results are given in Table 2.

Table 2

Amount of added FeCl ₃ CN ~ concentration of the treated water (ppm) (ppm)

500 2.1

10OO 1.5

1500 1.3

Β0983Θ / 05Α1

2753A01

As can be seen from Table 2, a large amount of FeCl is required in the method of Comparative Experiment 2, in order to largely remove the cyanide ions. But when the amount of FeCl- increases, the amount of that formed also increases Sludge and thereby the operating costs are increased.

Comparative experiment 3

FeCl ₂ (250 ppm) was added to the same waste water used in Example 1 and the mixture was rapidly stirred for 2 minutes. Then the pH was adjusted to 7 with sodium hydroxide and the mixture was stirred for an additional 2 minutes and then slowly for an additional 10 minutes. It was coagulated and separated. However, since the flake coagulability was very poor, coagulation and separation could not be carried out well. Therefore, 1 ppm of a polyacrylamide coagulant was added, but complete coagulation and separation was still not possible.

The treated water obtained after the flakes were separated was filtered through No. 5 filter paper (JIS T-3801 standard). A CN concentration of 0.8 ppm was found in the filtrate, but a brown precipitate of Fe (OH) _{3 formed in the filtrate on standing.}

It was found that the pH at which the filtrate does not precipitate on standing is 9.2. Will the sewage treated at this pH, it has a CN concentration of 1.8 ppm.

809838/0541

Comparative experiment 3 thus shows that the removal of CN ~ was good, but that the coagulation and separation was good

2+
was difficult. In addition, Fe remained and an attempt to carry out the treatment at a high pH

2+ -

Avoiding Fe resulted in CN dissolution.

Example 2

2 (200 ppm) were added in the same manner as described in Example 1 to a gas water which contained 15 ppm of cyanide ions and which had previously been subjected to a biological oxidation treatment. The pH of the mixture is adjusted to 8.4 with sodium hydroxide and then 150 ppm FeCl _{3 are} added. The treated water had a CN concentration of 0.6 ppm. No precipitate formed in the treated water. The pH of the treated water was 7.3 and the water had a residual iron content of 0.4 ppm. This means that the gas water was well treated.

Example 3

A gas water according to Table 4 was selected from those in Table 4 treated conditions, whereby the procedure (A) - (B) - (C) - (D) as indicated in the flow chart of the drawing, was applied. The biological treatment stages were carried out continuously while the pre-treatment stage and the post-treatment stage has been carried out on a rudimentary basis.

809838/0541

The biological treatment steps were performed as described below. The specification of the test facility is shown in Table 3.

Table 3

Specification of the test facility

Biological level
(B) Biological level
(C) Fixed bed type
biological be
plot Treatment with
Activated sludge and
Activated carbon Storage tank for waste water 200 1 Ventilation tank 2.5 1 (2 tanks) 10 1 Settling tank 5 1 10 1 Storage tank for the
treated wastewater 50 1 50 1 Insertion pump
the starting liquid
speed 0-30 ml / min 0-30 ml / min Circulating pump
let the mud - 0-30 ml / min Air pump 15 N l / min 15 N l / min Air flow meter 0-5 N l / min
(2 air flow
knife) 0-10 N l / min Surface of the filling
materials 0.11 m ² _ Material of the filler
terials Polyvinylidene
chloride fleece

809838/0541

2753AQ1

The gas water that is in the pretreatment stage (stripping of ammonia and neutralization with sodium hydroxide), the first biological treatment was carried out in the aeration tank Treatment stage introduced with a flow rate of 12 l / day. Air was in the aeration tank at one flow rate from 2 to 4 N l / min. The amount of dissolved oxygen was maintained at 3 to 6 ppm and the pH of the liquid in the aeration tank was determined using adjusted to 6 to 7 with an automatic pH regulator. During the presence of the gas water in the aeration tanks (each tank had a capacity of 2.5 1) During 10 hours, the gas-water became aerobic and, optionally, anaerobic in the decomposition and oxidizing action Microorganisms that were on the surface of the fillers and inside the spaces between the fillers, subject. As a result, a reduction in the COD " found by about 60%.

