Water reuse in industry: 7 steps to use the same water twice

Water reuse in industry means using again, inside the plant, water that has already been through a process, after treating it to the level the next use requires. Rinse water can go to floor washing; treated effluent can feed the cooling tower. The result is less water bought or abstracted and less effluent discharged. The way to implement it starts with metering: without knowing how much each process consumes, and in what condition water leaves it, there is no way to match the water left over with the use that accepts it.

In short:

• Reuse is using again water that has already been used. Harvesting rainwater is something else, although it belongs to the same alternative water sources project.
• The biggest opportunities usually lie in the utilities: cooling towers, washing of areas and equipment, toilet flushing and irrigation.
• The federal basis in Brazil is CNRH Resolution No. 54/2005. Law No. 14,546/2023 directs the federal government to encourage the non-potable reuse of grey water, including in industry.
• The step most often skipped is the first one: metering consumption by area.
• It works at scale: Aquapolo, in São Paulo’s ABC region, produces up to 1,000 litres per second of reuse water for the Capuava Petrochemical Complex.

What is water reuse?

Water reuse is the planned use of water that has already been used, wastewater, for a new purpose. When it goes treated straight to the new use, without first passing through a river or aquifer, it is direct reuse, the form that CNRH Resolution No. 54/2005 regulates for non-potable purposes.

Four concepts often get mixed up:

• Reuse: water leaves one use and goes to another, after the treatment needed. Example: the plant’s treated effluent supplies yard washing.
• Recycling or recirculation: water returns to the same process, in a loop. Example: cooling water circulating between machines and the tower.
• Grey water and black water: grey water comes from sinks, showers and washbasins; black water from toilets. Grey water carries less organic load and is the simplest to reuse.
• Rainwater harvesting: the water has not been used before, so it is not reuse, but it usually belongs to the same project, with its own standard, ABNT NBR 15527.

What types of water reuse are there in industry?

Each type starts from a different source and serves different uses. What decides the treatment is the quality the next use requires, not the highest quality possible.

Type	Where the water comes from	Typical uses	Treatment
Cascade reuse	A process that requires good-quality water	A less demanding process, such as pre-washing	Little or none
Recirculation	The process itself	The same process, such as cooling and parts washing	Filtration and chemical control
Internal treated effluent	The plant’s own treatment station	Cooling tower, floor washing, irrigation, toilet flushing	Polishing according to use, from filtration to membranes
External reuse water	The city’s sewage treatment plant	Cooling, boilers and processes	Done by the producer, with membranes and reverse osmosis
Grey water	Washbasins, showers and changing rooms	Toilet flushing and outdoor washing	Simple to moderate

External reuse water depends on a sewage treatment plant close to the industrial hub. Aquapolo, which treats domestic effluent in São Paulo’s ABC region, can produce up to 1,000 litres per second of reuse water and has already delivered about 138 billion litres in 13 years to the Capuava Petrochemical Complex, a volume equivalent to the consumption of a city of roughly 500,000 people, according to Diário do Grande ABC.

Where does reuse pay off most in a plant?

Reuse pays off most where there is high volume and low quality demand. In many plants, that is in the utilities, not the product:

• Cooling towers. They replace the water that evaporates and the water discharged as blowdown. This is usually the plant’s largest non-potable volume, and it accepts reuse water with control of hardness, silica and microorganisms.
• Washing floors, yards, trucks and equipment. It needs little quality and consumes volume every day.
• Toilets and urinals. A classic use of treated grey water, in administrative buildings and changing rooms.
• Irrigation of green areas. Seasonal, but simple to supply.
• Boilers. They accept reuse, but only after advanced treatment, such as reverse osmosis and demineralisation. This is the use that makes the project most expensive.

In food, beverages and pharmaceuticals, water that touches the product follows the sector’s health rules, and reuse usually stays in the utilities.

Brazilian industry has already shown the effect at scale. According to the National Confederation of Industry (CNI), the automotive industry cut water use in vehicle manufacturing by 50% between 2008 and 2013, with reuse systems, rainwater harvesting and recycling among the measures, and the chemical industry cut water abstraction by 25% between 2006 and 2016.

How do you implement water reuse in 7 steps?

