Little is known about sludge disposal.

1. What are the disposal methods of sludge?

1. The water content of sludge produced by sludge concentration sewage treatment plant is as high as 99%, so it is necessary to concentrate the sludge before subsequent disposal.

The water content of the concentrated sludge is about 95%. 2. Sludge dehydration and drying The sludge with a moisture content of 95% has a high moisture content, which is not convenient for the later disposal and utilization of sludge.

Therefore, it is necessary to carry out sludge mechanical dehydration or sludge drying treatment. Sludge mechanical dewatering equipment includes stacked spiral dewatering machine and plate-and-frame filter press, which can dewater sludge to 80%-85%.

Sludge drying equipment adopts dehumidification heat pump drying technology and low temperature waste heat drying technology, which can dry sludge to 10%. Sludge drying. Sludge disposal method (1) sanitary landfill This disposal method is simple, easy to operate, low in cost, and the sludge does not need to be highly dehydrated and has strong adaptability.

The gas produced by landfill is mainly methane, which will cause explosion and combustion if proper measures are not taken. (2) Land-use sludge has the advantages of low investment, low energy consumption and low operating cost, and the organic part can be converted into soil improver, which is a promising disposal method.

(3) Incineration of incineration sludge after drying is a common disposal method. It can carbonize all organic matter, kill pathogens and reduce sludge volume to a great extent; However, its disadvantages are large investment in treatment facilities, high treatment cost and high maintenance cost of equipment, which produces strong carcinogen dioxin.

(4) Sludge composting is an important aspect of sludge composting, which is a process of fermentation by using microorganisms in sludge.

2. Sludge treatment method

After treatment and concentration, the water content of sludge can be reduced to 95%~97%, which is similar to paste.

Concentration can reduce sludge. Gravity concentration is a widely used sludge treatment method with a history of more than 50 years.

Mechanical concentration appeared in the United States in the 1930s. This method has the advantages of small floor space and low cost, but the operation cost and mechanical maintenance cost are high. Air flotation concentration appeared in America 1957.

This method has good solid-liquid separation effect and has been widely used. The methods of sludge concentration mainly include gravity concentration, air flotation concentration, belt gravity concentration and centrifugal concentration, as well as microporous concentration, diaphragm concentration and biological flotation concentration.

Natural sedimentation and gravity separation are the most energy-saving sludge concentration methods, and no additional energy is needed. Gravity concentration is only a process of sedimentation and separation, and it is the main method of sludge concentration by forming a high concentration sludge layer in sedimentation.

Independent gravity concentration is completed in an independent gravity concentration tank, and the process is simple and effective, but long residence time may produce odor, which is not suitable for all sludge; If it is applied to the concentration of excess sludge from biological phosphorus removal, a large amount of phosphorus will be released, and its supernatant needs chemical phosphorus removal. Gravity concentration method is suitable for primary sludge, chemical sludge and biofilm sludge.

Sludge treatment: the principle of centrifugal concentration method is to concentrate by using centrifugal force with different solid-liquid specific gravity in sludge. Centrifugal concentration method is characterized by its own system, good effect and simple operation; But the investment is large, the power cost is high, and the maintenance is complicated; Suitable for biological and chemical sludge in large and medium-sized sewage treatment plants.

2) The purpose of sludge treatment and stabilization is to degrade the organic matter in sludge, further reduce the water content of sludge, kill bacteria and pathogens in sludge, and eliminate odor, which is the key step for effective utilization of sludge. Sludge stabilization methods mainly include composting, drying and anaerobic digestion.

Anaerobic digestion: Anaerobic digestion is a commonly used stabilization technology in sludge treatment. Sludge anaerobic digestion is also called anaerobic biological stability of sludge. Its main purpose is to reduce high-energy substances in the form of carbohydrate, protein and fat in raw sludge, that is, to transform high-molecular substances into low-molecular-weight substance oxides through degradation.

Anaerobic digestion is an anaerobic biochemical reaction to decompose organic matter in sludge under anaerobic conditions, which is an extremely complicated process. Aerobic digestion of sludge appeared in 1950s, which is very similar to activated sludge process.

