Impact of the surface characteristics of rainwater tank material on biofilm development

In order to determine the impact of rainwater construction material on the development of a biofilm, three materials were tested: concrete, clay, and PVC. The biofilm attachment was initially more effective on clay coupons, but, after a period of three days, concrete coupons produced a greater quantity of biofilm than clay and PVC, in that order. The heterotrophic plate count in the rainwater indicated that this quantity tended to first increase following a rainfall, and then decrease. The new materials seemed to attach themselves to the existing biofilm on the wall and/or sediment in the form of small particles. The presence of fecal coliforms in the biofilm coupons was noted after major rainfall events, and this was correlated with the increase in fecal coliforms in the water. This study concluded that the most favorable support for biofilm development is concrete, clay, and PVC, in that order.