Air was added to the aeration tank at the second biological Treatment stage was introduced in a flow rate of 2 to 3 N l / min and the amount of dissolved oxygen was increased to 2 up to 4 ppm. The pH of the liquid in the stink aeration was adjusted to 6 to 7 using an automatic Regulating device set. The concentrations of the activated sludge and the activated carbon in the aeration tank were 4100 and 39000 ppm, respectively. The weight ratio of the activated sludge to activated carbon was 1: 9.5. The amount of addition of regenerated Activated carbon was 1520 ppm and the amount of the freshly activated carbon was 80 ppm based on the raw material. While the gas water was in the aeration tank for 12 hours, it was purified and clarified by the synergistic effect of the

809838/0541

- ₄₀ - 2753A01

biological oxidation effect of the activated sludge and the physical absorption effect of activated carbon. The amount of circulating sludge was 100% by volume based on the amount of supplied inflowing liquid.

At the coagulation and sedimentation stage, it becomes 200 ppm Iron (II) chloride to the water to be treated in the biological Treatment step (C) is added and the mixture is rapidly stirred at 150 rpm for 2 minutes and then becomes sodium hydroxide added to adjust the pH to 8.5. To this 100 ppm iron (III) chloride are added and then the mixture is stirred rapidly at 150 rpm for 2 minutes and then slowly at 30 rpm for 10 minutes. Then the Liquid filtered through a filter paper (NO 5-C JIS standard).

Example 4

A gas water having the composition shown in Table 4 was prepared using the same procedural features as in Example 3 among those shown in Table 4 Conditions treated. In this example, the gas water became an activated sludge treatment immediately after the pretreatment step and then subjected to a post-treatment stage.

The results obtained in Examples 3 and 4 are shown in Table 4.

809838/0561

Table 4 pH Example 3 Example 4 BOD ₅ (ppm) Ammonia- Ammonia- COD _11n (ppm) stripping stripping SCN connections and pH-An and pH-An Pretreatment (ppm) fit fit level CN connections 9.5 9.5 Raw gas (ppm) 2960 2830 water Phenols (ppm) 4500 4300 NH ₃ (ppm) 680 655 30th 25th pH 1O2O 980 BOD ₅ (ppm) 3100 3300 COD ^ (ppm) Biological SCN connections Treat (ppm) level CN connections 6.1 6.5 Inflow (ppm) 1850 1700 sending gas
water Phenols (ppm) 3000 3000 NH ₃ (ppm) 670 650 20th 20th 622 500 810 450

809838/0541

Table 4 (continued)

First biological treatment stage

conditions

Example 3

Biological treatment in a fixed bed

Example 4

COD volume loading (kg / m ³ .D) 7.2

CÖD surface

loading

(g / m ² .D)

Ventilation time
(Hours 10 Activated sludge Flow away-
of the gas was
ser PH
BOD ₅ (ppm)
^C0D Mn ⁽ PP ^m) 6.7
300
1270 1.0 SCN connections
(ppm) 580 0.25 CN connections
(ppm) 18th Phenols (ppm) 10 Second bio
logical Be
action
step treatment
with revitalized
mud and
Activated carbon conditions COD volume
charge
(kg / mJ-D) 1.27 COD-SS loading
(kg / -D) 0.31

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Table 4 (continued)

concentration
of mud
(ppm) Example 3 Example 4 Second bio
logical Be
action
step concentration
of activated carbon
(ppm) treatment
with revitalized
mud and
Activated carbon Activated sludge conditions Amount of trains
added active
coal (ppm) 4100 3950 Ventilation time
(Hours) 39000 BOD ₅ (ppm)
COD "(ppm)
Mn ^r ™ 1600 (rain
rated: 1520
fresh: 80) SCN connections
(ppm) 12th 36 Flow away
de s Gaswas
ser CN connections
(ppm) 3.8
20th 30th
350 Phenols (ppm) 0.01
(Track) 40 15th 18th 0.01
(Track) 5

809838/0541

Table 4 (continued)

BOD ₅ (ppm) Example 3 Example 4 Aftertreatment
level COD _Mn (ppm) Flaking
and down
beat and
Filter
through sand Flow away-
of the gas was SCN connections
(ppm) less than 2
(Traces) 20th ser CN connections
(ppm) 12th 115 Phenols (ppm) less than
0.1 (tracks) 40 0.6 0.8 less than
0.01 (traces) 0.5 Entire Be
ventilation
time in the
biological
Treatment
stages
(Hours) 22nd 36

Ratio of returned sludge

COD volume loading

COD surface loading

100% by volume based on the volume of the raw gas water

COD of the inflowing liquid per day per m im Ventilation tank

COD of the inflowing liquid per day per m ^ des filling material present in the ventilation tank

- 45 -

Θ09838 / 05Λ1

COD-SS loading

COD of the inflowing liquid per day per kg suspended solids in the aeration tank.

