Effects of Indirect Wastewater Reuse on Water Quality and Soil Environment in Paddy Fields

Abstract

The objectives of this study were to monitor and assess the environmental impacts of indirect wastewater reuse on water quality and soil in paddy fields. Yongin monitoring site (YI) irrigated from agricultural reservoir and Osan monitoring site (OS) irrigated with treated wastewater diluted with stream water were selected as control and treatment, respectively. Monitoring results for irrigation water quality showed a significant statistical difference in salinity, exchangeable cation and nutrients. Pond water quality showed a similar tendency with irrigation water except for the decreased difference in nutrients due to the fertilization impact. Soil chemical properties mainly influenced by fertilization activity such as T-N, T-P, and P2O5 were changed similarly in soil profiles of both monitoring sites, while the properties, EC, Ca, Mg, and Na, mainly effected by irrigation water quality showed a considerable change with time and soil depth in treatment plots. Heavy metal contents in paddy soil of both control and treatment did not exceed the soil contamination warning standards. This study could contribute to suggest the irrigation water quality standards and proper agricultural practices including fertilization for indirect wastewater reuse, although long-term monitoring is needed to get more scientific results.

Irrigation Water Quality Standards for Indirect Wastewater Reuse in Agriculture: A Contribution toward Sustainable Wastewater Reuse in South Korea

“…Even for sites irrigated by relatively clean water derived from a reservoir, an average of about 15,700 MPN/100 mL of total coliform was detected [20]. It was also found that the total coliform of the irrigation water containing untreated wastewater was about 77,000 MPN/100 mL [21].…”

“…This indicates that the subjected level of total coliform can be easily found in nature and is inadequate as an indicator for microbes. The E. coli concentration of irrigation water with high levels of total coliform concentration was measured to be 13, 46, and 107 MPN/100 mL for reservoir water, indirect wastewater reuse water, and irrigation water containing untreated wastewater, respectively [20,21]. For fecal coliform, the concentrations for the subjects above were 5000, 180, and 633 MPN/100 mL, respectively [20,21].…”

“…Through examining the water quality of sites that adopt indirect wastewater reuse for paddy irrigation in South Korea, an average of 19,000 MPN/100 mL of total coliform was detected during the irrigation period [20]. Even for sites irrigated by relatively clean water derived from a reservoir, an average of about 15,700 MPN/100 mL of total coliform was detected [20].…”

“…The E. coli concentration of irrigation water with high levels of total coliform concentration was measured to be 13, 46, and 107 MPN/100 mL for reservoir water, indirect wastewater reuse water, and irrigation water containing untreated wastewater, respectively [20,21]. For fecal coliform, the concentrations for the subjects above were 5000, 180, and 633 MPN/100 mL, respectively [20,21]. Considering the high measurement of fecal coliform, even for conventional irrigation water derived from a reservoir, there needs to be a practical regulation using E. coli, which can well reflect the pathogenic microorganism such as the regulations of Spain, Greece, and Italy.…”

“…Therefore, without additional treatment, it is suggested that diluted treated wastewater be used restrictively [19]. In addition, when using treated wastewater for rice paddy irrigation, the water showed a significant level of salinity compared to conventional irrigation water, and total coliform concentration surpassed the levels of the water quality standards for direct wastewater reuse [20,21]. Previous studies suggest that the quality of irrigation water from streams fails to meet the agricultural water quality standards due to the effects of WWTP effluent [14,22]; thus, the water quality needs to be managed to ensure safe and sound crop production.…”