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Wyatt Africa: Mini Sewage Plants

We are able to design, manufacture & install a true packaged "aerated activated sludge system". The complete plant is factory pre-assembled before transport to site. The system employs well proven technology similar in operating principles to any large sewage treatment plant used for municipal sewage.

The unit comprises a steel welded tank suitably stiffened and shotblasted and epoxy coated for corrosion protection. The tank is divided by means of partition walls into separate aeration and settlement compartments. The aeration equipment consists of two blowers with galvanized pipework and nozzles. The diffusers are designed to ensure uniform bubble distribution of air over the entire width of the aeration tank to meet the requirements of the sewage load.


Raw sewage from the housing units would discharge into a three chamber concrete septic tank with twenty four hour minimum retention time. The purpose of the septic tank is threefold:

  1. To trap fat, rags & paper.
  2. The reduce the organic loading by removal of faecal solids by 30%.
  3. To provide some degree of flow balancing.

Septic tank effluent will flow by gravity into our AEROGEST system which consists of a single tank for up to 270 people and a double unit for populations above that. The package plant includes a steel tank for incorporating an aeration reactor and clarifier settlement tank - in two separate sections.

The reactor operates on the extended aeration diffused air activated sludge principle in which a culture of micro organisms (activated sludge) are continuously mixed and aerated with septic tank effluent. Air is provided via two duty/standby generously rated blowers. The air is introduced into the mixture of sludge and sewage (mixed liquor) from a series of down pipes at one end of the tank and then through WYATT diffusers which provides highly efficient oxygen transfer from air to liquid. There would be a retention time of approximately twenty two hours based on the average daily flow through the system.

The system is designed to consistently meet the Water Act Standards. In particular an ammonia content of <3mg/l and faecal coliforms of <100 counts/100ml and all the recently prescribed Metro requirements. The system comes with all the necessary internal pipework, walkways and a separate weatherproof electrical control panel.

The plant is guaranteed to meet the Water Act and Metro requirements provided that the design load is not exceeded and a maintenance/operating contract is implemented. We can provide this service.



  • The Aerogest is a complete self-contained sewage treatment system designed to treat new sewage or grey water from a septic tank to S.A. General Standard/General Limit, which is suitable for disposal to stream or irrigation.
  • The system employs the extended aeration activated sludge principal using diffused aeration and blowers. Activated sludge is the preferred treatment process for all medium to large municipal systems worldwide.
  • The Aerogest is completely fabricated and built in the factory from epoxy coated/galvanized mild steel components to best workshop practice. It is shipped to site by low loader and off-loaded onto suitable above or below ground foundation. If all inlet and outlet and power connections are ready, the system can be operational within 48 hours.
  • Once setup, the plant is stable and can operate unattended except for 10 minute daily checks. It is strongly recommended that process operation in monitored regularly - preferably twice a month - to maintain optimum performance.


  • Can treat either raw sewage or grey water from septic tank
  • Extended aeration principle ensures stable waste sludge which can be dewatered on simple drying beds or recycled back to septic tank if one is installed. Alternatively, waste sludge can also be removed approx. every 6/12 months by vaccum tanker.
  • No odour or foaming problems or fly nuisance. very low noise, splashing and aerosol formation.
  • Reliability - 100% duty and 100% standby blowers with auto restart.
  • Highly efficient Wyatt PTFE sintered diffusers which are easily removed and cleaned whilst the rest of the system operates.
  • Direct and easy access to all operating components for cleaning and process monitoring.
  • Can be started up immediately by import of good quality activated sludge from an existing plant or naturally within 2-4 weeks.
  • Full operational flexibility for cyclical low/high loads by separate timer sequence control of air blowers.
  • Can be installed above or below ground. Visually unobtrusive if installed below ground.
  • Rapid installation within 48 hours if all services are prepared (reticulation in / out, civil works, electrical power)
  • Long life + 20 years for mild steel. Indefinite for 304 S.S
  • May be installed in a suitable building or outside without special precaution.


5mm mild steel plate with reinforced sections
Exposed Pipework Galvanized flanged / screwed fittings
Walkways Galvanized mild steel expanded Mentis grating
Corrosion Protection All components except galvanized are shot blasted and painted 2 coats Copon. Colour emerald green or blue.
Air Blowers 100% duty and 100% standby blowers are Mapro side channel type or equal fitted with air relief valve and inlet silencer or filter.
Diffusers Sintered PTFE Wyatt high efficiency diffusers
Chlorination Sodium hypochlorite dosing tank and metering pump controlled by dose adjustment and timer
Electrical Weatherproof panel with hand/off/auto selectors with ammeters, hour meters and 96 x 15 min nib timers 380 volt direct on-line motor starters with auto restart on auto selection in the event of power failure
Air Control Fully adjustable individual timers for both duty / standby blowers. Individual air control valve for each diffuser set.
Sludge Pump Adjustable rate sludge return from clarifier to aeration tank and for wasting to septic tank or drying beds by simple air lift pump operated by duty air blower.
Eductors Hydraulic surface skimming eductors (either 2 or 4). Remote floating debris on the clarifier surface back to the aeration tank simply and effectively.


  • Units are shipped to site complete on low loader for offloading onto previously prepared concrete foundations - above or below ground to occupy a minimum ground area.
  • Provided inlet / outlet reticulation and electrical power is available, units can be up and running within 48 hours from delivery to site.


  • All standard quotations include commissioning and one additional monitoring visit by process chemist.
  • Comprehensive operating and maintenance instructions are provided on commissioning / hand over.
  • Long term contracts are available for operating, performance monitoring and maintenance as extras to basic cost.


(with septic tanks) These are typical and MUST be confirmed for final selection.


Hilton College – KZN Installed in 2010/11