Growth kinetics of microalgae cultivated in different dilutions of fresh leachate for sustainable nutrient recovery and carbon fixation

Fresh leachate (FL) is toxic liquid generated from a solid waste transfer station. It is complex due to the presence of concentrated inorganics, nutrients, and degradable organic matter. Microalgae are an option for nutrient removal, however, only a few studies have reported raw leachate treatment using microalgae. Most of them emphasize on the need for its dilution to lighten the colour and minimize the toxicity and turbidity. In the present study, the effect of different dilutions of fresh leachate on the growth and nutrient recovery potential of Scenedesmus sp. was investigated. Fresh leachate dilutions viz. 5%, 10%, 15%, 20% and 25% fresh leachate were prepared using wetland treated municipal wastewater (MW) and growth kinetics of Scenedesmus sp. was studied. The highest biomass production of 2.75 gdw L−1 and carbon dioxide fixation rate of 243 mg L−1 d−1 was observed in 15% fresh leachate which was 172% and 157% higher than wetland treated municipal wastewater, respectively. Similarly, the highest removal rate of 3.27 and 0.036 mg L−1 d−1 for NH4+- N and NO2- - N was also observed in 15% fresh leachate. All dilutions and wetland treated municipal wastewater showed more growth and nutrient removal compared to 100% fresh leachate. Specific growth rate (µ) and doubling time of microalgae in 15% fresh leachate were 0.17 per day and 4.03 days, respectively.