When foreign nutrients are consumed, microorganisms consume their own bodies to generate energy to maintain life activities. This is the endogenous metabolic stage of microorganisms.

Endogenous metabolites of cell tissue are CO2, NH3 and H2O under aerobic conditions, while NH3 will be further oxidized to nitrate under aerobic conditions. The reaction of aerobic digestion of sludge can be expressed by the following equation: C6H7NO2+7O2→5CO2+NO3-+3H2O+H+ In the above equation, C6H7NO2 is the element composition of cell tissue.

The method has the advantages of high degradation degree, odorless stability, easy dehydration, high fertilizer content, simple operation and management, low capital construction cost and the like. However, the operation cost is high, the amount of digested sludge is small, and the degradation degree fluctuates greatly with temperature.

The discussion of composting technology began at 1920. Composting systems can be divided into three categories: strip composting system, static aerobic composting system and equipment composting system. The sludge of urban sewage treatment plant contains a lot of nutrients such as nitrogen, phosphorus and potassium, which can promote the growth of plants and crops and has good fertilizer efficiency. After composting, it can achieve the purpose of stabilization, harmlessness and resource utilization.

Composting is a stable process of aerobic decomposition of organic matter by psychrophilic bacteria and thermophilic bacteria. Its characteristics are that it can generate a certain amount of heat, the high temperature lasts for a long time, and it can be harmless without external heat source. The general technological process of composting is mainly divided into four processes: pretreatment, primary fermentation, secondary fermentation and post-treatment.

After composting, the properties of sludge are improved, the water content is reduced (below 40%), and it becomes loose, dispersed and fine-grained, which can kill pathogenic bacteria and parasites (eggs) and is convenient for storage, transportation and use. Lime stabilization technology Lime stabilization technology began in 1950s. Under the condition of adding lime and keeping a certain pH value for a certain time, infectious bacteria can be killed, and odor can be prevented and suppressed.

This technology is simple in operation, low in cost and easy to dehydrate after treatment. The final disposal of sludge can be agricultural or sanitary landfill.

Ferment sludge into organic fertilizer. If you add some cow dung, it will ferment into high-quality organic fertilizer. The specific operation method is as follows: 1, adding bacteria. 1 kg Gymboree fertilizer starter can ferment about 4 tons of sludge+cow dung.

It is necessary to add about 30-50% organic matter such as cow dung, straw powder, mushroom residue, peanut shell powder, rice husk and sawdust according to the weight ratio in order to adjust ventilation. If rice husk and sawdust are added, the fermentation time should be prolonged because of their high cellulose lignin.

Strain dilution: Add 5- 10 kg of rice bran (or substitutes such as bran and corn flour) to each kg of starter, stir and dilute evenly, and then spread evenly into the pile, the use effect will be better. 2. Stacking: After the materials are prepared, pile them while spreading bacteria. The height and volume of piles should not be too short or too small. Requirements: pile height 1.5-2m, width 2m and length 2-4m. 2. Stir well and ventilate.

Gymboree fertilizer starter needs good oxygen fermentation, appropriately increase oxygen supply measures, stir evenly, frequently turn over and ventilate. Otherwise, it will lead to anaerobic fermentation, produce odor and affect the effect.

4. Moisture. The water content of fermented materials should be controlled at 60~65%.

Moisture judgment: Hold a handful of materials tightly, see a watermark between your fingers, do not drip, and it is appropriate to spread it when landing. Less moisture leads to slow fermentation, and more moisture leads to poor ventilation, which also leads to the work of "spoilage bacteria" and produces odor.

5. temperature. The initial temperature should be above 15℃ (it can be operated in all seasons and is not affected by seasons, so it is suitable for indoor or greenhouse fermentation in winter), and the fermentation temperature should be controlled below 70-75℃.

6. done. From the second day to the third day, when the temperature reaches above 65℃, the boat will capsize. Generally, fermentation can be completed within one week. The substance was dark brown, and the temperature began to drop to normal temperature, indicating that the fermentation was completed.

If there are too many auxiliary materials such as sawdust, sawdust and rice husk, the fermentation time should be extended until it is completely decomposed. Fermented organic fertilizer is effective, safe and convenient to use, resistant to diseases and promoting growth, and can also improve soil fertility.

