The development of biofilms on the inner-pipe surfaces of drinking water constitutes one of the major microbial problems, which contributes to the deterioration of water quality and entails potential health risks for consumers. Data about the biofilm’s microflora of real chlorinated drinking water distribution systems (DWDS) were collected, on the ground in Sidi-Bel-Abbes (SBA) city, Algeria. A set of analyses were conducted to evaluate, to identify, and to determine the prevalence of bacterial organisms isolated from biofilms. Thirty biofilm samples were collected from the internal walls of the drinking water pipes. The bacterial abundance and the composition of biofilm’s communities were analysed by heterotrophic plate counts and identified by Gram’s reaction, cultural features and biochemical characterisation. Despite the presence of free residual chlorine in the drinking water, biofilm density varied between 2.4x10⁵ and 9.8x10⁸ colony forming unit/cm² (CFU/cm²). Simultaneously, a higher diversity of the bacterial communities was detected. They were listed in two bacterial groups. The predominant group was Gram-negative bacilli, with a rate of 67.86%, including Pseudomonas, Escherichia, Klebsiella, Enterobacter, Citrobacter, Yersinia, in which Pseudomonas aeruginosa was at the top rate. However Gram-positive cocci group rate was 32.14%; including two genera Staphylococcus and Enterococcus, in which Staphylococcus aureus and coagulase-negative Staphylococcus represented the majority of isolated strains. Therefore drinking water biofilms constitute a reservoir of opportunistic pathogens which can be harmful to human health. For this reason, it is recommended to optimise the water treatment sectors in Algeria so as to limit biofilm’s development, water quality degradation, and protect public health.

Ismahane Halima AZZI