Use of activated rice husk biochar for the removal of metals and microorganisms from treated leachates from landfills

Surface water, groundwater, and soil are all heavily polluted by leachates from landfill. In underdeveloped countries, many of these are not treated due to the high costs of implementing wastewater treatment plants. In Colombia, there are few sanitary landfills that comply with the standards for leachate discharge to nearby water sources. In this work, the potential use of activated rice husk biochar for the removal of polypollutants associated with leachates (metals and microorganisms) has been studied. For this, rice husk residues have been used in a pyrolysis process in a fixed-bed reactor. This biochar has been activated through a physicochemical process, with which the surface area has been improved with KOH activation. Batch adsorption experiments were carried out to evaluate the removal of metals and microbes. Metal removal was determined using an ICP-EOS analysis, while the total microorganisms were calculated using the UFC g−1 colony count. It has been found that during three cycles, biochar achieves a high percentage of removal of microorganisms (up to 100% in four of the five cycles evaluated) and metals (<95% cycle 1, <80% cycle 2, and <65% cycle 3). On the other hand, with respect to the toxicity tests, a percentage >50% has been found up to the cycle 3. In compliance with the regulations, up to the fourth cycle, this is complied with, in terms of contaminant removal efficiencies, but after cycle 5, there is a loss in efficiency.