Dirty.

3. What are the common treatment methods of sewage sludge?

Several common methods of urban sewage treatment-activated sludge treatment method is the so-called activated sludge method, which has the advantages of strong treatment capacity and good water quality after treatment.

Its general composition includes aeration tank, sedimentation tank, sludge discharge and reflux system. Sewage to be treated and activated sludge reflux into the aeration tank to mix, and then contact with the air in it to increase the oxygen content and produce metabolic reaction.

The fully stirred mixed liquid becomes suspended, so the organic pollutants and oxygen in it can react with microorganisms. Next, it enters the sedimentation tank, and the original suspended matter will settle down and be isolated, so the effluent from the sedimentation tank is pure water.

Generally, the sludge in the sedimentation tank will flow back, thus ensuring a certain concentration of suspended solids and microorganisms in the aeration tank. The reaction in the aeration tank will make microorganisms multiply, so excessive microorganisms should be discharged from the sedimentation tank to maintain the stability of the whole system.

In addition to oxidizing and decomposing organic matter, activated sludge must also have a certain coagulation and sedimentation ability, so that it can be separated from the mixed liquid and then pure water can be obtained at the outlet. The disadvantage of activated sludge process is that the capital cost is too high and it is not easy to implement.

Biofilm treatment method The so-called biofilm method is a method to treat organic pollutants in sewage through microorganisms attached to the surface of some solid objects. It is basically consistent with the development time of activated sludge process.

The so-called "biofilm" is the image of microorganisms attached to the solid surface, which is generally an ecosystem composed of very dense aerobic bacteria, anaerobic bacteria, protozoa and algae. The solid medium attached to the biofilm is called carrier or filter material, so the outward biofilm can be divided into anaerobic layer, aerobic layer, adhesion layer and moving water layer.

The basic operation process of the whole method is that the biofilm first absorbs the organic matter in the water layer, then decomposes by aerobic bacteria, and then anaerobically decomposes by anaerobic bacteria, and the moving water layer constantly updates the biofilm through flow, thus repeatedly realizing the purification of sewage. Biofilm method is generally applied to the treatment of sewage in small and medium-sized cities. The treatment structure used is biological filter or biological turntable, and biological filter is generally used in southern China.

Due to the continuous innovation of materials and technology, biofilm technology has made great progress in recent years. Because microorganisms in biofilm process are generally fixed on fillers, the ecosystem is relatively stable, the energy consumed by microorganisms is much smaller than that of activated sludge process, and there is less excess sludge.

Biofilm method has the advantages of high efficiency, strong impact resistance, low sludge output and convenient transportation, which makes it very competitive in various treatment methods. The disadvantages of biofilm process are high cost and low unit treatment efficiency.

Therefore, further reducing cost and improving efficiency are the main directions of biofilm research in the future. Oxidation treatment Oxidation treatment is a widely used pretreatment method of urban sewage, which has great potential.

According to the type of oxidant and reactor, it can be divided into chemical oxidation, catalytic oxidation and photocatalytic oxidation. Among them, the chemical oxidation method is relatively simple to operate, but the effect is not obvious enough, the running cost is high, and it is not widely used in practical work.

In order to improve the treatment effect and reduce the cost, people have found some other oxidation technologies. One of these new methods is photocatalysis.

It is characterized by simple equipment, mild conditions, strong oxidation ability and thorough treatment effect. It is widely welcomed in sewage treatment.

Photocatalytic reaction is a chemical reaction that occurs through the action of light. In the process of reaction, molecules are transformed into excited States by absorbing light waves with specific wavelengths, and then undergo chemical reactions to form new substances, or become intermediate chemical products to promote thermal reactions.

The activation energy required by photochemical reaction comes from light, and the utilization of light energy in solar energy through photoelectric conversion and photochemical conversion is a very hot research field. Photocatalytic oxidation technology combines O2, H2O2 and other oxidants with light radiation through photo-excited oxidation.

