JPH0255118B2 - - Google Patents

Description

[Detailed description of the invention]

Among the wastewater discharged from the steelmaking process at a steelworks, the wastewater discharged from equipment related to coke plants contains many types of pollutants and has a high concentration. For example, the chemical oxygen demand (hereinafter abbreviated as COD) of wastewater from coke factory-related equipment accounts for 40 to 70% of the total COD of wastewater discharged from steelworks, and the wastewater from coke factory-related equipment is harmless. Establishing technology to smoothly carry out the oxidation process is a very important issue. Wastewater discharged from coke factory-related equipment includes gas waste generated during coal carbonization, wastewater discharged from coke oven gas purification equipment, coke oven gas condensate, and organic compounds generated during coal carbonization, chemicals, fertilizers, etc. This includes wastewater discharged from chemical plants that manufacture products such as chemicals. These wastewaters contain organic compounds such as phenol and cresol, and inorganic compounds such as ammonia salts, cyanide salts, thiocyanate salts, sulfide salts, and thiosulfate salts, and have a high COD of 5000 to 8000 ppm.
The water is dark brown in color and cannot be discharged into public waters as is. For this reason, steel mills with coke plants,
The detoxification treatment of wastewater at chemical plants and city gas plants involves first removing free and/or fixed ammonia in the wastewater by distillation, diluting it 2 to 6 times with seawater and/or fresh water, and then subjecting it to aerobic activation. The usual treatment method is the sludge method. Activated sludge treatment of wastewater from coke factory-related equipment mentioned above can be easily performed if activated sludge from municipal sewage is used as a seed sludge and acclimatized with the wastewater, but stable treatment is not possible. is quite difficult. The reason for this is that the composition of wastewater from coke factories is quite different from that of municipal sewage, and little research has been conducted.
This is because the treatment performance of these wastewaters is not fully understood. For example, the COD volumetric load, which is the basic design value for the aeration tank of an activated sludge treatment facility, was COD2
~3Kg/aeration tank m ³ days, but now COD1
It is becoming Kg. This means that the current capacity of aeration tanks is two to three times larger than it was 15 years ago. As described above, the basic design values of the above-mentioned activated sludge treatment technology for coke factory-related wastewater are not clear even by the manufacturer of this device, and therefore it is difficult to say that it is a sufficiently established technology. In addition, wastewater from coke plants has a very complex composition and contains cyanide, sulfides, etc. that are harmful to activated sludge. Furthermore, the quality of these wastewaters varies greatly depending on the operating conditions of the factory and other factors. For example, coke production decreases and coke oven temperature increases from 50 to 70℃
When the concentration decreases, the concentration of COD, cyanide, sulfide, etc. in the gas waste fluid increases significantly. In addition, changes in coke oven gas refining conditions, chemical plant operating conditions, etc. change the properties of wastewater discharged from these facilities. In addition, activated sludge treatment of wastewater from coke factory-related equipment has large fluctuations in the amount of pollutants (hereinafter referred to as COD load amount) flowing into the activated sludge treatment equipment.
If the amount of toxic substances flowing into the system increases rapidly, activated sludge treatment may not proceed smoothly and the quality of the treated water may deteriorate. For example, if the COD load fluctuates greatly, non-filamentous bulking will occur in the activated sludge in the aeration tank, causing problems with floating and outflow in the settling tank of the activated sludge treatment equipment, and the concentration of suspended substances in the treated water will increase. water quality will deteriorate. Furthermore, when components harmful to activated sludge, such as cyanide and sulfides, increase, the function of activated sludge is inhibited, the decomposability of COD, phenol, thiocyanate, etc. decreases, and the concentration of these substances in treated water increases. No fundamental recovery technology has been established for such malfunctions in activated sludge treatment, and the technology for recovering from malfunctions is based on trial and error.For this reason, once a malfunction occurs, it cannot be recovered in a short period of time, and it may take 3 to 6 months. It can even last for a long time. For this reason, it is extremely important to prevent malfunctions in activated sludge treatment of wastewater from coke plants. From this perspective, the present inventors conducted research on activated sludge treatment of wastewater discharged from coke factory related equipment, and found that these wastewaters can be stably treated by the activated sludge method and that good treated water quality can be obtained. Invented an activated sludge treatment process for wastewater from coke factory equipment. Next, a stabilized activated sludge treatment process for wastewater discharged from coke factory-related equipment according to the present invention is shown in FIG. 1, and this process will be described in detail.
