DEMONSTRATIONS

Wick St Lawrence sewage treatment works Trial

Wessex Water’s Wick St Lawrence plant receives flow from about 20,000PE, and is located a few miles north of Weston-super-Mare, Somerset, UK. The wastewater treatment process includes screens, primary settlement tanks, an oxidation ditch, secondary tanks and final polishing lagoons before its effluent is discharged into coastal waters. The controlling aeration for the ASP is supplied by four 15kW surface aerators with a target DO of 1.5mg/l O2. Prior to the Oxifiniti trial, Wessex Water had installed additional temporary surface aeration to meet peak demand.


Trial Objectives

The main objective was to compare the Oxfiniti box (max 40kW) performance against the four surface aerators (max 60kW). This was to be achieved by: –
  1.  Quantifying aeration energy savings;
  2.  Identifying other operational savings;
  3.  Observing health improvements in the oxidation ditch, secondary clarifiers and on sludge;
  4.  Identifying other significant benefits regarding maintenance, Health & Safety issues etc. which were not quantified.

Trial Results

Energy Savings, Reduced Carbon emissions and Power – A total energy saving of 21% (258 kWh) a day and hence reduced Carbon emissions. Unlike the existing 4 surface aerators the Oxfiniti box O2 output was a constant base load and was not optimised to obtain maximum savings. The max. power of the Oxfiniti box was 40kW, whereas the surface aerators max. was 60kW;
Water Quality and Plant Health – the oxidation ditch and the secondary clarifiers both showed visual improvements in appearance. A result of healthier micro-organisms.

Energy Measurements


Thames Water Performance Trial

The Oxfiniti treatment process was set up at a Thames Water wwtw oxidation ditch site outside of London. The site was suffering from intermittent filamentous bacteria problems. But as soon as the Oxfiniti process injected oxygen into the ditch the mousse layer broke down.


Results

The trial demonstrated energy savings, reduced sludge handling costs and ease of operation.
1-Ammonia /Filamentous Bacteria Treatment
The Oxfiniti process has shown its affinity to oxidise ammonia very quickly and breakdown surface ‘mousse’ caused by filamentous bacteria.
2-Water Quality and Plant Health – The oxidation ditch and the secondary clarifiers both showed visual improvements in appearance. A result of healthier micro-organism activity.


Contractors

Contract 1 – Anglian Water

Supplementary Treatment During FBD Maintenance
Working with an Anglian Water contractor, O2NRG and its partner Euroby were tasked with setting up a supplementary oxygen supply to facilitate treatment in an ASP basin during the routine maintenance of fine bubble diffusers. The Oxfiniti process which has a small footprint was set up alongside the basin away from the main contractors equipment delivering a constant 40kg O2 per hour 24/7 for 6 weeks.
Fig.3 FBD Diffusers Refurbishment

Results

960kg/day O2 Supplemented Treatment
The Oxfiniti process delivered a 960kg of O2 per day during the 6-week period of FBD maintenance. This additional treatment enabled the ASP to be treated and the discharge remain within permit conditions during the major refurbishment. The small footprint of the Oxfiniti process allowing the major work to take place unhindered.

Contract 2 – South West Water

Supplementing Treatment Increased Loading
When UK towns organise major festivals they attract a huge increase in population for a short period, the local services are put under significant pressure. In Cornwall an annual festival of Music and Surfing event attracts over 50,000 visitors putting a major additional load on the sewage works. Oxfiniti set up alongside the treatment basin to supplement the existing aeration/oxidation process for the duration of the festival enabling the utility to treat the increased loadings.


Results

• Supplementary Treatment – Oxfiniti in combination with existing aeration treated the additional loadings without breaching permit conditions.
• Water Quality and Plant Health – The oxidation ditch and the secondary clarifiers both showed visual improvements in appearance. A result of healthier micro-organisms.

Contract 3 – Thames Water

A gearbox on an oxidation ditch failed causing the main brush aerator at Ripley wwtw to fail causing a lack of aeration. The failing treatment caused an increase in ammonia in the final effluent approach its permit level. On starting up the Oxfiniti process this ammonia immediately dropped preventing a potential permit failure.
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