Device and method for synergistically treating alkaline calcium-containing wastewater and sludge by anaerobic digestion

Abstract

The present invention discloses a device and a method for the coordinated treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion. The device includes an anaerobic digestion tank, an absorption tower, and a compressor. A first pipeline is connected between the top of the anaerobic digestion tank and the bottom of the absorption tower. A second pipeline is connected between the top of the absorption tower and the bottom of the anaerobic digestion tank. The compressor is arranged on the second pipeline. A storage tank for storing alkaline calcium-containing wastewater is also connected to the top of the absorption tower. The device for the coordinated treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion according to the present invention can coordinately treat the two according to the characteristics of high pH and high calcium of the alkaline calcium-containing wastewater and the property of high CO2 content in biogas, solves the problems existing in the subsequent MBR treatment of the alkaline calcium-containing wastewater, and improves the quality of biogas production and the efficiency of anaerobic digestion treatment. It has the advantages of high system integration, simple principle, strong popularization, high use value, and good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage and sludge treatment, and relates to a device and method for the collaborative treatment of sewage and sludge anaerobic digestion. Background Art

[0002] The comprehensive collaborative and green low-carbon treatment of urban waste such as sludge, sewage, and garbage has become an industry development trend. As an important way of sludge disposal, sludge co-incineration can improve the sludge dewatering efficiency, reduce the moisture content, and remove corrosive substances such as iron and chlorine elements, so that it meets the requirements for incineration with garbage for power generation. Among them, the sludge alkaline hydrolysis dewatering technology has the advantages of good dewatering effect, low moisture content of the sludge cake, and no iron and chlorine. However, the pH of the sludge press filtrate produced is extremely high (pH 12 - 13), the calcium content is high, and the nitrogen concentration is high. If the sludge press filtrate is directly subjected to MBR biochemical treatment, there will be problems of biochemical performance inhibition and fouling and blockage on the membrane surface. If acid neutralization treatment is used, there are defects such as large acid consumption, high cost, and high chloride ion content; if processes such as ammonia stripping and membrane filtration are used, there are problems of poor environmental protection, difficult treatment of by-products, large investment and operation costs, and low treatment efficiency. In addition, in the comprehensive solid waste treatment park, a large amount of biogas will be generated during the anaerobic digestion of sludge, landfill leachate, and kitchen wastewater. The biogas produced has problems of low methane concentration (CH4 50 - 60%, CO2 25 - 35%) and high sulfur content (H2S 1000 - 10000 ppm). On the one hand, it affects the calorific value efficiency of the biogas utilization facilities, and on the other hand, it increases the pretreatment cost of biogas desulfurization, etc. At the same time, the high concentration of hydrogen sulfide reduces the activity of methanogenic bacteria, thus affecting the anaerobic digestion treatment efficiency. Therefore, how to overcome the above problems is of great significance for promoting the effective disposal of alkaline calcium-containing wastewater and realizing the effective utilization of anaerobic digestion biogas.

[0003] So far, no device and method for the collaborative treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion have been seen. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a device and method for the collaborative treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is:

[0006] An apparatus for the co-treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion, comprising an anaerobic digestion tank, an absorption tower and a compressor; a first pipeline is connected between the top of the anaerobic digestion tank and the bottom of the absorption tower for introducing the biogas generated in the anaerobic digestion tank into the absorption tower; a second pipeline is connected between the top of the absorption tower and the bottom of the anaerobic digestion tank, and the compressor is arranged on the second pipeline for introducing the purified biogas in the absorption tower into the anaerobic digestion tank; a storage tank for storing alkaline calcium-containing wastewater is also connected to the top of the absorption tower.

[0007] For the above-mentioned apparatus, further improved, the height-diameter ratio of the absorption tower is 5-10:1; a spray head for spraying alkaline calcium-containing wastewater is provided at the top of the absorption tower; the spray head is connected to the storage tank for storing alkaline calcium-containing wastewater through a third pipeline.

