Cyanobacterial biofilms on sedimentation basins in a water treatment plant in South Korea

Abstract

We studied periphytic algal biofilms that formed in the sedimentation basins (SBs) of a water treatment plant (WTP) in South Korea. The submerged cement wall of the basin was heavily coated by mats of algal filaments, which resembled a small sheet of carpet. These biofilms were more common in the dry season (spring and autumn), than the rainy season (summer) and winter. Oscillatoria and Phormidium (Cyanobacteria) were predominant in the biofilm of the SB walls, where the water was stagnant. Lyngbya (Cyanobacteria) and Oedogonium (Chlorophyta) were dominant on the walls of overflow weirs and troughs of the SB, where there was a substantial current. As the biofilm matured, the assemblages were detached from the walls and floated as “scum” on the water, causing contamination. Many factors control the development of cyanobacterial biofilms on the walls of WTPs, including the nutrient levels of the raw water, and interstitial or pore water of biofilm assemblages, temperature, and irradiance. We isolated and grew unialgal cultures of the five most important cyanobacteria of the WTP biofilm. Oscillatoria splendida strongly produced the musty odor from the cultures. We suggest implementation of antifouling strategies to reduce the formation of biofilm on the wall and contamination of water supplies.