Evaluating the manganese removal capabilities of mushroom compost under anaerobic conditions using fed-batch reactors

Abstract

Abandoned mine drainage often contains heavy metals and trace metals, that when left untreated, contaminate surrounding soil and water rendering them unable to support life or maintain ecological functions, and impacts the natural environment. These metals must be removed in order to prevent environmental damage. Historically, two types of treatment systems have been proposed to treat mine drainage: passive treatment systems (PTS) or active treatment facilities. The latter of these options use chemicals harsh on the environment while the former option utilizes natural processes. Previous research done on PTS show that the removal of the trace metal manganese (Mn) in anaerobic systems can be unpredictable, necessitating further research on Mn behavior.

This study utilized 1-L fed-batch reactors to create an anaerobic environment similar to the conditions found in vertical flow bioreactors (VFBR), a common unit-process in passive treatment systems. All treatments and the control contained a 1:3 ratio of liquid and spent mushroom compost. Mushroom compost is a readily available organic substrate often used in vertical flow bioreactors (VFBR) to remove heavy and trace metals from PTS; it is for these reasons it was chosen as the substrate in this experiment. This study manipulated ionic strength, to try and understand how Mn may be retained or released in the varying conditions. Water quality was observed over the course of seven weeks and organic matter was sacrificed at the end for analysis. Organic matter analysis utilized a modified Tessier sequential extraction method to obtain the location of where manganese occurred.