Options for treatment of ammonia in landfill leachate.
Thesis DisciplineWater Resource Management
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Treatment of landfill leachate is often needed to remove ammonia nitrogen (free ammonia and dissolved organic nitrogen) because high concentrations are known to negatively impact on waterways and the wastewater treatment process. The objective of this study was to examine ways to reduce ammonia nitrogen in landfill leachate. The methods explored were coagulation–flocculation, adsorption and system integration methods. For coagulation–flocculation treatment: jar test experiments explored the best coagulant, effective dose, pH control, mixing regimes and the use of polyelectrolytes. Three conventional coagulants – anhydrous ferric chloride, hexahydrate ferric chloride and aluminium sulfate – were examined, alongside three commercial cationic polyelectrolytes. The best coagulant was anhydrous ferric chloride, and the coagulant dosage and pH were found to be very crucial. Anhydrous ferric chloride showed removal of about 20%, 29% and 77% of ammonia nitrogen, Chemical Oxygen Demand (COD) and colour respectively at an optimum dose of 2,000 mg/L at pH 7. The mixing regimes and polyelectrolyte additions were insignificant in ammonia nitrogen removal.
Sorption using local soils (type A, B, C and D) and zeolite was also studied. The four local soils were equally ineffective in removing ammonium from landfill leachate (< 5.0% removal); in contrast, zeolite was somewhat effective (23%).
Two system integrations were analysed: one between coagulation–flocculation and biological nitrification, and the other between adsorption and coagulation–flocculation. Obstacles encountered in biological nitrification made it challenging to draw a conclusion as to its potential. In contrast, the integration of an adsorption method with coagulation–flocculation achieved maximum reductions of ammonia nitrogen, COD, colour and turbidity of 36%, 47%, 96% and 85% respectively from landfill leachate. This treatment, however, still produces landfill leachate with high (1,450 mg/L) ammonia nitrogen concentrations.