I. Overview of the Project
1. Project background
With the development of economy and the improvement of people's living consumption level, the amount of municipal solid waste is increasing day by day. At present, there are no engineering measures for the harmless treatment of urban garbage. Basically, all the garbage is simply piled up and treated without harmless treatment, and its hygiene requirements are far from meeting the hygiene standards of environmental protection laws and regulations.
These simple garbage dumps have caused a series of environmental pollution problems. Show in:
First, garbage is piled up in the open air, emitting a stench, polluting the atmospheric environment, and can be smelled around several square kilometers, seriously affecting the landscape. Second, there is no isolation measures for garbage, and the leachate produced by it pollutes groundwater and surrounding surface water, which greatly threatens the health of residents.
Third, pollute the surrounding soil and make it lose its proper function.
The urban economy continues to grow, the population continues to increase, and consumer goods are also increasing. If the garbage is not treated harmlessly, it will lead to a major disaster, so the landfill treatment project of domestic garbage is established.
2. The main content of engineering design
The main contents of the treatment engineering design of municipal solid waste sanitary landfill include: general layout (site selection and site overall design, etc. ), landfill technology, prevention and control engineering, leachate collection and discharge engineering, leachate treatment engineering, groundwater and surface water treatment engineering, landfill gas collection and utilization design, environmental monitoring design, site closure engineering, auxiliary engineering (such as greening and roads), equipment selection, secondary pollution prevention design, economic analysis, etc.
3. Design scale
According to the urban population size, per capita garbage output and other factors, the initial treatment scale of municipal solid waste sanitary landfill is determined to be 600 tons/day.
4. Technical and economic indicators
Garbage disposal scale: 210.9 million tons/year; Storage capacity of landfill: 6193200m3; Service life: 2 1 year; Leachate treatment scale: 300 tons/day; Leachate treatment standard: Grade III; Volume of regulating tank: 20,000m3; total cost of garbage disposal: 2,845,800 yuan/year; Payback period of investment: 12.95 years.
Two. general layout
1. Location selection
The site selection of this landfill site was selected after comprehensive and careful consideration from the aspects of engineering, economy, environmental science, policies and regulations.
1) from the economic point of view, this landfill can meet a certain storage capacity, which can accommodate 600~ 1200t/d of garbage treatment; There are avenues nearby, only 9.87 kilometers away from the city center, with convenient transportation and reasonable transportation distance. There are a considerable amount of earth and stone around the site, which are used for natural impervious layer and overburden clay.
2) From the engineering point of view, the site has proper natural topography as landfill space, and its topography, landform and soil conditions are suitable; The permeability coefficient of natural formation is below 10-7cm/s, with a certain thickness and good geological conditions. The evaporation of the station is greater than the precipitation, and it is not in the area where the typhoon passes, and the incidence of heavy rain is also low. Located in the downwind direction of atmospheric mixing and diffusion, that is, the meteorological conditions are suitable.
3) From the environmental point of view, the site is 2000 meters away from the special water supply area, and the foundation is located at the highest water level elevation of at least 1 m, which has little impact on surface water and groundwater. At the same time, the site is 2000 meters away from the residential area, and the downwind of the residential area has little effect on the residential area.
4) From the perspective of policies and regulations, the establishment of this landfill conforms to the urban development plan and the requirements of the local urban environmental sanitation development plan.
To sum up, the site is determined to be a landfill.
2. Overview of the website
The landforms of the landfill are two valleys, which basically run in the north-south direction. The valley is open and separated by a hill in the middle, and the two valleys meet at the southern end. The whole site covers an area of 40 square kilometers.
The climate of the landfill is subtropical monsoon climate, with northerly winds in winter and southeast winds in summer, and the annual rainfall is above 1000ml. The site belongs to the hydrogeological type of double-layer structure, with shallow aquifer and general water content, and the clay is mainly clay with relatively stable thickness. Under natural conditions, the weathered aquifer of loose layer powder and bedrock weathering crust has good anti-seepage and anti-pollution performance.
3. General plan
The landfill treatment project consists of four parts: living area, landfill area, leachate treatment area and biogas power generation area. The whole plant covers an area of about 40 square kilometers, of which the landfill covers an area of about 25.3 square kilometers, the leachate treatment area is about 5 square kilometers, and the rest is 13.7 square kilometers. (See attached figure 1. )
The layout of the whole plant is designed according to the current requirements of the country, the actual topography, hydrogeology, wind direction and the needs of landfill technology.