[0008] For the above-mentioned apparatus, further improved, a filter is provided on the second pipeline between the absorption tower and the compressor; the second pipeline extends into the interior of the anaerobic digestion tank and is arranged at equal intervals in the form of multiple branch pipes.

[0009] For the above-mentioned apparatus, further improved, it further comprises: a sludge filter press for filtering the digested sludge in the anaerobic digestion tank; a fourth pipeline is connected between the sludge filter press and the storage tank for collecting the alkaline filtrate in the sludge filter press.

[0010] For the above-mentioned apparatus, further improved, it further comprises a sedimentator and an MBR tank connected in sequence to the water outlet of the absorption tower; the water outlet of the absorption tower is of a "U" shape; the sedimentator is an inclined tube sedimentator.

[0011] As a general technical concept, the present invention also provides a method for the co-treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion, which is processed by using the above-mentioned apparatus.

[0012] For the above-mentioned method, further improved, it comprises the following steps:

[0013] S1. Circulate the biogas generated in the sludge anaerobic digestion tank into the absorption tower to purify the alkaline calcium-containing wastewater.

[0014] For the above-mentioned method, further improved, the gas-liquid ratio in the absorption tower is controlled to be 5-10:1 during the purification process; the residence time of the alkaline calcium-containing wastewater in the absorption tower is 30 min - 60 min; after the purification process is completed, it further comprises: sequentially introducing the purified wastewater into the sedimentator and the MBR tank.

[0015] For the above-mentioned method, further improved, it further comprises the following treatment:

[0016] S2. Feed the digested sludge generated in the anaerobic digester into a filter press for pressure filtration to obtain filtrate under pressure.

[0017] S3. Feed the filtrate under pressure into an absorption tower for purification treatment together with the alkaline calcium-containing wastewater.

[0018] In the above method, further improved, the solid content in the anaerobic digester during operation is 5% - 10%; the quality of the filtrate under pressure is that the pH is 12 - 13, the total hardness in terms of CaCO3 is 2000 mg / L - 4000 mg / L, the ammonia nitrogen is 1500 mg / L - 2500 mg / L, and the total alkalinity in terms of CaCO3 is 6000 mg / L - 10000 mg / L.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] (1) The present invention provides a device for the collaborative treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion. The biogas generated in the anaerobic digester is fed into the absorption tower for collaborative treatment with the alkaline calcium-containing wastewater in the comprehensive solid waste treatment park. By using the components such as CO 2、 H2S in the biogas to carry out gas-liquid reactions with the alkalinity, calcium ions, and calcium hydroxide substances in the alkaline calcium-containing wastewater, the pH and hardness of the alkaline calcium-containing wastewater are reduced. At the same time, the CO2 and H2S contents in the biogas are effectively reduced, ultimately achieving the purpose of improving the biodegradability of the wastewater, reducing membrane fouling and blockage, and improving the quality and treatment efficiency of the biogas produced by anaerobic digestion. The device for the collaborative treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion according to the present invention can combine the characteristics of high pH and high calcium of the alkaline calcium-containing wastewater with the property of high CO2 content in the biogas for collaborative treatment, solve the problems existing in the subsequent MBR treatment of the alkaline calcium-containing wastewater, and improve the quality of the biogas produced and the anaerobic digestion treatment efficiency. It has the advantages of high system integration, simple principle, strong popularization, high use value, and good application prospect.

[0021] (2) The present invention provides a method for the collaborative treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion. By using the device of the present invention to carry out collaborative treatment on the alkaline calcium-containing wastewater and biogas, not only can the biogas be effectively purified and the quality of the biogas be improved, but also when the biogas is used for heat energy utilization, the calorific value efficiency is increased and carbon emissions are reduced. Moreover, by reducing the hydrogen sulfide content in the digester, the inhibitory effect of hydrogen sulfide on methanogens is reduced, and to a certain extent, the biogas production rate and treatment efficiency are increased. At the same time, the pH and hardness of the alkaline calcium-containing wastewater can be effectively reduced, enabling it to better meet the subsequent treatment, such as improving the biodegradability and membrane fouling and blockage problems. The method of the present invention does not require adding chemical agents to adjust the pH, remove hardness, and desulfurize the biogas, can significantly reduce the overall operation cost, has good environmental protection, no by-products, high treatment efficiency, and can achieve treating waste with waste, and can achieve the effects of collaborative carbon reduction, pollution reduction, and efficiency increase. Brief Description of the Drawings

[0022] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0023] Figure 1 It is a schematic diagram of the device for the collaborative treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion of the present invention.

