Veolia Water Technologies & Solutions


Simple & Sustainable Intensification of Activated Sludge

Upgrading wastewater treatment plants for capacity expansion or nutrient removal is challenged by process complexity, the need for larger tank volumes and increased energy consumption.

ZeeLung is an innovative solution that maximizes the treatment capacity from existing tank volumes while also reducing energy consumption. Conventional solutions require the construction of new tanks and other process intensification technologies are complex and energy-inefficient. ZeeLung, on the other hand, is a simple solution that increases treatment capacity in existing assets and reduces energy.

Resilient, simple & sustainable wastewater process intensification

Overview & Benefits

ZeeLung Overview

ZeeLung MABR is a next-generation biofilm process that employs a gas permeable media to deliver oxygen to a biofilm that is attached to the surface of the media.

ZeeLung maximizes treatment capacity in existing tank volumes while also reducing energy consumption.

During secondary treatment, bacteria metabolize nutrients and organics - and need a flow of oxygen to get it done. Oxygen is typically pumped through diffusers to create bubbles. But most of the oxygen rises to the surface without being used and valuable energy is wasted. At Veolia, we saw a new approach. While conventional solutions require the construction of new tanks, ZeeLung increases treatment capacity in existing assets and reduces energy use. ZeeLung enables process intensification and process resilience. The result is expanded treatment capacity stabilized cold-temperature performance and rapid response to load changes.

ZeeLung solves the following treatment challenges:

  • Increase treatment capacity
  • Augment ammonia removal•Implement nitrogen removal
  • Enable biological phosphorous removal

ZeeLung Benefits

  • Process Intensification: Up to 50% more treatment capacity and/or performance in existing tank volumes
  • Process Resilience: The attached growth biofilm is resilient to load variations and upset conditions
  • Simple Solution: ZeeLung cassettes are installed into existing bioreactor tanks, avoiding the need to build new tanks and allowing fast implementation
  • Energy Reduction & GHG Mitigation: 4X reduction in aeration energy & N2O mitigation potential

How It Works

How ZeeLung Works

Oxygen is delivered to the biofilm by diffusion – without the use of bubbles. The result is 4X lower energy consumption for oxygen transfer than fine bubble aeration. Pollutants, such as ammonia and organics, diffuse from the bulk solution into the biofilm where bacteria in the biofilm have optimal conditions to remove them

large-ZeeLung biofilm

large-ZeeLung construction

The product is a reinforced media with a yarn-based core supporting multiple gas permeable filaments. This construction – referred to as a “cord” – is flexible yet unbreakable. Multiple cords are potted into top and bottom headers to create a module and modules are installed in a steel frame that forms a cassette. Cassettes are deployed in the mixed liquor in a biological reactor. Low-pressure air is delivered to the cassettes for transfer of oxygen and mixing of the system.



Installing ZeeLung cassettes into an activated sludge reactor increases the inventory of biomass in the system without increasing the mixed liquor concentration. As a result, the same reactor volume has more treatment capability.

large-ZeeLung Reactor

large-ZeeLung Counter Diffusion

The process interaction of oxygen and pollutants is different in a ZeeLung system compared to conventional active sludge and biofilm processes. With ZeeLung, oxygen and substrates – such as ammonia and organics – enter the biofilm from opposite sides in a counter-diffusion configuration. This creates conditions that favor the growth of nitrifiers in the biofilm.This can be explained by the high diffusivity of ammonia into a biofilm, as compared to organic substrates, and the availability of dissolved oxygen which is highest at the media surface. Preferential growth of nitrifiers versus heterotrophs means that the ZeeLung biofilm “supercharges” nitrification in an activated sludge system. Simultaneous nitrification and denitrification can be achieved by installing ZeeLung cassettes in an anoxic zone.

ZeeLung cassettes are simply deployed into existing tanks with minimal impact on the existing equipment and operations. This makes ZeeLung a cost-effective and versatile solution for augmenting plant performance.

ZeeLung Severn Trent


Case Studies

ZeeLung demonstrates low energy, small footprint treatment at the North Toronto Treatment Plant

The North Toronto Treatment Plant is one of four wastewater treatment facilities owned and operated by the City of Toronto. It was originally commissioned in 1929 and has been in operation for nearly a century. Like many plants in Canada, it is required to achieve a higher level of treatment than it was originally designed for.The City used this upgrade project as an opportunity to evaluate innovative technologies for energy savings and enhanced treatment in a compact footprint.The City chose to implement an MABR upgrade on one-quarter of the existing secondary treatment plant.The plant includes online instrumentation to facilitate monitoring and optimization of the MABR system performance, as well as comparison with conventional activated sludge lanes


ZeeLung upgrade increases treatment capacity at the Yorkville-Bristol Sanitary District

The Yorkville-Bristol Sanitary District (YBSD) provides wastewater collection and treatment services for the City of Yorkville, Illinois, population 18,000. With the plant operating near the design organic load, YBSD sought a cost-effective solution to accommodate new industries planning to move into the city.Increasing treatment capacity of the existing facility would avoid the need to build a new treatment plant and therefore reduce the cost to YBSD’s rate payers. The plant also wanted a solution that would address future regulations regarding phosphorous discharge. YBSD selected ZeeLung technology to upgrade its treatment plant. The upgraded plant is designed to enable increased treatment capacity within the existing footprint while also reducing the plant’s energy consumption.


