Biological Wastewater Treatment


Bioflo+ media with attached biomass for COD removal

Although the activated sludge suspended growth process is the most common process for large municipal wastewater treatment facilities, traditional fixed film or attached growth processes, in which the biomass grows on a support medium, are widely used for smaller municipal works and many industrial applications.

The traditional fixed film trickling filter is a natural draft process but forced draft fixed film processes like Submerged Aerated Filters (SAF) and Moving Bed Biofilm Reactors (MBBR), are showing significant benefits by comparison with conventional activated sludge. The capacity of an activated sludge plant is dependent on the concentration of biomass and its performance is a function of the microbial population. Fixed film media can provide a much higher biomass concentration, which means higher loading and smaller footprint, and can provide micro-climates which encourage the growth of specific microbes.

Examples of applications:

Trickling filter (TF)

WastewaterThe media used in trickling filters needs a high surface area but must have a sufficiently open structure not to restrict the natural draft air flow. Traditional filters used blast furnace slag but modern plastic media like Biofil and Bioball provide a much higher surface area per unit volume of media with a low air side pressure drop. This makes these media ideal for replacing old media and uprating existing filters. Selecting the right media will also enhance nitrification by providing a protected area for the growth of nitrifying bacteria.

Advantages of Warden Biomedia

  • Easy replacement of old or damaged media
  • Improved performance
  • Reduced “snails problems”
  • High resistance to erosion

Submerged Aerated Filter (SAF)

WastewaterThe submerged aerated filter consists of a series of cells containing buoyant media retained by a screen with air distribution fed from a blower. Because there is no limitation on air flow through the media, it is possible to use media with higher surface area per unit volume than in trickling filters and Bioball and Biomarble media have proved highly efficient in SAFs. Again, the media can be selected to provide a protected area for nitrifying and denitrifying bacteria and similar species.

Advantages of Warden Biomedia

  • Buoyant media
  • High removal efficiencies
  • Maximized surface area per unit volume
  • High organic loadings

Moving Bed Biofilm Reactor (MBBR)

WastewaterIn moving bed biofilm reactors the buoyant media is free to move within an aerated reaction chamber. The MBBR integrated fixed film activated sludge (IFAS) is essentially an activated sludge suspended growth process but with the biomass fixed to the media. It can perform all the same process variations such as nitrification, denitrification and biological phosphorus removal but with a higher biomass concentration which means higher organic loadings and smaller footprint. Media can be easily retrofitted into existing activated sludge plants for flow and load uprates. Small sized media with high surface area such as Biopipe 600, Biopipe+, Biotag, and Bioflo+, available in polypropylene or high density polyethylene, have a proven MBBR track record.

Advantages of Warden Biomedia

  • High surface area for biofilm attachment
  • Increased treatment capacity
  • Higher biomass concentration
  • Easy conversion of activated sludge to IFAS
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