The impact of treated wastewater and biosolids from the municipal wastewater treatment plant on water and carbon dioxide effluxes from soils

The goal of this study was to evaluate the effect of products from a municipal wastewater treatment plant on the H₂O and CO₂ effluxes from two soils. The net H₂O and CO₂ effluxes were measured at the surface of nine beds with two different soils (Cambisol and Arenosol) and two crops (maize or vegetables). Soils in some beds were amended with stabilized sewage sludge (bed with Cambisol and maize) or composted sewage sludge (two beds with Cambisol and both crops) or were irrigated with treated wastewater (two beds with Cambisol and both crops, and one bed with Arenosol and vegetable). Remaining beds were irrigated with tap water (two beds with Cambisol and both crops, and one bed with Arenosol and vegetable). While stabilized and composted sewage sludge positively affected the CO₂ emission, the effect of treated wastewater was not confirmed. Different treatments had negligible effect on the water efflux, which was mainly affected by the plant canopy that influence the temperature of the soil surface. Statistical analyses showed that trends of the CO₂ efflux with respect to various scenarios measured on different days changed during the season. No significant correlations were found between the average H₂O and CO₂ effluxes and measured soil properties.