Net Zero Water plays a key role in creating resilient and sustainable cities of the future. Capturing, treating, and reusing water on-site reduces dependency on external water sources and mitigates the risk of shortages. In rapidly urbanizing areas, this approach helps manage demand, prevents overextraction of groundwater, and minimizes strain on municipal infrastructure. It also enhances environmental protection by reducing wastewater discharge and promoting circular water use. Ultimately, Net Zero Water enables cities to adapt to climate change, conserve vital resources, and support long-term urban sustainability.
What is Net Zero Water?
Net Zero Water refers to a building or community that captures or reuses as much water as it consumes annually. It aims to significantly reduce dependence on external water supplies and eliminate discharge to municipal wastewater systems.
Benefits of adopting IGBC Net Zero Water
The Net Zero Water Rating System is designed to reduce water consumption and promote the use of alternative water sources to meet a building or project's total water demand.
- Improved water efficiency, resulting in a reduction of annual water consumption by approximately 30–50% compared to the national baseline.
- An overall reduction in water costs by around 30%.
- Decreased dependency on raw water sources.
In addition to these measurable benefits, the intangible advantages of Net Zero Water include enhanced compliance with local regulations and the promotion of sustainable water conservation practices. The rating system adopts a performance-based approach to evaluate buildings. It has been developed to be both comprehensive and user-friendly, ensuring ease of implementation without compromising on effectiveness.
The program aligns with key national priorities, such as:
- Reducing the overall national water demand through improved water efficiency.
- Promoting the use of alternative water sources to offset freshwater demand.
- Minimizing reliance on raw water.
- Encouraging water conservation at a national scale to help ensure long-term water security.
Key Strategies in IGBC Net Zero Water Design:
- Rainwater Harvesting
- Greywater Recycling
- Blackwater Treatment and Reuse
- Low-flow Fixtures and Appliances
- Native Landscaping
Case Study: Net Zero Water Project – Bangalore
Project Overview
Location: Bangalore
Project Type: Residential
Objective: Achieve Net Zero Water compliance through efficient water management systems.
- Landscape Area of the project – 770.53 Sq. m
- STP Capacity – 15 kl/d
- Number of Rainy Days – 62.7 Days
- Rainwater Tank Capacity – 30 M3/Day
- Number of Rainwater Pits – 6
- Pit Capacity – 28.76 M3/Day
- Full Time Equivalent – 334
1. Water Demand Calculation
The Project team has installed water-efficient plumbing fixtures to improve water efficiency
- Total Fresh water Requirement - 6071 kl/ Annum
- Total Flush water Requirement – 1463 kl / Annum
- Total water Requirement – 7534 kl/ Annum
2. Annual Rainwater harvesting capacity
The Project team has designed a rainwater harvesting system to capture at least ‘one-day rainfall’* runoff volume from the roof and non-roof areas
- Total average rain water available for re-use/year – 1454.0 m3/year
- Total average rain water harvested via recharge pit /year – 1294.7m3/year
3. Waste Water Treatment
The Project team has provided an on-site wastewater treatment system to treat 100% of wastewater generated in the project, to the quality standards suitable for reuse as prescribed by the Central (or) State Pollution Control Board
- STP Treated Water available for reuse – 6781 kl/ Annum
- STP Treated Water reused for Flushing – 1463 kl / Annum
- STP Treated Water reused for Landscaping – 1442 kl/Annum
- Excess treated water available – 3562 kl/ Annum
Achieving Net Zero Water
The Project meets net zero water by meeting Water Performance Ratio > 0.50 & Water back to the source ≥ 1.0
Advantages of Net Zero Water in this project
- Sustainability: Reduces strain on municipal water supply and local aquifers.
- Cost Savings: Decreased dependency on water tankers and municipal supply over time.
- Environmental Benefit: Lower water discharge and runoff, reducing pollution.
- Resilience: Greater independence during water shortages or droughts.
Conclusion
The Net Zero Water initiative at this project in Bangalore stands as a forward-thinking model for sustainable urban development. By effective PHE design of integrating fresh water reduction, rainwater harvesting, greywater reuse, and on-site wastewater treatment, the project not only meets its entire water demand internally but also significantly reduces environmental impact. This approach fosters long-term water security, lowers operational costs, and supports ecological balance.
Net Zero Water for this residential project is worth its weight in gold, considering the drought Bangalore faced last summer. People can live without electricity, but cannot live without water. At Conserve, we design the PHE systems of a residential to come as close to net-zero water as possible, as the value of water is priceless.
