Utilities have an obligation to provide safe workplaces and better environmental outcomes. To meet these goals, James Cummings can help utilities to select the most effective activated carbon technology for their operating environment.
As ESG shifts from aspiration to obligation across Australia’s water and wastewater industries, James Cumming is emerging as a critical partner in helping utilities to meet these accelerating expectations. With decades of experience in water, wastewater and air treatment, the company is proactively aligning its operations, technologies and services with the environmental, social and governance standards now reshaping the sector.
Across Australia, utilities are facing an intensifying climate forcing a re-examination of how water resources are managed. Environmental responsibilities now demand long-term climate adaptation, carbon reduction and more efficient, sustainable treatment practices. For wastewater management this includes the critical area of emissions control.
Communities are also calling for greater transparency and stronger public health outcomes from utilities. These utilities must fundamentally rethink how their services are planned, delivered and monitored. This is where the innovation of a company like James Cumming has practical and evidence-based solutions to ongoing challenges like emissions and vapours.
James Cumming’s experience and expertise with extruded activated carbon is a leading example of how innovation is meeting some of the ongoing challenges of the industry. The reduction of hydrogen sulphide (H₂S) and volatile organic compounds emissions in sewer networks is an active example of how the company can work with utilities to work towards safe and healthy working conditions and better emissions outcomes.
Extrusion enhancing reactivity
Hydrogen sulphide (H₂S) and volatile organic compounds (VOCs) remain two of the most persistent operational challenges in wastewater networks. Rising mains, pump stations, inlet works and anaerobic catchments all create the conditions that drive biological sulphate production – and with it, corrosive, odorous and potentially hazardous gas emissions.
While utilities have long relied on activated carbon to mitigate these emissions, advances in extruded activated carbons (EAC) – particularly those chemically impregnated to enhance reactivity – have reshaped the landscape of what’s possible in odour and gas-phase contaminant control.
According to James Cumming this begins with an understanding of how chemisorption works and why impregnants matter.
Chemisorption — the foundation of modern odour control
Odour and gas-phase contaminants are removed from air streams through two fundamental mechanisms:
1. Physical adsorption
This is the mechanism behind standard granular activated carbon (GAC) and unimpregnated extruded carbon.
- • Gas molecules adhere to the carbon’s internal pore structure via van der Waals forces
- • The process is reversible, meaning high humidity or temperature changes can reduce capacity
- • Ideal for low-molecular-weight compounds and general VOC polishing
While physical adsorption is simple and cost-effective, it is not well suited to reactive gases like H₂S at elevated concentrations. These compounds tend to saturate pores quickly or pass straight through without meaningful retention.
2. Chemical adsorption (Chemisorption)
Chemisorption is the mechanism that underpins impregnated extruded activated carbons, and it is essential for treating H₂S and other reactive sulphur species.
In chemisorption:
- • The gas reacts chemically with impregnates such as potassium hydroxide (KOH), sodium hydroxide (NaOH), potassium iodide (KI), or copper oxide (CuO)
- • The reaction is irreversible, forming stable, non-volatile solid salts
- • Breakthrough capacity is far higher, even under high humidity conditions
- • Heat is generated as a by-product of the reaction, an indicator of conversion rather than mere adsorption.
Chemisorption effectively transforms H₂S into benign compounds, preventing re-release and allowing utilities to manage periods of extreme loading without immediate media change-out.
Why extruded activated carbon has become the utility standard
Traditional GAC beds remain useful in polishing applications – especially where VOCs or siloxanes dominate – but for most sewage odour control and rising main applications, EAC now provides clearer advantages.
1. Uniform pellet geometry
Extruded carbon is manufactured as cylindrical pellets (typically 3–4 mm), giving:
- • Lower pressure drop
- • Higher bed uniformity
- • Reduced channelling
- • Deeper penetration profiles
For enclosed vessels at pump stations and rising mains, where confined-space entry is common, this stability improves safety and asset longevity.
2. Higher bulk density = Higher working capacity
Extruded pellets pack more carbon mass per cubic metre compared with many GAC grades.
In chemisorption applications where the limiting factor is reaction capacity per volume, EAC delivers materially higher life between change-outs, depending on the operating conditions.
3. Lower dust and improved handling
Pellets generate less dust during loading/unloading, reducing safety risks and improving on-site visibility during confined-space carbon change-outs.
Evaluating the technology options — GAC vs EAC vs impregnated EAC
Utilities today have four primary carbon media pathways. Each is suited to different operating contexts.
