What Is Wastewater Treatment Sludge?

Sludge treatment: A process of reducing, stabilizing, and harmless sludge, such as concentration, quenching, dehydration, stabilization, drying, or incineration.

Sludge treatment is carried out on sludge

The status of sludge treatment and disposal in China In recent years, under the role of China's energy conservation and emission reduction policies and active finance, urban sewage treatment has developed rapidly, and water environment treatment has also achieved significant results. But at the same time, a large amount of sludge generated during sewage treatment has not been effectively treated, causing great harm to the environment and seriously affecting the implementation of China's energy conservation and emission reduction strategies and policies. ^[2]

As a solid waste, sludge has become the second largest source of solid waste pollution after urban garbage pollution. The main disposal methods of traditional sludge include landfill, incineration, sea discharge, and agricultural use. However, the traditional treatment method also has some disadvantages. It cannot use the sludge as a resource and cannot meet the current technical requirements for sludge treatment. Therefore, it is of great practical significance to develop new technologies for sludge treatment and resource utilization. The sludge treatment and disposal should be comprehensively considered from the aspects of environmental pollution, sanitation safety and economic benefits. New sludge treatment technology with energy recovery and utilization will play an irreplaceable role in sludge treatment and disposal. ^[3]

With the strengthening of environmental protection and people's further recognition of the limitations of existing sludge treatment and disposal technologies, countries around the world are investing heavily in research and development of new technologies in an effort to find more economical and reasonable sludge treatment solutions.

Sludge treatment technology

This technology uses a sludge washing process. First, the organic material in the sludge is washed out, the inorganic material is separated from the sludge, and the organic sludge is concentrated for high-temperature anaerobic digestion. The precipitated sludge is washed to wash out half of the solid inorganic sludge in the sludge, reducing half of the biological treatment volume, saving engineering investment and treatment costs; treating the organic sludge separately, removing the sediment of the inorganic sludge in the reactor, Reduced equipment wear and reactor maintenance; the washed sludge washed out most of the heavy metals and inorganic sludge in the sludge, which improved the quality of organic fertilizer; the washed sludge can also produce pavement color Brick, permeable brick. Other innovative processes: ultra-high temperature anaerobic digestion, multi-stage anaerobic digestion, biogas residue floating, etc., the biological treatment speed of sludge has increased several times and the biogas production has increased by more than 20%.

Sediment sludge biological treatment system, the engineering design innovation adopts the buried, compact, multi-stage digestion reactor design. Several independent anaerobic digestion reactors have you, me, and you in one, save building materials. Concrete structures are inexpensive. The existing anaerobic digestion reactors at home and abroad have generally adopted the above-ground structure. The above-ground structure can make equipment equipped for easy maintenance and favorable biogas residue discharge to prevent biogas residue precipitation. The engineering design of the biological treatment system well solves the maintenance of supporting equipment and biogas sedimentation. The system is equipped with less equipment and only requires a few water pumps, that is, if the water pump is broken, it can be replaced in less than 20 minutes to ensure that the equipment is maintained and maintained. The precipitated sludge is washed to remove the inorganic sludge that is easy to settle, and the organic sludge will float without sedimentation after being blown by the blowing system. The buried anaerobic digestion reactor not only has less investment and does not occupy land, but also can prevent earthquakes, lightning strikes and long service life, and reduce heat loss in the digestive system.

Sludge treatment sludge fermentation technology

There are three traditional sludge treatment methods: incineration, landfill and resource utilization. Most countries use incineration technology, but the investment is huge, which is likely to cause air pollution. Domestic landfill is used, but it takes up a lot of land, and it will cause secondary pollution to the environment. Large and medium-sized cities such as Shanghai in China have very few land regeneration resources, which is difficult. Use this method for a long time. Chen Liqiao said that the use of microorganisms to treat sludge has a bright future. After field test and practical application of the sewage treatment plant, economic benefits of about 150 yuan can be obtained for each ton of sludge treated. Shanghai produces about 1.4 million tons of sludge every year. If 20% of the sludge is treated by microbial aerobic fermentation, the direct economic benefit is about 42 million yuan. In addition, the use of microbial aerobic fermentation can also eliminate the malodor of sludge, effectively control the secondary pollution of sludge, and also have significant environmental benefits. ^[4]

