Coliform bacteria in sediments around three marine sewage outfalls

The distribution of califorms in the sediments around three marine sewage outfalls was investigated. It was found that coliform fields extended for considerable distances around the two outfalls discharging unchlorinated primary treatment effluent and that a less extensive field existed around the outfall discharging more highly treated sewage. In general, the coliforms in the sediments were found in areas beneath the path of movement of the effluent field in the surface water. It is probable that the bulk of the coliforms reach the sediments by sedimentation from the overlying waters. Although the coliforms in the sediments must persist for a sufficiently long period to permit the accumulation of large numbers by deposition from low count waters, no precise estimate of the survival time in the sediment could be made (DBO).