The light used is mainly ultraviolet light, including uv-H2O2, uv-O2 and other processes, which can be used to treat refractory substances such as CHCl3, CCl4 and PCBs in sewage. In addition, in the Feton system with ultraviolet light, there is a synergistic effect between ultraviolet light and iron ions, which greatly accelerates the decomposition of H2O2 into hydroxyl radicals and promotes the oxidative removal of organic matter.

The so-called photochemical reaction is a chemical reaction that can only be carried out under the action of light. In this reaction, the light energy absorbed by the molecule is excited to a high energy state, and then the electronically excited molecule carries out a chemical reaction.

The activation energy of photochemical reaction comes from the energy of photons. In the utilization of solar energy, photoelectric conversion and photochemical conversion have always been very active fields in photochemical research.

The application of photochemistry in environmental protection began to be studied in the early 1980s, in which the photochemical degradation of pollution was paid special attention, including photocatalytic degradation without catalyst and catalytic degradation. The former mostly uses ozone and hydrogen peroxide as oxidants to oxidize and decompose pollutants under ultraviolet irradiation; The latter is also called photocatalytic degradation, which can be generally divided into homogeneous and heterogeneous.

Homogeneous photocatalytic degradation mainly takes Fe2+ or Fe3+ and H2O2 as the medium, and degrades pollutants through photo-Fenton reaction, which can directly utilize visible light. Multiphase photocatalytic degradation is to add a certain amount of photosensitive semiconductor materials into the polluted system, and at the same time, combine with light radiation with a certain energy, so that the photosensitive semiconductor is excited to generate electron-hole pairs under the irradiation of light, and dissolved oxygen and water molecules adsorbed on the semiconductor react with the electron-hole to generate radical with strong oxidation, such as OH, and then all or almost all pollutants are mineralized through addition, substitution and electron transfer with hydroxyl groups of pollutants, and finally other ions such as CO2, H2O and NO3- are generated. Compared with photochemical degradation without catalyst, photocatalytic degradation is more active in environmental pollution control.

At present, oxidation treatment has attracted wide attention because of its advantages of low cost and high efficiency. In addition, it also has a good prospect in the advanced treatment of sewage and the treatment of refractory organic wastewater, which has become a research hotspot at home and abroad.

4. Sludge treatment method

After sludge treatment, the water content of sludge can be reduced to 95%~97%, which is similar to paste.

Concentration can reduce sludge. Gravity concentration is a widely used sludge treatment method with a history of more than 50 years.

Mechanical concentration appeared in the United States in the 1930s. This method has the advantages of small floor space and low cost, but the operation cost and mechanical maintenance cost are high. Air flotation concentration appeared in America 1957.

This method has good solid-liquid separation effect and has been widely used. The methods of sludge concentration mainly include gravity concentration, air flotation concentration, belt gravity concentration and centrifugal concentration, as well as microporous concentration, diaphragm concentration and biological flotation concentration.

Natural sedimentation and gravity separation are the most energy-saving sludge concentration methods, and no additional energy is needed. Gravity concentration is only a process of sedimentation and separation, and it is the main method of sludge concentration by forming a high concentration sludge layer in sedimentation.

Independent gravity concentration is completed in an independent gravity concentration tank, and the process is simple and effective, but long residence time may produce odor, which is not suitable for all sludge; If it is applied to the concentration of excess sludge from biological phosphorus removal, a large amount of phosphorus will be released, and its supernatant needs chemical phosphorus removal. Gravity concentration method is suitable for primary sludge, chemical sludge and biofilm sludge.

Sludge treatment: the principle of centrifugal concentration method is to concentrate by using centrifugal force with different solid-liquid specific gravity in sludge. Centrifugal concentration method is characterized by its own system, good effect and simple operation; But the investment is large, the power cost is high, and the maintenance is complicated; Suitable for biological and chemical sludge in large and medium-sized sewage treatment plants.

2) The purpose of sludge treatment and stabilization is to degrade the organic matter in sludge, further reduce the water content of sludge, kill bacteria and pathogens in sludge, and eliminate odor, which is the key step for effective utilization of sludge. Sludge stabilization methods mainly include composting, drying and anaerobic digestion.

