Evaluation and Development of a Thermophilic Aerobic Digester at Castle Donington Sewage‐Treatment Works

Abstract

An investigation into the practicality of thermophilic aerobic digestion has been in progress at Castle Donington since 1989. The work has been carried out in a glassed steel insulated digester of 123 m3 capacity. Both auto-entraining and blower-assisted venturi systems have been evaluated.Both aeration systems were able, under favourable conditions, to remove at least 50% of the sludge COD. It was found that the additional flexibility of the blower venturi combination was necessary to accommodate crude sludges varying from 2% to 12% dry solids.Originally the plant was intended to operate at above 55°C with a 10-day retention period. In practice retention periods at this temperature have been at least 15 days. The process has proved relatively susceptible to inhibition and requires the air supply to be closely matched to the load.The revenue costs have been, at best, around f47.3hDS. This is competitive with small-scale anaerobic digestion, but not with the large digestion centre approach widely used in the UK. Unless pasteurization becomes a requirement for agricultural disposal, thermophilic aerobic digestion is unlikely to find wide use in this country.

Application of thermophilic aerobic digestion in protein enrichment of high strength agricultural waste slurry for animal feed supplementation

“…It is a versatile but relatively new process, which is increasingly being accepted for waste treatment, either in standalone processes, or as part of integrated two‐stage, aerobic–thermophilic/anaerobic–mesophilic, or aerobic–thermophilic/anaerobic–thermophilic processes 6. The advantages of TAD over conventional processes include the capacity for rapid, cost effective waste stabilization2, 7, 8 and pasteurization 9–11. The profile of TAD is rising both in Europe and North America due to various pieces of legislation seeking to limit pathogen levels, particularly those of human or animal origin, in wastes intended for land or sea application and disposal 12…”

Protease and xylanase activities and thermophilic populations as potential process monitoring tools during thermophilic aerobic digestion

“…As a relatively new process, it is increasingly being accepted for waste treatment, either in stand‐alone processes, or as part of an integrated two‐stage, aerobic–thermophilic/anaerobic–mesophilic, or anaerobic–thermophilic process 1. It is a reputedly versatile low technology whose advantages over conventional processing include the capacity to achieve rapid, cost effective waste stabilisation,2, 3 and pasteurisation 4–6. TAD is particularly suited for use with waste being considered for upgrading and recycling as animal feed supplement, as is currently the case with many agricultural and food industry wastes,7–10 and also for the rapid treatment of otherwise recalcitrant wastes, on account of the biochemical versatility of thermophiles involved in the process 11, 12.…”