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

Abstract

A novel process of combining mesophilic (<35°C) anaerobic digestion with the thermophilic (55°C) aerobic digestion process (AN-TAD) was designed to stabilize sludge and economize aeration energy. Effects of stabilization and sludge properties for AN-TAD process were evaluated by batch experiments during a 25 d digestion period. The sludges digested by AN-TAD process achieved the requirements for Class-A sludge standard. The sludge at total solid (TS) 5.4% had the highest value of decay coefficient K(d(55)) at 0.1851 d(-1) among the three TS contents according to the first-order kinetics equation. Oxidation reduction potential at below 0 mV remained for sludges at TSs of 6.5%, 5.4%, and 4.6% for at least 15 d because of initial hydrolytic-acidification. Concentrations of nitrogen and phosphorus in sludges at TSs of 6.5%, 5.4%, and 4.6% gradually increased up to the highest values in the supernatant during the initial 13 d, causing low utilized value in land application as a fertilizer. Prolonging the retention time for more than 15 d was considered because soluble phosphorus precipitated in the solid phase. High content of soluble organic matters of the soluble chemical oxygen demand, protein, and polysaccharide in the supernatant caused deterioration in sludge dewaterability rates.

Pathogenic members of Escherichia coli & Shigella spp. Shigellosis

“…In the work by Astals and co-workers E. coli was reduced by 2.2 log 10 units in 20 days using a mesophilic digestion process, whereas in a thermophilic digestion process produced a reduction of 4.2 in 15 days was observed (Astals et al, 2012). In an attempt to save energy and stabilize the sludge, a method combining a mesophilic anaerobic digestion for 3 days followed by a thermophilic aerobic process was developed (Cheng et al, 2015). A reduction of more than 4 log 10 units after a 10-day digestion was attained using this method.…”

Sludge Treatment and Disposal in MENA Countries

“…TAD's future is promising, mainly due to increasing measures for the agricultural reuse of sludge. The process still requires development, especially in terms of operational control (Andreoli et al 2007).Batch experiments applied a combined of mesophilic (˂35ºC) anaerobic digestion with the thermophilic (55ºC) aerobic digestion process (AN-TAD), the produced sludge achieved the requirement for Class-A sludge standards (Cheng et al 2015).…”

Comparison of pre- and inter-stage aerobic treatment of wastewater sludge: Effects on biogas production and COD removal

“…Combined aerobic-anaerobic biological treatments more completely degrade sludge and other organic wastes than either does alone. Despite some comparison, exactly how organic matter utilisation differs between aerobic and anaerobic communities is not clear (Burton, 1992;Kumar et al, 2006;Dumas et al, 2010;Tomei et al, 2011;Monlau et al, 2013;Braguglia et al, 2014;Cheng et al, 2015).…”