Reuse of treated effluent for agriculture

Re-use of Treated Waste Water/effluent (TWW) for sub-irrigation in agriculture serves the dual purpose of supplying water to crops and diminishing emissions of Contaminants of Emerging Concern CECs into surface water. To investigate such re-use, at two field sites that have climate adaptive drainage facilities TWW is introduced by sub-irrigation through the drainage system to store water until summer, when the crop needs it. Subject of research is to investigate how sub-irrigation/drainage cycles can be optimally designed and operated, to raise groundwater levels towards the root zone and decrease CECs emission to surface water. As emission of CECs to the deeper groundwater or CEC uptake in crops should be negligible (stand still-principle), operation should take the complicated 3 dimensional flow and transport routes into account. These routes can be highly dynamic, as they are also affected by erratic weather. Analysis of flow, CEC transport and degradation, and the supply of water and CECs to the root zone are monitored at both field sites. A characterisation of a broad selection of CECs present in the TWW in the laboratory is based on column experiments. To test the validity of derived sorption, mobility and degradation parameters, column experiments are done for different conditions. With numerical modelling, the agreement between model and column breakthrough is determined. Using the same parameters, the fate of CECs in the field is modelled and compared with observations. In a final step, the models are used for a risk and regional upscaling assessment.