A type dependent effect of treated wastewater matrix on seed germination and food production

Abstract

Municipal wastewater treated by membrane bioreactor, either aerobically (AeMBR) or anaerobically (AnMBR), can be reused to irrigate crops. However, post-AeMBR and post-AnMBR effluent have different water quality that may impact crop growth and yield. This study aims to assess for differences in water quality from both AeMBR and AnMBR, and determine if the type of treated wastewater matrix would impact seed germination and crop yield. Compared to post-AeMBR and control, post-AnMBR effluent had a negative impact on seed germination for both tomatoes and lettuces. The use of post-AnMBR but not post-AeMBR effluent also resulted in a higher number of unripe tomato fruits at the time of harvesting. However, when post-AnMBR effluent was diluted to 25% and 75% v/v with tap water, higher lettuce biomass was harvested compared to the same concentrations of post-AeMBR effluent and control. The observed differences in germination and yield were likely due to differences in the concentrations of heavy metals (e.g. Zn) and steroids or phytohormones (e.g. testosterone, gibberellic acid) present in both post-MBR effluents. This study demonstrated that the type of treated wastewater generated from different upstream treatment technologies can potentially impact crop yield based on the crop type. By understanding how the type of treated wastewater affect downstream agricultural activities, changes in management practices can be made accordingly.