Preparation method of biological denitrification composite carbon source

Abstract

The invention discloses a preparation method of a biological denitrification composite carbon source, and belongs to the technical field of sewage treatment and composite carbon sources. Aiming at the physiological characteristics of denitrifying microorganisms, the invention provides the preparation method of the biological denitrification composite carbon source, and the obtained carbon source is scientific and reasonable in component type collocation, can participate in a plurality of productivity and metabolism processes of the microorganisms, meets the nutritional requirements of the microorganisms, provides sufficient energy for the denitrification process, and has a good application prospect. The prepared biological denitrification composite carbon source has the advantages of being short in biochemical starting time, beneficial to keeping balance of activated sludge microbial populations after being used for a long time and the like, the COD equivalent can exceed 1250,000 mg / L, B / C is 0.78 or above, and the biological denitrification composite carbon source has higher denitrification efficiency, better biodegradability, lower sludge yield, high cost performance and good market application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment and composite carbon source, and specifically relates to a method for preparing a biological denitrification composite carbon source. Background Art

[0002] Composite carbon source (IDN-N) technology is an innovative environmental protection technology that uses a combination of different carbon sources to control water quality, promote the growth and reproduction of microorganisms in water, and thus reduce the concentration of organic pollutants in water. The core of composite carbon source technology is to meet the nutritional needs of different microorganisms by providing a variety of carbon sources, enhance the diversity and metabolic activities of microbial communities, and improve sewage treatment efficiency. Composite carbon sources are usually composed of a variety of carbon compounds, such as glucose, sodium acetate, ferrous sulfate, etc. The effects of these ingredients vary, and the appropriate types and proportions can be selected according to water quality conditions and treatment requirements.

[0003] The advantages of composite carbon source technology lie in its diversity, efficiency, targeting, rapidity and environmental friendliness. Compared with traditional single-component carbon sources, composite carbon sources are more conducive to the diversity of microorganisms in biochemical systems and have higher system customization. In addition, composite carbon sources can also reduce sludge production, increase COD equivalent, and are easy to operate at low temperatures, making them environmentally friendly. With the improvement of people's environmental awareness and the advancement of sewage treatment technology, the market demand for composite carbon sources as an efficient and economical sewage treatment consumable will further expand.

[0004] At present, most of the composite carbon sources on the market are simply combined with multiple single carbon sources in different ratios. On the one hand, commonly used carbon sources such as glucose, sodium acetate, and short-chain alcohols have different defects such as high cost, high sludge yield, nitrite accumulation, strong corrosiveness, and sludge swelling. On the other hand, although the selected multiple carbon sources are beneficial to the diversity of microorganisms in the biochemical system, based on the cost of sewage treatment, the COD equivalent of the composite carbon sources that can be widely used on the market is between 300,000 and 1 million mg / L, and the B / C is less than 0.55. Its biodegradability is general and it is difficult to further improve the removal effect of TN. In view of this, in order to improve the denitrification efficiency and effluent quality, it is still necessary to develop a better composite carbon source material. Summary of the invention

[0005] In view of the problems raised in the background technology, the purpose of the present invention is to provide a method for preparing a biological denitrification composite carbon source. The composite carbon source prepared by the process of the present invention can achieve a COD equivalent of more than 1.25 million mg / L, a B / C of more than 0.78, and has higher denitrification efficiency, better biodegradability and less sludge production, high cost performance, and good market application prospects.

[0006] The present invention provides a method for preparing a biological denitrification composite carbon source, comprising the following steps: Step 1: Mix crude glycerol with N-methyldiethanolamine, 1,3-propylenediamine and sodium ethoxide, react at 40-60°C for 16-24 hours, then heat to 60-80°C, add sodium ethoxide and continue to react for 4-8 hours, wash the obtained reaction product, and vacuum evaporate the upper liquid to obtain low-carbon polyols; Step 2: Mix the low-carbon polyol obtained in step 1 with refined glycerol and sodium acetate, heat and ultrasonically stir, and finally add a trace amount of auxiliary agent to obtain a biological denitrification composite carbon source.

[0007] Furthermore, the amounts of the raw materials used in step 1 are respectively as follows: 1000 parts of crude glycerol, 100-150 parts of N-methyldiethanolamine, 50-100 parts of 1,3-propylenediamine, and 5-10 parts of sodium ethoxide; wherein the sodium ethoxide is added in two portions, and the mass ratio of the two additions is 1:(2-4), and the glycerol content of the crude glycerol is 80%-90%.

