A novel method of rural sewage disinfection via root extracts of hydrophytes

•Isolation and identification of root exudates from five hydrophytes in CWs.•Coliphages T4 and f2 were well removed by root extracts of P. hydropiper.•The EC50 of P. hydropiper root on coliphages T4 and f2 was 0.6 and 7.6 mg L−1, respectively.•The IR of saturated n-butanol phase on T4 and f2 was found to be the strongest.

Based on the model organisms of coliphages T4 and f2, this study aimed to select hydrophytes that has a strong inhibition to viruses and can provide the scientific basis for using hydrophyte allelochemicals to reduce the virus concentration in constructed wetlands (CWs). Double agar overlay method was used to evaluate the inhibition of hydrophyte root extracts on coliphage growth through the plaque forming unit assay. The effects on coliphages T4 and f2 of the root extracts from five hydrophytes (i.e., Phragmites communis, Typha latifolia, Arundo donax, Polygonum hydropiper, and Polygonum orientale) were investigated. Results showed that the inhibition of root extracts from P. hydropiper was more effective on T4 and f2 than on other hydrophytes. Median effective concentration (EC50) of P. hydropiper root on coliphage T4 was 0.6 mg L−1, and the EC50 on coliphage f2 was 7.6 mg L−1. Five solvents, namely, petroleum ether, chloroform, ethyl acetate, n-butanol, and distilled water, were used to extract and separate allelochemicals, which can inhibit coliphage growth, from P. hydropiper root. The inhibition rate (IR) of saturated n-butanol phase on T4 and f2 was found to be the strongest, followed by the ethyl acetate phase. The major components were identified via gas chromatography–mass spectrometry. According to the outcome, purchasing four alternative substances of allelochemicals verified the inhibitory effect on coliphage. Results showed that all the IRs on coliphage were below 40% when the concentration of four synthesized compounds were 10 mg L−1. To provide a novel method of rural sewage disinfection, the specific allelochemicals of P. hydropiper root, which strongly inhibit coliphages, still require further extraction, isolation, and evaluation. Moreover, the inhibitory mechanism should be discussed in depth.