Ammonia is a persistent contaminant in landfill leachate, anaerobic digestion effluent and industrial wastewater. It harms watercourses and makes discharge consents hard to meet and conventional biological or chemical treatment is often too costly or impractical when ammonia loads are high. Ammonia stripping works by heating the liquid so ammonium ions convert into ammonia gas, then passing air through a packed column to carry that gas out of solution. The stripped ammonia is either destroyed in a thermal oxidiser, which converts it to nitrogen and water while recycling the heat or captured as a saleable product.