Because the city is always in the prevailing wind direction of southeast monsoon in summer and northerly wind in winter, according to the seasonal changes of topography and wind direction, the landfill area is located in the east, and a green belt is set around the landfill area. This can avoid the seasonal change of wind direction, cause certain odor pollution to the landfill area and affect local residents.
The living area includes administrative office building, machine maintenance workshop, fountain square, pavilion, green belt, etc. Leachate treatment area includes water pump house, sedimentation tank and regulating tank. Of course, there are a series of green decorations around it. Leachate treatment area and biogas power generation area are set as close as possible to landfill area to facilitate fluid transportation.
Three. Landfill operation technology
Sanitary landfill is usually transported to the landfill every day, and then enters the landfill after judging the nature and measurement. The garbage is unloaded at the designated unit operation point, then pushed by bulldozer, and then crushed by roller. After layered compaction to the required height, cover clay and polyethylene film on it, and repeat the above processes of unloading, pushing, compacting and covering. The work unit is covered with one layer every day. The compaction density of garbage is greater than 0.8t/m3. The thickness of each layer of garbage is 2.5~3.0m, and the covering thickness of miners is 15~30cm. Usually, four layers of garbage form a large unit, and the soil is covered by 45~50cm.
When filling, push it from right to left first, and then push it from front to back. The connecting line between the left, middle and right is arc-shaped, which makes the drainage on the coverage flow smoothly to both sides and enter the drainage ditch or side ditch. In order to reduce the infiltration of rainwater into the garbage, the connection between the front and rear parts is inclined to a certain extent. External slope 1: 4, and the top of the slope is not less than 2%. After the unit thickness reaches the design thickness, it can be temporarily closed and covered with 45~50cm thick clay. And evenly compacted, and 15cm thick nutrient soil is added to plant shallow-rooted plants. Finally, the covering thickness is greater than1m.
The operation mode of landfill is divided into zones and units, provided that the zones and units are divided, and then layered landfill operation is considered. In order to prevent the spread of pollution to the greatest extent, during the landfill operation, the sub-landfill areas under the landfill operation are exposed, covered with plastic film every day, and other areas are covered in the middle or temporarily closed.
The first operation is to level the bottom of the reservoir area of the first regional landfill. In the actual process of landfill operation, it should be considered to combine with the temporary operation road in the landfill operation reservoir area. The height of the first landfill operation is 2m away from the level, and then the setting of the second landfill operation unit is started.
With the increase of landfill height, the available effective area of landfill operation is also increasing. It's convenient to use gas at this time. The landfill unit that has been temporarily closed can connect the gas pipeline with the surrounding mobile gas gathering station through the vertical gas well in the middle of the gas guide gabion, and then the gas can be reused.
The operation sequence of the whole landfill area is: first area, then area, repeated area, and then the second phase of the project is started. The second-stage landfill project will form a new horizontal area with the first-stage landfill area, and continue to landfill upwards. After the pile body is formed, the landfill will be temporarily closed and the third-stage landfill operation will be carried out. The process flow chart of landfill operation is as shown in the figure:
Process flow chart of landfill operation
Four. Seepage prevention engineering and leachate treatment design
1. Seepage control works
1. 1 impervious material
At present, from the practice at home and abroad, high-density polyethylene (HDPE) membrane is the most widely used and successful one in garbage sanitary landfill, and it has the best durability compared with other impervious materials. From the point of view of anti-seepage performance and economy, it is more suitable to use the high-density polyethylene (HDPE) membrane with the thickness of 1.5mm in this project. Considering its friction performance, it is better to use rough HDPE film on the slope than to be safe. However, because there is enough clay layer in the design, the main seepage control structure of this project adopts smooth HDPE film with a thickness of1.5 mm.
1.2 impervious structure
Strict anti-seepage systems are installed at the bottom, slope and regulating pool of the landfill to make them impervious to water to prevent groundwater pollution. The core part is a double-layer high-density polyethylene (HDPE) film. In addition, a collection layer is provided.
