Performance Evaluation of a Rainwater Harvesting System: A Case Study of University College Hospital, Ibadan City, Nigeria

Abstract

Provision of water supply to meet urban demands is increasingly facing complex challenges due to water scarcity, population growth, ageing infrastructure, variability and uncertainty under climate change. Rainwater harvesting system (RWHS) can augment water supply to meet urban and rural needs with added economical and financial benefits. This study assessed the hydraulic and financial performance of a RWHS for the University College Hospital in Ibadan. Storage capacity, water savings, sensitivity analysis and MonteCarlo simulation were optimised using a Raincycle model. A comprehensive assessment of the proposed system was carried out, considering seven specified and eleven unpredictable variables. The specified variables are: basin area, pump hydraulic power, initial surface runoff, storage capacity, pump capacity, UV unit hydraulic power and operating period while the unpredictable variables are: filter coefficient, precipitation profiles, runoff coefficient, interest rates, energy cost, water demand, water rates, total cost, disposal and asset retirement obligation. The water savings and RWH performance were determined and return period was evaluated. The result of maximising storage capacity found 78.1% of demand could be met. The analysis of maximising water reduction revealed seven reservoir sizes with a prospective long-term profit. A 12 m3 tank estimated to save $51,072 over 50 years with a payback period of 1 year was found to be the best. The important effect of a given set of conditions on the economic feasibility of a RWHS was revealed by MonteCarlo simulation. The findings showed a significant reduction in the total fresh water consumption and the total cost can be obtained. The potential of using RWH as an alternative source of water for the Children’s ward is high. This method can be used for other sections of the hospital such as the accident and emergency unit.