Example 5

Example 3 is repeated, but iron (II) sulfate and iron (III) sulfate are used instead of iron (II) chloride and
Iron (III) chloride used. The treatment conditions and the results obtained are shown in Table 5 together with the results obtained in the case of using the iron chlorides of Example 3.

- 46 -

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Table 5

Coagulation-Sedimentation Iron Chloride Iron Sulphate Level

conditions Iron (II) salt 200 300 (ppm) 88 84 As Fe (ppm) pH (NaOH ver 8.5 8.4 turns) Iron (III) salt 100 150 (ppm) 34 55 ALsFe (ppm) 20th 22nd Influence COD (ppm) 3.8 4.7 de liquid
ability (from Mn
BOD ₅ (ppm) less than less than flowing SCN connections 0.01 (traces) 0.01 (traces) liquid (ppm) 15th 13th from the two
ten biolo
gischen Be CN connections
(ppm) less than less than action Phenols (ppm) 0.01 (traces) 0.01 (traces) step) 12th 14th Outflow COD (ppm) less than 2 less than 2 de liquid
] / Λ · ί + ■ ane Mn
BODc (ppm) (Traces) (Traces) JS.CX L- CtUo
the coagu- less than less than 1ation SCN connections 0.01 (traces) 0.01 (traces) Sedimentary (ppm) tier level CN connections 0.6 0.7 (ppm) less than less than Phenols (ppm) 0.01 (traces) 0.01 (traces)

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All values in Table 5 were measured in the same way as in Table 1.

Examples 6-13

Gas water according to Table 6 was among those given in Table 6 Conditions treated. Only the biological treatment was carried out continuously during the pretreatment and post-treatment was carried out in batches.

The biological treatment stage was carried out in the following way:

The pretreated gas water was made using an activated sludge device of the flow type in an aeration tank with a capacity of 10 1 and a settling tank with a capacity of 10 1, which were connected to each other, treated. The concentration of activated sludge and activated carbon in the aeration tank were 3780 and 16540 ppm, respectively. The weight ratio of the Activated sludge to activated carbon was 1: 4.4.

The gas water that had previously been treated to remove the ammonia and that had been pretreated with pulverized Activated carbon, was adjusted to pH 6.5 with sulfuric acid and then added to the aeration tank at a flow rate of 10 l / day introduced. Air was drawn into the aeration tank at a flow rate of 4 to 5 N l / min introduced so that the amount of dissolved oxygen was maintained at 2 to 4 ppm. The gas water was kept for 12 hours

809838/0541

linger in the aeration tank and was during this time it through the synergistic effect of the biological oxidative decomposition by activated sludge and absorption Activated carbon cleaned. It then flowed into a subsequent settling tank, where it was subjected to solid-liquid separation. The supernatant liquid was transferred to a water tank and part of it was used for analysis collected. On the other hand, part of the separated sludge was left as excess sludge from the bottom of the settling tank deducted. The rest was returned to the aeration tank. The amount of recirculated sludge was 100% based on the volume of the incoming gas water.

In the pre-treatment stage, the absorption was pulverized with Activated charcoal was carried out using an activated charcoal obtained from the post-treatment stick and which was added to the gas water in an amount of 4000 ppm, whereupon the mixture was then mixed for 60 minutes stirred.

In the aftertreatment stage (D), FeCl (the amount is given in Table 7 in each case) is added to the gas water and the mixture is quickly stirred at 150 rpm for 2 minutes. Sodium hydroxide is then added to adjust the pH to 8.5. FeCl _{3 is then} added (the amount used in each case is shown in Table 7) and the mixture is vigorously stirred for 2 minutes at 150 rpm. Finally, the mixture is slowly stirred at 30 rpm for 10 minutes and then coagulated and the separation carried out.

In the step (E) (absorption treatment with pulverized

809838/0541

Activated charcoal) a powdered activated charcoal was used, which regenerates according to the oxidation method with moist air had been. 4000 ppm of activated carbon was added to the gas water and the mixture was stirred for 60 minutes.

