Autothermal thermophilic aerobic digestion of municipal sludges: A one‐year, full‐scale demonstration project

Abstract

A three-facility, full-scale pilot program was undertaken at three small wastewater treatment plants in British Columbia, Canada. The project concludes several years of investigation and one year of plant evaluations for sludge treatment using autothermal thermophilic aerobic digestion (ATAD). Process effectiveness was shown by demonstration of pasteurization, stabilization, and odor acceptability. Control parameters were accessed by use of oxidation reduction potential (ORP), temperature, pH, air flow rates, and energy use. Dewaterability was also studied. The studies concluded that the ATAD process was suitable for use in small communities. The information presented is taken from the final project report and is supplemented with design suggestions for use when considering the ATAD process. Water Environ. Res., 65,849 (1993).Autothermal thermophilic aerobic digestion (ATAD) is a compact, fully enclosed digestion process which requires relatively small reactors, small volumes of air, adequate energy for complete mixing, and a concentration of biomass and organics sufficient to ensure the high temperature sludge digestion. Heat is produced from energy release due to organic decomposition. The process is described as autothermal; other than mixing energy, no other heat source is required. Thermophilic temperatures of 55° to 70°C can be obtained in the reactors. The reactors are normally operated on a semi-continuous or batch basis, and at these temperatures and with sufficient residence time, pasteurization and stabilization are assured. The small volume, low energy, and low instrumentation requirements make the process cost-competitive with other processes such as mesophilic aerobic digestion, anaerobic digestion, and composting. The potential benefits are a pasteurized stable sludge with low handling risk, and a process which can be used safely for sludge digestion in small to medium-size communities throughout North America.To investigate claims of the suitability of ATAD for domestic sludge treatment, a full-scale demonstration study was undertaken at three small wastewater treatment plants in British Columbia, Canada. Although previous work has been undertaken in Great Britain, Europe, and North America using high-temperature aerobic digestion, details of operation are either proprietary, give misinformation, or are often incomplete. Early attempts at the design of these facilities lacked information on process, design, and operating criteria to secure process stability and odor control. Investigations by many others (Kabrick

Inactivation of <i>Enterococcus</i> in Compost-Amended Soils

“…Under field conditions, other variables, such as solar radiation and dryness, may also affect the survival of pathogens 19) . Increase in temperature showed to increase the inactivation rate of all soil types.…”

“…The moisture content was set to 25% with ultra-pure water, because the moisture content at field capacity for sandy loam and clay soils are 14.7% and 22.6%, respectively 19) .…”

Reduction of sludge production and recycled nutrients loading by high-rate aerobic digestion(CaviTec II) with inorganic sludge separation and sludge solubilization

“…호기성소화 및 호기/무산소 소화에서 고형물 및 질소와 인의 영양염류 변화는 비교적 많이 연 구되어 왔으며 (Mavinic et al, 1982), 단순 포기 식 호기성 소화보다는 슬러지의 자기분해시 발생 되는 열을 이용하여 소화 효율을 높이는 ATAD 공법(Autothermal Thermophilic Aerobic Digestion) (Kelly et al, 1993), pH 저하를 방지하 Table 9. Characteristics of recycle water 사 사…”

Effects of stabilization and sludge properties in a combined process of anaerobic digestion and thermophilic aerobic digestion

“…Previous researchers have stated that altering the feed concentration can effectively control the temperature in ATAD. [9][10][11] However, the feed concentration exceeds that for an ATAD system, oxygen-limited conditions and related odours develop. [10] Thus, feed concentration should be carefully investigated to find a proper inflow content, and controlled to prevent upsetting the digester by introducing high or low organic loads that result in thermal shocks.…”