Treatment of Agricultural Wastewater Containing Pesticides by Hydrophytic Method as a Preliminary Method of Water Recovery

Abstract

The purpose of this study was to determine the feasibility of using a hydrophytic method to degrade selected pesticides (pyraclostrobin and boscalid) from agricultural waste (wastewater) and to evaluate their removal efficiency. This will allow the recovery of water and raw materials from agricultural wastewater. In addition, a biopreparation was used to increase the efficiency of the process and the rate of degradation and reduce the half-life of the compounds in wastewater. Pesticides, which are commonly used in agriculture, were selected for the experiments. The study was conducted on a pilot scale, in two identical hydrophytic treatment systems supported and not supported by microorganisms. At the same time, in order to identify pesticides, an analytical method based on liquid chromatography-tandem mass spectrometry was optimized, enabling the determination of applied pesticides in wastewater with satisfactory sensitivity, accuracy and precision. The kinetics of pesticide decomposition in the hydrophytic bed were determined on the basis of mathematical models and equations of the dynamics of pesticide disappearance in wastewater. The parameters of the DT50 half-life of pesticides in wastewater and the parameters of theoretical time to reach the concentration level of 0.01 mg/L were determined. The use of three different layers (0.15, 0.40 and 0.15 m) of chemically inactive granulometrically differentiated (2 ÷ 8, 8 ÷ 20 and 20 ÷ 80 mm) filter material influenced the high treatment efficiency. During the entire experimental period, the wastewater feeding the bed was treated satisfactorily. The determined parameters of the pesticide half-life in DT50 wastewater ranged from 2.33 to 3.29 for microorganisms and 3.42 to 3.79 without microorganisms. The determined parameters of the theoretical time to reach the concentration of 0.01 mg/L t0.01 were about 22 and 38 days for microorganisms and 33 and 44 days without microorganisms. Thus, it can be unequivocally concluded that the biopreparation has influence on reducing the half-life of the tested pesticides.