Ten well water samples were analyzed for the development of bacterial load using 1%, 5% and 10% concentrations of alum which was added to each 100ml of well water samples to determine the effect of alum on the microbial load of well water from Rural and Urban Areas in Enugu State. After exerting an effect on the well water sample, the supernatants and sediments were analyzed for development of bacteria colonies by viable cell counts. It was observed that the effect of alum on bacterial load increases as the percentage concentration of the of alum increases, however, further increase in the concentration of alum has no effect on the bacterial load, and this can be observed in well water from Ufuma Achara layout, Agbani Nkanu, Ugbo Paul Abakpa, Ohofia Uwani and Amodu Awkunanaw. On the other hand, from1% to 5% concentration of alum has no effect on the supernatant of well water from Amaokwe Achara layout, but however, with increase in concentration of about 10% it began to exert an effect on the bacterial load of both the supernatants and sediments.