The engineering challenge isn’t confined to a single component or discipline. It sits at the interfaces between them.

As treatment requirements increase and existing assets are expanded, upgraded or adapted, these interfaces multiply. A technically sound design developed in isolation can still create problems elsewhere in the plant, leading to redesign, difficult construction sequencing, compromised access or operational inefficiencies.

For complex treatment infrastructure, successful delivery requires more than strong individual disciplines. It requires an integrated design approach, supported by design management that maintains alignment from concept through construction and commissioning.

Managing the interfaces

Multidisciplinary engineering isn’t just about assembling the required disciplines; it’s about coordinating where their requirements intersect.

A process decision can change hydraulic requirements, equipment selection and structural loading. Mechanical equipment influences penetrations, access, lifting and maintenance provisions. Hydraulic levels affect structural geometry and site grading. Electrical, instrumentation and control systems bring another set of requirements, all of which need to be accommodated without compromising process performance, constructability or access.

Designing for change

Changes propagate. Early interface management is therefore critical. Decisions made during concept and preliminary design establish parameters that can become increasingly difficult and expensive to change as design progresses.

Integrated design management creates visibility across dependencies, enabling clashes, competing requirements and design assumptions to be identified and resolved before they become embedded in the design.

Research into major infrastructure projects reinforces the value of design flexibility when requirements change, or uncertainty emerges. Rather than simply reacting to change, the aim is to preserve enough flexibility to respond throughout the project lifecycle.

Performance in detail

Water-retaining structures illustrate why integration matters. Tanks, reservoirs, clarifiers, digesters and containment structures need to satisfy structural performance criteria while controlling cracking and leakage under sustained hydraulic loads and exposure conditions.

Concrete specification, reinforcement detailing, joint design, waterproofing and exposure conditions all influence long-term performance. Watertightness comes from getting these elements to work together from crack control and joint detailing through to concrete specification and construction methodology.

Structural design is only part of the equation.

Process geometry, hydraulic levels, penetrations, pipe thrusts, equipment loads, embedded items and maintenance requirements all interact with the structure. A late change to a penetration isn’t just a process or mechanical issue; it can affect reinforcement, crack control, waterproofing and ultimately durability.

Australian liquid-retaining concrete structures are covered under AS 3735-2001 Concrete structures for retaining liquids (currently under revision), reflecting the fact that conventional structural adequacy alone isn’t sufficient. These structures also need to remain serviceable and durable, as leakage, cracking or deterioration can compromise operation and asset life.

Whole-of-life performance is central to design. Optimising solely for construction can shift cost and complexity downstream into inspection, maintenance, repair or future modification. Instead, integrated engineering considers the entire asset lifecycle: how it will be built, commissioned, operated, maintained and eventually adapted.

Blueprints for buildable plants

Moving from a coordinated model to a constructable plant introduces another set of interfaces.

Treatment plants can involve constrained sites, complex temporary works, major lifts, buried services and construction adjacent to operating assets. Brownfield projects add another layer, with existing infrastructure that may need to remain live while new systems are connected, commissioned and brought online.

Constructability needs to inform design from the outset, not be tested retrospectively. Considering constructability early allows the permanent works to reflect how the plant will actually be built – from access and staging to lifting strategies, shutdown requirements and commissioning sequences.

It also exposes assumptions. Where does one discipline’s scope stop and another begin? Who owns a penetration, an embedded item or an equipment interface? Are design loads consistent between supplier information and structural documentation? Can an item be installed in the sequence assumed by the design?

Small coordination issues in design can become much bigger problems on site.

Integrated engineering in practice

BG&E’s work on the Orchard Hills Water Filtration Plant Reliability Upgrade demonstrates the importance of multidisciplinary coordination in a complex operational environment. Working for CPB Contractors, BG&E provided design management and integration alongside hydraulic, civil, structural, mechanical, materials and balance-of-process engineering.

The upgrade introduces new pre-treatment infrastructure and associated chemical, pipework, power, and site works, requiring close coordination among disciplines while maintaining the operating plant’s functionality.

At the $500 million Belmont Desalination Plant, SYSTRA BG&E is delivering structural design, documentation and construction-phase support across process buildings, storage tanks, support structures and ancillary facilities.

The plant will provide up to 30 million litres of rainfall-independent water each day. Its seafront location, exposure to concentrated brine and deep sandy soils create significant durability and engineering challenges, reinforcing the need to integrate structural design with process requirements and long-term asset performance.

The long view

Water infrastructure needs to perform for decades, not years. The plant commissioned today may need to accommodate different population loads, treatment standards, technologies and climate conditions over its operating life.

Australia has 726 urban wastewater treatment plants, with Infrastructure Australia identifying population growth, climate change and ageing assets as placing unprecedented pressure on their capacity. South Australia alone is expected to require around $12.9 billion in water and wastewater asset renewal over the next 30 years.

Similar pressures are evident internationally. The UK has around 9,000 wastewater treatment plants, while the current five-year investment programme for England and Wales provides for Â£104 billionof expenditure across the water sector.

Across these markets, the challenge is similar: adapting ageing infrastructure to changing demand and increasingly complex treatment requirements.

Future-proofing means avoiding decisions today that unnecessarily close off options tomorrow. That requires adaptability to be considered across disciplines from the outset.

Resilience also means designing for conditions that may differ from those experienced today. Changing rainfall patterns, drought, flooding and temperature extremes can affect water availability, asset performance and operating requirements, making climate risk a whole-of-life design consideration.

Key questions include: Can hydraulic systems accommodate future flows? Can structures accept additional equipment or altered loads? Is there physical space for expansion? Can new process trains be incorporated without major interruption to existing operations? Can equipment be replaced as technology changes?

Integrated design allows these questions to be considered collectively, balancing upfront investment with adaptability, whole-of-life value and system-wide resilience.

Integration: an engineering discipline

Complex water and wastewater projects don’t fail because engineers forget how to design tanks, foundations, pipework or structures. Risk accumulates where systems, disciplines and project stages meet.

Design management is more than administrative coordination. It’s an engineering function that manages interfaces, challenges assumptions, maintains design intent and ensures individual technical solutions work as part of the whole.

Bringing multidisciplinary engineering and design management together creates more constructable, operable and adaptable assets, with fewer surprises carried from the design office onto site.

Start the conversation

Complex treatment plants demand engineering that works across disciplines, not just within them. Contact us to discuss how coordinated engineering can reduce risk and support the delivery of your next project, or explore our Water Infrastructure services.

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