UC Riverside

Global water scarcity poses a major challenge to agricultural productivity. This dissertation investigates the use of recycled water for irrigation, focusing on the occurrence of pharmaceutical and personal care products (PPCPs), their accumulation in edible crops, and the impact of irrigation water quantity on this accumulation. Analysis reveals that PPCPs, including sulfamethoxazole, are present in recycled water at concentrations ranging from 130-1400 ng/L in secondary effluent and 25-400 ng/L in tertiary effluent. The study shows that PPCP uptake and accumulation vary between leafy and fruity vegetables, with diclofenac and fluoxetine being most prevalent in each, respectively. Key factors affecting PPCP accumulation include transpiration rate and osmotic adjustments under limited water availability. The research explores two strategies: recycled wastewater effluent irrigation and limited irrigation rates, aimed at mitigating PPCPs accumulation and conserving irrigation water. A 14-week field trial on St. Augustine turfgrass assesses the effects of UV persulfate (UV/PS) treatment and limited irrigation rates on PPCPs accumulation and plant health. Results indicate that UV/PS treatment effectively removes 60% of carbamazepine and over 99% of other PPCPs from recycled water, significantly reducing PPCP levels in turfgrass leaves and roots. Limited irrigation at 60% ETo increases carbamazepine accumulation and canopy temperature, suggesting higher water stress compared to 80% ETo. Additionally, greenhouse experiments with lettuce, carrot, and tomato, using PPCP-spiked recycled water, UV/PS treated recycled water, and tap water at 60%, 80%, and 100% crop evapotranspiration rates (ETc), show that UV/PS treatment reduces PPCP accumulation by over 99%. Lettuce benefits from reduced irrigation, while carrot and tomato show increased accumulation due to osmotic adjustment. Combining UV/PS treatment with deficit irrigation conserves water, maintains crop yield, and minimizes PPCP accumulation. The findings offer valuable insights for developing strategies to safely and effectively reuse recycled water in agriculture, supporting sustainable practices and improving food safety.