How Do Engineers Design Landfill Leachate Treatment Systems?

Leachate treatment is designed around a variable, high-strength wastewater: biological treatment for organics and ammonia followed by membrane processes for dissolved contaminants, with the train sized for worst-case wet-weather flows and effluent limits set by the discharge permit — after minimizing generation with covers and stormwater diversion. The cheapest gallon of leachate to treat is the one that never forms. Every serious leachate design I've reviewed starts with the water balance — covers, diversion, and operations — and only then sizes treatment.

Equalization is the unsung hero. Leachate flow and strength swing with rainfall and operations, and nothing downstream works well with shock loads. A properly sized equalization tank turns a spiky influent into something the biology can handle. Biological treatment does the heavy lifting on organics and ammonia — nitrification and denitrification for the nitrogen, which is often the permit driver. Membranes polish: ultrafiltration protects the RO, and RO removes the dissolved solids, metals, and trace organics that biology leaves behind. The structural and MEP design around the plant — tanks, buildings, power, controls — is standard industrial work, but the process sizing is leachate-specific and has to be done from real influent data, not textbook values.

Leachate plants get judged on their worst week, not their average month. Size for the wet season, the high-ammonia phase, and the equipment outage — because all three will happen. What I require in a leachate treatment design.

• Start with generation minimization: covers, diversion, and operations before treatment sizing
• Base process design on measured influent data across seasons — never on assumed averages
• Size equalization for real storm-driven flow swings, not the monthly average
• Design concentrate disposal as part of the train — evaporation, solidification, or permitted recirculation
• Meet permit limits at worst-case influent with redundancy on the critical process steps