Wastewater generated during food processing is commonly treated using land-application systems which primarily rely on microbes in the soil to treat wastewater by transforming nutrients and organic compounds into benign byproducts. Naturally occurring metals in soil may be chemically reduced via microbially mediated oxidation-reduction reactions as oxygen becomes depleted. Metals such as manganese, iron, and arsenic are water soluble in their reduced forms and may lead to contamination of groundwater.A column study was conducted at Michigan State University to investigate impacts of land-application of wastewater. Oxygen content and volumetric water data was collected via soil sensors for the duration of the study. The pH, chemical oxygen demand, alkalinity, total iron, and total manganese in the influent and effluent water for each column were evaluated. Average organic loading, organic load per dose, and hydraulic rest period were shown to have statistically significant impacts on effluent water quality using Spearman's Rank Correlation Coefficient.This study verifies that excessive organic loading of land application systems causes mobilization of naturally occurring metals and ineffective wastewater treatment, but also indicates the need for consideration of organic dose load and hydraulic rest period in treatment system design. Findings from this study demonstrate application of water to soil twice daily may encourage soil aeration and allow for increased organic loading while limiting metal mobilization.
Read
