First of all, we came to the sludge drying plant which is subordinate to the West District Water Plant of Fuzhou City. The West District Water Supply Plant of Fuzhou City undertakes the task of supplying water to the West District of Fuzhou City, supplying 4 million tons of water every day. The purpose of this sludge drying plant is to treat the sludge discharged from the water plant. Under the teacher's explanation, we learned that different treatment programs should be formulated according to the nature of the treatment object and the different treatment objectives. In treating these sludges, we first need to reduce the mobility of the sludge, that is, to reduce its water content, so that it will change from flowing to immobile, and finally become solid, and then be landfilled or reused, for example, as fertilizer. The main objective of the work in treating sludge is to separate the mud from the water, where the water is of three types: free water, surface water and capillary water. The water content of untreated sludge is 99%, and the water content of treated sludge is generally reduced to 55%-60%, and only after incineration will the water content of sludge be reduced to 10%, and of the water contained in the sludge at the beginning, 10% is free, 20%-30% is surface water, and most of the rest is capillary water. Considering the target of treatment, cost and the nature of the target of treatment, only the free water and surface water in the sludge are required to be gotten rid of here, so that the solid waste will not flow. According to the nature of sludge, this drying plant has developed such a process flow: after the sludge is generated from the water purification plant and transported to the drying plant; firstly, coagulant is injected into the sludge, which is a coagulation process, and this is to make the surface water free; and then the sludge is transported to the high-density clarification tanks, where the free water of the sludge is separated, and the clarified water will be directly discharged into the Minjiang River, and this is because the clarified water is not recontaminated. This is because the clarified water is not re-contaminated, and the separated precipitated sludge, most of which is transported to the drying bed using the principle of evaporation for drying, after drying the sludge is transported to the landfill for disposal, and a small portion of the separated sludge is re-entered into the high-density clarifier after the sludge reflux and then processed again. After this series of introduction, we began to visit the internship. First, we came to the dosing room. Here we saw a kind of flocculant called polyacrylamide (PAM) also called flocculant, this kind of flocculant mainly plays the role of bridging, is a kind of organic flocculant, organic flocculant according to the molecular weight of the different roles played by the different flocculants, these flocculants firstly to enter the dissolution of dissolved drug dissolver with the stirrer to make it dissolved, and then these drugs through the dosing pump to enter the high-density clarification tank, in the process, the application of the plunger to achieve the principle of maintaining a stable flow, and the application of the principle of maintaining a steady flow. In this process, the plunger principle should be applied to realize the maintenance of a stable flow rate, and the use of circulation to regulate, at the same time, it should be noted that in the dissolver must be equipped with ladders and cleaning pools around the periphery, which is the requirement of the environmental engineering. After coming out from the dosing room, we entered another operation room, where there are many valves and pumps, among which the more important one is the lifting pump, which controls the lifting and returning of sludge through the switching of valves, and meanwhile, the turbidity and PH value of sludge are also supervised and controlled by the on-line monitoring equipment. Next, we came to the high-density clarifier, here there is a mixer is used to promote the contact between mud and medicine, here there is also a slant pipe sedimentation tank, and the suspended sludge layer will form a filter, it and the sludge backflow to ensure the structure of high-density clarifier, which is also taken into account the economic issues. Finally, we came to the drying bed, which is the place of sludge drying, sludge from the inclined tube sedimentation tank through the transportation of the sludge pipe and finally came to the drying bed, the design of the drying bed is related to the regional climatic pattern, when the evaporation is greater than the local precipitation and there is enough area, then the precipitation factor can be disregarded, due to the drying bed also produces the clarification of the water, so there is a drying bed around the wall of the machine, through the wall of the machine to The height of the water surface in the pool is adjusted and the clarified water filtered by the sand layer will also be discharged directly into the Min River.
