Evaluation of wastewater reuse and suitability for agricultural purpose in Akure, Nigeria

Abstract

The suitability of six waste water sources for drinking and irrigation purposes in Akure, metropolis Nigeria was assessed. Waste water samples were collected from six sources (Tisco limited located at Akure North Local Government Area, FUTA Post-graduate Hotel, a Residential Quatre, State General Hospital Akure, Mandate Restaurant located at the South Gate of the Federal University of Technology, Akure  and Mr Bigg Akure)  in Akure, Nigeria. These were analysed for biochemical properties determination. The parameters determined include: pH, turbidity, alkalinity, electrical conductivity (EC), dissolved oxygen (DO), biochemical oxygen demand (BOD₅) and total solids (TS). Others were chloride (CL-), total dissolved solids (TDS), total suspended solids (TSS), lead (Pb), nitrate (NO₃), sulphate (SO₄^-2), oil and grease (O/G), coliform count and heavy metals. The parameters were determined using APHA (2005) standard procedures and results obtained were subjected to statistical analysis. Also, parameters such as Sodium Absorption Ratio (SAR), Na percentage, Magnesium Hazard (MH), Kelley’s index (KI), and soluble sodium percent (SSP). All the wastewater samples investigated contained a considerable degree of contamination which indicated the pollution of the wastewater. The results for the waste water indicated that the pH ranged from 5.37 – 7.6, EC ranged from 384.67 – 1656.7 µs/cm, TDS ranged from 2462 - 10604mg/l, TS ranged from 16899 – 34438 mg/l, acidity ranged from 230 – 662 mg/l, alkalinity ranged from 81.3 – 415 mg/l, chloride ranged from 82.77 – 457.08 mg/l, TH ranged from 24.3 – 89 mg/l, turbidity ranged from 7.93 – 188.55 NTU, Dissolved Oxygen ranged from 0.00 – 9.20mg/l, BOD ranged from 0.00 – 1096 mg/l, Sulphate ranged from 51.27 – 190.09 mg/l, nitrate ranged from 4.08 – 17.27 mg/l , and O/G ranged from 0.64 – 15.32 mg/l . Statistical analyses showed significant (p<0.05) differences at specific confidence levels. Most of the values were above the maximum permissible levels of FAO, WHO and NSDWQ standards for drinking water and were mostly below or within the permissible range for irrigation according to FAO standard. Also, parameters such as SAR, SSP, KI, MH indicated the suitability of the waste water for irrigation. Results showed that the wastewater treatment is required to achieve minimum acceptable level for domestic reuse, public awareness on the dangers inherent in the possible re-use of the waste water for domestic purposes need be carried out.