eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2020-03-30 17 1 191 203 10.13005/bbra/2823 35599 article Marwa E. El-Sesy 1 Belal N.A.Mahran 2 Microbiology Department, Central Laboratory for Environmental Quality Monitoring (CLEQM), National Water Research Center (NWRC), Cairo, Egypt. Organic Department, Central Laboratory for Environmental Quality Monitoring (CLEQM), National Water Research Center (NWRC), Cairo, Egypt. This study expounded the ability to use Psidium guajava leaves extract as coagulant, fecal coliform removal and for decreasing values of some heavy metals. The optimum dosages of Psidium guajava leaves extracts needed for treatment the collected wastewater samples were studied. The Physico-chemical characterization and bacteriological analysis for wastewater samples were determined before and after treatment. Results demonstrated that the turbidity removal is observed up to 73 % and fecal coliform removal about 97% using 1.5 mg/L of Psidium guajava leaves ethanol extract. There is a marked decrease in the values of some heavy metals as copper, zinc, chromium, cadmium and lead values. The antimicrobial activity of leaves extracts against some pathogenic bacteria using disc diffusion method and viability test was examined, revealed bactericidal effect on Staphylococcus aureus, Bacillus cereus and E. coli. Studying the ultra-structure of E. coli and Bacillus cereus cells treated with MICs extracts of Psidium guajava leaves revealed the deformation of cells accompanied with rupture of cell membranes at certain sites and leakage of cellular contents. Using gas chromatograph Mass Spectrometry (GC-MS), to identify chemical compositions of Psidium guajava leaves extract and their bioactive components indicate the presence of β-Caryophyllene and Alpha-Bisabolol that reveled the biological activities of Psidium guajava as Antimicrobial. Psidium guajava leaves extract seems to be environmental friendly and an effective agent in treatment wastewater. https://www.biotech-asia.org/vol17no1/the-antibacterial-and-coagulant-activity-of-psidium-guajava-leaves-extracts-in-purification-of-wastewater/ Antibacterial Activity; Extracts; Heavy Metal Gc-Ms; Psidium Guajava; Wastewater