The current development of sludge treatment and disposal in urban water purification plants is summarized as follows: in the past, the construction of urban water purification plants, sludge treatment has been a neglected part of the people pay more attention to the sewage treatment of industrial production, before the 1970s, the construction of water purification plants in various countries to deal with sludge water treatment facilities, mostly along the sewage treatment plant sewage and sludge treatment methods for the design and application of the main The use of sludge ponds and drying field treatment and sludge. With the development of urbanization, the sixties began, the researchers staff began to seriously study the water treatment plant sludge treatment and sludge disposal work, investigated the water treatment plant sludge and water treatment plant water purification process between the relationship between the water treatment plant sludge, explored the water treatment plant sludge discharge and sewage plant sludge discharge differences and similarities, seventy, the U.S. federal government promulgated the cloth "Water Pollution Control Act," which requires that the states set standards, water treatment plant sludge must be treated and then discharged The U.S. federal government enacted the Water Pollution Control Act in the 1970s, requiring states to set standards that water plant sludge must be treated before it is discharged. Its development goal is: by the end of the seventies, the application of practicable technology to rationalize sludge treatment, and require all types of water plants to eliminate the pH value of sewage and total suspended solids to meet the standard. By the early 1980s, the economy of the sludge treatment process must be taken into account, requiring the reuse of the precipitated liquid or filtrate after sludge treatment; by the mid-1980s, environmental pollution caused by sludge discharge will be eliminated on a nationwide scale. Japan in 1975 also promulgated cloth "water quality pollution prevention law", the provisions of the water purification plant without sedimentation tanks and filters, its discharge water must be treated to meet the water quality discharge standards. In recent years, the United States, Russia, Japan, Britain, France and other developed countries, large and medium-sized cities in the new water purification plant are set up in a more complete, high degree of automation of sewage and sludge treatment facilities. Centrifugal dewatering, pressurized dewatering and other mechanical dewatering methods are commonly used. Some European water purification plants, due to the low suspended solids content in the raw water, turbidity is small, the mud content of water plant drainage is small, often discharged sludge is discharged directly into the municipal sewage management, transported to the nearest sewage plant unified sludge treatment, according to the relevant information, the amount of water purification plants in many European countries after the concentration and dewatering of sludge, accounting for all the sludge amount of water purification plants of 70%. Sludge off the use of specific technologies, due to the natural conditions and habits of countries, there are obvious differences. However, the general trend in recent years is that the use of drying sound and drying ponds is reduced, centrifugal and filter press dewatering gradually dominate.
China's water purification plant sludge treatment and disposal work started late, due to the water purification plant sludge, in the past are generally considered to be composed of the original solid components of the water body is comparable to the only increase in the treatment process of some of the flocculating agent, very little impact on the environment, and thus so far the vast majority of the sludge from the water purification plant is still directly discharged into the water, but with the growing importance of the government of China's water resources protection work However, with the increasing attention paid by our government to the protection of water resources, especially the continuous expansion of the city scale, the discharge of mud from the water purification plant has gradually become prominent, according to rough statistics, China's largest city, Shanghai City, the water purification plant each year through the discharge of sludge into the water body of the suspension of up to 300,000 tds (tons of dry solids), the organic matter according to the content of 10%, up to more than 30,000 tds. Water purification plant sludge is being closely watched by the relevant departments, "Chinese People's Republic of China *** and the State Water Law", "Chinese People's Republic of China *** and the State Water Pollution Prevention and Control Law" and a series of water resources protection laws and regulations promulgated and implemented, our country in the eighties of the sludge discharge from the water purification plant has been put on the agenda for harmless treatment of sludge in the water plant has become an important task of the current domestic urban water supply industry.
Water purification plant is a direct victim of water pollution, due to raw water pollution to the water purification process in the technology to bring many difficulties caused by the rising cost of water purification, protection of water sources, take the road of sustainable development, water purification plant sludge discharge to first achieve the discharge standard is the responsibility of the next generation.
Leaving the sludge treatment plant, our next stop is Fuzhou Fengquan Environmental Protection Group.
