The water sector has changed significantly over recent decades, writes Seamus Kelly CEng MIEI.

What was once primarily a conversation about treatment compliance, discharge standards and operational performance has evolved into something broader. Today, the sector is increasingly concerned with sustainability, resilience, decarbonisation and long-term stewardship of critical public infrastructure.

Climate change, ageing assets, energy costs and environmental expectations are reshaping the way infrastructure is designed, operated and renewed. Engineers are increasingly required to balance public health protection, environmental performance, sustainability objectives and infrastructure resilience.

At the same time, a recurring observation has emerged. Progress is not always achieved through increasing complexity. In many instances, the most effective engineering solutions are those that simplify systems, reduce life cycle burdens and create infrastructure that is easier to operate, maintain and steward over time.

This article explores three themes that increasingly influence the future direction of water infrastructure:

• Sustainability;
• Sanitation;
• Stewardship.

Together they form a broader conversation about conservation – not only of water, but also of energy, infrastructure and environmental quality. 

Figure 1 – Wastewater infrastructure in context: Modern wastewater treatment infrastructure sits at the intersection of public health, environmental protection, sustainability and long-term stewardship of public assets.

Beyond compliance

Historically, the purpose of water and wastewater infrastructure was straightforward:

• Protect public health;
• Supply safe drinking water;
• Collect and treat wastewater;
• Protect receiving waters.

These objectives remain fundamental.

However, modern infrastructure is increasingly expected to:

1. Improve energy performance.
2. Reduce carbon emissions.
3. Demonstrate climate resilience.
4. Deliver long-term value.
5. Support environmental sustainability.

As expectations evolve, success can no longer be measured solely by compliance. Increasingly, it is measured by how effectively infrastructure delivers environmental, social and economic value throughout its life cycle.

Sustainability through performance

One of the most significant developments in recent years has been the growing recognition of the relationship between water and energy.

Every stage of water and wastewater treatment requires energy. Within activated sludge facilities, aeration systems frequently represent the largest single consumer of electricity and therefore one of the largest opportunities for sustainability improvement.

Reducing energy demand delivers multiple benefits simultaneously:

1. Lower operating costs.
2. Reduced greenhouse gas emissions.
3. Improved resilience.
4. Better sustainability performance.

Perhaps more importantly, it encourages engineers to think critically about how systems perform and where investment can deliver the greatest overall benefit.

One of the recurring observations emerging from energy and sustainability programmes is that performance improvement is rarely achieved through a single intervention. More often, it results from a detailed understanding of how a system behaves over time and how individual assets contribute to overall performance.

This is especially relevant in wastewater treatment, where energy use is shaped by several connected factors, including process design, hydraulic performance, asset condition, control strategy and operational practice. Improvements that seem modest on their own can combine to deliver significant long-term benefits.

Perhaps the most valuable outcome of detailed performance assessment is not simply the identification of energy savings, but an improved understanding of the system. Once engineers can clearly see where energy is being consumed and why, they are better positioned to make informed decisions about investment, optimisation and future infrastructure development. In this sense, measurement becomes much more than a reporting tool; it becomes a mechanism for understanding how infrastructure can be improved, simplified and sustained over the long term.

Figure 2 – Average daily power consumption before and after optimisation. Average daily power consumption before and after aeration optimisation works at Site C. The results demonstrate how targeted engineering improvements and process optimisation can deliver sustained reductions in energy demand while maintaining treatment performance.

Case Study: Finding opportunity through data

One recurring lesson from sustainability programmes is that meaningful improvement begins with measurement.

Portfolio-wide energy assessments demonstrated significant variation between facilities performing broadly similar functions. Understanding these differences allowed engineering effort to be directed towards opportunities offering the greatest potential benefit.

Table 1 – Energy performance and improvement opportunities across seven facilities

Site	Annual Consumption (kWh/year)	Aeration Share	Energy Conserved (kWh/year)	Reduction (%)
Site A	2,193,398	44.5%	330,942	33.9
Site B	2,109,609	62.1%	630,130	48.1
Site C	1,616,697	46.5%	561,735	74.7
Site D	365,362	70.5%	109,124	42.4
Site E	304,692	71.4%	109,253	50.2
Site F	277,845	83.8%	98,446	42.3
Site G	94,900	42.6%	19,404	48.0

Facilities anonymised and ranked by annual electricity consumption.

