Completely quantified garbage leachate refers to a highly concentrated wastewater that forms from the moisture contained in the garbage itself at the landfill, rain and snowwater entering the landfill, and other water sources, after deducting the saturation water content of the garbage and cover soil layers, and passing through the garbage and cover soil layers.
The water quality of landfill leachate is quite complex, typically containing high concentrations of organic matter, heavy metal salts, SS (suspended solids), and ammonia nitrogen. Landfill leachate not only pollutes soil and surface water sources but also contaminates groundwater. There have been many studies on the removal of CODCr from landfill leachate, generally employing biological treatment methods. However, the treatment effectiveness is not very satisfactory, and the operational costs are relatively high.
Feature
Anaerobic ABR: Designed with a rational and effective program to address the characteristic of elevated COD concentration in late-stage leachate.
BAF: Under the new standards, increased pressure to meet total nitrogen requirements; the BAF's ammonia nitrogen and total nitrogen removal efficiency is superior to other equipment.
Anoxic Reactor Tank: Further total nitrogen removal is achievable.
Ultrafiltration membrane bioreactor: Effectively increases sludge concentration in the biochemical unit, removes organic matter, ammonia nitrogen, total nitrogen, and other pollution indicators, and serves as a pretreatment process before subsequent nanofiltration membrane work.
Reverse Osmosis: Retains organic matter and heavy metal ions while preventing the accumulation of heavy metals within the system.
Coagulation Sedimentation: Treat the concentrated wastewater promptly to prevent the accumulation of organic matter within the system during circulation.
Process Features
1. Utilizing mature technology to meet the new standard requirements
2. Nitrogen removal (ammonium nitrogen and total nitrogen) is one of its major features.
3. Compact land requirement, cost-effective investment, and low operation costs
4. Short construction period
5. Easy maintenance and management
6. Streamlined the cumbersome task of construction drawing design
7. Detachable and transportable
Hazards and Handling
Most cities in our country use sanitary landfilling as the primary method for waste disposal, and this will remain the basic approach for urban domestic waste management in the coming period. While sanitary landfilling is a common waste disposal method, it also poses numerous pollution issues, particularly with the large amounts of leachate generated during the landfilling process. Improper handling of this leachate can lead to severe contamination of nearby water bodies and soil.
Pollution characteristics
Leachate is wastewater that seeps out during the disposal and landfilling process of garbage due to fermentation, rainwater erosion, and infiltration from surface water, groundwater. The main sources consist of four aspects: the inherent moisture in the garbage, water produced by biochemical reactions in the garbage, the backflow of groundwater, and atmospheric precipitation. Among them, atmospheric precipitation is characterized by its concentration, short duration, and recurrence, accounting for a large portion of the total leachate volume. Leachate is a complex, high-concentration organic wastewater, whose properties depend on factors such as the composition of the garbage, particle size, compaction level, local climate, hydrological conditions, and landfilling time. Generally, it has the following characteristics:
1.1 The water quality is complex and highly harmful. Studies have shown that the analysis of organic pollutants in leachate using GC-MS co-employment technology has detected 63 main organic pollutants in the leachate, with 34 having a reliability of over 60%. Among them, there are 6 alkenes, 19 carboxylic acids, 5 esters, 10 alcohols and phenols, 10 aldehydes and ketones, 7 amides, 1 aromatic hydrocarbon, and 5 others. One has been confirmed as a carcinogen, 4 as cocarcinogens or synergistic carcinogens, 1 as a mutagen, and 6 have been listed on China's "blacklist" of priority environmental pollutants.
1.2 High concentrations of CODcr and BOD5. The concentrations of CODcr and BOD5 in the leachate can reach up to 90,000 mg/L and 38,000 mg/L, respectively, even higher. 1.3 High ammonia nitrogen content, which increases with the extension of landfilling time, up to 1,700 mg/L. Nitrogen in the leachate mostly exists in the form of ammonia nitrogen, accounting for about 40%-50% of TNK.
1.3 Significant Water Quality Variations. Based on the age of the landfill, leachate is categorized into two types: one is the young leachate from landfills less than 5 years old, characterized by high CODcr and BOD5 concentrations and strong biodegradability; the other is the old leachate from landfills over 5 years old. As fresh waste gradually turns into aged waste, its pH value approaches neutral, with CODcr and BOD5 concentrations decreasing, a reduced BOD5/CODcr ratio, and increased ammonia nitrogen concentration.
1.5 High Metal Content. The leachate contains more than a dozen metal ions, with iron and zinc being high during the acidic fermentation stage, with iron concentrations reaching about 2000 mg/L; zinc concentrations about 130 mg/L; lead about 12.3 mg/L; and calcium even up to 4300 mg/L [4].
1.6 Imbalanced Microbial Nutrient Ratios in the leachate, primarily due to an imbalance in the C:N:P ratio. Generally, the BOD5:P ratio in typical leachate is usually greater than 300.
Impact on the Environment
An investigation into the leachate treatment at a landfill site revealed that, to date, approximately 800,000 tons of leachate have been processed. Concurrently, around 320,000 tons of leachate overflowed from the wastewater lagoon directly into the receiving water body, with an additional 96,000 tons stored within the lagoon. Chemical analysis at the wastewater lagoon outlet showed an average CODcr of 2800 mg/l, BOD5 of 1750 mg/l, ammonia nitrogen of 708 mg/l, total nitrogen concentration of 700 mg/l, and an average chromaticity of 251 degrees. Metal content was low, and organic matter contained up to 12 carbon numbers, primarily cycloalkanes, esters, carboxylic acids, phenols, and sulfur. After treatment, the water discharged into the receiving water body had a CODcr of 283 mg/l, still exceeding the standard by 1.83 times, BOD5 of 108 mg/l, exceeding the standard by 2.6 times, NH3-N of 190 mg/l, exceeding the standard by 11.67 times, total nitrogen of 679 mg/l, chromaticity of 133 degrees, and contained a large amount of organic matter. This indicated that the wastewater treatment process at the site had not yet met the standards for effluent discharge. Consequently, the water quality of the primary receiving water body at the landfill has significantly deteriorated, which has drawn high attention from local authorities.
Process improvement
In response to the issues present at the landfill, the following suggestions for improving the wastewater treatment facilities are proposed:
In selecting processing techniques, we should shift from old thinking patterns, abolish those processing schemes that fail to meet the processing standards, and adopt the energy-saving MVC steam compression evaporation treatment process.
(2) Enhance the operational management of oxidation ponds. We hope that this improvement will enable the treated wastewater to meet the standard for discharge, effectively controlling the pollution caused by leachate to the surrounding environment.
(3) Employing the terminal ion exchange process as a security filtration system can effectively prevent fluctuations in ammonia-nitrogen indices.
Waste leachate treatment manufacturers
Zhongke Guosheng is a team jointly established by Guangzhou Zhongkang Environmental Protection and the Chinese Academy of Sciences, specializing in the treatment of high-concentration and difficult industrial wastewater. It is applied in the treatment of high-concentration wastewater in the petrochemical, food breeding, surface treatment, dyeing and papermaking, garbage leachate, and hazardous waste industries, providing more options for wastewater solutions, significantly reducing costs for clients, and promoting green environmental protection and energy-saving.
