Aerobic Thermophilic Stabilization (ATS)

Photo: Aerobic Thermophilic Stabilization (ATS)

Sludge stabilization is a process in which organic substances are degraded. When the ATS technology is used, this reaction is carried out with the use of aerobic microorganisms. In this process, energy is released from sludge, causing heating up to more than 50° C. In this way such high speeds of degradation of organic substances are achieved that 7 - 9 days of storage suffice for the process. The metabolism of aerobic organisms leads to the inactivation of pathogenic bacteria and viruses, i.e., to hygienisation, and therefore a valuable fertilizer can be obtained.

This technology is mainly suitable for biological wastewater treatment plants from 5,000 to 50,000 PE, i.e., where building a gas management facility would not be economical.

An advantage of ATS as compared to AD is a considerable saving of investment costs, as the reactor is several times smaller. The technology also solves the issue of sludge hygienisation, and it can be suitably deployed in food-processing WWTPs or for intensification, where the existing equipment does not meet the capacity and there is no room for its extension.


  • Saving 2/3 of the volume of sludge management
  • Low investment costs
  • The result is a valuable type A fertilizer
  • Tested technology (more than 25 years)
  • Stabilization and hygienization carried out at the same time
  • Short storage times
  • Low spatial requirements
  • High process stability
  • Process flexibility
  • Possibility of operation expansion
  • Use in industry and in the municipal sphere
  • The ATS technology meets the requirements of international regulations, e.g., US EPA 503


Suitable for aerobic thermophilic processing are excess sludge and a mixture of primary and secondary sludge, and also, e.g., liquid manure. If hygienization is required besides stabilization, storage for at least 23 hours at a temperature greater than 50° C must be achieved. Two-stage equipment of the ATS type, with discontinuous operation, meets these demands. Once a day, stabilized and hygienized sludge is removed from reactor 2 and transported to the balancing tank. After the removal of stabilized sludge from reactor 2, this reactor is refilled with partly stabilized sludge from the pre-heating reactor 1. Reactor 1 is then filled with raw sludge. In larger systems, individual stages may consist of more tanks. In the first stage, temperatures between 35° C and 50° C are achieved, and in the second stage between 50° C and 60° C.