The bottom structure is: filter layer, main filtrate collection layer, protective layer, main impervious layer, main impervious layer, secondary impervious layer, secondary impervious layer, protective layer and construction bottom layer from top to bottom. The corresponding anti-seepage materials are: light cloth soil, 600mm thick gravel diversion layer, 500g/m2 nonwoven geotextile layer, 1.5 mm smooth high density (HDPE) film, 500g/m2 nonwoven geotextile layer, 1.5 mm smooth high density (HDPE) film and 500 g/. See the table below and attached figure 2.
Filling garbage layer
filter layer
Light working soil distribution
Main filtrate collection layer
600mm thick gravel diversion layer
covering layer
500g/m2 nonwoven geotextile layer
Main impermeable layer
1.5mm smooth HDPE film
Secondary filtrate impervious layer
500g/m2 nonwoven geotextile layer
Secondary impermeable layer
1.5mm smooth HDPE film
covering layer
500g/m2 nonwoven geotextile layer
Build the bottom surface
Basic soil
The seepage control structure of the slope and the regulating pool, like the bottom of the field, is considered from the safest point of view and cannot be sloppy.
2. Leachate collection and discharge system
2. 1 leachate diversion layer (i.e. primary filtrate collection layer and secondary filtrate collection layer)
Leachate main collection layer: 600mm gravel layer shall be laid on the non-woven geotextile protective layer, with the particle size of 20~40mm, and it shall be laid according to the principle of coarse on the top and fine on the bottom, so as to prevent landfill garbage from blocking gravel joints and affecting the leachate diversion effect.
Leachate secondary collection layer: directly installed under the main impervious layer to monitor whether the main impervious layer leaks. If there is leakage, it can be found and collected in the secondary blind ditch.
2.2 Leachate Leaching Blind Ditch
Leachate diversion blind ditch is responsible for the final discharge of leachate, which is discharged from the site into leachate sedimentation tank and regulating tank for treatment. In order to facilitate the collection and discharge of leachate, longitudinal blind ditches are set up in each district, in which the main collection layer is laid with perforated flower tubes with a diameter of DN250mm, and the blind ditch section is formed by the diversion layer, which is wrapped with 150g/m2 woven geotextile. The secondary blind ditch is composed of permeable hoses, which has strong water permeability and is less affected by garbage settlement. After the laying of the secondary blind ditch is completed, the intermediate covering will be started.
3. Groundwater drainage system
The process design of landfill must consider the possible groundwater discharge at the bottom of landfill reservoir area. The groundwater drainage ditch is located about 2m below the leachate drainage ditch. Firstly, geotextile with filtration rate of 150g/m2 is laid in the ditch, then perforated HDPE flower pipes with DN200 are laid, and finally graded macadam is backfilled to the top of groundwater drainage ditch.
4. Leachate treatment project
4. 1 landfill leachate
Landfill leachate is light brown or dark brown, and its chromaticity is between 2000 and 4000. Corruption has a strong smell, complex components, strong toxicity and high organic matter content, and there are more than five kinds of pollutants listed in the "blacklist" of priority control pollutants in China; The concentrations of chlorine and nitrogen are high, and the concentrations of BOD5 and COD are much higher than those of ordinary sewage.
Landfill leachate comes from three aspects: one is the moisture carried by the garbage itself; The second is the water produced by the decomposition of organic matter in garbage; Third, atmospheric precipitation and groundwater enter the landfill through various channels. Among them, atmospheric precipitation and groundwater entering the site are the key factors to determine the amount of leachate produced.
The relationship between leachate produced by landfill and time can be divided into the following stages:
1) adjustment period: at the initial stage of landfill, the water in the garbage gradually accumulates and oxygen exists, and anaerobic fermentation and microbial action are slow, so the amount of leachate is less at this stage.
2) Transition period: At this stage, microorganisms in the filtrate gradually change from aerobic to facultative or anaerobic, and leachate begins to form, and the presence of volatile organic acids can be detected.
3) Acidification stage: most of the filtrate contains volatile organic acids, the pH value decreases, the COD concentration is extremely high, and the BOD5/COD ratio is 0.4~0.6, so it has good biodegradability and dark color, belonging to the initial leachate.
4) Methane generation stage: In this stage, the organic matter is converted into CH4 and CO2 by methanogenic bacteria, and the pH value rises, while the COD concentration drops sharply. The ratio of BOD5/COD is 0. 1~0.0 1, which has poor biodegradability and belongs to late leachate.
