Bioremediation Potential of Chlorococcum humicola Alcoholic Extract Against Escherichia coli Isolated from Contaminated Wastewater

Escherichia coli is a common water contaminant of wastewater and a severe health risk to the environment and human beings. Hence, the idea of using bio-extracts of microgreen algae as a non-toxic and eco-friendly approach for wastewater treatment and its de-bacterial load was developed. E. coli was isolated from Rustumiyah wastewater treatment plant in Baghdad and cultured using the Prescott method. Chlorococcum humicola was isolated from a stream in the Jadriya area and cultured in Chu-13 medium under controlled laboratory conditions. The algae's bioactive compounds were extracted using chloroform, and various concentrations of the extract (0.07, 0.15, 0.31, 0.62, and 1.25 mg/L) were prepared. The concentrations were introduced into a bacterial culture and sterile wastewater and incubated for 72 hours. The numbers of bacterial cells were daily counted, and the growth rate, percentage removal (RA), and percentage mortality (MP) were calculated. The quality of water of the wastewater before and after treatment was also analyzed with standard parameters (pH, BOD, COD, nitrate, and phosphate). The results showed a significant decrease in the cell number of E. coli against increasing concentration and exposure duration of algal extract. For example, at concentration 1.25 mg/L, the cell number decreased to 49 CFU/ml at 24 hours of exposure, while in the control group, it was 480 CFU/ml. The maximum rate of bacterial removal was 89% at the highest concentration, and the rate of bacterial death percentage had an obvious rising trend with the increase of concentration and exposure time (up to 89% after 72 hours at 1.25 mg/L). In terms of water quality, it was found that there was a significant reduction in COD and BOD with the increasing concentrations of extracts, demonstrating the purification of water. Nitrate and phosphate concentrations also reduced, promoting the algae's ability to eliminate excessive nutrients. The current study demonstrates the high biological effectiveness of Chlorococcum humicola algae extract in inhibiting the growth of E. coli bacteria in wastewater, as well as in improving the chemical and physical water quality parameters. Algal extracts are proposed as green, non-toxic biological treatment agents in wastewater treatment systems, especially in developing countries that are suffering from water pollution and resource scarcity