[0024] Legend Explanation:

[0025] 1. Anaerobic digestion tank; 2. Sludge filter press; 3. Storage tank; 4. Absorption tower; 5. Compressor; 6. Settler; 7. MBR tank; Q1: Recirculating biogas; Q2: Pretreatment recirculating biogas; Q3: Produced biogas; L1: Alkaline filtrate; L2: Pretreatment filtrate; S1: Digested sludge; S2: Dry mud cake. Detailed Embodiments

[0026] The present invention will be further described below with reference to the accompanying drawings of the specification and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0027] In the following embodiments, unless otherwise specified, the materials and instruments used are commercially available. The processes used are conventional processes, the equipment used is conventional equipment, and the data obtained are the averages of more than three repeated experiments.

[0028] Embodiment 1

[0029] As Figure 1 shown, the device for the collaborative treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion of the present invention includes an anaerobic digestion tank 1, an absorption tower 3 and a compressor 5. A first pipeline is connected between the top of the anaerobic digestion tank 1 and the bottom of the absorption tower 4 for introducing the biogas generated in the anaerobic digestion tank 1 into the absorption tower 4. A second pipeline is connected between the top of the absorption tower 4 and the bottom of the anaerobic digestion tank 1. The compressor 5 is arranged on the second pipeline for introducing the purified biogas in the absorption tower 4 into the anaerobic digestion tank 1. The top of the absorption tower 4 is also connected to a storage tank 3 for storing alkaline calcium-containing wastewater.

[0030] In this embodiment, the height-to-diameter ratio of the absorption tower 4 is 5:1. A spray head for spraying alkaline calcium-containing wastewater is provided at the top of the absorption tower 4, and the spray head is connected to the storage tank 3 for storing alkaline calcium-containing wastewater through a third pipeline.

[0031] In this embodiment, a filter is provided on the second pipeline between the absorption tower 4 and the compressor 5. The filter combines a coarse filter (gravel or packing) and a fine filter (ceramics). At the same time, the second pipeline extends into the interior of the anaerobic digestion tank 1 and is arranged at equal intervals in the form of multiple branch pipes.

[0032] In this embodiment, the device further includes a sludge filter press 2 for filtering the digested sludge in the pressure filtration anaerobic digestion tank 1. A fourth pipeline is connected between the sludge filter press 2 and the storage tank 3 for collecting the alkaline pressure filtrate in the sludge filter press 2.

[0033] In this embodiment, it further includes a sedimentator 6 and an MBR tank 7 that are successively connected to the water outlet of the absorption tower 4. The water outlet of the absorption tower 4 is of a "U" - shaped structure. The sedimentator 6 is an inclined tube sedimentator.

[0034] A method for co - treating alkaline calcium - containing wastewater and sludge anaerobic digestion uses the device in the above - mentioned embodiment for treatment, and includes the following steps:

[0035] (1) After the municipal sludge is treated by the anaerobic digestion tank 1, the digested sludge S1 enters the sludge filter press 2 for squeezing and dewatering. Using lime and flocculant as sludge dewatering conditioners, the produced dry sludge cake S2 enters the waste incineration plant for co - incineration with waste to achieve the terminal disposal of sludge, and the produced pressure filtrate enters the storage tank 3.

