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The study investigates water quality in a small water body in an agricultural catchment in a zone of temperate climate (East Poland). The pond is affected by annual mass cyanobacterial blooms, limiting its use. The improvement of the state of water quality involved the application of underwater aerating reactors. The economic analysis of their application was also an important issue. The analysis of the effectiveness of the proposed solution was conducted from February to October 2021. The results from the analysis of water from the pond showed that the nutrient content and phytoplankton structure conformed to the trophic status of eutrophy–hypertrophy. The primary factors causing excessive eutrophication of the pond included nutrient supply from the river, sediments, and fallen tree leaves. No development of cyanobacterial scum was observed in the water body, a phenomenon which was interpreted as the effect of the operation of the aerators ensuring additional water circulation in the pond and promoting its aeration. It was found that permanent improvement of the water quality in the studied water body is largely dependent on limiting the nitrogen and phosphorus supply to the pond. This should involve the application of systems combining traditional hydrotechnical infrastructure with Nature-Based Solutions (NBS). The economic analysis of the use of underwater aeration reactors confirmed the validity of searching for alternative solutions to power them, e.g., a photovoltaic installation. When designing a reactor system with a photovoltaic installation, it is necessary to choose the correct dimensions to reduce construction costs and, thus, increase the profitability of the potential investment.
Chmiel et al. (Sun,) studied this question.