Sector Utilities
Year completed 2016
Project location London
Client Thames Water
Products used Hydrotech® HSF2220 Discfilters with self cleaning nozzles
 
 

Context

Thames Water WTW at Slough serves a population equivalent of 250,000 using the activated sludge process. Over the years, Thames Water has made a major investment in improving the works to protect the River Boveney.

In 2005, Thames Water installed three of Veolia’s Hydrotech® HSF2220 Discfilters to improve the quality of the final effluent at Slough. The Discfilter uses a series of rotating segmented discs that support 10 micron polyester filter fabric panels. As the wastewater flows from the inside to outside of the disc segment, suspended solids including biomass flocs and precipitated phosphates are captured on the fabric and removed from the effluent.

With its low backwash water volume, typically only 1-3% of throughput, low power consumption and minimum maintenance by comparison with competitive technologies this proved to be not only cost effective but also sustainable.

Challenge

In 2016, Thames Water began to experience blockages and subsequent failures of the strainers that protect the backwash nozzles on the Discfilters. On investigation, this proved to be due to an infestation of sewage snails which, over the past few years, had become a major nuisance to the industry. The snails’ shells create serious operational problems right through the process, within aeration basins, secondary clarifiers and tertiary treatment.

Paradoxically, the problem had been created by improvements in treatment process technologies. The combination of low pollutant levels, higher dissolved oxygen, warm water and nutrients provides an ideal habitat for the snails, and removing the shells from the treatment process can be a costly and labour intensive exercise often necessitating a temporary works shut down. As the failure frequency increased, Andy Moore, Thames Water’s Performance Manager, asked Veolia Water Technologies for help.

Solution

Having identified the cause of the problem, Veolia’s engineers designed a modification to the backwash system of the three Discfilters. Retrofitting new self-cleaning nozzles allowed the strainer to be removed whilst obviating nozzle blockage, reducing strainer replacements and lowering maintenance. Andy was pleased with the result: “I estimate we will recover the cost of the modification in under two years”, he says, “and we have now added a fourth HSF2220 Discfilter – with the backwash system upgrade, of course!”


Context

Thames Water WTW at Slough serves a population equivalent of 250,000 using the activated sludge process. Over the years, Thames Water has made a major investment in improving the works to protect the River Boveney.

In 2005, Thames Water installed three of Veolia’s Hydrotech® HSF2220 Discfilters to improve the quality of the final effluent at Slough. The Discfilter uses a series of rotating segmented discs that support 10 micron polyester filter fabric panels. As the wastewater flows from the inside to outside of the disc segment, suspended solids including biomass flocs and precipitated phosphates are captured on the fabric and removed from the effluent.

With its low backwash water volume, typically only 1-3% of throughput, low power consumption and minimum maintenance by comparison with competitive technologies this proved to be not only cost effective but also sustainable.

Challenge

In 2016, Thames Water began to experience blockages and subsequent failures of the strainers that protect the backwash nozzles on the Discfilters. On investigation, this proved to be due to an infestation of sewage snails which, over the past few years, had become a major nuisance to the industry. The snails’ shells create serious operational problems right through the process, within aeration basins, secondary clarifiers and tertiary treatment.

Paradoxically, the problem had been created by improvements in treatment process technologies. The combination of low pollutant levels, higher dissolved oxygen, warm water and nutrients provides an ideal habitat for the snails, and removing the shells from the treatment process can be a costly and labour intensive exercise often necessitating a temporary works shut down. As the failure frequency increased, Andy Moore, Thames Water’s Performance Manager, asked Veolia Water Technologies for help.

Solution

Having identified the cause of the problem, Veolia’s engineers designed a modification to the backwash system of the three Discfilters. Retrofitting new self-cleaning nozzles allowed the strainer to be removed whilst obviating nozzle blockage, reducing strainer replacements and lowering maintenance. Andy was pleased with the result: “I estimate we will recover the cost of the modification in under two years”, he says, “and we have now added a fourth HSF2220 Discfilter – with the backwash system upgrade, of course!”


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Downloads
  • Brochure - Hydrotec discfilters
    Brochure - Hydrotec discfilters
    2pp 363.85KB
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  • Case study: Thames Water snails
    Case study: Thames Water snails
    1pp 192.23KB
    Download
 
 
 
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Thames Water tackles snails at Slough WTW