Chapter 2 - Algal intervention as nature-based solution for treatment of landfill leachate

Abstract

Waste management is a global environmental challenge. Municipal solid waste (MSW) is typically dumped in an open area or an engineered landfill. MSW dump sites and landfills pose several air, ground, and surface water contamination issues. Rainwater percolates in the MSW and generates landfill leachate (LL), which contains several toxic contaminants. This untreated LL has the potential for polluting the groundwater and surface water resources. Landfill leachate contains heavy metals, pesticides, dissolved organic carbon, nitrogenous compounds, phosphorus, etc., and their removal is necessary before discharge. There are several potential physical, chemical, and biological technologies for the removal of such compounds. Chemical techniques are generally expensive and their economic feasibility in many developing countries is still debatable. Moreover, they add an additional chemical load to the environment. The biological treatment methods are being widely adopted for the removal of several pollutants from the wastewater as an alternative. Constructed wetlands and algal treatment are two widely accepted biological approaches in the removal of contamination from wastewater streams. Nitrogenous compounds (ammonium, nitrate, and nitrite) and phosphorus act as pollutants in LL and are nutrients for the algal growth. Therefore, different species of microalgae can be effectively used for the removal of these pollutants from the LL. Generally, raw LL has a high concentration of heavy metals and other toxic compounds which limit the direct removal process. The pretreatment of LL and dilution are important factors that affect the algal biomass growth and remediation process. LL needs to be diluted at least to 40% and the best nitrogen removal with the help of microalgae has been reported at 10% dilution. The removal of phosphorus from LL through microalgae is quicker as compared to nitrate and ammonium. The combination of algal treatment approaches can be used for the remediation of LL at a larger scale solely or in combination with other technologies and has economic feasibility.