Steps Toward Sustainable Labs: Smarter RO Units for Water and Energy Savings

Date: 28/08/2025
Read Time: 5 minutes
Author: Dr. Surani McCaw, B.E. (Chemical) 

Key points:

• Laboratories are resource-intensive, consuming high levels of energy and water, generating significant plastics and CO₂ emissions, which makes sustainability improvement especially impactful 

• RO is more efficient than distillation but often wastes water. Poorly designed lab RO units recover only 20–25% of feedwater, while well-designed systems with larger membranes can achieve 50–75% recovery. 

• Sustainable system design requires energy efficient technologies (e.g. VSD pumps, standby modes), CO₂ removal, and appropriate matching of water purity (Type I/II/III) to application needs, to minimise waste and operating costs.

• Benchmarks and best practice are key, adopting standards such as ASHRAE 189.1 helps labs set recovery targets, minimise reject water, and align with UN SDGs 6, 12, and 13. 

Scientists tackle some of the world’s most complex challenges, yet laboratory operations themselves can unintentionally harm the environment. While research often addresses climate change and sustainability, many laboratory practices remain outdated, contributing to unnecessary emissions and resource use. 

The Green Lab movement has emerged in response, promoting environments that are both sustainable and scientifically rigorous. By rethinking water, energy, and consumables, laboratories can reduce their footprint without compromising research outcomes. 

Laboratories are resource-intensive, with disproportionate environmental impacts compared with offices or other facilities:

• Energy – Labs use 3–10 times more energy per square metre than offices, with fume hoods and ULT freezers as major drivers.*
• Water – Consumption is ~4 times higher than in offices, largely due to autoclaves and DI water production.*
• Plastics – Labs produce ~2% of global plastic waste, much of it single-use and difficult to recycle.*
• Carbon emissions – Even routine tests generate measurable CO₂e footprints.*

Encouragingly, sustainable practices often improve both efficiency and productivity while reducing environmental harm.

Source: *National Library of Medicine, Medical Journal of Australia

RO in Context: From Distillation to RO

Water purification is fundamental in laboratories, but the technology choice directly affects sustainability. Distillation was once the standard but is highly energy-intensive. Reverse osmosis (RO) has become dominant due to its lower energy demand.

However, RO is not inherently sustainable. Poorly designed systems can waste water, consume excess energy, and increase plastic waste.

How Efficient Is RO? Water Waste and Benchmarks

• Distillation typically achieves >95% conversion.
• Laboratory RO often achieves only 20–25% conversion, meaning most feedwater is discharged as waste.

In Australia, there are currently no standards specifying minimum RO recovery rates. Guidance instead focuses on reuse opportunities and risk-based design. By contrast, ASHRAE Standard 189.1 (American Society of Heating, Refrigerating and Air-Conditioning Engineers – High-Performance Green Buildings) requires RO and nanofiltration systems with capacities above 100 L/h (27 gal/h) to limit reject water to ≤60% of feedwater and encourages onsite reuse of reject streams. Using ASHRAE as a benchmark can help Australian suppliers design RO systems that reduce water wastage and improve sustainability in laboratories.

Unlike distillation, RO requires supplementary processes to maintain water quality and control microbial growth:

• UV irradiation
• Bacterial or endotoxin removal filters
• Continuous recirculation

While these measures are essential, they also produce waste through consumable replacements, which impacts overall sustainability.

It is important to note that, while onsite wastewater reuse is widely promoted in standards, the treatment and infrastructure required to restore waste to fit for purpose quality can, in some cases, outweigh its environmental benefits.

Sustainability in laboratory water purification depends strongly on water demand. For low-to-medium demand laboratories (≤ 200 L/h), decentralised RO systems are generally preferred. These units are easier to maintain and can be designed to minimise reject water and consumable waste. Point-of-use RO systems can also be optimised by incorporating design features from larger systems, achieving water conversion rates of up to 50%.

