Landfill leachate treatment using fungi and fungal enzymes: a review

Landfill leachate raises a huge risk to human health and the environment as it contains a high concentration of organic and inorganic contaminants, heavy metals, ammonia, and refractory substances. Among leachate treatment techniques, the biological methods are more environmentally benign and less expensive than the physical–chemical treatment methods. Over the last few years, fungal-based treatment processes have become popular due to their ability to produce powerful oxidative enzymes like peroxidases and laccases. Fungi have shown better removal efficiency in terms of color, ammonia, and COD. However, their use in the treatment of leachate is relatively recent and still needs to be investigated. This review article assesses the potential of fungi and fungal-derived enzymes in treating landfill leachate. The review also compares different enzymes involved in the fungal catabolism of organic pollutants and the enzyme degradation mechanisms. The effect of parameters like pH, temperature, contact time, dosage variation, heavy metals and ammonia are discussed. The paper also explores the reactor configuration used in the fungal treatment and the techniques used to improve leachate treatment efficacy, like pretreatment and fungi immobilisation. Finally, the review summarises the limitations and the future direction of work required to adapt the fungal application for leachate treatment on a large scale.