5) Maturity: At this time, the available components in leachate are greatly reduced, the biological stabilization of bacteria tends to stop and stop gas production, the system changes from anaerobic to aerobic, and the natural environment is restored.
4.2 landfill leachate treatment process scheme
According to the monitoring data of leachate quality at home and abroad, BOD5/COD in leachate is 0.2 ~ 0.8. At first, the biodegradability of landfill leachate is good, but with the passage of time, its biodegradability will gradually decrease. Leachate from municipal solid waste sanitary landfill belongs to sewage with high nitrogen content and high organic concentration, and its flow rate and load are constantly changing. Therefore, this project plans to combine biological treatment with physical and chemical treatment, supplemented by advanced treatment, so that the two complement each other and maximize the treatment effect.
The equipment used is EGSB reactor and microfiltration device (CMF). The combined process of EGSB reactor +CASS reaction tank+microfiltration device (CMF)+ biofilter+reverse osmosis (RO) is proposed for its sewage treatment project, as shown in the figure:
Figure: Process flow of landfill leachate treatment
4.3 Process design
(1) regulating pool: the capacity of regulating pool is 20,000m3. Before the sewage enters the regulating tank, the pH value is adjusted by adding acid or alkali to make it in the anaerobic slightly alkaline stage, thus providing stable conditions for its next anaerobic reaction.
(2)EGSB reactor: (See attached figure 3)EGSB is a kind of expanded granular sludge bed, which is developed on the basis of UASB reactor, inherits almost all the advantages of UASB and has more advanced technology. As an efficient anaerobic bioreactor, it has high sludge concentration and volume load, can adapt to certain fluctuations of water quality and quantity, and has strong impact load resistance. In addition, it can decompose high molecular organic matter which is difficult to biodegrade into small molecules, which is helpful to improve the biodegradability of organic matter and greatly reduce the treatment load of subsequent units. Biogas generated by EGSB reactor is transported to biogas power generation area for power generation. Its characteristics are as follows:
1) takes granular sludge as the technical core.
2) The height of EGSB reaches 15m, while that of UASB is only 5.5m at the same volume, so the EGSB area is smaller, the influent distribution is more uniform, and the mass transfer effect is better.
3) Because the granular sludge of EGSB is suspended, the contact effect with water is better and the removal rate of organic matter is higher.
4) 4) The sludge amount of EGSB reactor can reach 50,000 ~ 60,000 mg/L, while the sludge amount of UASB reactor is only half of its capacity. Therefore, EGSB bears higher influent concentration, higher impact resistance and higher load.
5) When treating high-concentration organic wastewater, the treated effluent does not circulate, which can further save energy consumption and reduce operating costs.
(3)CASS reaction tank: circulating activated sludge system. It is developed on the basis of sequencing batch activated sludge process, and an anoxic biological selection zone is set at the front end of the reaction tank, as shown in the attached figure. Its advantages are: no secondary sedimentation tank is needed, which saves capital investment and occupies a small area; The reaction tank consists of anoxic pre-reaction zone and aerobic main reaction zone, which has good removal effect on refractory organic matter, good effluent quality and no sludge bulking; Has good nitrogen and phosphorus removal effect; High degree of automation and simple operation; After dilution, the influent concentration of CASS tank decreases, and the gradient of organic pollution concentration becomes smaller, which is beneficial to improve the biological treatment effect.
(4) Biological filter: The sewage from CASS reaction tank is very beneficial to biological treatment, so the biological filter can well remove the remaining organic matter. Excess sludge is discharged into sludge storage tank and backfilled after being treated by filter press.
(5) Microfiltration device: CMF is a closed-circuit continuous operation system with hollow fiber microfiltration membrane as the central processing unit, and specially designed pipelines, valves, self-cleaning units, dosing units and PLC automatic control units. When the water to be treated is filtered by microfiltration membrane under a certain pressure, it can be physically separated, so that most of the residual organic matter can be effectively removed, thus realizing the combination of physical and biological treatment, making up for each other and exerting greater removal effect.