[0008] The main sources of crude glycerol include the hydrolysis, saponification and transesterification of vegetable oils (such as soybean oil or palm oil) and animal oils (such as beef fat). It is a colorless, odorless, non-toxic but sweet viscous liquid. The main components of crude glycerol include glycerol, water, ash, acid radicals, organic matter, etc. If crude glycerol is directly used as a carbon source, the impurities it contains will affect the quality of the carbon source, and even have a large side effect on the biochemical system, which will eventually lead to substandard water quality of the treated water. Purification of crude glycerol into refined glycerol requires pretreatment (filtration, precipitation, centrifugation and other processes), acidification, separation, neutralization, decolorization, distillation, cooling, adsorption and other processes to complete the purification work, which is expensive. Therefore, the method of the present invention directly uses crude glycerol to prepare low-carbon polyols, which not only bypasses the high cost investment of crude glycerol purification, but also significantly improves the COD equivalent and biodegradability of the composite carbon source base material. The preparation of low-carbon polyols is completed by reacting crude glycerol with N-methyldiethanolamine and 1,3-propylenediamine under the action of sodium ethoxide, avoiding the strict technical conditions such as high temperature and hydrogenation required in the traditional process of preparing polyols, and reducing the production and preparation costs. The present invention uses crude glycerol as the main basic chemical raw material, which is low in price and easy to obtain, and provides an effective method for the development of the biological denitrification composite carbon source.

[0009] Furthermore, the stirring rate of the mixing in step 1 is 100-200 rpm, and the same stirring is maintained during the subsequent heating reaction.

[0010] Furthermore, in step 1, the reaction product is washed with deionized water, and the upper layer of liquid is vacuum evaporated at a temperature of 100° C. for 6-8 h.

[0011] Furthermore, the low-carbon polyol in step 1 includes ethylene glycol, propylene glycol, and glycerol.

[0012] Furthermore, the amounts of the raw materials in step 2 are respectively as follows by weight: 500-600 parts of low-carbon polyols, 300-350 parts of refined glycerol, 50-100 parts of sodium acetate, and 1-2 parts of trace auxiliary agents; the trace auxiliary agents are composed of vitamin B2 and water-soluble phosphates.

[0013] Furthermore, the parameters of the heating and ultrasonic stirring are: heating temperature 45-60° C., ultrasonic power 35-40 kW, stirring rate 300-500 rpm, and processing time 20-30 min.

[0014] The present invention further mixes the low-carbon polyol prepared above with an appropriate amount of refined glycerol, sodium acetate and a trace amount of auxiliary agent. Under the conditions of heating and ultrasonic stirring, each carbon source can achieve mutual compatibility and uniform distribution in the liquid system, and has excellent stability. It can not only shorten the adaptation time of microorganisms in the biochemical system and improve the processing efficiency, but also further improve the biodegradability and denitrification efficiency of the obtained composite carbon source.

[0015] Furthermore, during the heating and ultrasonic stirring process, the pH value of the mixed solution needs to be measured in real time, and a pH regulator is added to keep the pH value of the mixed solution between 6 and 8.

[0016] Furthermore, the pH adjuster is acetic acid, oxalic acid, citric acid, sodium hydroxide or baking soda.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The biological denitrification composite carbon source prepared by the process of the present invention has been identified as a non-corrosive, non-volatile, low-temperature non-solidifying colorless liquid, and has the advantages of being able to be added as a stock solution, convenient transportation, storage, and addition management, and no safety hazards. The composite carbon source of the present invention is targeted at the physiological characteristics of denitrifying microorganisms, and the component types are scientifically and reasonably matched. It can participate in multiple energy-generating metabolic processes of microorganisms, meet the nutritional needs of microorganisms, and provide sufficient energy for the denitrification process. The biological denitrification composite carbon source of the present invention has the advantages of short biochemical startup time and long-term use is conducive to maintaining the balance of activated sludge microbial populations. It can ensure the efficient and stable operation of the biochemical treatment system and has good market competitiveness. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0020] Example 1 A method for preparing a biological denitrification composite carbon source, comprising the following steps: 1. Take 1000 parts of crude glycerol (glycerol content 86.2%) by weight, mix and stir evenly with 130 parts of N-methyldiethanolamine, 70 parts of 1,3-propylenediamine and 2 parts of ethanol, heat to 50°C, stir and react at 160 rpm for 20 hours. After the reaction is completed, heat the obtained product to 70°C, add 6 parts of sodium ethoxide, stir and react at 160 rpm for 6 hours, wash the obtained reaction product with deionized water, take the upper layer of liquid and vacuum evaporate at 100°C for 8 hours to obtain low-carbon polyols.

