Various sludges have their own characteristics, and many technologies are applicable to these sludges. The technologies used are different depending on the treatment requirements. The sludge treatment generally includes landfill, fertilizer, power generation, heating, etc. method. So let’s talk about the specifics of the sludge treatment methods, and what are the different treatment methods.
Sanitary landfill
The disposal method is simple, easy, and low in cost, and the sludge does not need to be highly dehydrated and has strong adaptability. However, there are also some problems in sludge landfill, especially the formation of landfill leachate and gas. Leachate is a heavily polluted liquid that can contaminate the groundwater environment if sited or improperly operated. The gas produced by landfills is mainly methane, which can cause explosions and combustion if appropriate measures are not taken.
Land use
Direct use of sludge land is considered to be the most promising disposal method due to the advantages of low investment, low energy consumption, low operating cost and organic component conversion into soil improver. Scientific and rational land use can be reduced. The negative effects of sludge. The use of forest land and municipal greening has become an effective way of sludge land use because it is not easy to cause pollution of the food chain. The use and use of sludge for the repair and reconstruction of heavily disturbed land (such as mine land, forest harvesting sites, landfills, and severely damaged areas) reduces the potential threat of sludge to human life. Both the sludge was disposed and the ecological environment was restored.
Incineration
The application of wet sludge to direct incineration is more common. It is not only difficult to directly incinerate without drying the sludge, but it is also extremely uneconomical in terms of energy consumption. The sludge treatment method with incineration as the core is one of the most thorough sludge treatment methods. It can completely carbonize organic matter and kill pathogens, which can minimize the sludge volume. However, the disadvantage is that the treatment facility has large investment and treatment. High cost, high equipment maintenance costs, and the production of strong carcinogen dioxin.
Sludge drying
Sludge drying is a treatment method that uses artificial heat source to deep dewater sludge with industrial equipment. Although the direct result of sludge drying is the decrease of sludge moisture content (dehydration), its application purpose and effect are compared with mechanical dewatering. There are big differences.
Sludge mechanical dewatering (including sludge concentration), the purpose of its application is to reduce the volume of sludge treatment (sludge concentration and mechanical dewatering can usually reduce the sludge volume by about 4 times), but the dewatered sludge cake In addition to the water content and related physical properties, such as the difference between fluidity and undisturbed sludge, its chemical and biological properties are not changed by dehydration.
Sludge drying requires an artificial heat source due to the requirement of increasing the evaporation strength of water. The operating temperature (for sludge particles) is usually greater than 100 ° C. The effect of drying on sludge is not only deep dehydration but also heat treatment effect. In addition, the sludge drying treatment product can control the water content below 20%, that is, the level of inhibiting the microbial activity in the sludge, so the sludge drying treatment can simultaneously change the physical, chemical and biological characteristics of the sludge.
New technology
With the strengthening of environmental protection and people’s further understanding of the limitations of existing sludge treatment and disposal technologies, countries all over the world are investing heavily in research and development of new technologies to find a more economical and rational sludge treatment program.
Free processing
The technology innovation uses a sludge washing process to first wash out the organic matter in the sludge, separate the inorganic material sludge soil, and then concentrate the organic sludge for high temperature anaerobic digestion. The precipitated sludge is washed and washed out of the semi-solid inorganic sludge soil in the sludge, reducing the biological treatment amount by half, saving engineering investment and treatment cost; treating the organic sludge separately, removing the precipitation of the inorganic sludge soil in the reactor, Reduce equipment wear and maintenance of the reactor; the precipitated sludge is washed and washed out of the sludge, which is easy to precipitate heavy metal and inorganic sludge soil, which improves the quality of the organic fertilizer; the washed sludge soil can also produce pavement color Brick, permeable brick. Other innovative processes: ultra-high temperature anaerobic digestion, multi-stage anaerobic digestion, biogas residue floating, etc., sludge biological treatment speed increased several times and biogas production increased by more than 20%.
Precipitated sludge biological treatment system, engineering design innovation uses buried, compact, multi-stage digestion reactor design, several independent anaerobic digestion reactors, you and I have you integrated, saving building materials, using The concrete structure is inexpensive to manufacture. The existing anaerobic digestion reactors at home and abroad generally adopt the above-ground structure, and the above ground structure can make the equipment convenient for maintenance and facilitate the biogas residue discharge to prevent the precipitation of the biogas residue. The biological treatment system engineering design has well solved the maintenance of supporting equipment and the deposition of biogas residue. The system is equipped with few equipments, only a few pumps are needed, that is, the pump is broken and replaced with one for less than 20 minutes to ensure that the equipment maintenance does not stop; The precipitated sludge is washed to remove the inorganic sludge soil which is easy to precipitate, and the organic sludge floats and floats and does not precipitate. The buried anaerobic digestion reactor not only has low investment, does not occupy land, but also can prevent earthquakes, lightning strikes and long service life, and reduce heat loss of the digestive system.
