Global Development of the ATAD Process and its Significant Achievements in Energy Recovery and Utilization

This paper traces development of the autothermal thermophilic aerobic digestion (ATAD) process from the 1960s in Germany to its first usage in North America in the 1980s and forward. It shows significant improvements in the process including much better aeration, better odor control, higher volatile solids destruction, and production of a relatively easy to dewater biosolids. Further the ATAD process can produce a product with no detectable levels of pathogens, one that readily meets requirements for vector attraction reduction and further be very well stabilized in terms of the reduction of putrescible and potentially odorous material. A concern that has been a problem for the process is how to utilize all the energy/heat produced by the microorganisms that treat the sludge. This was initially investigated in the 1970s, but this paper goes much further in showing how that heat can and is being used constructively to reduce the overall energy requirements of the wastewater treatment plant. Lastly a discussion occurs of how the large quantities of heat produced might further be used.