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Ammonia Oxidising

Case Study - Ammonia Oxidising Bioreactor - London 2012 Games

Contract In Brief:  
Location: Contract:
London 2012 Games - Olympic Park Groundwater Pump & Treat Ammonia Bioreactor
HBR Role: Specialist Analysis: Contract Period:
Main Contractor using
CampbellReith as design team

Main Contractor

EnviroGene Ltd, South Wales 1.5 years
Contract Value:

£1.35M

HBR Site Management    
Contracts Manager: Project Manager: Site Manager:
Charles Ratcliffe Julian Garwood  Terry O’Neil

Project Background:

Following a successful competitive tender process HBR were awarded a design, build and operation contract to treat ammonia impacted groundwater beneath 4 hectares of the Olympic Park for the London 2012 Olympic Games. 

The challenges faced by the HBR design team were multiple and complex. A variety of constraints had to be overcome, notably: -

• Building and operating the system within areas currently under construction by others.

• Reducing the concentration of the ammonia plume from 100mg/l to 40mg/l within the first year of operation.

System Design:

The original design — based on a series of horizontal extraction wells — was amended to 40 No. vertical wells due to the repositioning of stadia foundations and service corridors. 

Well spacing and pumping rates were confirmed following on-site pumping trials.

Each well was fitted with an independent deep well pump linked to carrier pipes, creating a series of well circuits, with each circuit feeding into the bioreactor tank. The principal treatment sequences comprised: -

• 900m3 bioreactor tank, fitted with powerful air-injectors to ensure continuous supply of oxygen to the microbes;

• Lamella screen to remove suspended solids from the treated water which contained high levels of microbes. Solids pumped back to bioreactor;

• Sand filter to further clarify water and remove residual particulate metals;

• Activated carbon filter to remove dissolved phase contaminants (final polishing step) prior to discharge to foul sewer. 

Build and operation Phases:

The above-ground process plant was established in a single area with abstraction wells drilled and installed using standard methods. Carrier pipes were chosen to minimise disruption to other earthworks and civil engineering contractors working across the platform.

The bioreactor was initially populated with a culture of specific ammonia oxidising microbes to kick start nitrification of ammonia to nitrite. After successful commissioning of the system to demonstrate reliably of the bioreactor, the efficiency and health of the microbes were periodically monitored by the HBR remediation engineer. 

This was done by culturing the active microbes on BioTraps (cartridges filled with carbon beads) immersed within the bioreactor. Polymerase Chain Reaction (PCR) analysis of the recovered microbes was undertaken by Envirogene to identify the type and numbers present. 

Due to fluctuations in abstraction rates and contaminant concentrations across the plume a critical feature of the design allowed for flow rates from each circuit to be adjusted to harmonise the mass of ammonia entering the bioreactor. This was vital in ensuring the microbial population remained stable and functioning. In total some 70,000m3 of groundwater was processed. 

The plant was decommissioned after successful remediation of the plume to below the a required SSTL’s. This allowed full development of the remaining platform.

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                 Chemical v Physical v Biologicalv Complex Sorting v Water Treatmentsv Complimentary Processes

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