LANDFILL LEACHATE TREATMENT OPTIONS & TIPS

Landfill leachate composition varies widely depending on the age of the landfill, the type of waste, precipitation and seasonal factors. As a result, treatment options vary. If the operating permit allows, leachate can be disposed to sewer for treatment at wastewater treatment plants (WWTP). It can also be transported for deep well or injection well disposal. However, if discharge to sewer or deep wells is not feasible, then treatment is required. The following outlines typical discharge limits of concern, treatment options and tips.

Typical Discharge Limits of Concern

  USA EPA Monthly Average Limit for  Surface Discharge (mg/L) Typical Leachate
Total Solids (TS) 88 2,000 to 45,000
Biological Oxygen Demand (BOD)   37 200 to 5,000
Organics: phenol, benzoic acid, p-cresol - 200 to 5,000
Ammonia   4.9 40 to 5,000
Zinc 0.11 0.1 to 10

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  USA EPA Monthly Average Limit for  Surface Discharge (mg/L) Typical Leachate
Total Solids (TS) 88 2,000 to 45,000
Biological Oxygen Demand (BOD)   37 200 to 5,000
Organics: phenol, benzoic acid, p-cresol - 200 to 5,000
Ammonia   4.9 40 to 5,000
Zinc 0.11 0.1 to 10

Treatment Systems

Due to the wide variability of leachate, choosing the right treatment option requires understanding leachate composition and treatment objectives. Depending on the objectives, a combination of systems may be required.

Reverse Osmosis (RO):

  • RO is the most dominant and widely practiced desalination technology for removal of total dissolved solids (TDS)
  • RO can be employed to remove ammonia when operated at pH ~4.5 to 5.5, but downstream polishing will likely be required to achieve < 4.9 mg/L ammonia
  • RO is low cost and reliable, but requires notable pre-treatment, reliability on scaling waters is challenging, and does not concentrate landfill leachate much past 60,000 mg/L resulting in low recoveries and high brine volumes
  • Modified RO units are available that are more reliable on landfill leachate

Evaporator / Concentrator:

  • Thermal evaporation systems that treat leachate to produce freshwater and concentrated brine
  • Brine concentration limited to ~150,000 to 200,000 mg/L TDS
  • Two types of evaporators: (1) open to atmosphere evaporators that discharge vapor and volatile emissions to atmosphere, (2) closed evaporators that re-condense vapor and volatiles
  • Notable corrosion challenges especially when ammonia exceeds 500 mg/L, requiring titanium or super duplex stainless steel wetted surfaces adding notably to cost
  • Ammonia will volatize unless pH suppressed to convert to ammonium
  • Phenols will evaporate and require post-treatment
  • Chemical softening pre-treatment (lime and soda ash) may be required for scaling fluids

SaltMaker Evaporator Crystallizer:

  • Low temperature, reliable evaporator-crystallizer that can treat raw leachate or leachate RO brine to produce freshwater and high concentration brine (~300,000 mg/L TDS without de-foaming agents upstream). Can concentrate further if foaming agents removed.
  • Designed from non-corroding parts for operation on high strength leachates
  • No pre-treatment required
  • Highly modular with no confined spaces enabling ease of economical maintenance and capacity expansion
  • Powered by low grade heat, can be provided by burning landfill gas
  • Learn more about the SaltMaker Evaporator Crystallizer

Biological Treatment (Nitrification-Denitrification):

  • Nitrification is the biological process of converting ammonia to nitrite and then to nitrate via oxidation. If required, denitrification can then convert nitrate to nitrogen gas via reduction as a second stage.
  • Results in ammonia destruction to Ngas when denitrification is employed
  • Requires large tanks and aeration chambers while being sensitive to changing water conditions, TDS, and low temperatures

Ammonia Splitter:

  • Electrochemical, membrane-based ammonia treatment system that is temperature and salinity insensitive
  • Eliminates ammonia by converting to nitrogen gas for permanent destruction, or by recovering it as a fertilizer product
  • Removes ammonia for destruction or recovery as a fertilizer product
  • Temperature and salinity insensitive, compact, and fully controllable
  • Only removes ammonia
  • Learn more about the Ammonia Splitter

Membrane Bioreactor (MBR):

  • Combination of a perm-selective membrane process (e.g. microfiltration or ultrafiltration) and a biological process (suspended growth bioreactor)
  • The membrane process acts as both a biological growth location and a filter, rejecting the solids material produced from the biological process. The membrane replaces a secondary clarifier or settling tank for solid/liquid separation which is used in conventional activated sludge (CAS) systems.
  • MBR systems only remove organic matter and can remove ammonia from the leachate; will not remove TDS

Moving Bed Biofilm Reactor (MBBR):

  • MBBR utilizes an aeration tank that circulates thousands of specialized polyethylene biofilm carriers. The biofilm carriers provide a protected surface area to support the growth of heterotrophic and autotrophic bacteria that break down organic matter in the water.
  • Biofilm processes require less space than activated sludge systems
  • MBBR systems only remove organic matter and can remove ammonia from leachate; will not remove TDS