[0036] (2) The circulating biogas Q1 in the anaerobic digestion tank 1 enters the lower part of the absorption tower 4 under the action of the pressure in the digestion tank and the suction pressure of the compressor 5. The alkaline pressure filtrate L1 in the storage tank 3 is pumped to the upper part of the absorption tower 4. The alkaline pressure filtrate L1 and the circulating biogas Q1 conduct a reverse contact reaction in the absorption tower. CO2 in the biogas combines with calcium in the alkaline pressure filtrate to form suspended CaCO3 and neutralize the pH in the pressure filtrate, and H2S in the biogas dissolves in the alkaline pressure filtrate. The chemical reaction formulas are as follows:

[0037] CO2 + 2OH- + Ca 2+ →CaCO3 + H2O

[0038] 2H2S + 2OH- + Ca 2+ →Ca(HS)2 + 2H2O

[0039] (3) The pre - treated circulating biogas Q2 at the upper part of the absorption tower 4 returns to the anaerobic digestion tank 1 after being pressurized by the compressor 5 to maintain the complete mixing state of the sludge. The produced biogas Q3 of the anaerobic digestion tank 1 enters the gas - using unit. The pre - treated pressure filtrate L2 at the lower part of the absorption tower 4 enters the sedimentator 6, and the pressure filtrate after sedimentation treatment enters the MBR tank 7.

[0040] In this embodiment, the height - to - diameter ratio of the absorption tower is 5:1, the inlet flow rate of the circulating biogas is 150 Nm 3 / h, and the inlet flow rate of the alkaline pressure filtrate is 30 m 3 / h, the gas-liquid ratio in the absorption tower is 8:1, and the residence time of the pressure filtrate in the absorption tower is 30 min. After detection, the biogas quality at the biogas outlet of the digestion tank is: CH4 67%, CO2 21%, H2S 240 ppm, and the average gas production per unit feed is 153 Nm 3 / t (calculated based on dry solid content). The quality of the pretreated pressure filtrate of the water outlet pipe at the lower part of the absorption tower is detected: pH 9.5, total hardness 210 mg / L, ammonia nitrogen 1760 mg / L, total alkalinity 5600 mg / L. After precipitation by the inclined tube settler, the pressure filtrate enters the MBR system for treatment without adding acid. Both the biochemical system and the membrane system operate stably, and the calcium carbonate precipitate pump pumps the precipitate into the sludge filter press.

[0041] Example 2

[0042] As Figure 1 shown, the device for co-treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion of the present invention includes an anaerobic digestion tank 1, an absorption tower 3, and a compressor 5. A first pipeline is connected between the top of the anaerobic digestion tank 1 and the bottom of the absorption tower 4 for introducing the biogas generated in the anaerobic digestion tank 1 into the absorption tower 4. A second pipeline is connected between the top of the absorption tower 4 and the bottom of the anaerobic digestion tank 1. The compressor 5 is arranged on the second pipeline for introducing the purified biogas in the absorption tower 4 into the anaerobic digestion tank 1. A storage tank 3 for storing alkaline calcium-containing wastewater is also connected to the top of the absorption tower 4.

[0043] In this embodiment, the height-diameter ratio of the absorption tower 4 is 8:1. A spray head for spraying alkaline calcium-containing wastewater is provided at the top of the absorption tower 4, and the spray head is connected to the storage tank 3 for storing alkaline calcium-containing wastewater through a third pipeline.

[0044] In this embodiment, a filter is provided on the second pipeline between the absorption tower 4 and the compressor 5. The filter combines a coarse filter (gravel or packing) and a fine filter (ceramic). At the same time, the second pipeline extends into the interior of the anaerobic digestion tank 1 and is arranged at equal intervals in the form of multiple branch pipes.

[0045] In this embodiment, the device further includes a sludge filter press 2 for filtering the digested sludge in the anaerobic digestion tank 1. A fourth pipeline is connected between the sludge filter press 2 and the storage tank 3 for collecting the alkaline pressure filtrate in the sludge filter press 2.

[0046] In this embodiment, a settler 6 and an MBR tank 7 are sequentially connected to the water outlet of the absorption tower 4. The water outlet of the absorption tower 4 is of a "U" shape. The settler 6 is an inclined tube settler.

[0047] A method for co-treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion uses the device in the above-mentioned embodiment for treatment, including the following steps:

[0048] (1) After the municipal sludge is treated by the anaerobic digestion tank 1, the digested sludge S1 enters the sludge filter press 2 for squeezing and dewatering. Lime and flocculant are used as sludge dewatering conditioners. The produced dry sludge cake S2 enters the waste incineration plant for co-incineration with waste to achieve the terminal disposal of sludge, and the produced filtrate enters the storage tank 3.

[0049] (2) The recycled biogas Q1 in the anaerobic digestion tank 1 enters the lower part of the absorption tower 4 under the action of the pressure in the digestion tank and the suction pressure of the compressor 5. The alkaline filtrate L1 in the storage tank 3 is pumped to the upper part of the absorption tower 4. The alkaline filtrate L1 and the recycled biogas Q1 carry out a reverse contact reaction in the absorption tower. CO2 in the biogas combines with calcium in the alkaline filtrate to form suspended CaCO3 and neutralize the pH in the filtrate. H2S in the biogas dissolves in the alkaline filtrate. The chemical reaction formulas are as follows:

[0050] CO2 + 2OH - + Ca 2+ →CaCO3 + H2O

[0051] 2H2S + 2OH - + Ca 2+ →Ca(HS)2 + 2H2O

[0052] (3) The pre-treated recycled biogas Q2 at the upper part of the absorption tower 4 returns to the anaerobic digestion tank 1 after being pressurized by the compressor 5 to maintain the complete mixing state of the sludge. The produced biogas Q3 of the anaerobic digestion tank 1 enters the gas-using unit. The pre-treated filtrate L2 at the lower part of the absorption tower 4 enters the sedimentation tank 6, and the filtrate after sedimentation treatment enters the MBR tank 7.

[0053] In this embodiment, the height-diameter ratio of the absorption tower is 8:1, the inlet flow rate of the recycled biogas is 250 Nm 3 / h, the inlet flow rate of the alkaline filtrate is 25 m 3 / h, the gas-liquid ratio in the absorption tower is 10:1, and the residence time of the filtrate in the absorption tower is 30 min. After detection, the biogas quality at the biogas outlet of the digestion tank is: CH4 70%, CO2 17%, H2S 180 ppm, and the average gas production per unit feed is 160 Nm 3 / t (calculated based on dry solid content). The water quality detection of the pre-treated filtrate at the outlet pipe at the lower part of the absorption tower: pH 8.2, total hardness 140 mg / L, ammonia nitrogen 1740 mg / L, total alkalinity 5350 mg / L. After sedimentation by the inclined tube sedimentation tank, the filtrate enters the MBR system for treatment without adding acid, and both the biochemical system and the membrane system operate stably. The calcium carbonate precipitate pump pumps it into the sludge filter press.

[0054] Comparative Example 1

[0055] Directly carry out biochemical treatment on the alkaline filtrate L1.

[0056] The results show that the biochemical effect is unstable and has strong inhibition. At the same time, there is a problem of frequent scaling in the membrane tubes. By adding hydrochloric acid to adjust the pH of the pressure filtrate to 9, the hydrochloric acid dosing cost is about 4 yuan per ton of water, and the chloride ion content in the water is high.

[0057] In Comparative Example 1, the operating temperature of the anaerobic digestion tank was 55 °C, the operating solid content was 10%, the biogas pressure in the tank was 18 mbar, and the quality of the biogas (recirculated biogas Q1) at the biogas outlet of the digestion tank was: CH4 61%, CO2 28%, H2S 800 ppm, and the average gas production rate per unit feed was 150 Nm 3 / t (calculated based on dry solid content).

[0058] In Comparative Example 1, the water quality test data of the alkaline pressure filtrate L1 were: pH 12.5, total hardness 2500 mg / L, ammonia nitrogen 1800 mg / L, and total alkalinity 7900 mg / L.

