Reuse of olive mill wastewater as a potential green algaecide to control the toxic cyanobacterium Microcystis aeruginosa in water bodies

Abstract

This work was undertaken to assess the potentialities of olive mill wastewater (OMWW) bodies as a new potential sustainable solution to control the toxic cyanobacterium (Microcystis aeruginosa) in water. Diluted raw olive mill wastewater (dROMWW) and polyphenols extracted from ROMWW (PEOMWW) were investigated in order to achieve high inhibition rates (IRs) efficiency and to compare between them. Microdilution and disc diffusion approaches were used in primary. Moreover, the growth and photosynthetic pigments of Microcystis culture in response to dROMWW and PEOMWW were investigated in secondary. The phenolic profiles of the potential allelochemicals were detected by High Performance Liquid Chromatography (HPLC). Inhibition rates (IRs) reached 92 and 96% under the two highest concentrations of dROMWW (3.125 and 6.25 mgL− 1) only after 4 days of experimentation. Then, it achieved 97% on 10 days under both dROMWW and PEOMWW treatments. The results of chlorophyll a (Chl-a) and carotenoid contents significantly decreased following exposure of M. aeruginosa to higher concentrations. HPLC analysis of PEOMWW revealed tyrosol, hydroxytyrosol, and quercetin that can be considered as the main potentially allelochemicals. Overall, the results demonstrate that dROMWW and PEOMWW inhibit the growth of M. aeruginosa, and could constitute a promising strategy both to valorize OMWW effluents and control cyanobacterial blooms (CyanoHabs) in Mediterranean water bodies. The effect of raw olive mill wastewater (ROMWW) and polyphenolic extracts (PEOMWW) on M. aeruginosa growth were investigated as a new potential allelochemical. ROMWW and PEOMWW showed highest inhibitory effects 97% on M. aeruginosa by reducing both cell growth and photosynthesis at concentrations 6.25 and 3.125 mgL− 1, respectively. ROMWW and PEOMWW extracts might be proposed as an eco-friendly and low-cost alternative to control cyanobacterial harmful algal blooms (CyanoHabs) in aquatic ecosystems.