Sequential Batch Reactor (SBR):

  • Activated sludge treatment process where oxygen is bubbled through a mixture of the wastewater and activated sludge to reduce organic matter
  • Completed in a batch process within multiple sequential tanks
  • SBR systems only remove organic matter and can remove ammonia from leachate; will not remove TDS

Treatment Options & Tips

Concern

Treatment Options

Tips

Low TDS Leachate
(<20,000 mg/L)

Reverse Osmosis

  • Requires RO designed for high fouling leachate waters, paying close attention to pre-treatment and planning for high brine volumes
  • RO has poor ammonia rejection unless operated at pH <5.5 (alkalinity in leachate may result in high acid costs)
  • Ultrafiltration (UF) pre-treatment is often required
  • Biological pre-treatment may add value (MBR)  if treating raw leachate
  • Lowest cost TDS removal technology if appropriate regarding chemistry fit, pre-treatment and brine management plans RO upstream of an evaporator can reduce evaporator size, cost, and energy consumption

Evaporator / Concentrator

  • Pre-concentrate with RO if capacities > 200 m3/day

SaltMaker

  • Pre-concentrate with RO if capacities > 200 m3/day

Moderate & High TDS Leachate (>20,000 – 40,000 mg/L)

Evaporator / Concentrator

  • Ammonia and low boiling point organics such as phenols evaporate and condense in the distillate
  • Air discharge and high energy considerations for open to atmosphere evaporators
  • Brine concentration limited to 200,000 mg/L

SaltMaker

  • Reliable solution for high TDS and variable composition leachate
  • Foaming at high brine concentrations > 300,000 mg/L if not planned for with pre-treatment
  • Ammonia evaporates and condenses in the distillate

Ammonia

Biological (Nitrification-Denitrification)

  • Does not remove TDS
  • Denitrification step is not always required if nitrates can be discharged (i.e. convert ammonia to nitrates, but not to nitrogen gas)
  • Limited to NH3 <1,000 mg/l and TDS <6,000 mg/L
  • Most reliable in stable temperatures and with non-fluctuating load
  • May require chemical or nutrient augmentation such as phosphoric acid and methanol
  • Not suitable for highly variable feed chemistry, process upsets may cause significant down time
  • Careful monitoring of dissolved oxygen required for complete reaction

Ammonia Splitter

  • Does not remove TDS
  • Requires electricity or solar PV augmentation of DC power load
  • De-ammoniated water requires post treatment pH adjustment

Organics

MBR, MBBR, or SBR

  • Does not remove TDS
  • Challenges with TDS > 6,000 mg/L
  • Carefully consider the impact of changing loads and temperatures on reliability

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Concern

Treatment Options

Tips

Low TDS Leachate
(<20,000 mg/L)

Reverse Osmosis

  • Requires RO designed for high fouling leachate waters, paying close attention to pre-treatment and planning for high brine volumes
  • RO has poor ammonia rejection unless operated at pH <5.5 (alkalinity in leachate may result in high acid costs)
  • Ultrafiltration (UF) pre-treatment is often required
  • Biological pre-treatment may add value (MBR)  if treating raw leachate
  • Lowest cost TDS removal technology if appropriate regarding chemistry fit, pre-treatment and brine management plans RO upstream of an evaporator can reduce evaporator size, cost, and energy consumption

Evaporator / Concentrator

  • Pre-concentrate with RO if capacities > 200 m3/day

SaltMaker

  • Pre-concentrate with RO if capacities > 200 m3/day

Moderate & High TDS Leachate (>20,000 – 40,000 mg/L)

Evaporator / Concentrator

  • Ammonia and low boiling point organics such as phenols evaporate and condense in the distillate
  • Air discharge and high energy considerations for open to atmosphere evaporators
  • Brine concentration limited to 200,000 mg/L

SaltMaker

  • Reliable solution for high TDS and variable composition leachate
  • Foaming at high brine concentrations > 300,000 mg/L if not planned for with pre-treatment
  • Ammonia evaporates and condenses in the distillate

Ammonia

Biological (Nitrification-Denitrification)

  • Does not remove TDS
  • Denitrification step is not always required if nitrates can be discharged (i.e. convert ammonia to nitrates, but not to nitrogen gas)
  • Limited to NH3 <1,000 mg/l and TDS <6,000 mg/L
  • Most reliable in stable temperatures and with non-fluctuating load
  • May require chemical or nutrient augmentation such as phosphoric acid and methanol
  • Not suitable for highly variable feed chemistry, process upsets may cause significant down time
  • Careful monitoring of dissolved oxygen required for complete reaction

Ammonia Splitter

  • Does not remove TDS
  • Requires electricity or solar PV augmentation of DC power load
  • De-ammoniated water requires post treatment pH adjustment

Organics

MBR, MBBR, or SBR

  • Does not remove TDS
  • Challenges with TDS > 6,000 mg/L
  • Carefully consider the impact of changing loads and temperatures on reliability

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