[0021] 2. Take 540 parts of the low-carbon polyol prepared in the above steps by weight, mix with 320 parts of refined glycerol and 120 parts of sodium acetate (50% aqueous solution) and pour into the reactor, electrically heated to 50°C, apply 40 kW ultrasound and stir at 400 rpm for 30 min. During the process, the pH value of the mixed solution needs to be measured in real time and acetic acid or baking soda is added to keep the pH value of the mixed solution between 6 and 8; finally, add 1 part of vitamin B2 and 1 part of sodium dihydrogen phosphate to obtain the biological denitrification composite carbon source.

[0022] Example 2 A method for preparing a biological denitrification composite carbon source, comprising the following steps: 1. Take 1000 parts of crude glycerol (glycerol content 86.2%) by weight, mix and stir evenly with 100 parts of N-methyldiethanolamine, 100 parts of 1,3-propylenediamine and 1 part of ethanol, heat to 60°C, stir and react at 140 rpm for 24 hours. After the reaction is completed, heat the obtained product to 70°C, add 4 parts of sodium ethoxide, stir and react at 140 rpm for 6 hours, wash the obtained reaction product with deionized water, take the upper layer of liquid and vacuum evaporate at 100°C for 7 hours to obtain low-carbon polyols.

[0023] 2. Take 600 parts of the low-carbon polyol prepared in the above steps by weight, mix with 300 parts of refined glycerol and 120 parts of sodium acetate (50% aqueous solution), pour into the reactor, electrically auxiliary heat to 55°C, apply 35 kW ultrasound and stir at a constant temperature of 400 rpm for 30 min. During the process, the pH value of the mixed solution needs to be measured in real time and acetic acid or baking soda is added to keep the pH value of the mixed solution between 6 and 8; finally, add 1 part of vitamin B2 and 0.5 part of sodium dihydrogen phosphate to obtain the biological denitrification composite carbon source.

[0024] Example 3 A method for preparing a biological denitrification composite carbon source, comprising the following steps: 1. Take 1000 parts of crude glycerol (glycerol content 86.2%) by weight, mix and stir evenly with 150 parts of N-methyldiethanolamine, 50 parts of 1,3-propylenediamine and 2 parts of ethanol, heat to 50°C, stir and react at 160 rpm for 16 hours. After the reaction is completed, heat the obtained product to 80°C, add 8 parts of sodium ethoxide, stir and react at 160 rpm for 8 hours, wash the obtained reaction product with deionized water, take the upper layer of liquid and vacuum evaporate at 100°C for 6 hours to obtain low-carbon polyols.

[0025] 2. Take 500 parts of the low-carbon polyol prepared in the above steps by weight, mix with 350 parts of refined glycerol and 120 parts of sodium acetate (50% aqueous solution) and pour into the reactor, electrically auxiliary heat to 50°C, apply 40 kW ultrasound and stir at 400 rpm for 25 min. During the process, the pH value of the mixed solution needs to be measured in real time and acetic acid or baking soda is added to keep the pH value of the mixed solution between 6 and 8; finally, add 1 part of vitamin B2 and 1 part of sodium dihydrogen phosphate to obtain the biological denitrification composite carbon source.

[0026] Comparative Example 1 The parameters of step 2 of Example 1 were referred to, except that refined glycerol was not used, and 860 parts of the low-carbon polyol prepared in step 1 of Example 1 were used as the main raw material to prepare the composite carbon source with sodium acetate.

[0027] Comparative Example 2 Referring to the parameters of step 2 of Example 1, 860 parts of refined glycerol and sodium acetate were directly used to prepare the composite carbon source.

[0028] Comparative Example 3 The parameters of step 2 of Example 1 are referred to, except that no ultrasonic treatment is applied during the preparation of the composite carbon source.

[0029] Test example The carbon sources obtained in the above Examples 1-3 and Comparative Examples 1-3 were subjected to performance testing (GB / T 11914), and the results are shown in Table 1.