First, wastewater generated from coke factory-related equipment, such as wastewater generated from coke factory 1, chemical plant 2, coke oven gas purification equipment 3, and condensed water 4 generated from piping for fuel gas such as coke oven gas, is treated as wastewater. Tanks 5 to 8 that can store wastewater for 7 to 10 days are installed depending on the type of wastewater, and wastewater is temporarily stored in these tanks. At this stage, the wastewater in the storage tanks 5 to 8 described above is subjected to a toxicity test 9 using a biochemical method at regular intervals, and wastewater that has almost no toxicity or is weakly toxic is directly sent to the homogenization tank 11. do. However, if the wastewater is found to be toxic as a result of this toxicity test, the wastewater is sent to the wastewater detoxification treatment facility 10, where it is detoxified and then sent to the homogenization tank 11. The wastewater homogenized in this way is transferred to homogenization tank 1.
1 to ammonia removal equipment 12, where free and/or fixed ammonia is removed by distillation. This wastewater is sent to the PH adjustment equipment 16, where the PH of the aeration tank is adjusted.
Adjust the pH by adding water or alkali so that the pH falls within the range of 7.0±0.5. Next, this pH-adjusted wastewater is sent to the dilution tank 18, where it is diluted 2 to 6 times as much as seawater and/or fresh water, and the temperature of the wastewater is adjusted to 30%.
After adjusting the temperature around ℃, it is sent to the adjustment tank 19 and from there is sent to the aeration tank 20 of the activated sludge treatment facility at a COD volumetric load of 1.5Kg ± 0.25Kg/aeration tank m ³ days, and then the activated sludge is treated. Do this. The treated water is separated from activated sludge in a sludge settling tank 21 and discharged. In addition, the ammonia removal equipment 12 is operated at 10 times a year due to regular repairs and inspections of boilers, distillation columns, etc.
It may be suspended for 1 to 30 days. In this case, such wastewater is not sent directly to the activated sludge treatment facility, but is sent to the high temperature PH adjustment facility 13 and heated to a temperature of 40 to 90℃.
The pH of the wastewater is adjusted to 7.0 to 8.0 by adding sulfuric acid at a temperature of 40 to
After aeration with air at 90℃, PH adjustment tank 1
6 and dilution tank 18, activated sludge treatment is carried out according to the method described above. The main points of the present invention comprising such a process are as follows. (1) Types of wastewater include wastewater generated from different routes, such as gas wastewater generated from coke ovens, wastewater generated from coke oven gas purification equipment, wastewater generated from chemical plants, and condensed water from fuel gases such as coke oven gas. Store each in separate tanks. Each of these tanks will have a capacity that can store 7 to 10 days worth of wastewater. (2) Each wastewater in the storage tank is tested for toxicity using a biochemical test method at regular intervals, and toxic wastewater is rendered harmless, free and/or fixed ammonia is removed, and activated sludge treatment is performed. . (3) When the ammonia removal equipment and/or auxiliary equipment is stopped for repair or periodic inspection, the aforementioned wastewater is
After adjusting the pH to 7.0 to 8.0 with sulfuric acid at a temperature of 90°C, pretreatment by aeration treatment is performed. (4) When performing activated sludge treatment on the wastewater in (2) or (3), the wastewater in (2) or (3) must be treated with fresh water and or Adjust the pH of the wastewater before diluting it 2 to 6 times with seawater. (5) In order to maintain the conditions of the aeration tank for activated sludge treatment in an optimal environment for activated sludge (bacteria), the COD load flowing into the aeration tank, PH,
Manage and control ORP. Next, the grounds and reasons for setting conditions regarding the main points of the present invention will be explained in detail. First, the reason why the tanks (5 to 8 in FIG. 1) were installed and the capacity was set for each waste water will be explained. The reason why tanks are installed for each type of wastewater is that the types of components harmful to activated sludge differ depending on the type of wastewater. The main harmful components of each wastewater are cyanide compounds, sulfides, etc. in gas wastewater from coke plants, sulfides, etc. in wastewater from coke oven gas purification equipment, and sulfides, etc. in wastewater from chemical plants. Corrosion inhibitors for equipment, biofouling inhibitors, algaecides, etc. used to prevent clogging of cooling pipes, and condensed water from various fuel gases contain cyanide compounds, sulfides, etc. It is. Furthermore, the types and concentrations of these harmful components vary considerably depending on factors such as factory operations. For this reason, when wastewater from different sources is stored in the same tank and subjected to detoxification treatment as described below, the detoxification treatment equipment becomes large due to the large number of types of harmful components and the amount of wastewater. Furthermore, the treatment process becomes complicated, and harmful components may not be sufficiently removed.