Sludge fermented organic fertilizer
There are three traditional sludge treatment methods: incineration, landfill and resource utilization. Many countries use incineration technology, but the investment is huge, which is easy to cause air pollution; landfill is used in China, but it needs to occupy a large amount of land, and it will cause secondary pollution of the environment. Domestic and other large and medium-sized cities in China have few land regeneration resources. This method has been adopted for a long time. Chen Liqiao said that the prospect of treating sludge with microorganisms is broad. Through the on-site test and practical application of the sewage treatment plant, the economic benefit of about 150 yuan can be obtained for each ton of sludge treated. In addition, the use of microbial aerobic fermentation can also eliminate the foul odor of the sludge, effectively control the secondary pollution of the sludge, and the environmental benefits are also significant.
The sludge is fermented into organic fertilizer. If some cow dung is added, it will be fermented into high-quality organic fertilizer. The specific operation method is as follows:
1. Add bacteria. 1 kg of gold baby fertilizer starter can ferment about 4 tons of sludge + cow dung. It is necessary to add 30-50% of cow dung, or straw powder, mushroom residue, peanut shell powder, or rice husk, sawdust and other organic materials in order to adjust the air permeability. If rice husk and sawdust are added, the fermentation time should be prolonged because of the high cellulose lignin. Strain dilution: add 5-10 kg of rice bran (or bran, corn flour and other substitutes) per kg of starter, mix well and then evenly sprinkle into the material pile, the effect will be better.
2. Build a pile. After the preparation, the bacteria should be built and the pile height and volume should not be too short and too small. Requirements: stack height 1.5-2 meters, width 2 meters, length 2-4 meters
3. Mix well and ventilate. Jinbao fertilizer fermenting agent needs good (consumption) oxygen fermentation, so it should increase the oxygen supply measures, so that mixing, digging, and ventilation are appropriate. Otherwise, it will lead to anaerobic fermentation and produce odor, which will affect the effect.
4. Moisture. The moisture content of the fermentation material should be controlled at 60-65%. Moisture judgment: hold a hand tightly on the material, see the watermark but not dripping, and it is appropriate to land. Low water fermentation, slow water and poor ventilation, can also lead to “septic bacteria” work and produce odor.
5. Temperature. The starting temperature should be better than 15 °C (the four seasons can be operated, not affected by the season, and the winter should be fermented indoors or in the greenhouse), and the fermentation temperature should be controlled below 70-75 °C.
6. Complete. On the 2-3rd day, the temperature should be over 65 °C. It should be overturned. Generally, the fermentation can be completed within one week. The material is dark brown and the temperature begins to drop to normal temperature, indicating that the fermentation is completed. If there are too many excipients such as sawdust, sawdust and rice husk, the fermentation time should be prolonged until fully decomposed. Fermented organic fertilizer, good fertilizer effect, safe and convenient to use, anti-disease and long-term, can also fertilize soil and so on.
Lime dosing technology
The dehydrated sludge enters the hopper, and lime and amino citric acid are added to the hopper. The amount of lime is 10% to 15% of the amount of wet mud, and the amount of amino citric acid is about 1% of the amount of lime. Since aminoguanic acid generates ammonia during the reaction, the sterilization effect of the entire process is enhanced and the reaction temperature is lowered. After the sludge, quicklime and amino citric acid are stirred in the hopper, they are pushed into the inlet of the plunger pump by the double screw feeder, sent to the reactor through the plunger pump, and stay at 70 ° C for 30 min, and the output product can be Meet the US EPA PART503 CLASS A standard. The reacted sludge is pumped to the silo, and the gas generated in the sealed container is discharged by the washing tower.
The characteristics of the process:
pH>12, long duration, complete sterilization; high pH makes most metal ions precipitate, which reduces its solubility and activity; the solid content of sludge can be increased to 30%; the odor in sludge is removed, the system Fully sealed, no environmental pollution; fully automatic system, easy operation and maintenance: adding a small amount of amino acid, reducing the amount of lime and reaction time, reducing operating costs.
