Algae growth occurs naturally in freshwater and brackish water sources. Like all plants, algae respond to sunlight and nutrients, and excessive algae growth will occur when environmental conditions are favorable. Aquatic water reservoirs (AWRs) are susceptible to excessive algae growth (eutrophication) when nutrients, particularly nitrogen and phosphorus, contaminate the water due to fertilizer leaching and runoff from agricultural areas. Furthermore, algal proliferation is more likely to occur when the water is calm with little to no flow, and when the temperature is warm (above 20°C).
Algae proliferation negatively impacts water quality. It can lead to odor issues and hinder AWR operations by clogging or blocking pumps, filters, and pipes. Additionally, when algae die, their decomposition depletes oxygen levels in the water source, further exacerbating water quality issues, including the release of iron and nutrients from sediments.
In countries such as the Netherlands, with highly intensive greenhouse agriculture, algae growth in AWRs is a common problem. In this country, the mandatory storage of 500 m3 of rainwater per year per hectare of greenhouse is required, and there is an obligation to reuse drainage water to a certain extent. Consequently, water stored in such AWRs is nutrient-rich, leading to the aforementioned algae problem.
A wide range of technologies/practices can prevent or treat algae proliferation, but their effectiveness varies and requires further research. A common solution is to cover ponds to prevent sunlight penetration, using methods like windbreaks or floating covers on the water surface. In a survey conducted among EU producers (central-eastern, Mediterranean, and northwestern regions), the satisfaction index for cover solutions was moderate. Other solutions involving the use of filters, chemicals (algicides), or continuous maintenance operations with high costs are not optimal.