Fermenting the sludge into organic fertilizer, such as adding some cow dung, will ferment into high-quality organic fertilizer. The specific operation method is as follows:
1. Add bacteria. 1 kg of Golden Baby Ferment Fermenter can ferment about 4 tons of sludge + cow dung. About 30-50% of cow dung, or straw powder, mushroom residue, peanut hull powder, or rice husk, sawdust and other organic materials need to be added in order to adjust the air permeability. Among them, if rice husks and sawdust are added, the fermentation time should be prolonged because of its high cellulose lignin. Bacterial dilution: Add 5-10 kg of rice bran (or bran, corn flour and other substitutes) per kilogram of starter, mix and dilute it, and then spread it evenly into the material pile. The effect will be better.
2. Build a pile. After preparing the material, build a pile while spreading bacteria. The pile height and volume must not be too short or too small. Requirements: The pile height is 1.5-2 meters, the width is 2 meters, the length is 2-4 meters. 2. Mix well and aerate. Golden Baby Ferment Fermenter needs good (aerobic) fermentation. Therefore, it is necessary to increase the oxygen supply measures, and it is advisable to mix well, turn it over and ventilate it. Otherwise, anaerobic fermentation will cause odor and affect the effect.
4. Moisture. The moisture of the fermentation material should be controlled at 60 to 65%. Moisture judgment: Hold the material tightly with your hand, see the watermark in your fingers, but do not drip, it is advisable to fall on the ground. Fermentation is slow with less water, poor ventilation with more water, and it will also cause "septic bacteria" to work and produce odor.
5. Temperature. The start-up temperature should be above 15 (it can be operated in four seasons and is not affected by the season, and it should be fermented indoors or in a greenhouse as much as possible in winter). The temperature of the fermentation should be controlled below 70-75 .
6. Done. The temperature should be overturned when the temperature reaches 65 or higher on the first 2-3 days. Generally, the fermentation can be completed within one week. The material is dark brown, and the temperature starts to drop to normal temperature, indicating that the fermentation is complete. If there are too many sawdust, wood chips, and rice husks, the fermentation time should be prolonged and fully decomposed.
Fermented organic fertilizers have good fertilizer effect, are safe and convenient to use, resist disease and promote growth, and can also improve fertility.

Sludge melting technology

Aiming at the secondary pollution in the sludge incineration process, researchers have developed the sludge melting technology, which enables the sludge to burn above the melting point of the incineration ash (usually 1300 ~ 1800 ° C), which can not only completely decompose the sewage Organic matter in the mud, killing germs, and the density of the formed slag is 2/3 higher than that of incinerated ash, which achieves the effect of greatly reducing the volume of ash and slag. The heavy metals in the sludge are immobilized because they are fixed in the glassy slag, so the slag after the sludge is melted can be used as a building material. ^[5]

Lime dosing technology for sludge treatment

The dewatered sludge enters the hopper, and lime and amino acid are added to the hopper. The amount of lime is 10% to 15% of the amount of wet sludge, and the amount of amino acid is about 1% of the amount of lime. Because amino acid generates ammonia gas during the reaction, the sterilization effect of the entire process is enhanced and the reaction temperature is reduced. After the sludge, quicklime, and amino acid are stirred in the hopper, they are pushed into the plunger pump inlet by the double screw feeder, and then sent to the reactor through the plunger pump, and stay at 70 ° C for 30 minutes. The output product can be Meet the US EPA PART503 CLASS A standard. After the reaction, the sludge is pumped to the silo, and the gas generated in the sealed container is discharged after being treated by the washing tower.

Features of this process: pH> 12, long duration, thorough sterilization; high pH precipitates most metal ions, reducing its solubility and activity; the solid content of sludge can be increased to 30%; the sludge is removed from the sludge Odor, the system is fully sealed, no environmental pollution; the system is fully automatic, easy to operate and maintain: adding a small amount of amino acid, reducing the amount of lime and reaction time, and reducing operating costs.

Carbonization technology for sludge treatment

Sewage process optimization can reduce the remaining sludge output. Sludge wall breaking and strong drying technology can improve the dewatering performance of sludge. Finally, sludge carbonization technology is used to achieve sludge resource utilization, and to resolve sludge output from the source. Finally, the goal of zero sludge discharge is achieved. ^[6]

The so-called carbonization of sludge is a process by which the water in the sludge is released, while the carbon value in the sludge is retained to the maximum, and the carbon content in the final product is greatly increased (Sludge Carbonization). Worldwide, sludge carbonization is divided into three main types.

High temperature carbonization. It is not pressurized during carbonization, and the temperature is 649-982 ° C. The sludge is first dried to a moisture content of about 30%, and then enters a carbonization furnace for high-temperature carbonization and granulation. Carbonized particles can be used as low-grade fuel, and its calorific value is about 8 360-12 540 kJ / kg (Japan or the United States). This technology can achieve the reduction and resource utilization of sludge, but due to its complicated technology, high operating cost, and low heating value content in the product, it has not yet been applied on a large scale.

Medium temperature carbonization. It is not pressurized during carbonization, and the temperature is 426-537 ° C. The sludge is first dried to a moisture content of about 90%, and then decomposed into a carbonization furnace. The process produces oil, reaction water (steam condensate), biogas (uncondensed air), and solid carbides. In addition, the technology is to carbonize the sludge after drying, and its economic benefits are not obvious. There is no other potential user except for a treatment plant in Australia.

(3) Low temperature carbonization. There is no need to dry before carbonization, pressurize to 6-8 MPa during carbonization, carbonization temperature is 315 ° C, carbonized sludge becomes liquid, water content after dehydration is below 50%, and it can be used as low-grade fuel after drying and granulation. , Its calorific value is about 15 048 20 482 kJ / kg (USA). This technology allows all biomass in the sludge to be cracked by heating and pressurizing, and 75% of the water in the sludge can be removed only by mechanical methods, which greatly saves energy consumption during operation. All the sludge is cracked to ensure the complete stability of the sludge. During the carbonization of the sludge, the heating value of most of the sludge was retained, which created a condition of 14t for the reuse of energy after cracking.