Across the facilities assessed, aeration represented between approximately 43% and 84% of total electricity demand. In several cases, potential reductions approaching 50% were identified through optimisation and redesign of aeration systems.

The broader lesson was not simply that energy can be saved. Rather, it demonstrated how data-driven decision making can help prioritise investment where it delivers the greatest operational, environmental and sustainability benefit.

Simplicity as a sustainability strategy

Discussions around sustainability often focus on new technologies. For much of the last century, engineering progress was frequently associated with adding infrastructure, adding controls and adding technology. While innovation remains essential, experience increasingly suggests that progress is not always achieved through greater complexity.

Many modern infrastructure systems have evolved over decades, accumulating equipment, instrumentation and operational requirements with each modification or upgrade. Individually these additions may be justified. Collectively, however, they can increase maintenance burdens, introduce additional failure modes and create operational dependencies that persist throughout the life of an asset.

One of the more interesting challenges facing engineers today is determining when complexity genuinely adds value and when simplification may provide a better long-term outcome.

In many cases, simpler systems can deliver equivalent or better outcomes. The benefits of simplification are often cumulative and may not be immediately apparent during project delivery. A valve removed today may eliminate decades of inspection, maintenance and replacement activities. A maintenance-intensive piece of equipment may appear insignificant within an overall scheme, yet over its operational life it will consume energy, require spare parts, create access requirements and introduce potential failure modes.

In wastewater infrastructure, this can include simplifying aeration systems, reducing pressure losses, eliminating unnecessary control devices or replacing maintenance-intensive equipment with passive alternatives. Such decisions can improve reliability, reduce operational burden and lower whole-life costs while continuing to deliver the required treatment objectives.

One example of this approach can be seen in the replacement of electro-mechanical mixers with coarse bubble mixing systems in anoxic zones. Traditional mechanical mixers introduce moving parts, maintenance requirements, inspection obligations and energy consumption. Where process conditions permit, coarse bubble mixing can achieve the same operational objective using significantly fewer components.

The result is not merely an energy saving. It is a reduction in maintenance burden, fewer inspection requirements, fewer potential failure modes and a simpler system for future operators to understand and maintain. In some cases, energy consumption can be reduced by approximately 50% while simultaneously improving maintainability and reducing life cycle cost.

Viewed in this way, engineering simplicity becomes a sustainability strategy in its own right. Less equipment often means less energy, less maintenance, fewer hazards and greater resilience.

Figure 3 – Diffuser installation works. Engineering improvements are not always about adding technology. Thoughtful redesign of aeration systems can improve performance while reducing energy demand.

Figure 4 – Completed fine bubble diffuser installation. Fine bubble diffuser systems improve oxygen transfer efficiency, reducing energy demand while maintaining treatment performance.

Experience within wastewater treatment increasingly demonstrates that sustainable engineering is often achieved by removing complexity.

Examples include:

• Reducing pressure losses;
• Eliminating unnecessary flow control devices;
• Simplifying control strategies;
• Reducing maintenance-intensive assets.

From this perspective, sustainability extends beyond carbon reduction. It also involves creating infrastructure that is simpler, safer and easier to operate throughout its life cycle.

Safety through design

The principle of simplification extends naturally to safety.

Traditionally, many operational risks have been managed through procedures and controls. Increasingly, engineers are asking a more fundamental question: can the hazard be designed out entirely?

Examples include:

• Reducing lifting operations;
• Eliminating working-at-height activities;
• Minimising over-water access;
• Improving ergonomics;
• Reducing routine maintenance interventions.

Figure 5 – Process improvement through simple engineering intervention. Relatively simple engineering interventions can improve hydraulic performance while reducing operational complexity and ongoing maintenance requirements.

Stewardship of infrastructure

Sustainability is frequently discussed in environmental terms. However, stewardship of infrastructure is equally important.