Therefore, we test each storage tank for toxicity, and only if toxicity is found, we use a shared detoxification equipment 1.
0 and performs detoxification treatment, the treatment equipment becomes smaller, the treatment process becomes simpler, and harmful components can be sufficiently removed. For this reason, it is advantageous to install a storage tank for each wastewater. Next, the capacity of the storage tank will be explained. Coke plants, chemical plants, coke oven gas purification equipment, etc. undergo periodic repairs, changes to operating conditions, or major repairs to equipment about once every seven to 10 days. Therefore, due to these repairs and changes in operating conditions, the amount of wastewater discharged from these factories and equipment, the concentration of harmful components, etc. change. For this reason, if the wastewater tank capacity is not sufficient, when wastewater with a high concentration of harmful components is discharged, the effects of the harmful components will immediately appear in activated sludge treatment.
The decomposition of COD, phenol, thiocyanate, etc. becomes poor, and non-filamentous bulking of activated sludge occurs, significantly deteriorating the quality of treated water. On the other hand, installing a large-capacity wastewater tank homogenizes harmful components and significantly reduces the impact on activated sludge treatment, but equipment costs are not efficient. For this reason, the effect of harmful components of wastewater on activated sludge treatment is small, and the most efficient capacity is the one that occurs every 7 to 10 days, taking into account the frequency of periodic repairs to factories and equipment, changes in operating conditions, etc. It is best to install a tank that can store wastewater. Next, the aforementioned biochemical toxicity diagnosis method for wastewater will be described in detail. First, the gas waste generated from coke factories contains substances such as cyanide and sulfides that are harmful to activated sludge (hereinafter referred to as bacteria), but the quantitative changes in these toxic substances are small, and Because it is diluted 2 to 6 times for sludge treatment, its toxicity is considerably reduced. However, wastewater from chemical plants, coke oven gas purification equipment, and condensed water from various fuel gases contain harmful substances such as sulfides and cyanide, but these wastewaters differ from the gas wastewater mentioned above. There is considerable variation in the concentration of harmful components, and when wastewater with a high concentration of harmful substances is mixed with gas wastewater and supplied to activated sludge treatment equipment after passing through ammonia removal equipment, the function of bacteria is inhibited and phenols, thiocyanine, The decomposability of COD and other substances decreases significantly, leading to deterioration of the quality of treated water, and the activated sludge becomes bulky, causing sludge to float to the surface and flow out, further deteriorating the quality of treated water. In order to prevent malfunctions in activated sludge treatment due to the inflow of such highly toxic wastewater into activated sludge treatment equipment, the present inventors tested the toxicity of the aforementioned wastewater at regular intervals using a biochemical method. We used the following method. This method collects the wastewater at regular intervals, adds a certain amount of activated sludge from the aeration tank of the activated sludge treatment equipment to the collected wastewater, and blows in enough air to make the dissolved oxygen in the mixture 6 ppm or more. . These were placed in a sealed container and stirred at a constant temperature of 30°C to measure the decrease in dissolved oxygen concentration.
