Algal blooms and the presence of cyanotoxins in surface water restrict the public from accessing lakes and beaches for drinking and recreational activities. An effort was taken in this on-site study to improve the surface water quality of a eutrophic lake, which has been under a swimming advisory for many years. A floating filtration unit with non-woven geotextiles as a sole filter media was tested for removing algae, nutrients, and suspended solids from overlying water under different lake conditions. Three non-woven geotextiles of different pore sizes were examined in different combinations and lake water quality was monitored for different physico-chemical, biological parameters. A YSI-EXO2 multiparameter probe was used for continuous online water quality monitoring during filtration. Depending on the initial water quality, excellent removal efficiency was observed as follows: 85-98% turbidity, 98-100% total suspended solids (TSS), 57-88% total phosphorus (TP), 33-66% chemical oxygen demand (COD) and 80-96% chlorophyll a (Chl. a.). The filtered lake water quality satisfied the norm set for oligotrophic lakes for TP and Chl. a. Results from this on-site study are very promising, showing the potential applicability of geotextile filtration as an ecologically attractive technique to improve the surface water quality of small aquatic bodies.
Keywords: Algae; Eutrophication; Filtration; Non-woven geotextiles; Suspended solids; Total phosphorus.
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