Soil cultivation for enhanced wastewater infiltration in soil aquifer treatment (SAT)

SummarySoil aquifer treatment is often employed as a tertiary treatment component of reclamation proceeding of wastewater for irrigation in agriculture. Reductions in infiltration rates due to increase in water repellency have been reported to be associated with organic matter (OM) accumulation in the soil (mainly in the top soil layer) as a result of treated wastewater (TWW) infiltration. Our aim was to reduce OM content in soils extensively loaded with TWW. Four model infiltration ponds were built to simulate large infiltration basins: three for TWW infiltration using different application regimes, and the fourth for freshwater (FW) infiltration (control). We examined changes in OM content, hydraulic conductivity (HC) and water repellency in these model ponds as a result of soil plowing. In field experiment, four soil-plowing events were performed. Reduced OM content and water repellency, and increased HC were found in all TWW-applied ponds following each soil plowing. These changes were attributed to OM burial in deeper soil layers elimination of the continuity of the OM based crust, and surface exposure of soil with low OM content. An overall reduction in OM content was found at the end of the experiment in all soil layers as a consequence of plowing. No changes in OM content, water repellency or HC were found in the FW-applied pond as a result of soil plowing.

► Infiltrating TWW induces pond soil surface water repellency and reduced infiltration.
► The accumulation of organic matter on the soil surface layer induces water repellency.
► Soil cultivation at the ponds reduced organic matter content at the soil profile.
► Soil cultivation at the ponds drastically reduced soil water repellency.
► Soil cultivation increased TWW infiltration into the soil in comparison to no cultivation.