1. Granular activated carbon (GAC)
Best for: VOC polishing, very low-H₂S environments, dual-use air + water treatment applications.
Strengths:
• Lower cost
• High surface area
• Effective for many VOCs and organic odours
Limitations:
• Poor if ineffective reactivity with H₂S
• Sensitive to humidity
• Breakthrough is unpredictable and often sudden
GAC is a poor choice for most rising mains for H₂S removal on their own.
2. Unimpregnated extruded activated carbon
Best for: Siloxane removal, certain VOCs, landfill gas polishing, mixed contaminant streams.
Strengths:
- • Higher density than GAC
- • Lower pressure drop
- • More uniform performance
Limitations:
- • Still dependent on physical adsorption
- • Very limited H₂S reactivity compared to impregnated media
Commonly used in landfill gas and biogas applications where siloxanes rather than H₂S dominate.
3. Mercaptan / Sulphur-targeted impregnated EAC (KI, CuO)
Best for: Sewer pump stations, rising mains, anaerobic catchments, inlet works.
Typical impregnants and why they matter:
Potassium iodide (KI)
- • Promotes catalytic oxidation of H₂S
- • Works well in high-humidity networks
- • Produces highly stable reaction products
- • Predictable breakthrough curves
Ideal for: Sewer pump stations and rising mains with variable loading.
Copper Oxide (CuO)
- • Highly reactive to H₂S
- • Effective at removing mercaptans and organic sulphur compounds
- • Often used in industrial wastewater gas streams
- Ideal for: Industrial networks or mixed industrial–municipal catchments.
4. Alkaline impregnated EAC (NaOH, KOH)
Best for: High-load H₂S conditions, emergency odour events, networks with extreme anaerobic conditions.
Sodium hydroxide (NaOH)
- • Higher reactivity than KI
- • Extremely fast H₂S conversion
- • Less expensive than KOH
- • More stable in humid environments compared with potassium hydroxide.
Potassium hydroxide (KOH)
- • Highly reactive base
- • Fastest chemisorption kinetics
- • More sensitive to moisture than NaOH
These media types excel in peak-load environments but require careful vessel ventilation and temperature monitoring due to exothermic reaction potential.
Why impregnants matter — matching chemistry to the network
Choosing the wrong impregnant is one of the most common issues seen across utility odour control systems. A network dominated by biodegradable organics behaves very differently from one with a significant industrial component.
Key decision criteria include:
1. Humidity level
• High humidity → choose KI or NaOH
• Very dry gas streams → unimpregnated carbon may suffice
2. Contaminant mix
• Predominantly H₂S → KI or NaOH
• Mercaptans and organic sulphur → CuO
• VOC-dominant streams → GAC or unimpregnated EAC
3. Required bed life
Utilities must balance:
- • Cost per change-out
- • Vessel access requirements
- • Downstream disruption
- • Climate variables
4. Safety & temperature considerations
- • Chemisorption generates heat
Proper vessel design and airflow are essential to prevent hotspots.
Designing a carbon odour unit for modern utility conditions
A well-designed system considers:
- • Pre-feeding air dilution and flow balancing
- Moisture control and condensate separation
- Avoiding channelling via proper distributor plate design
- Using staged beds for catastrophic loading events
- Monitoring pressure drop to predict carbon exhaustion
- Selecting carbon based on breakthrough curves, not price lists
The most successful utilities increasingly lean on performance-based procurement, evaluating cost per kg of contaminant removed rather than cost per cubic metre of carbon purchased.
Looking Ahead — The Next Generation of Activated Carbon Odour Control
Driven by tightening environmental regulations and community expectations, utilities are increasingly prioritising:
- Predictable breakthrough performance
- Lower maintenance requirements
- Safer confined-space entry
- Resilience under extreme weather patterns
- Australian-made supply chain security
- Extruded and impregnated activated carbons are at the centre of this shift, offering utilities a more controllable, more predictable, and more chemistry-aligned solution for managing H₂S, VOCs and associated emissions.
Long term solutions
Reducing odour and emissions in sewer networks is no longer a matter of simply “installing some carbon”. The chemistry, geometry and impregnation profile of the media play central roles in true long-term performance.
For utilities operating in increasingly variable and challenging network conditions, impregnated extruded activated carbon offers the most reliable pathway to controlling H₂S and VOC emissions – providing greater certainty, longer bed life and lower whole-of-life cost than other solutions. U
