Landfill Leachate Treatment: How to Size, Select and Budget an LTP

Two landfills a hundred kilometres apart can produce leachate that needs completely different plants. The first question is always the age and type of the waste. Young landfills (under five years) give acidic leachate with COD of 10,000–60,000 mg/L and a BOD/COD ratio above 0.5 — highly biodegradable, and a candidate for anaerobic pre-treatment. Old or stabilised landfills give dark, alkaline leachate with COD of 2,000–5,000 mg/L but a BOD/COD ratio below 0.1: most of that COD is humic and fulvic acid that no biology will touch.

Ammoniacal nitrogen is the second decider. At 500–1,500 mg/L, nitrification–denitrification in a well-designed MBR is economic. Above 2,000 mg/L the aeration energy and alkalinity demand climb steeply and air stripping ahead of biology starts to pay for itself. Chloride and TDS (commonly 5,000–20,000 mg/L) decide whether the polishing stage is nanofiltration, conventional RO or disc-tube RO, and whether a reject evaporator is unavoidable.

We therefore begin every leachate project with a sampling campaign: weekly composite samples through at least one dry-to-wet transition, analysed for pH, COD, BOD, TKN, ammonia, TDS, chloride, sulphate, alkalinity, heavy metals (Cr, Ni, Zn, Cu, Pb, Cd, Fe) and colour. Designing from a single grab sample is how leachate plants fail.

Leachate generation follows rainfall. A 10-hectare Indian landfill may produce 40–80 KLD in the dry months and 400 KLD or more in a heavy monsoon week. Sizing the treatment plant for the peak would leave it idle for eight months; sizing it for the average would flood the site every July. The answer is lined storage — a leachate pond or HDPE-lined tank holding 30–60 days of peak inflow — with the plant sized for roughly 1.5 to 2 times the annual average flow and run continuously.

For legacy dumpsite bio-mining contracts the profile is different again: flows are large and erratic for two to four years and then stop. Containerised or skid-mounted plants that can be moved to the next site are the right answer there, not civil structures.

1. Is BOD/COD above 0.4 and COD above 8,000 mg/L?Yes → anaerobic pre-treatment (UASB or anaerobic contact) before aerobic; biogas can heat or power part of the plant. No → skip straight to aerobic.
2. Is ammonia above ~1,500 mg/L?Yes → air stripping with acid scrubber, or high-pH lime stripping, ahead of biology. No → nitrification–denitrification in the MBR handles it.
3. Aerobic stageMembrane bioreactor with 20–40 day sludge age. Long SRT is essential for slowly degradable organics; conventional ASP with clarifiers rarely holds the biomass in leachate service.
4. Is residual COD after MBR above the outlet limit?Stabilised leachate: yes → advanced oxidation (Fenton, ozone or electro-oxidation) or rely on RO to reject it physically.
5. Salt and metalsTDS < 8,000 mg/L → conventional brackish RO after UF. TDS higher, or heavy fouling → disc-tube RO (DTRO), two stages, 70–80 % recovery.
6. RejectReturn to landfill (only where the licence allows and the landfill is lined and active), or MEE/MVR evaporator to ZLD. Budget for this from day one — the reject is 20–30 % of your flow.

Capital cost of a leachate treatment plant in India is typically several times that of an STP of the same capacity, because every stage is oversized for concentration and corrosion. The main drivers, in order: the concentrate handling method (an evaporator can be a third of the whole plant), membrane type (DTRO costs more than spiral-wound but survives), the ammonia route, and the amount of lined storage. Containerisation adds cost per KLD at small sizes but saves civil work, time and relocation cost on remediation contracts.

Operating cost is dominated by power (aeration for high ammonia, high-pressure pumps for DTRO, evaporator duty), chemicals (caustic or lime for stripping, antiscalant and cleaning chemicals for membranes, oxidant for AOP) and membrane replacement. A realistic OPEX model for a 100 KLD plant should include the reject route explicitly — a plant with evaporation can cost two to three times as much to run as one that returns concentrate to the landfill.

Indicative only: capital cost per KLD varies by a factor of three or more depending on leachate strength, reject route and containerisation. Ask us for a scheme-specific budget rather than a per-KLD number.

• Designed from one dry-season sample; the monsoon leachate is ten times stronger and the biology dies.
• Conventional clarifier-based ASP instead of MBR — biomass washes out, outlet COD never stabilises.
• No plan for RO reject; it is quietly pumped back into the landfill without permission, or stored until it overflows.
• Spiral-wound RO on high-TDS, high-organic leachate — membranes foul in weeks.
• Lime stripping without a scrubber — ammonia odour complaints and a plant nobody wants to operate.
• No alkalinity for nitrification — pH crashes, ammonia removal stops.

Sampling and characterisation, then a technology selection memo with two or three schemes and their life-cycle cost, then detailed engineering — PFD, P&ID, mass balance, hydraulic and equipment sizing — and supply, erection and commissioning of the selected scheme, containerised or site-built. We also audit and upgrade existing leachate plants that are not meeting norms. See the leachate treatment plant page for the full process description.