Many water and wastewater assets continue to provide essential services long after their original design life. Maintaining those services requires more than reactive maintenance. Good stewardship requires engineers to think beyond immediate operational issues and consider how decisions made today will influence infrastructure performance decades into the future. A seemingly minor design choice can affect maintainability, energy consumption, safety requirements, inspection regimes, and life cycle cost throughout the operational life of an asset.

Historically, engineering success has often been measured at the point of project completion. Increasingly, however, the true measure of success may be how effectively an asset continues to perform 20 or 30 years after construction. Infrastructure that is easier to operate, easier to maintain and less dependent on complex intervention often proves more resilient and ultimately more sustainable.

This perspective encourages a shift from focusing solely on capital delivery towards a broader consideration of whole-life value. Questions about safety, maintenance burden, operability, and long-term energy performance become just as important as initial capital cost. In this context, stewardship is not simply about preserving assets; it is about ensuring that infrastructure continues to deliver value to future generations.

It requires planned investment, life cycle thinking and a clear understanding of long-term asset performance.

Perhaps one of the most underappreciated aspects of engineering stewardship is recognising that future operators, maintainers and engineers will inherit the decisions made today. Design choices influence not only construction cost but also how safely an asset can be maintained, how much energy it consumes, how frequently intervention is required and how resilient it remains throughout its operational life.

The most successful infrastructure is often not that which incorporates the most technology, but that which continues to perform reliably with the least operational burden. This shift in thinking encourages engineers to consider not only the immediate requirements of a project but also the long-term experience of those responsible for operating and maintaining it. Stewardship therefore extends beyond the asset itself; it is a responsibility to future generations who will depend upon that infrastructure.

Figure 6 – Detail and whole-life performance. Small design and construction decisions can influence maintainability, reliability and life cycle cost for decades.

Effective stewardship requires engineers to consider not only individual assets but the interactions between entire systems. A well-maintained asset is valuable; a well-conceived system is often more valuable still.

The net zero utility

Renewable energy generation will undoubtedly play a significant role in the transition to net zero infrastructure. However, the challenge is equally one of energy management.

Water infrastructure already contains significant storage capacity through reservoirs, storage tanks and balancing facilities. Future opportunities may emerge to align pumping and treatment activities with renewable energy availability, grid conditions, and carbon intensity. In this way, water infrastructure may increasingly act as part of a wider sustainable energy system rather than merely consuming electricity.

Sanitation and society

Amid discussions of sustainability and climate targets, it is important not to lose sight of the fundamental purpose of water infrastructure. Sanitation remains one of the most significant engineering achievements in human history.

Safe wastewater treatment protects:

• Public health;
• Drinking water sources;
• Biodiversity;
• Rivers;
• Lakes;
• Coastal waters.

Whatever technological developments occur in the future, this responsibility remains unchanged.

Figure 7 – Engineering stewardship and environmental protection. Wastewater treatment infrastructure and the River Suir at Clonmel. The ultimate purpose of water infrastructure is not the treatment process itself, but the protection of public health, communities and the natural environment.

Conclusion

The conversation surrounding water infrastructure continues to evolve. What was once largely a discussion about treatment and compliance now encompasses sustainability, resilience, energy performance, asset stewardship and long-term infrastructure value.

Many of the challenges facing the sector will require innovation, investment and technological advancement. However, experience increasingly suggests that progress is not always defined by complexity. In many cases, the most sustainable solution is the one that achieves its purpose with the least complexity, the lowest life cycle burden and the greatest long-term value.

Ultimately, providing safe water and effective sanitation remains one of society's most important responsibilities. Achieving that objective sustainably will depend not only on the infrastructure that is built, but on how effectively that infrastructure is simplified, maintained, adapted, and stewarded over time. That, perhaps, is the real conversation about conservation.

Author: Seamus Kelly CEng MIEI is a Chartered Engineer and senior operations & maintenance plant manager with Murphy Process Engineering. He has more than 35 years’ experience in engineering and more than three decades in the water and wastewater sector. His work focuses on sustainable water infrastructure, asset stewardship, energy optimisation, and infrastructure resilience. Throughout his career he has been involved in the design, operation, and improvement of critical water infrastructure, with a particular interest in simplifying engineering systems to improve safety, operability, sustainability, and long-term asset performance.