Arrived here, our first step is to first visit the solid waste heat treatment and exhaust gas treatment device waste incineration exhaust purification device, where we visited the medical waste pyrolysis furnace, which is mainly on the medical waste pyrolysis incineration. First of all, the garbage enters into the pyrolysis furnace, in the pyrolysis furnace there is a high temperature of 1200 degrees Celsius for the garbage anoxic combustion, which will produce a large number of organic gases, and the tail gas mainly contains HF, HCL, di-Erwin, and some organic gases. After this, these gases from the pyrolysis furnace into the two combustion chamber and three combustion chamber, these gases into the two combustion chamber will be fueled combustion, and then into the three combustion chamber for further combustion, in the series of combustion, the organic components in the gas is completely burned, the rest is some acidic gases and dioxin. And then these gases will enter the emergency cooling tower, in the emergency cooling tower, the temperature of these gases will be reduced dramatically, from 750 degrees Celsius or more is cooled to about 200 degrees Celsius, which has a gas-liquid two-way nozzle can remove HCL and avoid the re-generation of the two Er Ying. Next, the gases coming out of the rapid cooling tower will enter the semi-dry de-acidification tower, where the acid gases will be removed by the neutralization of NaOH, Na2CO3 or Ca(OH)2, and all the water in this semi-dry de-acidification tower will be evaporated by the temperature of the flue gases, so that the incoming liquids are only left as solids, which avoids the disposal of waste liquids, and there is a rotating spraying device with a rotational speed of 16,000 rpm, which in turn makes the treatment of the exhaust gas more complete. The next exhaust gas into the bag filter, the composition of the exhaust gas is mainly dust, dioxin and a small amount of organic gases, in the bag filter there is an activated carbon powder spraying device, which uses activated carbon layer treatment to purify gas pollutants and dust, which makes the harmful substances in the exhaust gas is further reduced. The exhaust gas from the bag filter will next enter the activated carbon adsorption room, in which there are a large number of activated carbon fibers, which can further purify and absorb the harmful gases that have not been transformed by the treatment, in order to meet the exhaust gas emission standards. After that, the exhaust gas can enter the emission system, which should be designed according to the temperature and characteristics of the exhaust gas, and discharged into the external environment. In addition, during the visit, we will find that the pipeline through which the gas passes is curved in order to prolong the residence time of the gas, which is a detail to be considered in the engineering design process. This is the principle of the process flow of the medical waste pyrolysis furnace, which is illustrated as follows:
Pyrolysis Furnace
Second Combustion Room
Third Combustion Room
Acute Cooling Tower
Semi-Dry Acid Removal Tower
Bag Dust Collector
Activated Carbon Adsorption Room
Emission System
Here we also saw another set of devices, this is a set for the treatment of domestic waste which is also an incinerator, it mainly includes rotary kiln, cyclone dust collector, absorption tower, in which the rotary kiln is used to burn the waste, while the cyclone dust collector is used to remove the dust, and finally the absorption tower is used to remove acid. This is the general process flow of the domestic waste incinerator. From here, we can see that the treatment process for medical waste is a bit more complicated than that for domestic waste, due to the fact that medical waste has more hazardous components and is more complex in composition.
After visiting a series of solid waste thermal treatment and exhaust gas treatment devices, we came to the next object of the tour - enameled assembled tank sewage treatment equipment site.
This is a biological sewage treatment system, which works by using microorganisms to degrade organic matter. First, the sewage will enter the regulating pool, the regulating pool can be adjusted to the amount of sewage water and water quality, and then by the pump to control the amount of water entering the device will be sent into the device. After that, the sewage will enter the partially oxygenated pool, where the partially oxygenated bacteria play a major role, in this process, the outside world does not oxygenate the sewage, its purpose is to consume the organic matter in the sewage, hydrolysis and acidification of organic matter, the treatment rate of more than 50%. Then, the sewage will enter the first contact oxidation tank, where mainly aerobic microorganisms play a role, so it is necessary to oxygenate, after this, the sewage will enter the second contact oxidation tank, where most of the organic matter in the water will be decomposed, in the first contact oxidation tank and the second contact oxidation tank should be used to make the oxygen, microorganisms, sewage to get in touch with the full and react. From the second contact oxidation tank out of the sewage next to enter the second sink, in the second sink, suspended solids and water will be separated, from the second sink discharged from the water is to meet the emission standards of water. Under the teacher's introduction, we also learned that the sewage can also be purified of suspended solids through a sand filter, but because of the use of sand filter devices to repeatedly rinse, in the process of generating sewage, so this treatment is not often used. In addition to this biological purification method used in this unit, there are other biological purification methods such as contact oxidation and activated sludge.
Through a semester of introductory studies, we have a preliminary understanding of environmental engineering, the environment is the basic prerequisite for human survival and development, and human production and living activities on the environment is omnipresent is also significant, so as an earthling, we should do our best to protect the environment on which we depend for our survival, to protect the environment is to protect human beings themselves, to be a qualified environmental engineer, to be a qualified environmental engineer, to be a qualified environmental engineer, to be a qualified environmental engineer, to be a qualified environmental engineer, to be a qualified environmental engineer, to be a qualified environmental engineer, to be a qualified environmental engineer. To be a qualified environmental engineer to recognize the importance of the environment, to realize the responsibility on their shoulders is how significant, we need to seriously study the professional knowledge and master the professional knowledge learned, and through continuous practice to hone their own, so that the learned professional knowledge can be integrated, know how to use what you learn, so that you really become a qualified environmental workers, a qualified environmental Engineer! The regional aspects of this content, you can make some slight changes, I hope to help you ...