1. Meter and sectorise consumption. Build the water balance: how much comes in, how much goes to each process, how much evaporates and how much leaves as effluent. Without a meter per area, the balance becomes an estimate. Telemetry shortens this stage, because it reads the meters on its own and shows consumption hour by hour, including overnight.
2. Characterise the water left over. For each effluent, the flow and the quality: solids, organic load, conductivity, oils and whatever else the process leaves in the water.
3. Match supply and demand by quality. List what each use requires and connect the cheapest pairs first: water that already serves without treatment, then water that needs little.
4. Choose the treatment. From simple filtration to membrane bioreactors and reverse osmosis. Sizing starts from the quality the use requires and the real flow measured in step 1.
5. Test in a pilot. A small-scale test confirms the quality and stability of the treated water before the full investment.
6. Take care of rules and safety. A network and tank separate from drinking water and labelled, an environmental licence and a water-use permit when your state’s agency requires them, and a quality monitoring plan. A cross-connection between the reuse network and the drinking water network is the risk the project must eliminate.
7. Measure the result. Compare consumption before and after with a measurement and verification protocol. T&D measures savings under the international IPMVP protocol, with a baseline built from the consumption history, which makes the result auditable.

Which rules govern water reuse in Brazil?

There is no single reuse law. What applies is a set of rules, and each state’s environmental licence completes the picture:

• CNRH Resolution No. 54/2005: defines direct non-potable reuse and five categories: urban, agricultural and forestry, environmental, industrial and aquaculture purposes.
• Law No. 14,546/2023: amended Brazil’s Sanitation Law (Law No. 11,445/2007) so that the federal government encourages the use of rainwater and the non-potable reuse of grey water in new buildings and in landscaping, agricultural, forestry and industrial activities. The network and tank for this water must be separate from the public network, and the water needs treatment that ensures safe use.
• ABNT NBR 16783:2019: use of alternative non-potable water sources in residential, commercial, institutional, service and leisure buildings. It does not cover industrial processes, but it covers the plant’s support buildings.
• ABNT NBR 15527: rainwater harvesting.
• ABNT NBR 13969/1997: complementary effluent treatment and local reuse, with quality classes by type of use.

How much water can reuse save?

It depends on the process, which is why the number only appears after metering. Reuse projects usually come after fixing losses: there is no point treating and reusing water that is leaking.

That is the order T&D follows. SEA 360º measures, fixes losses and standardises the points of use, with a reduction of up to 70% of water spending in the full programme. Once the result is proven, SEA+ reinvests the savings in new water efficiency projects, such as reuse, automation, equipment replacement and rainwater harvesting.

Frequently asked questions

What is the difference between water reuse and water recycling?

In reuse, water leaves one use and goes to another, after the treatment needed. In recycling, or recirculation, it returns to the same process, in a loop. A plant usually has both: the cooling tower recirculates water, and treated effluent replaces the part that evaporates.

Is rainwater reuse?

No. Reuse is using again water that has already been used, and rainwater has not been. Both usually belong to the same alternative water sources project, but each has its own standard: rainwater harvesting follows ABNT NBR 15527.

Can reuse water go to the boiler?

It can, as long as it goes through advanced treatment, such as reverse osmosis and demineralisation, because a boiler requires very high-quality water. That is why it is usually the last use to receive reuse water, after cooling towers and washing.

Does water reuse need a licence?

It depends on the state and the type of reuse. Effluent treatment is usually already in the plant’s environmental licence, and changing where the treated water goes may require an update. Check with your state’s environmental agency before implementing.

Can reuse water be used for drinking?

No. CNRH Resolution No. 54/2005 covers direct non-potable reuse, and reuse for human consumption is not among its categories. Reuse water runs in a separate, labelled network precisely so it does not mix with drinking water.

Sources

• CNRH Resolution No. 54 of 28 November 2005, in Portuguese
• Law No. 14,546 of 4 April 2023, in Portuguese
• CBIC: ABNT NBR 16782 and 16783 published and NBR 15527 revised (2019), in Portuguese
• National Confederation of Industry: how industry contributes to efficient water use (2018), in Portuguese
• Diário do Grande ABC: Braskem and Aquapolo strengthen water security in the region (21/03/2026), in Portuguese