Aerobic wastewater digester offers energy efficiency

  • Technology


Water technology company Xylem has launched a new energy efficient wastewater aerobic digester under its Sanitaire brand.

The new digester incorporates Sanitaire aeration, decanting and process controls, as well as other Xylem brand technology – Flygt mixing and pumping, and YSI and WTW instrumentation. According to Xylem, each digester solution is engineered to order to meet the specific needs of projects.

Xylem says that the digester is suitable for newly constructed conventional activated sludge plants or upgrades to existing plants over 0.5 million gallons per day (MGD), as well as oxidation ditch upgrades and aerobic digester aeration retrofits. According to a statement from the company, the Vorelodos aerobic digester solution can decrease energy consumption by up to 90%, although it does not state what this figure is a comparison to.

According to Xylem, the energy reductions that can be achieved mean the system can effectively pay for itself within one year. It says the system also lowers chemical use as a result of alkalinity recovery and a reduction in the amount of phosphorus being returned to the main plant. There is also an automated decanting feature and aeration control, which the company says means staff time can be invested in other activities.

In the statement, Xylem says the results from tests carried out at Green Lake Wastewater Treatment Plant in Wisconsin between January 2016 and March 2017 showed that the Vorelodos aerobic digester reduced nutrients (nitrogen and phosphorus) being recycled back to the main treatment plant by more than 95% while simultaneously lowering energy consumption by 95%.  

Also in the statement, Glen McCarty, Director of Public Works, Green Lake Wastewater Treatment Plant, is quoted as saying: ‘Permitted levels of nitrogen and phosphorus in effluent water are becoming ever stricter in an effort to protect surface waters from eutrophication. At the same time, plants are required to reduce energy and chemical consumption and are often challenged with limited time and staff. Sanitaire Vorelodos enabled us to do more with less.’

Sarah Elger, Xylem’s Sanitaire Global Product Manager, is quoted as saying: ‘The Sanitaire Vorelodos aerobic digester is very effective, ensuring that up to 90% less phosphorus and nitrogen is returned to the main plant compared to a fully aerated digester. This in turn stabilizes the wastewater treatment process by ensuring that the supernatant that is recycled back to the main treatment plant does not introduce a ‘spike’ of nutrients. It also means that chemical quantity in secondary and tertiary processes is reduced due to stabilized pH and alkalinity recovery.’


  • Xylem, municipal wastewater