Measuring Water Reuse Across the University

Universitas Islam Sultan Agung (UNISSULA) measures the volume of water reused across university operations as part of its commitment to sustainable water management and efficient use of water resources.

During the 2025 reporting year, UNISSULA recorded water reuse from several sources, including treated wastewater, harvested rainwater, and greywater. These reused water streams support non-potable activities across the campus and reduce dependence on freshwater.

THE defines water reuse as the recycling of treated wastewater for beneficial purposes such as landscape irrigation, toilet flushing, industrial processes, and groundwater replenishment. The methodology also recognises reused greywater and harvested rainwater used again for appropriate purposes as water reuse.

Measured Water Reuse in 2025

UNISSULA recorded the following volumes of reused water during 2025:

The total measured volume of reused water in 2025 was therefore 25,294 m³.

These figures represent separate measured water-reuse streams and are consolidated to provide an institution-wide picture of water reuse.

Treated Wastewater Reuse

A substantial share of UNISSULA’s reused water comes from treated wastewater.

In 2025, the university recorded 12,451 m³ of treated wastewater reused for suitable non-potable purposes.

Treated wastewater can be reused for activities such as:

• landscape irrigation;
• pond replenishment;
• cleaning;
• selected toilet flushing; and
• other suitable operational uses.

The reuse of treated wastewater reduces the need to draw additional freshwater for activities that do not require potable water.

Harvested Rainwater Reuse

UNISSULA also measures the reuse of harvested rainwater.

During 2025, 5,612 m³ of harvested rainwater was reused across campus.

Rainwater collected from rooftops and other suitable surfaces can be stored and reused for activities such as:

• landscape irrigation;
• cleaning;
• pond top-ups; and
• selected toilet flushing.

The reuse of harvested rainwater supports more efficient use of natural water resources and reduces pressure on groundwater and other primary supplies.

Greywater Reuse

Greywater is another important component of UNISSULA’s water-reuse system.

In 2025, the university measured 7,231 m³ of greywater reused across campus operations.

Greywater may include water collected from sources such as sinks, showers, and air-conditioner condensate before treatment and reuse for appropriate non-potable purposes.

This practice supports a more circular approach to water management by extending the useful life of water before final discharge.

Institution-Wide Water Reuse Monitoring

The measurement of water reuse is not limited to one single source.

UNISSULA consolidates data from several reuse streams to understand the total amount of water recovered and reused across the university.

This includes:

• treated wastewater;
• harvested rainwater;
• greywater; and
• other non-potable water sources where applicable.

By recording these sources separately, the university can monitor changes in water reuse and identify opportunities to further improve water efficiency.

Supporting Water Conservation

Measuring reused water provides UNISSULA with a stronger basis for water-management planning.

The data help the university:

• understand how much water is being recovered;
• compare reuse between different sources;
• reduce freshwater demand;
• evaluate the effectiveness of treatment and harvesting systems; and
• support future improvements in water-reuse infrastructure.

This measurement process complements the university’s wider water-conservation and sustainability initiatives.

Relationship with Total Water Use

The measured water reuse of 25,294 m³ represents a substantial contribution to UNISSULA’s water-management system.

By reusing water for non-potable purposes, the university reduces the need to use fresh water for every campus activity.

This contributes to a more efficient and resilient campus water system.

Supporting Circular Water Management

UNISSULA’s water-reuse measurement supports a circular approach in which water is not treated as a single-use resource.

Instead, water is:

• collected;
• treated where necessary;
• stored;
• reused; and
• monitored.

This helps extend the useful life of available water resources and supports more sustainable campus operations.

Monitoring and Future Improvement

The measurement of water reuse also provides a baseline for future sustainability planning.

By tracking treated wastewater, rainwater, and greywater reuse, UNISSULA can identify trends, improve infrastructure, and expand reuse opportunities where technically appropriate.

The 2025 data therefore provide both an operational record and a basis for future water-efficiency improvements.