Determine the toxicity of wastewater based on the consumption rate of dissolved oxygen. The method for determining the toxicity of wastewater will be explained with reference to a typical oxygen consumption rate graph shown in FIG. First, the graph (b in Figure 2) of the oxygen consumption rate of non-toxic wastewater is used as a reference. For example, the oxygen consumption rate of wastewater containing toxic substances such as cyanide slows down as shown in FIG. 2a because the toxic substances such as cyanide inhibit the respiratory function of bacteria. In addition, in the case of wastewater containing reducing toxic substances such as sulfides, the reducing toxic substances consume oxygen, so dissolved oxygen rapidly decreases as shown in Figure 2 c, but then The rate of oxygen decline becomes slower. This is because the functions of bacteria are inhibited by toxic substances such as sulfides. In this way, the toxicity of each type of wastewater is measured automatically or manually, and non-toxic wastewater is directly transferred to the homogenization tank (11 in Figure 1), while highly toxic wastewater is transferred to the detoxification treatment facility (No. 1 in Figure 1). After being sent to 10) in the figure, where it is rendered harmless, it is sent to the homogenization tank (11 in Figure 1). The toxicity of these wastewaters may be measured once every 4 to 8 hours. In addition, when sending wastewater directly from each tank to the homogenization tank 11 or after detoxification treatment, it is possible to balance the amount of wastewater generated and the amount of treatment by sending the wastewater through different routes in the ratio of the amount of wastewater generated. preferable. In addition, in conventional biochemical methods for evaluating the toxicity of wastewater, pressure detection methods, such as Warburg manometers and coulometers, are often used. The measurement mechanism of these manometers is to absorb carbon dioxide gas, which is generated when inoculated bacteria (activated sludge) decomposes organic pollutants in wastewater, into an alkaline aqueous solution or soda lime, and reduce the pressure inside the measuring container at this time. The degree of decomposition of organic pollutants in wastewater, toxicity, and the activity of activated sludge are evaluated by converting the degree of oxygen consumption into the amount of oxygen consumed by the inoculated bacteria. These pressure detection methods involve many problems. For example, if the wastewater contains volatile sulfides, cyanide compounds, and other substances that are easily absorbed by alkaline aqueous solutions and soda lime, these will be absorbed by the alkali aqueous solution and soda lime, and the pressure inside the measuring container will be reduced. It behaves as if organic pollutants in wastewater are being decomposed. For this reason, conventional pressure detection methods are used to evaluate the toxicity of wastewater containing volatile sulfides, cyanides, and other compounds that are easily absorbed by alkaline aqueous solutions and soda lime, such as gas wastewater and wastewater discharged from coke factory related equipment. cannot be measured. Therefore, the conventional pressure detection method is inappropriate for evaluating the toxicity of wastewater containing volatile sulfides, cyanide compounds, and other compounds that are easily absorbed by alkaline aqueous solutions and soda lime. Application is optimal. Next, a method for detoxifying toxic wastewater will be explained. In the case of toxic wastewater containing cyanide, there are two ways to detoxify cyanide: adding iron salts to form a complex salt of cyanide and iron, and oxidative decomposition using ozone, hypochlorite, etc. As a method that does not have an adverse effect on sludge, the most suitable method is to form an iron-cyanide complex salt. Furthermore, in the case of toxic wastewater containing sulfides, the optimal method is to add water-soluble iron salts and calcium salts to the wastewater, either alone or in combination, to make them insoluble iron sulfides and calcium sulfides and render them harmless. In the case of wastewater in which cyanide and sulfide coexist, the optimal method is to add iron salt to render cyanide harmless by converting cyanide into a cyanide-iron complex salt and converting sulfide into iron sulfide. As mentioned above, if the toxicity of various wastewaters treated by the activated sludge method is measured by the biochemical method described above, and the toxic wastewater is treated to be harmless, then the activated sludge treatment is performed. Such malfunctions in activated sludge treatment do not occur, and the treatment can be carried out smoothly. Next, a method for treating a mixture of gas waste liquid and various wastewaters when the ammonia removal equipment is stopped, which is another feature of the present invention, will be explained. Mixed wastewater (hereinafter referred to as mixed wastewater) consisting of gas wastewater, wastewater from coke oven gas purification equipment, chemical plants, etc., and condensed water of various fuel gases, etc., is removed by ammonia removal equipment (12 in Figure 1) by distillation. The usual method is to remove free and/or fixed ammonia using an activated sludge method. Ammonia removal equipment using this distillation method may be shut down for about 10 to 30 days a year due to regular repairs and inspections of boilers, distillation equipment, etc. At this time, mixed wastewater with high ammonia concentration and pH is supplied to the activated sludge treatment facility. For this reason, the pH of the aeration tank for activated sludge treatment may become abnormally high, leading to malfunctions in activated sludge treatment. In this case, in order to prevent the PH from becoming abnormally high, a method is to neutralize the mixed wastewater with high ammonia concentration and PH with sulfuric acid and hydrochloric acid at the inlet of the aeration tank to prevent the PH from becoming high in the aeration tank. However, this method cannot completely prevent malfunctions in the activated sludge treatment of this mixed wastewater. The present inventors have invented a method for completely preventing malfunctions in activated sludge treatment when ammonia removal equipment is stopped. This method is applied to mixed wastewater with high ammonia concentration and pH from the homogenization tank (11 in Figure 1).
