Question 4 of 16: Leachate Treatment Processes

Question 4: Leachate Treatment Processes (6 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

(1) Biological treatment (aerated lagoon, sequencing batch reactor or activated sludge) — leachate is typically high in biodegradable organics (especially from young landfills), so aerobic biological treatment reduces BOD/COD and ammonia effectively, though it can struggle with the high ammonia and low biodegradability (low BOD:COD ratio) of leachate from older, more stabilized landfills. (2) Co-treatment at a municipal wastewater treatment plant — leachate is trucked or piped (in small controlled proportions relative to the plant's normal flow) to an existing WWTP, avoiding the capital cost of a dedicated on-site plant, provided the WWTP has hydraulic and toxicity/shock-load capacity to absorb it. (3) Membrane treatment (reverse osmosis / nanofiltration) — physically rejects dissolved salts, heavy metals and recalcitrant organics that biological processes cannot remove, producing a high-quality permeate at the cost of generating a concentrated reject stream that itself needs further management (e.g., evaporation, deep-well injection, or return to the landfill).