Housing density and bacterial loading in urban systems

An investigation was carried out, by the Metro Nashville-Davidson Department of Water and Sewerage Services, into the impact of septic tank overflows on faecal bacteria counts in urban streams discharging into the Cumberland river. Two sewered and 2 non-sewered catchments were investigated and sampled for Escherichia coli , faecal streptococci, faecal coliforms and fluorescence. The data are illustrated, and suggest that faecal bacteria counts, including E. coli , faecal streptococci and faecal coliforms, were higher in the sewered basins than in the non-sewered basins, and that the faecal bacteria densities were directly related to the housing density, population, apparent domestic animal density, development and per cent impervious area.