CMF device mainly includes pre-filtration system, microfiltration host, water supply system, backwashing system, compressed air system, chemical cleaning system and PLC automatic control system. See the figure below:
Figure: CMF microfiltration device
(6) Reverse osmosis device: The post-treatment of leachate usually adopts reverse osmosis process to remove medium molecular weight dissolved organic matter and most soluble salts. Because after a series of treatments, the organic concentration of sewage is greatly reduced, which is suitable for removing residual dissolved substances. In this way, the sewage has been further purified. Its effluent is sent to the water supply center or reused by adjusting the flow through the regulating pool.
Verb (abbreviation of verb) Design of collection and utilization of landfill gas
1. Main components of landfill gas
The main gases in landfill gas (LFG) include methane, carbon dioxide, ammonia, carbon monoxide, hydrogen, hydrogen sulfide, nitrogen and oxygen. The most important gases are methane and carbon dioxide. Its typical characteristics are: the temperature reaches 43~49℃, the relative density is about 1.02~ 1.06, it is saturated with steam, and its high heat value is 15630~ 19537kJ/m3.
Of course, although there are few trace gases produced by landfill, the composition is complex and toxic, which cannot be ignored.
2. Landfill gas collection method
This project adopts LFG active control system, that is, some vertical gas guide wells (see attached figure 6) or horizontal blind ditches are laid in the landfill. These gas guide wells and blind ditches are connected to pumping equipment through pipelines, and the pumping equipment pumps the gas guide wells and blind ditches to extract LFG. Due to the large landfill area and large landfill volume, the horizontal blind ditch is adopted, and the air is easy to enter the air extraction system, so the vertical pumping well is used for air extraction in this project. Considering the landfill thickness, landfill scale and other factors, the garbage unit is sealed, and then the gas is collected by drilling down the pipeline.
The active control system of landfill gas is mainly composed of pumping well, gas collector, condensate collecting well, pumping station, vacuum source, gas treatment station and gas monitoring equipment.
Generally, landfill gas active control system is divided into two types: internal landfill gas collection system and edge landfill gas collection system. Internal landfill gas collection system: this system is often used to recover landfill gas and control odor and surface emission, such as the active landfill gas collection system at the edge of the attached figure: this system mainly recovers and controls the lateral surface migration of landfill gas. Peripheral pumping wells are used to pump air.
3. Condensed water collection and discharge
Landfill gas will gradually cool during transportation, resulting in corrosive condensate containing many organic and inorganic chemicals. These condensates will vibrate the pipeline, restrict the air flow, increase the pressure difference and hinder the system operation. Therefore, a condensate collection system should be set up. In general, condensate collecting well is installed at the lowest part of gas gathering pipeline to avoid pressure difference increase and vibration.
4. Gas delivery system
The collected gas is finally collected in the main pipeline and transported to the gas-fired power plant by the blower. Its conveying pipeline material adopts PE.
5. Utilization of landfill gas
Due to the large-scale landfill project, the amount of garbage treated is also large, and the biogas generated is considerable and lasts for a long time, so the landfill gas of this project is mainly used for power generation. The overall process flow of gas treatment and utilization is shown in the following figure:
Figure: Process flow of landfill gas treatment and utilization
(See attached figure 7 for its biogas turbine power generation burner)
Environmental monitoring design of intransitive verbs
Environmental monitoring must be carried out in the management of landfill sites, and environmental monitoring is the evaluation level of the operation status of garbage disposal facilities. The monitoring content involves the determination of atmosphere, groundwater, surface water, leachate, landfill gas, pile settlement, fly density and landfill garbage. The monitoring items are as follows:
Monitoring project
executive standard
explain
surface water
PH, SS, BOD5, CODcr, NH3-NNO2, NO3-N, Cl-, TP, etc.
The background monitoring of the landfill is carried out in three times, once in dry season, once in peak season and once in normal season, and twice in peak month.
underground water
PH, total hardness, chloride, CODcr, water level ammonia nitrogen, volatile phenol, cyanide, Escherichia coli, etc.
Pollution Control of Domestic Waste Landfill Site (GB 16889—— 1997)
Flush the monitoring well 3 days before sampling, and the amount of water pumped during flushing is 3~5 times of the water stored in the well, and adjust the monitoring index if necessary. The monitoring points are groundwater monitoring wells and domestic wells. It is monitored three times a year, and the sampling time is in April, August and165438+1October respectively. (see attached figure 5)
infiltration
PH, SS, BOD5, CODcr, NH3-N Escherichia coli, etc.