Comparative experiments 4 to 11

Gas water according to Table 6 was in the same way as in Treated in Examples 6 to 13, with the exception of the aftertreatment stage (D). In the aftertreatment stage (D), 500 ppm FeCl. (172 ppm as Fe) were added to the gas water and the mixture was rapid at 150 rpm for 2 minutes stirred and then slowly stirred at 30 rpm for a further 10 minutes.

The results obtained in Examples 6 to 13 and the comparative experiments 4 to 11 are given in Table 6.

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2753A01

Tabel

Treatment conditions
and analysis data example
6th Comparison
attempt 4 example
7th Comparison
attempt 5 Pre-treatment stage Ammonia wiper
step r
Yes

Absorption stage with powdered activated carbon

Type of biological treatment stage

Dilution ratio in biological treatment

Type of dilution water

AS AS

Raw gas water 9.4 pH 1480 BOD, ppm 2500 COD _Mn , ppm 650 SCN compounds, ppm 6.2 CN compounds, ppm 500 Phenols, ppm 3300 NH ₃ , ppm Incoming water
in biological Be
plot 9.4 PH 1480 BOD, ppm

9.5 1840 2800 650 10.5 700 3500

8.5 1480

- 51 -

809838/0541

Continuation of table 6 example Comparative example Comparison 6th attempt 4 7 attempt 5 COD ^ _1n , ppm 2500 - "■ _> /
2500 SCN compound, ppm 650 650 CN compound, ppm 6.2 6.1 Phenols, ppm 500 500 NH ₃ , ppm 3300 450 Drained water
from the biological
treatment

BOD, ppm 300 200 50 30th COD .., ppm
Mn 800 260 350 80 SCN compound, ppm 450 220 70 40 CN compound, ppm 4.8 2.5 3 1.4 Phenols, ppm 50 10 5 0.2 Dispensed water after
aftercare BOD, ppm 200 30th COD ", ppm
Mn 260 80 SCN compound, ppm 220 40 CN compound, ppm 0.7 0.5 Phenols, ppm 10 0.2 Treatment conditions
in the ventilation tank COD volume loading,
kg-COD / m ^ / day Γ
1.20 1, 20 COD-SS loading,
kg-COD / kg-SS / day 0.29 0.30 Concentration on Be
live sludge, ppm 4100 3950 Concentration on active
coal, ppm - -

Note: AS: activated sludge

AS + AC: activated sludge + activated carbon

The values given in the table were determined in the same manner as in table 1

- 52 -

809838/0541

Continuation of table 6

Treatment conditions example Comparative example Comparison j \ and analysis data 8th attempt 6 9 attempt 7 Pre-treatment stage Ammonia wiper ^ ^r step Yes Yes Absorption stage with powdered Activated carbon There There Kind of biological Treatment level AS AS + AC Dilution ratio in the biological treatment 1 1 Type of dilution water A. Kones baswasser

BOD, ppm

COD ^ _1n , ppm

SCN compound, ppm

CN compound, ppm

Phenols, ppm

ppm

9.5

2100

3400

7OO

7.5

9OO

4000

Incoming water
in biological treatment

BOD, ppm

COD _14n , ppm

SCN compound, ppm

CN compound, ppm

Phenols, ppm

ppm

6.5

710

1500

700

5.3

270

910

- 53 -

809838 / 05A1

Continuation of table 6

8th Drained water
from the biological
treatment BOD, ppm 15th COD.,, Ppm 150 SCN compound, ppm 30th CN compound, ppm 2.7 Phenols, ppm 3

Example comparative example comparative experiment 6 9 experiment 7

4.3

0.01 2.1 0.01

Dispensed water after

BOD, ppm , ppm 11 11 3.1 3.1 COD _11n , ppm ppm 60 60 10 10.0 SCN connection 20th 20th 0.1 0.1 CN connection, 0.4 1.2 fewer
than 0.3 0.8 Phenols, ppm 0.1 0.1 fewer
than 0.01 fewer
than 0.01

Treatment conditions in the aeration tank

COD volume loading,
kg-COD / m ^ / day Γ
1.50 1.47 COD-SS loading
kg-COD / kg-SS / day 0.370 0.390 Concentration on Be
live sludge, ppm 4050 3780 Concentration on active
coal, ppm 16540