Sulfuric acid was added at a temperature of 90℃ to adjust the pH to 7.0 to 8.0, and then the pH-adjusted wastewater was transferred to an aeration tank (1 in Figure 1).
4), where air is blown in at least 1/2 of the amount of mixed wastewater for treatment. If hydrochloric acid is used to adjust the pH, ammonium chloride fumes will be generated during air aeration, which will deteriorate the surrounding environment, so sulfuric acid is best. Even if the mixed wastewater that has been subjected to pH adjustment and air aeration is treated by the activated sludge method, there will be no inconsistency in the activated sludge treatment. In this method the PH
The reason why the treatment is carried out at a temperature of 7.0 to 8.0 degrees and a temperature of 40 to 90 degrees is based on the experience that has been found that only within these ranges will the treated wastewater be treated with activated sludge without causing any problems. The exhaust gas generated from the aeration tank is sent to an exhaust treatment facility (15 in Figure 1) for treatment. Next, the PH adjustment equipment at the inlet of the aeration tank for activated sludge treatment (16 in Figure 1) and the oxidation-reduction potential (hereinafter referred to as ORP) of the aeration tank for activated sludge treatment (20 in Figure 1)
and PH management. The mixed wastewater mentioned above contains thiosulfate ions, sulfite ions, sulfide ions, etc. in fairly high concentrations. These reducible sulfur compounds are oxidized by activated sludge treatment to partially produce sulfuric acid. As a result, the pH of the aeration tank for activated sludge treatment drops abnormally, and the decomposition of phenol, thiocyanide, COD, etc. drops significantly, and tree-like filamentous fungi occur in the activated sludge in the aeration tank. bulking occurs, and the quality of treated water deteriorates significantly due to sludge flow. In order to prevent such problems, the best method is to maintain the pH of the aeration tank at 7.0±0.5, and a method of adjusting the pH of the mixed wastewater that flows into the aeration tank before diluting it with seawater and/or fresh water. is good. That is, a PH sensor is installed in the aeration tank, and acid or alkali is added to the mixed wastewater depending on the PH change in the aeration tank. In addition, when adding acid or alkali directly to the aeration tank, if high concentration is added, the aeration tank has a very large capacity of 1000 to 5000 ^m3 , so the PH may locally increase.
may become abnormal and have an adverse effect on activated sludge, and the method of adding low-concentration acids and alkalis is unsuitable because the tanks for these agents become large. Therefore, the method of controlling PH by adding highly concentrated acids and alkalis to mixed wastewater takes time to adjust the PH in the aeration tank, but it does not cause the problems mentioned above and makes activated sludge treatment smoother. can be done. Next, the aeration tank of the activated sludge treatment equipment (2 in Figure 1)
0) management will be explained. The aeration tank is managed by measuring the pH, concentration of dissolved oxygen, activated sludge, nitrite nitrogen, etc., and the settling ability of activated sludge. In addition, activated sludge treated water
Concentrations of PH, COD, phenol, thiocyanate, ammonia and nitrite nitrogen, suspended solids, etc. are measured and controlled. In addition to this, the amount of pollutants flowing into the aeration tank, such as the amount of COD load, is also an important management item. Even if activated sludge treatment of gas waste liquid is managed using these methods, activated sludge may malfunction and the quality of treated water may deteriorate. In the case of activated sludge treatment of gas waste liquid, the above control items alone are not sufficient;
Some appropriate control items are required. As a result of research on this point, the present inventors have found that in addition to the above management items, the aeration amount and the amount of inflowing sludge are managed using the ORP of the aeration tank as an index, and the above-mentioned biochemical measurement method of mixed wastewater is used. Toxic wastewater detoxification treatment method, PH
Adjustment - If activated sludge treatment of gas waste liquid is performed in comprehensive combination with aeration method and PH management control method of aeration tank, treatment can be carried out more stably than conventional methods, and treated water with low COD can be produced. can get. We will explain why stable treatment can be achieved by controlling the amount of aeration and the amount of inflowing pollutants using ORP as an indicator. The aforementioned mixed wastewater contains reducing substances such as sulfides, thiosulfate compounds, and sulfite compounds. When these wastewaters are supplied to activated sludge treatment equipment, the oxidizing power of the aeration tank weakens, reducing the decomposition of COD components such as phenol and thiocyanine, leading to a deterioration in the quality of treated water. However, by installing an ORP sensor in the aeration tank and measuring the oxidizing power of the aeration tank, ORP