Anaerobic digestion: Anaerobic digestion is a commonly used stabilization technology in sludge treatment. Sludge anaerobic digestion is also called anaerobic biological stability of sludge. Its main purpose is to reduce high-energy substances in the form of carbohydrate, protein and fat in raw sludge, that is, to transform high-molecular substances into low-molecular-weight substance oxides through degradation.

Anaerobic digestion is an anaerobic biochemical reaction to decompose organic matter in sludge under anaerobic conditions, which is an extremely complicated process. Aerobic digestion of sludge appeared in 1950s, which is very similar to activated sludge process.

When foreign nutrients are consumed, microorganisms consume their own bodies to generate energy to maintain life activities. This is the endogenous metabolic stage of microorganisms.

Endogenous metabolites of cell tissue are CO2, NH3 and H2O under aerobic conditions, while NH3 will be further oxidized to nitrate under aerobic conditions. The reaction of aerobic digestion of sludge can be expressed by the following equation: C6H7NO2+7O2→5CO2+NO3-+3H2O+H+ In the above equation, C6H7NO2 is the element composition of cell tissue.

The method has the advantages of high degradation degree, odorless stability, easy dehydration, high fertilizer content, simple operation and management, low capital construction cost and the like. However, the operation cost is high, the amount of digested sludge is small, and the degradation degree fluctuates greatly with temperature.

The discussion of composting technology began at 1920. Composting systems can be divided into three categories: strip composting system, static aerobic composting system and equipment composting system. The sludge of urban sewage treatment plant contains a lot of nutrients such as nitrogen, phosphorus and potassium, which can promote the growth of plants and crops and has good fertilizer efficiency. After composting, it can achieve the purpose of stabilization, harmlessness and resource utilization.

Composting is a stable process of aerobic decomposition of organic matter by psychrophilic bacteria and thermophilic bacteria. Its characteristics are that it can generate a certain amount of heat, the high temperature lasts for a long time, and it can be harmless without external heat source. The general technological process of composting is mainly divided into four processes: pretreatment, primary fermentation, secondary fermentation and post-treatment.

After composting, the properties of sludge are improved, the water content is reduced (below 40%), and it becomes loose, dispersed and fine-grained, which can kill pathogenic bacteria and parasites (eggs) and is convenient for storage, transportation and use. Lime stabilization technology Lime stabilization technology began in 1950s. Under the condition of adding lime and keeping a certain pH value for a certain time, infectious bacteria can be killed, and odor can be prevented and suppressed.

This technology is simple in operation, low in cost and easy to dehydrate after treatment. The final disposal of sludge can be agricultural or sanitary landfill.

Ferment sludge into organic fertilizer. If you add some cow dung, it will ferment into high-quality organic fertilizer. The specific operation method is as follows: 1, adding bacteria. 1 kg Gymboree fertilizer starter can ferment about 4 tons of sludge+cow dung.

It is necessary to add about 30-50% organic matter such as cow dung, straw powder, mushroom residue, peanut shell powder, rice husk and sawdust according to the weight ratio in order to adjust ventilation. If rice husk and sawdust are added, the fermentation time should be prolonged because of their high cellulose lignin.

Strain dilution: Add 5- 10 kg of rice bran (or substitutes such as bran and corn flour) to each kg of starter, stir and dilute evenly, and then spread evenly into the pile, the use effect will be better. 2. Stacking: After the materials are prepared, pile them while spreading bacteria. The height and volume of piles should not be too short or too small. Requirements: pile height 1.5-2m, width 2m and length 2-4m. 2. Stir well and ventilate.

Gymboree fertilizer starter needs good oxygen fermentation, appropriately increase oxygen supply measures, stir evenly, frequently turn over and ventilate. Otherwise, it will lead to anaerobic fermentation, produce odor and affect the effect.

4. Moisture. The water content of fermented materials should be controlled at 60~65%.

Moisture judgment: Hold a handful of materials tightly, see a watermark between your fingers, do not drip, and it is appropriate to spread it when landing. Less moisture leads to slow fermentation, and more moisture leads to poor ventilation, which also leads to the work of "spoilage bacteria" and produces odor.

5. temperature. The initial temperature should be above 15℃ (it can be operated in all seasons and is not affected by seasons, so it is suitable for indoor or greenhouse fermentation in winter), and the fermentation temperature should be controlled below 70-75℃.