[0059] Based on the above results, it can be seen that the method for co-treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion of the present invention, by using the device of the present invention to co-treat alkaline calcium-containing wastewater and biogas, can not only effectively purify biogas, improve the quality of biogas, improve the calorific value efficiency and reduce carbon emissions when biogas is used for heat energy utilization, but also reduce the inhibitory effect of hydrogen sulfide on methanogens by reducing the hydrogen sulfide content in the digestion tank, improve the biogas production rate and treatment efficiency to a certain extent. At the same time, it can also effectively reduce the pH and hardness of alkaline calcium-containing wastewater, making it better meet subsequent treatment, such as improving biodegradability and membrane fouling problems. The method of the present invention does not require adding chemical agents to adjust pH, remove hardness and desulfurize biogas, can significantly reduce the overall operating cost, has good environmental protection, no by-products, high treatment efficiency, and can achieve waste treatment with waste, and can achieve the effects of collaborative carbon reduction, pollution reduction and efficiency increase.

[0060] The above is only disclosed by the present invention with preferred embodiments, but it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the disclosed methods and technical contents. Therefore, any simple modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. An apparatus for the collaborative treatment of alkaline calcium-containing wastewater and sludge anaerobic digestion, characterized in that It includes an anaerobic digestion tank, an absorption tower and a compressor; a first pipeline is connected between the top of the anaerobic digestion tank and the bottom of the absorption tower for introducing the biogas generated in the anaerobic digestion tank into the absorption tower; a second pipeline is connected between the top of the absorption tower and the bottom of the anaerobic digestion tank, and the compressor is arranged on the second pipeline for introducing the purified biogas in the absorption tower into the anaerobic digestion tank; a storage tank for storing alkaline calcium-containing wastewater is also connected to the top of the absorption tower; a spray head for spraying alkaline calcium-containing wastewater is arranged at the top of the absorption tower; the spray head is connected to the storage tank for storing alkaline calcium-containing wastewater through a third pipeline; the second pipeline extends into the interior of the anaerobic digestion tank and is arranged at equal intervals in the form of multiple branch pipes; it also includes: a sludge filter press for filtering the digested sludge in the anaerobic digestion tank, a sedimentator and an MBR tank connected in sequence to the water outlet of the absorption tower; a fourth pipeline is connected between the sludge filter press and the storage tank for collecting the alkaline filtrate in the sludge filter press.

2. The device according to claim 1, characterized in that, The height-diameter ratio of the absorption tower is 5 to 10:

1.

3. The device according to claim 2, characterized in that, A filter is provided on the second pipeline between the absorption tower and the compressor.

4. The device according to any one of claims 1 to 3, characterized in that The water outlet of the absorption tower is of a U-shaped structure; the sedimentator is an inclined tube sedimentator.

5. A method for co - treating alkaline calcium - containing wastewater and sludge anaerobic digestion, characterized in that, The device described in any one of claims 1 to 4 is used for treatment.

6. The method according to claim 5, characterized in that, It includes the following steps: S1. Circulate the biogas generated in the sludge anaerobic digestion tank into the absorption tower to purify the alkaline calcium-containing wastewater.

7. The method according to claim 6, wherein During the purification process, the gas-liquid ratio in the absorption tower is controlled to be 5 to 10:1; the residence time of the alkaline calcium-containing wastewater in the absorption tower is 30 min to 60 min; after the purification process is completed, it also includes: sequentially introducing the purified wastewater into the sedimentator and the MBR tank.

8. The method according to claim 6 or 7, characterized in that, It also includes the following treatment: S2. Introduce the digested sludge generated in the anaerobic digestion tank into the filter press for filtering to obtain a filtrate. S3. Introduce the filtrate into the absorption tower to carry out purification treatment together with the alkaline calcium-containing wastewater.

9. The method according to claim 8, wherein The solid content in the anaerobic digestion tank during operation is 5% to 10%; the quality of the filtrate is that the pH is 12 - 13, the total hardness in terms of CaCO3 is 2000 mg / L to 4000 mg / L, the ammonia nitrogen is 1500 mg / L to 2500 mg / L, and the total alkalinity in terms of CaCO3 is 6000 mg / L to 10000 mg / L.

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