ZeeLung delivers a future-proof nutrient removal upgrade for Hespeler Wastewater Treatment Plant

The Hespeler Wastewater Treatment Plant (WWTP) in Cambridge, Ontario is one of 13 plants serving the more than 600,000 residents of the Region of Waterloo. To help meet its projected growth, the Region needed to upgrade the Hespeler WWTP.This WWTP consisted of an activated sludge system that was permitted for TSS and BOD removal and was facing a need to increase capacity and anticipate a future ammonia removal requirement. Rather than building more activated sludge tanks, the Region of Waterloo upgraded the plant with a ZeeLung MABR solution in order to save 50% of the capital cost of a conventional upgrade.The ZeeLung MABR system preserves space on the site and saves aeration energy.The ZeeLung system has been in operation since the end of 2022


ZeeLung demonstrates low-energy ammonia removal for Severn Trent Spernal Sewage Treatment Works

The Spernal-Redditch Sewage Treatment Plant located near Birmingham, UK is home to Severn Trent Water’s Resource Recovery and Innovation Centre where technologies compatible with a low energy and circular economy approach can be evaluated. In 2020, Severn Trent commissioned a ZeeLung MABR upgrade of an existing activated sludge lane to demonstrate the potential of the technology to treat increased ammonia loads associated with population growth and changing wastewater composition in existing infrastructure. The project has also focused on how ZeeLung MABR can reduce energy consumption and mitigate N2O emissions to support the UK water industry commitment to carbon neutrality


ZeeLung process intensification demonstration at the Chicago O’Brien Water Reclamation Plant

The Metropolitan Water Reclamation District of Greater Chicago (MWRD) has over 100 years of history as a leader in developing and adopting innovative technologies to manage and treat wastewater. The O’Brien Water Reclamation Plant (OWRP) treats municipal sewage with some industrial contribution at an average daily flow of 230 mgd and wet weather peaks of 500 mgd. The plant is challenged to meet its ammonia limit during first flush events in the early spring due to the combination of peak flows and cold temperatures.MWRD partnered with Veolia to evaluate ZeeLung for its potential to intensify the biological treatment process by providing nitrification in a much smaller tank volume than that required for conventional activated sludge, thereby effectively expanding the capacity of the existing aeration tanks to institute an anaerobic zone for enhanced biological phosphorous removal (EPBR), without the need to construct additional infrastructure


ZeeLung technology delivers a compact, low-energy, high efficiency decentralized wastewater treatment

Burwood Brickworks in Victoria, Australia, is designed to be the world’s most sustainable retail centre. Two important aspects of this are water reuse and energy efficiency. Therefore, the developers of this commercial real estate sought a low-energy water reuse solution for treatment of the blackwater and stormwater collected on the retail site.Aquacell, a global leader in designing and building commercial recycled solutions, selected ZeeLung MABR technology from Veolia to be part of their design in delivering an energy efficient recycle and reuse solution for the Burwood Brickworks project. Treated water will be reused within the Burwood Brickworks site for flushing, cooling, irrigation, and other uses.The solution was installed in September 2019 and commissioned in 2020. It is an example of how ZeeLung MABR technology can be combined with other treatment solutions to deliver excellent and sustainable wastewater treatment solution for decentralized water reuse


ZeeLung compact, low-energy nutrient upgrade demonstration in the United Kingdom

Population growth in the United Kingdom (UK), has resulted in the need to extend treatment works capacity in areas where land is at a premium and site footprint is limited. Increased population has also led to more stringent nutrient removal treatment consents. These drivers require solutions that can intensify treatment of existing systems while minimizing lifecycle cost.Veolia partnered with a water company in the southern UK and a leading EPC firm to evaluate ZeeLung as a solution to upgrade activated sludge plants for capacity expansion. A ZeeLung demonstration system was designed to simulate upgrading a typical UK sewage treatment works. The specific treatment objectives were based on typical treatment consents for the UK, specifically BOD5 at 10 mg/L and ammonia at 2 mg/L.The demonstration project proved that ZeeLung technology can intensify nutrient removal, providing nitrification at short SRT and low temperatures while also reducing energy consumption



Literature & Webinars


zeeDENSE*: Super-Intensification of Activated Sludge


Veolia’s zeeDENSE is a state-of-the-art application coupling ZeeLung MABR & inDENSE continuous flow densification technology for super-intensification of activated sludge plants.

Learn more here.


ZeeLung Technology