Real-world sustainability analysis of an innovative decentralized water system with rainwater harvesting and wastewater reclamation

Jian Zang,Manish Kumar,David Werner

doi:10.1016/j.jenvman.2020.111639

Abstract

This study investigated an innovative decentralized water system which combined rainwater harvesting with wastewater reclamation to generate 39% of the water resources needed for a higher education institution with student and staff accommodation in India. We collected performance data to critically appraise the current water system, design alternatives and water management optimization opportunities. The campus was recently built in a hot, semi-arid region of India with a summer, monsoon and winter season. It represented in a microcosm the vision of leading Indian engineers for a more sustainable urban systems future. We collated the water infrastructure costs, blue and recycled water demands, chemical demands, electricity demands and operational costs over a calendar year. The annual institutional water demand was 379,768 m3, of which 32% was sourced from reclaimed wastewater, and 7% from roof-collected rainwater. Electricity consumption was 0.40 kWh/m3 for drinking water treatment, and 0.62 kWh/m3 for wastewater treatment, in line with median values reported for centralized systems. Rainwater harvesting and wastewater reclamation accounted for 42% of the water infrastructure costs, with a predicted payback period of >250 years through reduced operational costs. Scenario analysis recommended a water system design alternative with wastewater reclamation for ground maintenance only, which was predicted to yield similar environmental benefits, with an infrastructure cost payback period of only 15 years. Scenario analysis also revealed how better water management to address leakage, and more drought-tolerant landscaping, could improve environmental metrics of the current system by up to 52% and reduce operational costs by up to 23%. Reducing high domestic water usage was found to be essential to secure gains achieved with water infrastructure innovations. Rainwater harvesting had high infrastructure costs, and water policy in low- and middle-income countries should instead support wastewater reclamation and best practice in water management.

Highlights

Climate change is predicted to increase vulnerability of global water resources, and rising human water demands are an even bigger threat to global water security (Vorosmarty et al, 2000)
The institutional water demand per person living on campus was 403 L per capita per day (LPCD)
The 280% increase in domestic academic demand, as compared to the Indian national median in 2010, is much higher than the 7% reduction in river water use achieved by rainwater harvesting

Summary

Introduction

Climate change is predicted to increase vulnerability of global water resources, and rising human water demands are an even bigger threat to global water security (Vorosmarty et al, 2000). Domestic water demand in the world is projected to increase from 235 km in 2010 to 290 km in 2025. Most of this increase is projected for low- and middle-income countries due to their higher population growth rates, relatively rapid urbanisation and increase of per capita water use from the existing low levels, due to income growth (Rosegrant and Cai, 2002). Conventional water supply and wastewater treatment systems are very energy intensive (Liu et al, 2016), and provide questionable templates for water infrastruc ture expansion in low- and middle-income countries (Mohapatra et al, 2014).

Methods

Results

Conclusion