Aeration tank inspection and repair

The aeration tank plays a critical role in the MBR process at our client’s site, but after 7 years of operation, some visible corrosion on the outside of the tank highlighted the need for inspection, cleaning, and repairs. With only one aeration tank on-site, maintaining uninterrupted operations posed a significant challenge.

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Our team developed an innovative solution: repurposing one of two adjacent balance tanks into a temporary aeration tank. This approach, combined with strategic pipework upgrades, not only ensured process continuity during the repair but also enhanced the site’s future maintenance efficiency and cost-effectiveness.

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Establishing a temporary aeration tank

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To set up the temporary aeration tank we needed to establish temporary aerators into a cleaned and emptied balance tank, and divert the flow to the temporary aeration tank and then out to the MBRs. To enable this process we delivered:

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Installation, operation, and removal of four temporary submersible radial aerators in the balance tank to maintain oxygen levels for COD removal.
Installation, operation, and removal of two temporary transfer pumps: one for transferring mixed liquor from the temporary aeration tank to the MBRs, and a second for moving mixed liquor between the permanent aeration tank and the temporary tank.
Installation of temporary power supply cables and control panels for all aerators and pumps, using an existing feed pillar.
Installation of control float switches in the temporary aeration tank and MBR tanks for automated pump operation and high-level flow inhibition.
Removal and reinstallation of roof panels on the balance tank to crane-lift aerators.
Addition of a 250mm nozzle and stainless-steel pipework to enable gravity flow from the anoxic tank to the balance tank, ensuring uninterrupted operation.
Permanent updates to pipework to facilitate quicker and more cost-effective maintenance in the future.

Emptying the aerator tank prior to clean and inspection

The cleaning and inspection process

Before starting the project, Balance Tank 1 was emptied, thoroughly cleaned, ventilated, and fitted with a nozzle to prepare for its temporary conversion into an aeration tank.

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Week 1: Setting Up a Temporary Aeration Tank

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Once all the equipment was delivered to the site, selected roof panels were removed from the balance tank using crane lifting, with measures in place for working at height.
The hired submersible aerators were carefully lifted into the tank by crane, installed, and set up with the temporary diversion pumps, pipework, hoses, and starter panels.
Power supplies were connected to the aerator and pump starter panels, incorporating float switches to enable automated operation.
Finally, the temporary aeration tank was filled to a level that fully immersed the aerators, allowing the aerators and pumps to be commissioned and brought into operation.

‍Week 2: Transition to Temporary Operations

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The temporary aeration tank was connected temporarily to the Anoxic Tank outlet to enable flow.
The mixed liquor was transferred from the permanent Aeration Tank to the temporary aeration tank.
A full clean of the permanent aeration tank took place, followed by a detailed inspection.

Weeks 3–4: Repairs and Testing

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All identified issues were repaired, and all air diffusers within the tank were replaced with new units.
Filled the repaired tank with water to immerse the diffusers and tested for uniform air distribution.

Week 5: Restoration and Final Improvements

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Mixed liquor was pumped back from the temporary aeration tank to the repaired permanent tank.
The pipework was reconnected to restore the original flow arrangement.
All hired aerators, pumps, and associated equipment were removed from the site.
Roof panels were reinstalled on Balance Tank 1 and the tank’s original feed pump system was reinstated.
Newly installed rigid pipework was left between the Anoxic Tank and Balance Tank 1 in place to allow for quicker and easier maintenance in the future.

Aeration tank inspection and repair

Establishing a temporary aeration tank

The cleaning and inspection process

The Outcome

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