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809838/0541

Continuation of table 6

Handling conditions and analysis data

Example Comparative Example Comparative 10 Trial 8 11 Trial 9

Pre-treatment stage

Ammonia stripping stage

Absorption stage with powdered activated carbon

Kind of biological
Treatment level
Dilution ratio
nis in biologi
treatment AS
23 9.2 AS + AC
23 Type of dilution
water Industry
water 2530 Industry
water Raw gas water 3450 pH I. 650 BOD, ppm 25th COD _Mn , ppm 7 50 SCN compound, ppm 3,500 CN compound, ppm Phenols, ppm NH- ,, ppm

Incoming water in biological treatment

BOD, ppm

COD _Mn , ppm

SCN compound, ppm

CN compound, ppm

Phenols, ppm

NH-

ppm

7.2 992 1521 310 8.2 3 60 300

- 55 -

809838/0541

Continuation of table 6

Drained water from the biological

Example Comparative Example Comparative 10 Trial 8 11 Trial 9

BOD, ppm , ppm 8.5 COD ", ppm
Mn pmn 250 SCN connection 10 CN connection, 5.2 Phenols, ppm 0.5

5.9

3.4

0.01

Released water according to dSE.NachbehandlurKj

BOD, ppm

^C0D Mn ' ^ppm

SCN compound, ppm

CN compound , ppm phenols, ppm

5.7 5.7 4.5 4.5 80 80 15th 15th 7th 7th 0.01 0.01 0.7 2.8 0.5 0.9 0.2 0.2 0.01 0.01

Treatment conditions in the aeration tank

COD volume loading,
kg-COD / m ³ / day 1.51 \ r
1, 50 COD-SS loading,
kg-COD / kg-SS / day 0.398 0.403 Concentration on Be
live sludge, ppm 3790 3720 Concentration on active
coal, ppm 16500

-56 -

809838/0541

Continuation of table 6

Treatment conditions and analysis data

Example Comparative Example Comparative 12 Trial 10 13 Trial 11

Ammonia stripping stage e

Absorption stage
with powdered activated carbon

Type of biological treatment stage

Dilution ratio in biological treatment

Type of dilution water

BOD, ppm

COD _Mn , ppm

SCN compound, ppm CN compound, ppm Phenols, ppm

3 '

ppm

Incoming water in biological treatment

BOD, ppm

CODj _1n , ppm

SCN compound, ppm CN compound, ppm Phenols, ppm

AS

1, 82

Industrial water

ppm

7.4

1210

1650

3 60

15.3

410

1925 9.2

2100

3000

50
28

50
500

AS + AC

1, 89

Industrial water

7.4

1150

1580

340

14.8

400

1850

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809838/0541

Continuation table

Example comparative example comparative

attempt 11

12th attempt 10 13 Drained water
from the biological
treatment BOD, ppm f ^ ι COD. ppm
Mn 48 25th SCN compound, ppm 310 250 CN compound, ppm 180 100 Phenols, ppm 13.2 10.5 20th 8th

Dispensed water after

BOD, ppm , ppm 20th 20th 13th 13th COD _M ppm
fin, ppm 95 95 75 75 SCN connection 80 80 60 60 CN connection, 0.8 8.5 0.6 7.1 Phenols, ppm 2.0 2.0 0.5 0.5

Treatment conditions

COD volume loading, kg-COD / m ^ / day COD-SS loading, kg-COD / kg-SS / day

Activated sludge concentration, ppm

Activated carbon concentration, ppm

1 0.356

3975

1 .48 0.361 4100 16300

809838/0541

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iron Table 7 Iron (III) salt (ppm) FeCl ₂ FeCl ₃ as Fe ¹¹¹ Example no. 100 (II) salt (ppm) 150 50 6th 75 as Fe ¹¹ 150 50 7th 75 44 150 50 8th 100 33 150 50 9 100 33 150 50 10 75 44 150 50 11 200 44 3OO 100 12th 200 33 300 100 13th 88 88

809838/0541

Claims (17)