6. done. From the second day to the third day, when the temperature reaches above 65℃, the boat will capsize. Generally, fermentation can be completed within one week. The substance was dark brown, and the temperature began to drop to normal temperature, indicating that the fermentation was completed.

If there are too many auxiliary materials such as sawdust, sawdust and rice husk, the fermentation time should be extended until it is completely decomposed. Fermented organic fertilizer is effective, safe and convenient to use, resistant to diseases and promoting growth, and can also improve soil fertility.

5. Treatment steps of sludge treatment

Residual activated sludge-sludge concentration tank-sludge digestion-sludge dehydration-sludge disposal

The remaining activated sludge is pumped into the sludge concentration tank for precipitation, and the supernatant is discharged into the reflux pipe for sewage re-treatment.

After concentration, the water content of sludge is from 99. % to 94%. If a sewage treatment plant with a daily capacity of 200,000 tons can consider sludge digestion, the digestive system of a sewage treatment plant with a small daily capacity will be gone.

Sludge is generally dewatered by frame machine, belt filter press or centrifuge. After being treated by dewatering equipment with water content of 94%, the water content of dry mud cake can reach below 80%.

Then it is sent to landfill, sludge composting, incineration and other disposal measures by the sewage treatment plant.

6. The sewage treatment knowledge, to be specific,

Modern wastewater treatment technology can be divided into four categories according to the principle of action: physical method, chemical method, physical and chemical method and biological method.

There are five common biological treatment methods for wastewater: activated sludge method, biofilm method, anaerobic biological digestion method, stabilization pond and wetland treatment. Aerobic treatment: activated sludge process and biofilm process. Anaerobic treatment: various anaerobic digestion methods.

Primary treatment: physical treatment mainly removes suspended solids and oil pollutants in layered or emulsified state in water through various treatment units such as precipitation or air flotation.

Secondary treatment: it is mainly a biological process, which removes dissolved BOD in primary water, further removes suspended solid substances, and in some cases removes a certain amount of nutrients, such as nitrogen and phosphorus.

Tertiary treatment: the treatment methods include chemical treatment and filtration, which mainly remove suspended solids and nutrients.

7. What is the difference between sludge treatment and disposal?

Sludge disposal refers to giving sludge a final destination: either as fertilizer applied to farmland, greening and other soils and becoming a part of the soil; Or use it as a resource to form useful materials, such as paving slag, cement, brick making and so on. Either landfill, no use, waste of land resources, abandon it.

Any process that fails to reach the final placement can be counted as treatment. For example, sludge composting, sterilization and solidification can produce safe fertilizer efficiency; Incineration will eventually produce ash, which accounts for more than 40% of the original dry matter, so landfill or utilization should be considered; Drying is to remove most of the water in the mud cake, save transportation costs, reduce land occupation and pay less landfill costs, and provide conditions for other final disposal schemes to be reduced, hygienic and economical.

8. Sludge treatment and disposal

Regarding the treatment of sludge, we must first analyze the types of sludge.

Generally speaking, sludge from sewage treatment plants has the following treatment processes: dehydration, sludge drying, carbonization, incineration, melting and landfill.

At present, the domestic process only realizes dehydration by physical means. At present, there are various dehydrators on the market, most of which are operated by electric energy. Through dehydration, the water content of municipal sludge can be reduced to about 80%~85%, and if a large number of polymer materials and lime are added for mixing, the water content may be lower.

Drying treatment belongs to a relatively new field. Heat sources such as steam, hot air and flue gas can further evaporate water and reduce the water content of sludge. Generally speaking, the odor of sludge can be greatly reduced to below 40%, and of course it can also be reduced to 20% or even lower, but the energy consumption is relatively high.

Carbonization belongs to the commercialization of sludge with high calorific value. There are high temperature carbonization, medium temperature carbonization and low temperature carbonization technologies, of course, low temperature carbonization has the lowest energy consumption; The heat source is fossil fuel. Not all sludge can be carbonized. Carbonization is generally a process after drying. Carbonized products can usually be reused as fuel. The curing of carbonized heavy metals remains to be studied. Full text reading: