The application of treated wastewater for the irrigation of fast-growing trees - Field experiments on constructed wetland
Abstract
Due to the progressive decrease in precipitation in the Czech Republic, the need for the irrigation of agricultural crops is steadily increasing. It is proposed that the problem of a lack of water resources might be partially solved via the reuse of treated wastewater in certain agricultural sectors however there is a very little known about the possible advantages or disadvantages of such sources of water under the local climate conditions.
For this purpose, a semi-operated irrigation field was established at Hostětín in the Zlín region of the Czech Republic which was subsequently planted with willow cuttings (Salix viminalis L.). The plants were irrigated by means of two different water sources - wastewater from the local municipal treatment plant and local groundwater.
During the 2018 and 2019 growing seasons, we observed the significantly enhanced growth of the wastewater irrigated willows - biomass yield was of 6.6 and 31.3 t/ha respectively under wastewater irrigation conditions, while only 1.0 and 1.8 t/ha was produced under fresh water irrigation conditions. The biomass quality was assessed via calorific values and showed lower gross and net calorific values for the wastewater irrigated willow biomass, i.e. 18.5 and 17.2 MJ/kg of dry matter respectively compared to 19.2 and 17.9 MJ/kg.
However, the overall high yields of the biomass more than compensated for this disadvantage. This study confirmed the hypothesis that treated wastewater can be used in agricultural areas in which it does not endanger either public health or the environment.