ERG (Air Pollution Control) Ltd

- System for Odour Control



ERG's designers can match the air extraction rate and odour loading of each part of a sewage treatment plant to the odour control required for that area. Combining the basic building blocks of CIFs (catalytic iron filters), biofilters/bioscrubbers and dry media filters, and using intelligent design to look at the site as a whole, ERG's DryCat system is an optimised odour control solution for small and medium sized sites.

ERG (Air Pollution Control)’s DryCat System matches odour treatment to odour source

This tailor-made solution uses well-established odour control building blocks to treat odour problems. The DryCat System is technically optimised, with low capital and operating costs.

Key benefits

  • Low capital cost and low running costs
  • No chemicals on site – operator friendly
  • Compact design – optimised footprint
  • Outlets to
  • Small biofilter so easy to maintain
  • CIF and biofilter bed life 3-5 years
  • Impregnated carbon filter bed life >1year
  • High room ventilation rates only add a small increment to capital and running costs

Units installed and operating successfully at

  • Southern Water
    • Tunbridge Wells STW
  • South West Water
    • Dawlish STW, Sidmouth STW and Cornborough STW
  • North of Scotland Water
    • Dingwall STW
  • Yorkshire Water
    • Whitby STW
  • Anglian Water
    • Boston STW and Ingoldmells STW
  • West of Scotland Water
    • Oban STW, Rothesay STW
    • Campbeltown STW and Helensburgh STW
  • Welsh Water
    • Felinfach STW

The DryCat System comprises at least two of the three basic “building block” equipment items. In all cases, the equipment selection and sizing is matched to the site requirements.

Catalytic Iron Filter (CIF)

  • rusting iron media removes H2S in one or two stages to efficiencies of 50-80%
  • used for bulk removal of high H2S loads (50-500ppm) in small gas flows (typically less than 3,000m3/hr)
  • ideal for treating highly odorous air flows from sludge tanks, sludge presses, imported/exported sludge pumping stations


  • cost effective method of removing H2S to good efficiency from medium air flows
  • traditional peat and heather technology – well proven
  • cheap to install and operate
  • protected from damaging peak H2S loads by the CIF
  • assured outlet H2S concentration by carbon filter
  • ideal for treating medium-odour air from preliminary and primary treatment areas

Impregnated carbon filter

  • caustic impregnated carbon to polish H2S to <50ppb and mercaptans to <100ppb
  • guaranteed boundary levels in ppb H2S or OU/m3
  • cheap to run as the majority of the H2S is removed by the upstream CIF and biofilter
  • bed life designed to suit site requirements, typically >1year
  • ideal for treating general ventilation air from process buildings

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