PATENT LAWYERS DR. ING. E. HOFFMANN (1930-1974) DIPL.-ING. W.EITLE DR. RER. NAT. K. HOFFMANN DIPL.-ING. W. LEHN DIPL.-ING. K. FDCHSLE DR. RER. NAT. B. HANSEN ARABELLASTRASSE 4 (STERNHAUS) · D-8000 MÖNCHEN 81 · TELEPHONE (089) 911087 · TELEX 05-29619 (PATHE) 30 007 o / wa NIIGATA ENGINEERING CO. LTD., TOKYO / JAPAN Process for the treatment of wastewater containing cyanide ions. PATENT CLAIMS 1. Process for the treatment of cyanide ions containing Sewage, characterized in that one (1) adding an iron (II) salt to the wastewater and thereby precipitating the cyanide ions in the wastewater as iron (II) ferrocyanide and insoluble Turnbull's blue, (2) Adds an alkaline agent to the waste water, converting the iron (II) ions contained therein into Fe (OH) ₂ and (3) Adding a ferric salt to the waste water - —4—
with the formation of / Fe (CN) _6- /, which occurs in the Adding an alkaline agent to the wastewater forms as insoluble Prussian blue. 809838 / 0S41 2. The method according to claim 1, characterized in that the iron (II) salt or iron (II) chloride
Is iron (II) sulfate. 3. The method according to claim 1, characterized in that the iron (III) salt or iron (III) chloride
Is ferric sulfate. 4. The method according to claim 1, characterized in that the amount of added iron (II) salt is so
is large that the amount of Fe within the range «
of x ¹ , which of the following equations y = 0.213x - 3.8
χ ¹ = χ + 25 (mg / 1) is calculated, where y is the concentration (mg / 1) of the cyanide ions in the inflowing water and χ the iron content
(mg / 1) in the ferrous salt, and that the amount of the ferric salt added is so large that the weight ratio of Fe / Fe is 0.5 to 3. 5. The method according to claim 1, characterized in that an alkaline agent is used for the waste water
Adjustment of the pH value to 7.5 to 9.5 there. 6. The method according to claim 1, characterized in that the treatment in stage <2) is carried out
is after the precipitate formed in step (1) has been separated and removed. 7. The method according to claim 1, characterized in that that the wastewater is a gas water from the scrubbing process 809838/0641 originates in a coke oven gas, the gas water one after the other (A) was subjected to a treatment step to reduce the ammonia content to about 1000 ppm or less, (B) the gas water has been treated using a microorganism, and (C) the gas water was treated in an aeration tank with powdered activated carbon and activated sludge in the liquid. 8. The method according to claim 7, characterized in that that in the aeration tank the concentration of activated sludge is 2000 to 5000 mg / 1, the concentration of activated carbon 10,0OO to 50,000 mg / 1 and that the mixing weight ratio from activated sludge to activated carbon 1: 2 to 1:20 is. 9. The method according to claim 1, characterized in that the waste water is a gas water from the washing stage of a coke oven gas and the waste water was successively (A) subjected to a treatment stage in which the ammonia content in the gas water is reduced to about 1000 ppm or less, ( B ¹ ) a treatment stage in which the gas water is treated with activated carbon and (C) a stage in which the gas water is treated in an aeration tank with pulverized activated carbon and activated sludge. 10. The method according to claim 7, characterized in that that the precipitate is separated and removed after treatment with the ferric salt and that the treated water is then treated with activated carbon. 11. The method according to claim 9, characterized in that that the precipitate is separated off and removed 809838 / 0SA1 after treatment with iron (III) salt and that that treated water is then treated with activated carbon. 12. The method according to claim 1, characterized in that that the cyanide ion from a cyano complexion of copper, cadmium or zinc, which is in the Wastewater is located. 13. The method according to claim 12, characterized in that the cyanide ion is derived through Dissociation of a cyano complex ion by adjusting the pH of the wastewater to 3 or less than 3. 14. The method according to claim 7, characterized in that that the activated carbon used in the treatment of the gas water is recovered and the recovered one Activated carbon is regenerated and reintroduced into the cycle. 15. The method according to claim 14, characterized in that the regeneration of the activated carbon by a Oxidation method takes place with moist air. 16. The method according to claim 9, characterized in that that the activated carbon used in the treatment of the gas water is recovered, the recovered one Activated charcoal regenerates and brings the activated charcoal back into the cycle. 17. The method according to claim 16, characterized in that the treatment of the activated carbon after a Oxidation process is carried out using moist air. 809838/0541