EFFECT OF UNTREATED SEWAGE DUMP ON THE QUALITY OF GROUNDWATER IN IDDO COMMUNITY, LAGOS, NIGERIA

Abstract

This study was carried out to assess contamination of groundwater in Iddo as a result of many yearsof untreated sewage dump into the adjacent Lagos lagoon. Water samples were collected from fivedifferent sites in the lagoon at certain intervals. Similarly, water samples were collected from five boreholesand seven hand – dug wells sited in the immediate neighbourhood of the sewage dump sites.Sampling covered both the dry and wet seasons and tested for faecal coliform (FC) counts along withother parameters such as Biochemical Oxygen Demand (BOD) and salinity in order to determine theireffects on the density of faecal coliforms. Analysis of parameters was subjected to standard proceduresand data presented in simple statistics. Results for faecal coliform in boreholes ranged from 20-100 total plate count (TPC) /ml in dry season and 5-100 TPC/ml in wet season, while in well water, thevalues are >100 TPC/ml (dry season) and 30 TPC/ml – TNTC (too numerous to count) (wet season).In the lagoon water samples, faecal coliform counts are generally greater than 100 TPC/ml in dry seasonand varied between 100 TPC/ml and TNTC in wet season. BOD values of the lagoon varied fromND (not detected) to 2.8 mg/l (dry season) and 2.4-3.8 mg/l (wet season) with salinity values 3.27-3.45% and 0.70-0.96 % in dry and wet season respectively. Coliform values were higher than World HealthOrganisation standard in drinking water. Results of analysis showed that both surface water andgroundwater in Iddo community are heavily contaminated by the disposal of untreated sewage dumps