The monitoring points are: leachate collection well and leachate treatment facility discharge port, which are monitored three times a year, and the sampling time is April, August,165438+1October respectively.
atmosphere
TSP, odor intensity, ammonia, hydrogen sulfide, methyl mercaptan, etc.
There is a monitoring point in the upwind direction and a monitoring point in the downwind direction. When the wind direction is not fixed, it can be increased appropriately. Monitoring twice a year, sampling time in April and August respectively.
landfill gas
Methane, carbon dioxide, carbon monoxide, N2, oxygen, H2, H2S, etc.
The monitoring point is the biogas collection nozzle, which can monitor one point. Monitoring once a year, and it is required to be carried out in August.
Fly density
Technical standard for environmental monitoring and pollution control of domestic waste landfill site
After the landfill is put into use 1~3 years, it will be monitored four times a year, preferably from July to September.
noise
Field boundary noise
Measurement method of noise at boundary of industrial enterprises
Seven. ancillary works
The ancillary works of landfill include civil engineering, road engineering, water supply and drainage engineering, fire fighting engineering, power supply and distribution design, automatic control instrument design, garbage metering, communication, energy saving, greening and so on.
1) civil engineering: the living area is mainly a comprehensive building, which consists of office building, staff canteen and staff dormitory on duty. The architectural modeling of the complex building and the central square are integrated into a complete space in front of the factory, which has a strong sense of movement and plays a role in guiding the sight and people flow.
2) Road engineering: When the circular curve in road design is less than 150m, the superelevation of 5%~6% shall be adopted at the radius of the curve, and the subgrade widening transition section shall be set. Its ancillary works mainly include road drains, culverts, slope protection, earth retaining piers, signs, etc.
3) Water supply and drainage project: Its water consumption design includes the sum of road spraying, greening water, domestic water, fire fighting water, car washing water and unforeseeable water.
4) Fire fighting project: The fire fighting design of this project includes living area and landfill operation area. Combustible gas detectors and alarm instruments should be calibrated and maintained at ordinary times.
5) Power supply and distribution design: The installed capacity of equipment in this project is 453.97KW, and all electrical equipment is 380/220V low-voltage equipment.
6) Design of automatic control instrument: including statistical summary, condition monitoring, online monitoring of environmental protection, office automation, etc.
7) Garbage metering: As the processing capacity of this project is 600~ 1200t/d, about 200~400 garbage trucks enter the site every day, that is, about 30 cars enter the site every hour on average, that is, about 1 car enters the factory for weighing every 2 minutes. Therefore, two weighbridges are set for calculation.
8) Communication: telephone communication lines and small telephone exchanges are set up. The factory is equipped with four direct dial telephones, which are located in the general manager's office, the deputy manager's office, the general dispatching room and the management section, and the other fax telephone is located in the office.
9) Energy saving: choose vehicles with low energy consumption for landfill operation; Choose efficient leachate delivery pump, etc.
10) Greening: the green belt is a combination of point, line and surface, including squares, lakes, fountains and flower beds. The landfill area and the living area are separated by a green belt with the width of10 ~15m. Different tree species are collected and blended with each other to arrange layered greening landscapes with different colors, heights and shapes.
Eight. Site closure project
The final covering system of landfill mainly consists of five layers: topsoil, protective layer, drainage layer, barrier layer and foundation layer/gas gathering layer. The final covering materials are compacted clay, geomembrane and geosynthetic clay layer. Only by combining these three can we achieve the best economic and environmental benefits.
The final covering system of the landfill is 15cm shallow covering soil layer, 60cm protective layer, HDPE geomembrane, geotextile drainage layer and 45cm compacted clay layer from top to bottom. See attached figure 4 for its field sealing structure.
1) 15cm shallow ground cover topsoil: it can promote plant growth and protect barrier layer, and provide certain water holding capacity.
2)60cm protective layer: its function is to store the water infiltrated into the covering layer until it is lost by transpiration of plants; Separate garbage from excavators and plant roots; Reduce the possibility of human contact with garbage; Protect the lower layer in the covering system from the damage and damage of the covering material caused by excessive dry-wet alternation and freezing; Lateral drainage.
3)HDPE geomembrane: A 1.5mm smooth high-density (HDPE) membrane consistent with the impervious material of the foundation cushion system is adopted, and it is combined with the upper and lower clay layers to form a composite impervious structure.
