Herbicides help increase agricultural yields significantly, but they may negatively impact the life of non-target organisms. Modifying the life cycle of primary producers can affect other organisms in the food chain, and consequently in the whole ecosystem. We investigated the effect of common herbicides Roundup® Classic Pro (active substance glyphosate) and Garlon New (triclopyr and fluroxypyr) on aquatic organisms duckweed Lemna minor and green algae Desmodesmus subspicatus, and on the enzymatic activity of soil. We also compared the effects of Roundup® Classic Pro to that of a metabolite of its active substance, aminomethylphosphonic acid (AMPA). The results of an algal growth test showed that AMPA has a 1.5× weaker inhibitory effect on the growth of D. subspicatus than the Roundup formula, and the strongest growth inhibition was caused by Garlon New (IC50Roundup = 267.3 µg/L, IC50Garlon = 21.0 µg/L, IC50AMPA = 117.8 mg/L). The results of the duckweed growth inhibition test revealed that Roundup and Garlon New caused 100% growth inhibition of L. minor even at significantly lower concentrations than the ready-to-use concentration. The total chlorophyll content in the fronds was lowest when Garlon New was used. The highest dehydrogenase activity was observed in soil treated with Garlon New, and the lowest in soil treated with Roundup® Classic Pro. The results of this study showed that all three tested substances were ecotoxic to the tested organisms.

Reverse osmosis is widely used as one of the most effective and advanced technologies for the treatment of leachate from landfill sites. Unfortunately, high leachate contamination—above all, ammonia nitrogen—affects membrane selectivity and is reflected in permeate quality. Furthermore, iron contained in leachate can facilitate chelates forming, which reduces the membrane anti-fouling capacity. The addition of a pre-treatment step could alleviate the adverse impact of the pollutants. As such, we investigated pollutant removal by phycoremediation. Initial ecotoxicity tests of three algal strains (Scenedesmus obliquus (S. obliquus), Desmodesmus subspicatus (D. subspicatus), and Chlorella vulgaris (C. vulgaris)) identified D. subspicatus as the strain most tolerant to leachate toxicity. Subsequently, D. subspicatus was cultivated in six landfill leachates of different origin and, after the cultivation, removal rates were determined for ammonia nitrogen and iron. Furthermore, the impact of input leachate parameters on remediation efficiency was also investigated. By phycoremediation, the reduction of up to 100% in iron and 83% in ammonia nitrogen load was achieved, which demonstrates the high potential of microalgae to mitigate environmental risks and reduce membrane foulant content.