[0030] Table 1

[0031] The biological denitrification composite carbon source prepared in Example 1 was used for a factory trial in a sewage treatment plant in Jiangxi Province. The factory trial period was 10 days. The trial results showed that the cumulative water treatment volume during the trial period was 16721 m 3 , the average total nitrogen of the influent of the biochemical pool 1# ditch was 51.43 mg / L, the average total nitrogen of the effluent of the biochemical pool 1# ditch was 10.6 mg / L, and the dosage of the composite carbon source was 1740 kg, which was significantly lower than the average cost per ton of water of the glucose carbon source in the water plant. (Glucose carbon source control group: the average total nitrogen of the influent of the biochemical pool 2# ditch was 48.6 mg / L, and the average total nitrogen of the effluent of the biochemical pool 2# ditch was 15.03 mg / L. It can be concluded that the denitrification efficiency of the composite carbon source of the present invention is significantly higher than that of glucose. Therefore, reasonable control of the dosage of the composite carbon source can reduce the cost per ton of water by more than 25%. During the trial stabilization period, the replacement dosage ratio of the composite carbon source to glucose was 1:3, and the replacement dosage ratio of the composite carbon source to sodium acetate (25%) was 1:10.

[0032] The embodiments described above only express several preferred embodiments of the present invention, and the descriptions thereof are relatively specific and detailed, but are not intended to limit the present invention. It should be noted that for those skilled in the art, the present invention may also have various changes and modifications, and any modifications, equivalent substitutions, improvements, etc. made within the concept and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a biological denitrification composite carbon source, characterized in that: The steps include: Step 1: Mix crude glycerol with N-methyldiethanolamine, 1,3-propylenediamine and sodium ethoxide, react at 40-60°C for 16-24 hours, then heat to 60-80°C, add sodium ethoxide and continue to react for 4-8 hours, wash the obtained reaction product, and vacuum evaporate the upper liquid to obtain low-carbon polyols; Step 2: Mix the low-carbon polyol obtained in step 1 with refined glycerol and sodium acetate, heat and ultrasonically stir, and finally add a trace amount of auxiliary agent to obtain a biological denitrification composite carbon source.

2. The method for preparing a biological denitrification composite carbon source according to claim 1, characterized in that: The amounts of the raw materials used in step 1 are respectively as follows: 1000 parts of crude glycerol, 100-150 parts of N-methyldiethanolamine, 50-100 parts of 1,3-propylenediamine, and 5-10 parts of sodium ethoxide; wherein the sodium ethoxide is added in two portions, and the mass ratio of the two additions is 1:(2-4), and the glycerol content of the crude glycerol is 80%-90%.

3. The method for preparing a biological denitrification composite carbon source according to claim 1, characterized in that: The stirring rate of the mixing in step 1 is 100-200 rpm, and the same stirring is maintained during the subsequent heating reaction.

4. The method for preparing a biological denitrification composite carbon source according to claim 1, characterized in that: In step 1, the reaction product is washed with deionized water, and the upper layer of liquid is vacuum evaporated at a temperature of 100° C. for 6-8 h.

5. The method for preparing a biological denitrification composite carbon source according to claim 1, characterized in that: The low-carbon polyols in step 1 include ethylene glycol, propylene glycol, and glycerol.

6. The method for preparing a biological denitrification composite carbon source according to claim 1, characterized in that: The amounts of the raw materials used in step 2 are respectively as follows by weight: 500-600 parts of low-carbon polyols, 300-350 parts of refined glycerol, 50-100 parts of sodium acetate, and 1-2 parts of trace auxiliary agents; the trace auxiliary agents are composed of vitamin B2 and water-soluble phosphates.

7. The method for preparing a biological denitrification composite carbon source according to claim 1, characterized in that: The parameters of the heating and ultrasonic stirring are: heating temperature 45-60° C., ultrasonic power 35-40 kW, stirring rate 300-500 rpm, and processing time 20-30 min.

8. The method for preparing a biological denitrification composite carbon source according to claim 7, characterized in that: During the heating and ultrasonic stirring process, the pH value of the mixed solution needs to be measured in real time, and a pH regulator is added to keep the pH value of the mixed solution between 6 and 8.

9. The method for preparing a biological denitrification composite carbon source according to claim 8, characterized in that: The pH regulator is acetic acid, oxalic acid, citric acid, sodium hydroxide or baking soda.

Images