An Alternative Source of Water Supply: Design and Construction of Rainwater Harvesting System for Domestic Use in Ovia-North East Local Government Area, Benin City, Edo State, Nigeria

Abstract

Demand for freshwater is on the increase due mainly to population growth and urbanisation. Many of the water systems that keep ecosystems thriving and feed a growing human population have become stressed. Rivers, lakes and aquifers are drying up or becoming too polluted to use. Hence, there is need for alternative water supply sources. With this in mind, there has been a growing attention on the potentials of rainwater harvesting as an alternative source of water supply. In this study, rainwater harvesting (RWH) system was designed for a 5-membered household in Ovia-North East LGA of Benin City, Nigeria. However, a prototype of the RWH system (mini system) was constructed to ascertain its suitability. It consist of a corrugated metal (zinc) sheet catchment of 6m², a collection system made of PVC pipes and a filter with granular activated carbon and fine sand and two locally available plastic storage drums having capacity of 100L each. Rainwater samples were collected from the storage drums and analysed for their suitability in domestic purposes. These samples were analysed for thirteen parameters, namely; pH, Electrical Conductivity (EC), Temperature, Turbidity, Total Dissolved Solids (TDS), Chloride (Cl), Ammonium Nitrogen (NH₄N), Nitrite (NO₂^-), Nitrate (NO₃^-), Iron (Fe), Zinc (Zn), Copper (Cu) and Coliforms Count (Col.) using standard methods. Results revealed that with a roof area of 40m², 75m³ reservoirs or tanks capacity will be required for dry period. It was observed that all parameters analysed were within acceptable limits for drinking water quality except for coliform bacteria. Although minimum level of coliform bacteria was observed, however pure water should be free from all kinds of coliforms, thus it is recommended that the addition of a disinfectant to the harvested rainwater is required to further improve it quality for domestic use. Also proper maintenance of the catchment area and storage containers could eliminate the presence of coliform bacteria and make rainwater safe for domestic purposes. This study has revealed that the harvested rainwater is of good quality and that the amount of rainwater to be stored with a 75m³ reservoirs or tanks will be more than enough for a 5-membered household to meet its domestic use throughout the whole dry periods of the year. Hence, RWH can serve as an alternative and viable source of water supply.

Keywords: Catchment Area, Collection System, Runoff coefficient, Rainwater Harvesting, Rainfall, Water Demand, Water Supply.

DOI: 10.7176/CER/14-7-01

Publication date: November 30^th 2022