Garbage leachate treatment methodology
Leachate constitutes a noxious, black or yellow-brown wastewater, endowed with a distinct and unpleasant odor, resulting...
Garbage leachate treatment methodology
Leachate constitutes a noxious, black or yellow-brown wastewater, endowed with a distinct and unpleasant odor, resulting from the administrative disposal of municipal solid waste in landfills.
The leachate incorporates an extensive variety of organic and inorganic substances, including various recalcitrant organic compounds (such as various aromatic compounds and humic substances), inorganic salts (such as ammonium, carbonate, and sulfate ions), and metal ions (such as chromium, lead, and copper).
Among these, the most distinctive feature of leachate from garbage is its elevated content of pollutants, most of which possess biological toxicity.
Typically, leachate accounts for 35%-50% of the landfill volume (by weight), and the concentration of pollutants can fluctuate up to 5 times.
There are three primary sources: the moisture inherent in the garbage itself, the infiltration of surface or groundwater, and the moisture generated by the degradation of organic matter in the garbage.
Challenges in the treatment of leachate from garbage
01
High ammonia nitrogen and high COD
The COD in the leachate of garbage can escalate to 90000 mg/L, and the ammonia nitrogen is generally above 2000 mg/L. Moreover, with the prolongation of landfill years, indicators such as total nitrogen in the water body will augment, rendering it even more challenging to attain standard discharge.
Traditional treatment methodologies, particularly the core biological treatment process, can generally efficiently eliminate ammonia nitrogen from leachate, but the removal of total nitrogen is suboptimal.
02
Complex composition, high concentration, high salinity
The leachate from garbage possesses high salinity and complex composition, encompassing more than 10 dissolved ions, heavy metals, and organic pollutants. Certain metal ions with high concentrations, such as iron, zinc, lead, and calcium ions, will exert a severe inhibitory effect on the biological treatment process.
The organic content is substantial, and it contains a significant amount of toxic and high molecular weight organic compounds. Utilizing a single physicochemical or biochemical process cannot achieve standard emissions, necessitating a combination of physicochemical and biochemical treatment processes for treatment.
03
Significant alterations in water quantity and quality
The water quality of leachate from garbage fluctuates considerably, and the yield exhibits seasonal variations, with the rainy season significantly higher than the dry season. The water quality and quantity of leachate vary substantially in different seasons and ages, posing challenges to the selection and operation of treatment processes.
04
High cost of carbon sources/Nutrients
Methanol and glucose are commonly utilized as carbon sources for the biochemical treatment of leachate from garbage, and their cost is substantially higher than that of composite carbon sources. Furthermore, numerous enterprises adopt membrane treatment processes primarily based on nanofiltration or reverse osmosis as the final deep treatment, culminating in long-term high costs for leachate treatment.
05
High emission standards
The national standards for wastewater discharge in the leachate industry are stringent, and there are even higher discharge standards for areas susceptible to severe environmental pollution problems.
06
The processing technology is intricate and the processing cost is high.
Presently, in order to achieve standard discharge, leachate treatment plants frequently adopt membrane treatment processes primarily based on nanofiltration or reverse osmosis as the final deep treatment, in addition to utilizing combination processes, resulting in long-term high leachate treatment costs.
Garbage leachate treatment methodology
(1) UASB＋SBR＋CMF＋RO
Process analysis:
The methodology is notably complex;
The amount of residual sludge is minute;
A segment of 20% to 28% of the concentrated solution must be processed;
The processing capability is susceptible to TDS and temperature fluctuations in water;
The lifespan of the membrane typically caps at 2-3 years.
(2) MBR＋NF/RO
Process analysis: The MBR process primarily contributes to nitrification of NH3-N, possessing restricted denitrification potential, high nitrate concentration in effluent, and elevated dissolved oxygen concentration; There is a startup phase for biological inoculation domestication in biochemistry, thus it is not advisable to initiate and cease the equipment at will, as equipment maintenance proves challenging; The system control prerequisites are high, and BOD, COD, and NH3-N are predominantly eliminated through biochemical processes. Ammonia can only be efficiently eliminated when the biochemical treatment efficacy is robust; Sludge possesses high concentration, robust stability, low viscosity, facile dewatering, and is not prone to spoilage.
(3) Pretreatment+secondary DTRO disc tube reverse osmosis methodology
Process analysis: The DTRO membrane assembly is prone to blockage and contamination, with high backwash intensity and brief membrane service life; 20%~25% concentrated solution necessitates treatment; The water production rate is susceptible to the conductivity, TDS, and temperature in the water, and the system is prone to instability; There is an accumulation issue of ammonia nitrogen and salt, which necessitates subsequent process treatment; The cost is relatively substantial.
(4) Pretreatment+MVC evaporation+ion exchange+ammonium crystallization recovery
Process analysis: The advantages of simplistic process, high degree of automation, stable processing and effect, and convenient management can conserve labor input; Equipment is prone to scaling and corrosion; Concentrated liquid is generated; High electricity consumption; High investment.
(5) Pretreatment+A/O system+Advanced oxidation+BAF
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