If the oxidizing power decreases below the set value, that is, the oxidizing power weakens, the amount of aeration is increased or the amount of inflowing pollutants is reduced to restore ORP to the set value. On the other hand, if the ORP becomes higher than the set value, the amount of aeration is reduced or the amount of inflowing pollutants is increased to return the ORP to the set value. like this
When ORP is managed, the decomposition of COD components such as phenol and thiocyanine in the mixed wastewater is significantly improved, and the production of nitrite nitrogen due to ammonia oxidation is eliminated, so nitrite ions are
Problems such as functional inhibition of COD-decomposing bacteria and floating outflow in the sludge settling tank have been completely eliminated, making it possible to perform stable treatment and obtain high-quality treated water. As explained above, when detoxifying the mixed wastewater from a coke factory using the activated sludge method, in order to perform the activated sludge treatment smoothly, stable treatment cannot be achieved even if only the activated sludge treatment is managed. However, by combining comprehensive technologies such as toxicity testing and detoxification treatment of mixed wastewater, ammonia removal, alternative technology when ammonia removal equipment is stopped, and appropriate management technology for activated sludge treatment, as in the present invention, it is possible to It has become possible to stably detoxify mixed wastewater from coke plants through sludge treatment. Next, examples of the present invention will be described. Wastewater generated from chemical plants (2 in Figure 1), coke oven gas purification equipment (3 in Figure 1), and condensed water of various gases (4 in Figure 1) is transferred to the aeration tank for aerobic activated sludge treatment. The oxygen consumption rate was measured using the activated sludge mixture, and based on the curve in Figure 2, it was determined that harmless wastewater,
Classified into cyanide-based toxic wastewater and sulfide-based toxic wastewater,
These wastewaters are stored in separate tanks. The non-hazardous wastewater is sent to the homogenization tank (11 in Figure 1). On the other hand, hazardous wastewater is sent to a detoxification treatment facility (10 in Figure 1), where it is detoxified and then sent to a homogenization tank (11 in Figure 1). To make hazardous wastewater harmless, cyanide wastewater was treated using the navy blue method, and sulfide wastewater was treated using the iron sulfide precipitation method. That is, cyanide-based wastewater was treated by adding a large excess of ferrous sulfate salt (Fe/CN molar ratio 5 to 8 times) to cyanide ions, adjusting the pH to 6 to 7 with calcium hydroxide, and performing air aeration. After that, the free cyanide ions in the treated water are reduced to 5ppm or less.
Water is sent to the homogenization tank 11 (11 in FIG. 1).
In addition, sulfide-based wastewater is adjusted to pH 7±0.5 by adding ferric chloride and using an alkaline agent such as calcium hydroxide or an acid such as sulfuric acid. The appropriate amount of ferric chloride to be added is approximately 1.5 times (molar ratio) to the sulfide ion (S″). When iron chloride is added to sulfide-based wastewater, iron sulfide precipitates are formed, but In particular, without separating this precipitate, the homogenization tank (first
Water is sent to 11) in the figure. The various wastewaters in the homogenization tank are sent to the steam blow distillation type ammonia removal equipment (12 in Figure 1), which removes 80 to 95% or more of free ammonia, and then sent to the PH adjustment equipment (16 in Figure 1). Adjust the pH of the wastewater using the pH adjustment equipment so that the pH of the aeration tank (20 in Figure 1) of the activated sludge treatment equipment can be maintained at 7.0±0.2. This pH-adjusted wastewater is mixed in a uniform mixing tank (Fig.
8), where it is treated with seawater and/or fresh water.
The wastewater is diluted 6 times and sent to the adjustment tank (Figure 1-19), where the wastewater is supplied to the activated sludge treatment equipment so that the COD load is 1.5±0.25Kg/MLSS・Kg・day. In activated sludge treatment equipment, the redox potential is 200~
Aerate to 250mV (gold-silver/silver chloride composite electrode). In addition, the pH of the aeration tank is 7.0±0.2
The temperature was controlled at 30℃. By performing this type of activated sludge treatment,
Compared to activated sludge treatment using conventional management methods, the treated water quality and sludge properties were significantly superior, as shown in Table 1, and there were almost no problems with activated sludge treatment.

