Treatment of Landfill Leachate Using an Advanced Microwave Reactor Coupled with a Batch and Continuous Algal Photobioreactor

Landfill leachate poses a significant environmental challenge due to its high concentrations of organic pollutants, nutrients, and toxic metals. This study presents a hybrid microwave-coagulation-algal (M-C-A) photobioreactor system that operates in batch and continuous-flow modes for effective leachate treatment. The hybrid system integrates microwave-assisted removal, coagulation, and algal bioremediation to enhance pollutant removal efficiency. Furthermore, the microwave pretreatment achieved 83.6% ammonia removal at 95 °C, thereby reducing leachate toxicity and enhancing the subsequent biological treatment. Coagulation using FeCl3 further removed 76% of the COD and 90% of the turbidity. The pretreated leachate was further subjected to algal photobioreactor treatment, during which optimal growth occurred at a 50% leachate dilution, resulting in 77% total nitrogen (TN) removal and 17% total phosphorus (TP) removal. In the continuous-flow algal sequencing batch reactor (ASBR), the maximum TN and TP removal rates were 23.50 and 2.66 g/m3/d, respectively. The heavy metals Zn2+ and Pb2+ were removed, with Fe removal reaching up to 92%. The harvested algal biomass exhibited a calorific value of 16.50 MJ/kg, indicating its potential for biofuel production. Finally, the integrated M-C-A system demonstrated efficient removal of organic matter, nutrients, and metals, while enabling biomass valorization. The continuous flow operation ensures scalability and operational stability, making it a promising sustainable technology for managing landfill leachate and recovering resources.