Monitoring Opportunistic Pathogens in Domestic Wastewater from a Pilot-Scale Anaerobic Biofilm Reactor to Reuse in Agricultural Irrigation

Bingjian Cui,Shengxian Liang

doi:10.3390/w11061283

Abstract

Wastewater reuse for agricultural irrigation in many developing countries is an increasingly common practice. Regular monitoring of indicators can help to identify potential health risks; therefore, there is an urgent need to understand the presence and abundance of opportunistic pathogens in wastewater, as well as plant phyllosphere and rhizosphere. In this study, an anaerobic biofilm reactor (ABR) was developed to treat rural domestic wastewater; the performance of pollutants removal and pathogenic bacteria elimination were investigated. Additionally, we also assessed the physicochemical and microbiological profiles of soil and lettuces after wastewater irrigation. Aeromonas hydrophila, Arcobacter sp., Bacillus cereus, Bacteroides sp., Escherichia coli, Legionella sp., and Mycobacterium sp. were monitored in the irrigation water, as well as in the phyllosphere and rhizosphere of lettuces. Pathogens like B. cereus, Legionella sp. and Mycobacterium sp. were present in treated effluent with relatively high concentrations, and the levels of A. hydrophila, Arcobacter sp., and E. coli were higher in the phyllosphere. The physicochemical properties of soil and lettuce did not vary significantly. These data indicated that treated wastewater irrigation across a short time period may not alter the soil and crop properties, while the pathogens present in the wastewater may transfer to soil and plant, posing risks to human health.

Highlights

Water scarcity has become a global problem; many countermeasures have been taken to meet the challenge in China and other countries
The reuse of domestic wastewater for agricultural irrigation is regarded as an option to address water scarcity, which could partially substitute for chemical fertilizer as nutrient sources
We revealed that the phyllosphere and rhizosphere contained different levels of opportunistic pathogens, which deserves greater consideration

Summary

Introduction

Water scarcity has become a global problem; many countermeasures have been taken to meet the challenge in China and other countries. Reclaimed wastewater provides an effective leverage to complement other conventional water resources supply, as well as alleviate water quality problems associated with pollutants discharge. Wastewater reuse for agricultural irrigation is regarded as a viable way to address the imbalance between water demand and supply, and may contribute to a sustainable agriculture [1,2]. Wastewater reuse for agricultural irrigation may have two implications: the first may affect soil fertility and crop productivity, and the second may pose human health risks and environmental hazards due to the accumulation of chemical and microbiological contaminants [3]. Conventional end-of-pipe solutions for wastewater treatment have been criticized from a sustainable view-point, in particular regarding recycling of nutrients in effluent, instead of being discharged directly [6]. A novel planning model, consisting of a reuse-centric performance assessment and optimization model to help design wastewater treatment plants for reuse

Methods

Results

Discussion

Conclusion