Animal waste tankering and disposal can be an expensive cost for animal centres such as the Chilterns Dog Rescue Society. As a charity that relies on donations for its funding, managing operational costs is key to its success. Due to WPL’s unique robust aerobic digestion system (RADS), a significant cost saving is being made in de-sludging by increasing tankering intervals. Reducing the frequency of de-sludging also means the initial cost outlay of the RADS is recuperated quickly with cost savings continuing for the whole operational life of the plant (up to 25 years based on asset life expectancy).

Animal waste is categorised as controlled waste (animal by-products ABP) and requires careful management as animal waste is known to be difficult to treat and is governed by more stringent waste regulations than domestic waste. Through research and development, in partnership with the University of Portsmouth, an independent and in-depth analysis into effluent quality and sludge degradation was monitored to successfully meet industry standards.

WPL robust aerobic digestion RADS

The Chilterns Dog Rescue Society required an off mains wastewater treatment solution that took into account the full time residential staff, washing machines, visitors and dogs. The re-homing centre had the RADS incorporated into the design of the WPL HiPAF Midi wastewater treatment plant currently being installed at their site. For this installation, the primary tank of the treatment plant had a tailored design. Dominic Hamblin, Technical Sales Manager stated:

‘In this instance, the WPL HiPAF Midi had a ‘v shaped,’ primary section encouraging the effective settlement of raw sewage thus ensuring effective sludge removal to the RADS via an airlift arrangement.’

The WPL systems have a number of distinct advantages

HiPAF Midi

  • Very robust process; consistently complying with discharge permit requirements.
  • Low operation and maintenance costs.
  • Capability of dealing with variable flows and loads (down to 10% of design load).
  • Small footprint, keeping installation costs down.
  • Ease of installation.


  • Extended de-sludge intervals reduces tankering costs and frequency without placing significant biological or hydraulic load on the rest of the plant.
  • Low maintenance with no internal mechanical moving parts, reliable side channel blowers requiring the minimal maintenance and quick release Bauer connector for de-sludging.
  • Minimal footprint with an integrated aerobic reactor and clarifier.
  • Ease of installation, saving valuable time on site.

The RADS can be retrofitted to existing treatment plants, septic tanks or incorporated into the design of a new packaged wastewater treatment system. TheHiPAF Midi and RADS have been successfully installed at many animal centres such as kennels, catteries and equestrian centres.