The wastewater from landfill leachate has high organic matter concentration, many types of pollutants, and great changes in water quality. If these wastewaters are not effectively treated, they will pollute the water environment in the area. Shanqing Environment uses the "pretreatment and impurity removal process + inclined plate sedimentation process + air flotation to remove suspended solids + UASB hydrolysis and acidification + A0 biofilm treatment + catalytic oxidation + RO reverse osmosis" process for this type of wastewater, so that the treated wastewater meets the standards for discharge or reuse.
1. Engineering Design
Water volume analysis: According to the relevant information provided by the owner, the wastewater treatment facility in this plan has a treatment capacity of 200 m³ /d, running 20 hours a day, and 10 m³ /h.
Source of sewage: leachate wastewater.
According to the relevant data of the same type of sewage, the wastewater quality is as follows:
Unit: mg/L (except pH)
Table 1 -1 Wastewater Influent Quality
According to the relevant standards in "Water Quality for Industrial Water Use in Urban Wastewater Recycling" (GB/T 19923-2005), the effluent can be reused for process and product water, direct cooling water, open circulating cooling water system supplementary water, washing water, etc. Specific indicators are shown in the table below:
Unit: mg/L (except pH)
Table 1 -2 Water output index table
2．Process flow and description
Figure 2-1 Process flow chart
2.1 Regulating pool
The role of regulation is mainly reflected in the following aspects:
1. Provide buffering capacity for sewage treatment load to prevent drastic changes in treatment system load;
2. Reduce the fluctuation of sewage flow entering the treatment system, so that the feeding rate of chemicals used in sewage treatment is stable and suitable for the capacity of the feeding equipment;
3. In terms of controlling the pH value of sewage and stabilizing water quality, the neutralization capacity of different sewage can be used to reduce the consumption of chemicals in the neutralization process;
4. Prevent high concentrations of salt from directly entering the biochemical treatment system;
5. When a factory or other system temporarily stops discharging sewage, sewage can still be input into the treatment system to ensure the normal operation of the system.
2.2 Self-cleaning filter
Wastewater is lifted to a self-cleaning filter to remove particulate matter and other impurities in the wastewater, facilitating the normal operation of subsequent process equipment .
2.3 Dissolved air flotation equipment
Principle: Under certain conditions, a large amount of air is dissolved in water to form dissolved air water, which is used as the working medium. By releasing the sudden decompression and rapid release, a large number of fine bubbles (1-10 m) are generated , which adhere to the m" alum flowers " in the wastewater after the coagulation reaction , so that the flocs float up, and the floating scum and floating oil are scraped off by a special scraping device to achieve the purpose of solid-liquid separation. The treatment effect depends on the surface state, particle size and specific gravity of the treated water particles.
2.4 UASB anaerobic tower
The anaerobic biological treatment process has low energy consumption; the organic volume load is high, generally 5-10kgCOD/m³·d, and the highest can reach 30-50kgCOD/m³·d; the amount of residual sludge is small; anaerobic bacteria have low nutritional requirements, strong resistance to toxicity, and high molecular weight of degradable organic matter; strong resistance to shock loads; the produced biogas is a clean energy source.
2.5 A/O Biochemical System
2.5.1 Process characteristics
(a) The process is simple, no external carbon source and post-aeration tank are required, the original sewage is used as the carbon source, and the construction and operation costs are low;
(b) Denitrification comes first, followed by nitrification, with internal circulation, using the organic substrate in the original sewage as the carbon source, which has a good effect and a sufficient denitrification reaction.
(c) The aeration tank is at the end, so that the denitrification residues can be further removed, improving the water quality of the treated water; strong aeration is used in the front section of the O section, and the gas volume is reduced in the back section to reduce the DO content of the internal circulation liquid to ensure the anoxic state of the A section.
(d) The stirring in section A only serves to suspend the sludge but avoid the increase of DO.
2.6 MBR system
2.6.1 Working Principle
A new type of treatment system that combines biological treatment with membrane separation technology. It uses membrane separation equipment immersed in an aerobic biological pool to intercept the activated sludge and macromolecular solids in the reaction tank. It can omit the final sedimentation tank and also has microfiltration, with a longer sludge age and less sludge volume.
2.6.2 Advantages
- High volumetric load , short residence time, replaces sedimentation and sand filtration, occupies a small area.
- MBR membrane can completely intercept sludge, no sludge settling problem, easy system operation and maintenance.
- Intercepts difficult-to-decompose high-molecular substances and effectively treats high-concentration organic wastewater.
- It can intercept nitrifying bacteria, achieve complete nitrification, and effectively remove ammonia nitrogen.
- It can block most pathogenic bacteria and reduce the amount of disinfectants used.
- Increase initial cost, but low operating cost, still more favorable in terms of total cost.
- Long sludge discharge cycle, maintain low F/M ratio, reduce sludge volume by more than 1/2 under biological autolysis.
- Suitable for special pollutant treatment, interception and domestication of dominant bacteria
- The sludge retention time can be quite long, and slow-growing microorganisms can be retained and multiplied, which is beneficial to special or removal of difficult to decompose pollutants.
- Suspended solids and turbidity are close to zero, suitable for water recovery
2.7 Ozone system
Principle: When oxygen passes through the discharge electric field between high-voltage AC electrodes, the oxygen molecules are dissociated into oxygen atoms under the bombardment of high-speed electron flow, and the oxygen atoms quickly react with oxygen molecules to form ozone molecules.
2.8 RO system
Figure 2-8-1 Reverse Osmosis Principle
2.8.1 Membrane Module
Reverse osmosis is the actuator of the entire desalination system, and its function is to remove soluble salts, colloids, organic matter and microorganisms from water. The reverse osmosis membrane of this system adopts a new type of polyamide composite membrane with large flux, anti-pollution and corrosion resistance.
The increase in water production is achieved by increasing the membrane area, rather than increasing the membrane flux and water supply pressure, so it can maintain a low fouling rate. In addition, it can maintain a high flow rate for a long time and extend the life of the membrane. The low operating pressure can enhance the operating economy of the system. The increase in membrane area can make the newly designed reverse osmosis system use fewer components, making the system more compact and saving installation costs.
Figure 2-8-1 Reverse Osmosis Device
The reverse osmosis device is the heart of the pre-desalting process of the project. Water treated by the reverse osmosis device can remove most of the impurities such as inorganic salts, organic matter, microorganisms, bacteria, etc.
Shanqing Environment uses the above process to treat 200 tons /day of landfill leachate wastewater to meet the discharge standards or reuse. The above case is for reference only. If you have other wastewater treatment related needs, please feel free to contact us for consultation. Shanqing Environment can provide you with more mature, reliable, efficient, energy-saving, low investment, low operating cost, and low secondary pollution water treatment processes and equipment.
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