Evaluation of Nutrient Recovery Potential through Wastewater Reclamation for Irrigation

To cope with water scarcity, assessing the viability of applying treated wastewater for irrigation – while preserving nitrogen and phosphorus – is gaining growing importance. For this objective, a small-scale activated sludge system receiving concentrated sewage with water demand for irrigation during summer was examined. This paper evaluates the facility’s performance with various combinations of loading parameters using a probabilistic method, complying with a probability of 98% regarding requirements of organic matter removal and 79% concerning full nitrification. A sensitivity analysis was conducted where sludge age was shifted from 21 to 5 days during the irrigation period, allowing organic biodegradation while preserving nutrients in the water. Excess biological phosphorus removal could be observed at low aeration intensity; however, it became negligible as the dissolved oxygen concentration increased. Length of the transitional period from summer to winter operation regarding biomass activity was found to be approximately one week. Results of the study highlight the potential for reuse of treated municipal wastewater for irrigation, with robust operational performance and efficient retaining of nutrients in activated sludge plants.