4) Geotextile drainage layer: geotextile with geotextile filter layer is used to reduce the water head of the barrier layer below it, so as to minimize the water infiltration through the covering system; Reduce pore water pressure in covering materials and improve slope stability.
5)45cm compacted clay layer: Compacted clay still has a certain anti-seepage effect, and it is economical and convenient to use with HDPE geomembrane.
After the site is closed, it must be maintained, including the continuous operation and monitoring of site maintenance and pollution control. Specifically, it includes: operation and monitoring of leachate treatment system, operation and monitoring of odor treatment system of leachate regulating tank, operation and monitoring of landfill gas drainage system, groundwater monitoring, surface water monitoring, ground subsidence monitoring, site maintenance, etc.
Nine. economic appraisal
1. Overview
The annual treatment capacity of the municipal solid waste landfill project is 2 1.9 million tons/year, the total landfill capacity is 6 1.92 million m3, and the service life is 2 1 year.
2. Main technical and economic indicators
Scale of garbage disposal; 2 1 0.9 million tons/year, total landfill volume: 610.93 million m3, service life: 21year. Labor capacity: 50 people, total project investment: 94,730,600 yuan, unit operating cost: 12.99 yuan/ton, financial internal rate of return: 6.03%, payback period: 12.95 years.
3. Financial analysis
3. 1 Cost-benefit estimation
1) calculation period: 2 1 year, in which the construction period is 12 months.
2) Total investment of the project: 94,730,600 yuan.
3) source of funds: apply for a state subsidy of 50 million yuan, and the rest will be raised by the city itself.
4) Formation of fixed assets, intangible assets and other assets: fixed assets are composed of engineering costs, various expenses except training fees for production workers, reserve funds, interest during construction period and adjustment tax for investment direction of fixed assets.
5) Operating cost estimation: estimate the cost by factors, including: outsourced materials, fuel, power, wages and welfare, maintenance, depreciation, management fees and financial expenses. So the total unit cost is 34.4 1 yuan/ton. Operating cost refers to the total cost after deducting depreciation of fixed assets, intangible assets and other assets and financial expenses. The annual average unit operating cost of this project is 12.99 yuan/ton.
6) Income estimation: If 48 yuan is charged for each ton of garbage disposal fee, the annual income will be 6,543,800 yuan+005,080 yuan.
7) Taxation: This project is a public welfare project, not for profit. There is no business tax.
8) Loan: No bank loan.
9) Profit estimation: the investment profit rate is 4.08%, and the investment interest rate tax is 4.08%.
3.2 Financial evaluation:
Profitability analysis: the financial internal rate of return is 6.03%, the payback period is 12.95 years, and the financial net present value is 257,900 yuan.
4. Economic analysis
Environmental benefits: after the implementation of this project, it can improve the urban environmental quality and make the garbage meet the requirements of harmless treatment, which has great environmental benefits; The improvement of the overall environmental quality is beneficial to people's physical and mental health and reduces the occurrence of diseases and medical expenses; The construction and investment of landfill increased employment opportunities and produced good social benefits; The improvement of urban environmental quality will attract more investment and promote the development of tourism and other tertiary industries, thus bringing great social and economic benefits.
5. Conclusion
1. The financial internal rate of return is 6.03%, which is greater than the acceptable minimum internal rate of return of 6%, and the financial net present value is greater than 0, so it has certain viability.
2. This project has great direct economic benefits (economic benefits brought by power generation) and indirect benefits, so its economic internal rate of return will be much greater than the financial internal rate of return, and its economic internal rate of return can also meet the requirements of being greater than the benchmark economic rate of return. Therefore, from the economic point of view, this project is feasible.
3. According to the above situation, the financial cost-benefit and economic cost-benefit of this project are good, and the project is feasible.
X.summary
The site selection, design, scheme selection, equipment selection and economic analysis of this landfill site have all gone through strict argumentation and repeated consideration before reaching a conclusion, and the state has also given considerable support. It is believed that the completion of this sanitary landfill treatment project of domestic garbage will be a great blessing for this city. The environmental sanitation level of this city will reach a new level, achieving a win-win situation for environmental and economic development, and will also contribute to the environmental protection cause in China.
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