Rainwater Harvesting: Microbial and Chemical Water Quality Assessment in Warri District

Abstract This study evaluated the microbial and chemical quality of harvested rainwater collected from the rooftops of different materials: zinc, aluminium, asbestos, and thatch from private dwellings and public places in Warri Refinery Petrochemical Company (WRPC), Warri, Delta State. A total of 20 rainwater samples were obtained across five rainfall events and analyzed using USEPA and APHA standard recommended methods for microbials procedures for physicochemical and microbiological parameters, including Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), dissolved oxygen (DO), nitrate, sulphate, calcium, magnesium, total coliforms, fecal coliforms, Escherichia coli, total heterotrophic bacteria (THB), and fungi (THF). BOD results obtained ranged from 1.40–1.40 mg/L, 1.60–1.30 mg/L, 1.80–1.40 mg/L and 2.10–1.50 mg/L for aluminum, zinc, asbestos, and thatch roofing material. COD values ranged from 3.26–3.41 mg/L, 3.72–3.13 mg/L, 4.19–3.20 mg/L, and 4.88–3.66 mg/L for aluminum, zinc, asbestos, and thatch roofs samples, respectively. DO values range from 4.60–6.10 mg/L in all the roofing materials. The calcium values ranged from 1.040 – 0.395 mg/L, 2.124 –0.659 mg/L, 2.816–1.006 mg/L, and 3.536–1.224 mg/L for zinc, aluminum, asbestos and thatch roofs, respectively, from the first fifth flush. Magnesium values ranged from 6.095–0.198 mg/L in all the roofing materials. NO3- values ranged from 0.02–ND mg/L, 0.03–ND mg/L, 0.19–0.01 mg/L and 0.06–ND mg/L for aluminum, zinc, asbestos, and thatch roofing materials. SO42- values range from 0.51–6 ND mg/L in all the roofing materials. T. Coliform values ranged from 140.0 -20.00 MPN/100mL, F. Coliform from 20.00-ND MPN/100mL, THB from 2.51 – 1.07 cfu/L, THF from 1.32- 0.08 cfu/L for all the roofing materials. E.coli was not detected in all the roofing materials. All harvested rainwater samples tested positive for total coliform counts were above the World Health Organization (W.H.O) stipulation for drinkable water of 0 MPN/100ML and 0 cfu/L for THB and THF respectively. The chemicals and elemental parameters in the water samples were relatively within the World Health Organization (W.H.O) standards of 4.00, 5, 10, 50, 250, 75 and 50 mg/L for DO, BOD, COD, NO3-, SO42-, Ca and Mg. The study revealed that harvested rainwater may not be suitable for direct or indirect drinking, without proper treatment, but could be used for many other domestic purposes.