【table】

[Table] Additionally, ammonia removal equipment that uses steam injection must be shut down at least once a year for periodic inspections of boilers, etc. In such cases, with conventional methods, wastewater that is highly toxic to activated sludge is treated directly with activated sludge, which impedes the function of activated sludge, causing activated sludge to malfunction and requiring a long period of time to recover. It takes. When the ammonia removal equipment is stopped due to periodic inspection, the wastewater is quantitatively sent from the homogenization tank 11 to the PH adjustment equipment (13 in Figure 1), where the temperature is 70.
℃, and adjusted the pH to 7.5 by injecting and mixing 5 kg of concentrated sulfuric acid per 1 m ³ of waste water. This pH-adjusted wastewater was sent to an aeration treatment facility (14 in Figure 1), where 3 to 5 times the amount of air was continuously blown into the wastewater.
The wastewater treated in this way is sent to the PH adjustment equipment (16 in Figure 1), and the PH is adjusted so that the PH of the aeration tank can be maintained at 7.0 ± 0.2. Activated sludge treatment was performed.
As a result, as shown in Table 2, the method of the present invention:
Compared to conventional methods, the treatment performance in terms of the quality of treated water and the properties of activated sludge was significantly superior, and when the method of the present invention was used, almost no problems occurred. In addition, with the conventional method, malfunctions tend to occur when the ammonia removal equipment is stopped due to regular repairs, etc., and it takes a long time to recover.

【table】

[Table] In addition, the exhaust gas generated from the aeration treatment equipment (14 in Figure 1) is washed with a sulfuric acid aqueous solution and a caustic soda aqueous solution in the exhaust treatment equipment (15 in Figure 1), and then washed with water. Furthermore, the waste heat of the coke oven is used to perform combustion, and after completely detoxifying the waste, it is discharged together with the exhaust gas of the coke oven. As described above, the method of the present invention is extremely superior to conventional methods, and has made it possible to stably perform wastewater treatment using activated sludge on an industrial scale over a long period of time.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a process in which mixed wastewater from a coke factory is rendered harmless by an activated sludge method according to the method of the present invention. FIG. 2 illustrates the relationship between toxicity and the consumption rate of dissolved oxygen when wastewater from a coke factory was subjected to a toxicity test by a biochemical method according to the method of the present invention. 1...Coke factory, 2...Chemical plant, 3...Coke oven gas purification equipment, 4...Fuel gas condensed water collection equipment, 5...Gas waste liquid storage tank, 6...Chemical plant wastewater storage tank, 7...Coke Storage tank for wastewater generated by furnace gas purification equipment, 8...Storage tank for gas condensed water, 9...Toxicity test facility for wastewater using a biochemical method, 10...Detoxification treatment equipment for wastewater, 11...Homogenization tank for wastewater, 12 ...Ammonia removal equipment, 1
3... PH adjustment equipment, 14... Aeration treatment equipment, 15... Exhaust treatment equipment, 16... PH adjustment equipment, 17... Seawater and/or fresh water, 18... Uniform mixing tank (dilution tank), 19...
Adjustment tank, 20...Aeration tank of activated sludge treatment equipment, 21
...Sludge settling tank, 22...Return sludge, 23...Treated water.

Claims (1)

[Claims] 1. When various types of wastewater generated from equipment related to a coke factory are mixed and treated by the aerobic activated sludge method, wastewater from different generation routes is temporarily stored in an amount equivalent to 7 to 10 days. A biochemical toxicity test is conducted using the dissolved oxygen concentration consumption rate measurement method using activated sludge seeded on each temporarily stored wastewater, and if no toxicity is found in the toxicity test. If the wastewater is found to be toxic, the wastewater is taken out and treated to detoxify the activated sludge, and then each wastewater is mixed homogeneously in the same tank based on the generation ratio. After removing free ammonia and/or fixed ammonia in the mixed wastewater using conventional methods, or pre-treating the wastewater by aeration while heating it, the pH of the wastewater is adjusted and diluted with seawater and/or fresh water. An aerobic activated sludge treatment method for wastewater generated from coke factory-related equipment, which is characterized in that aerobic activated sludge treatment is performed on wastewater generated from equipment related to a coke factory. 2. The method according to claim 1, wherein wastewater that is found to be toxic to activated sludge is treated to be detoxified by adding iron salts and/or calcium salts. 3. The method according to claim 1, wherein activated sludge treatment is performed after preliminary treatment by aeration with wastewater temperature adjusted to 40 to 95°C and pH to 7.0 to 8.0. 4. The method according to claim 1, in which aerobic activated sludge treatment is performed while controlling the pH and redox potential in the aeration tank.