For high-demand laboratories (≥ 300 L/h), careful system design is critical. Using multiple small RO units (e.g. three 100 L/h units) should be avoided, as this approach increases water and consumable waste. A capacity of 300 L/h serves as a benchmark for larger 4” × 40” RO membranes, which can achieve water recovery rates of 75% or more when designed correctly.

High-volume laboratories must weigh the trade-offs between centralised and decentralised/modular RO systems:

• Centralised RO – Offers high efficiency, supports storage and recirculation loops, and integrates well with UV and bacterial removal processes. However, it requires more complex design and specialist servicing.
• Decentralised/Modular RO – Provides scalability and simpler maintenance. A single 200 L/h unit is typically more sustainable than two 100 L/h units, reducing consumable use and servicing requirements.

Designing Energy Efficient RO Units

RO units can be engineered to reduce power consumption:

• Standby Mode – Reduces power draw during idle periods.
• Energy Saving Mode – Activates after prolonged inactivity.
• Variable Speed Drive (VSD) Pumps – Standard in RO units above 200 L/h, automatically adjusting pump speed to ringmain pressure demand for optimal efficiency.

Key Design Features for Sustainable RO Systems

Sustainable RO systems should incorporate:

• Integrated pressure booster pump – Achieves ~50% recovery vs. typical 20–25%.
• Replaceable membranes – Retain housings, replacing only membranes to reduce plastic waste.
• Two-pass RO – Direct feed to Type I systems, extends DI filter life, lowers operational costs.
• Semi-automatic chemical sanitisation – Improves efficiency and equipment lifespan and maintains water quality compliance.
• Integrated CO₂ degasser/scrubber – Protects Continuous Electro-deionisation (CEDI) cell and De-ionisation (DI) filter performance, reduces replacements, ensures compliance with resistivity standards.

These features collectively extend system life, minimise waste, and align operations with sustainability goals.

Why CO₂ Control Matters

DI cartridges and CEDI cells are highly sensitive to dissolved CO₂, which RO membranes do not remove. Excess CO₂ shortens their lifespan, increasing replacement frequency, consumable waste, and operational costs. CO₂ levels are influenced by water alkalinity and pH, and naturally high concentrations (e.g., in Melbourne) can significantly reduce system efficiency. While CO₂ removal is standard in larger water treatment systems, many small lab-scale units overlook this step, sometimes driven by increased consumable turnover for after-sales revenue.

Incorporating degassing or CO₂ scrubbing offers multiple benefits:

• Consistent water quality
• Extended DI and CEDI lifespan
• Improved energy and consumable efficiency
• Reduced environmental footprint

Effectively managing CO₂ reduces material consumption, waste, and energy use, directly improving sustainability and supporting the UN Sustainable Development Goals (SDGs):

• SDG 12 – Responsible Consumption and Production: Optimising consumable use.
• SDG 6 – Clean Water and Sanitation: Maintaining efficient water treatment processes.
• SDG 13 – Climate Action: Lowering energy use and emissions by extending system component life.

Sustainable laboratory water purification requires a shift from traditional, high-waste approaches to technically optimised RO system design. For low- to medium-demand laboratories and point-of-use benchtop RO units, recovery rates of ≥50% should be targeted, while centralised RO plants serving high-demand facilities should achieve ≥75%. Incorporating energy-efficient features such as VSD pumps, standby and energy-saving modes, CO₂ removal to protect downstream DI/CEDI, and two-pass RO configurations to extend consumable life reduces both operational costs and environmental burden. Aligning water purity with actual application needs further prevents unnecessary production of Type I water, lowering energy demand and consumable turnover. Benchmarked against frameworks such as ASHRAE 189.1, these measures provide laboratories with a clear pathway to minimise water wastage, plastic generation, and CO₂e emissions while maintaining compliance with rigorous quality standards. Partnering with organisations such as My Green Lab® can further strengthen sustainability initiatives, enabling laboratories to reduce their environmental footprint and advance toward more responsible, climate-conscious scientific research.