Effects of a sewage lagoon effluent on the water quality of the receiving stream

• Published in: Environmental pollution. Series A. Ecological and biological 1985, Vol.37 (1), p.71-86
• Main Authors: Okoronkwo, Nwadiuto, Odeyemi, Olu
• Format: Article
• Language: English
• Subjects: Applied sciences; Continental surface waters; Exact sciences and technology; Natural water pollution; Pollution; Water treatment and pollution
• ISSN: 0143-1471
• DOI: 10.1016/0143-1471(85)90025-X

The water quality of an activeky used small stream receiving the University of Ife sewage lagoon effluent was assessed down to 10 km below the pollution source. Faecal coliforms, total coliforms and heterotrophic bacteria were enumerated and the pH and dissolved oxygen values determined. Faecal coliform numbers in the region of the stream used to irrigate vegetables and farm crops in the dry season ranged from 10 5 to 10 6 100 ml −1 while populations as high as 10 2 to 10 4 100 ml −1 were obtained in the parts of the stream used for various domestic activities. Total coliform density ranged from 10 3 to 10 7 100 ml −1 in the actively used zone of the receiving stream. Furthermore, the total heterotrophic bacterial population of the receiving stream was raised from 10 4 to 10 8 ml −1 after mixing with the lagoon effluent, and was only reduced to about 10 5 ml −1 at 10 km downstream of the mixing point. The dissolved oxygen of the receiving stream dropped from 7·6 mg litre −1 to values less than 2 mg litre −1 on mixing with the effluent. The dissolved oxygen sag continued to 8 km downstream, after which detectable reaeration of the stream began. The various data strongly suggest that serious public health hazards could result from the use of this stream into which undisinfected sewage lagoon effluent is discharged.