Abstract
Climate change and the subsequent change in agricultural conditions increase the vulnerability of agricultural water use. Wastewater reuse is a common practice around the globe and is considered as an alternative water resource in a changing agricultural environment. Due to rapid urbanization, indirect wastewater reuse, which is the type of agricultural wastewater reuse that is predominantly practiced, will increase, and this can cause issues of unplanned reuse. Therefore, water quality standards are needed for the safe and sustainable practice of indirect wastewater reuse in agriculture. In this study, irrigation water quality criteria for wastewater reuse were discussed, and the standards and guidelines of various countries and organizations were reviewed to suggest preliminary standards for indirect wastewater reuse in South Korea. The proposed standards adopted a probabilistic consideration of practicality and classified the use of irrigation water into two categories: upland and rice paddy. The standards suggest guidelines for E. coli, electric conductivity (EC), turbidity, suspended solids (SS), biochemical oxygen demand (BOD), pH, odor, and trace elements. Through proposing the standards, this study attempts to combine features of both the conservative and liberal approaches, which in turn could suggest a new and sustainable practice of agricultural wastewater reuse.
Highlights
The lack of freshwater resources due to population growth and the degradation of water quality is becoming a big challenge for agricultural water [1,2]
Most of the currently suggested water quality standards are based on the direct wastewater reuse rather than the indirect wastewater reuse, which is a predominant manner in agricultural wastewater reuse [39]
In South Korea, during the dry season of May to June, which is when most of the irrigation activity occurs, irrigation water by indirect wastewater reuse contains a high level of total nitrogen (T-N) concentration due to the decrease in streamflow volume [14]
Summary
The lack of freshwater resources due to population growth and the degradation of water quality is becoming a big challenge for agricultural water [1,2]. Most of the currently suggested water quality standards are based on the direct wastewater reuse rather than the indirect wastewater reuse, which is a predominant manner in agricultural wastewater reuse [39] They have focused on the upland irrigation including vegetables and have not well considered the characteristics of irrigation water in paddy fields: Irrigation water for paddy rice production accounts for more than 70% of the total irrigation water in Asia [40], and paddy rice is the largest consumer of freshwater resources in South and Southeast Asia [41,42]. This study, examines existing water quality criteria for irrigation water and wastewater reuse, and analyzes the water quality standards of other countries to set agricultural water quality standards for indirect wastewater reuse considering both paddy and upland irrigation
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