Comparative Anaerobic and Aerobic Digestion Performance of Dewatered Sewage Sludge From Oxidation Ditch Processes

Anaerobic Digestion of Oxidation Ditch Sludge at Low Temperatures with Hyperthermophilic Pretreatment

“…Average total solids (TS) and volatile solids (VS) of the sludge were 15.6% and 12.8%, respectively. The effect of the feeding TS on biogas production was also evaluated, and the TS of 10% and 5% resulted in the similar biogas production performance [7]. In the present study, the digestate TS would be higher at lower digestion temperatures, which might affect digestion performance.…”

“…Laboratory-scale reactors with a working volume of 0.2 L were maintained in an anaerobic state without mechanical mixing. Difference in biogas production performance by anaerobic digestion experiments of dewatered sludge from WWTP-A with and without mechanical mixing was not observed under the low loading condition [7]. The temperatures were controlled at 35 ± 1°C, 30 ± 1°C, 25 ± 1°C, and 15 ± 1°C with water baths.…”

“…The raw dewatered sludge (A) or pretreated dewatered sludge (AH) were fed. The hyperthermophilic pretreatment of the substrate was carried out as follows: the raw dewatered sludge diluted to TS 5% was placed in a vial having an effective volume of 100 mL and put in an oil bath at 80°C for 24 h. Anaerobically digested dewatered sludge from WWTP-A under the feeding TS of 10% [7] was seeded at the beginning of operation. Operational conditions in the continuous experiment is summarized in Table 3.…”

“…3. Using a measured C, H and N containing ratio of the dewatered sludge obtained at WWTP-A on dry solids (DS) basis of 39.0, 5.8 and 7.2%DS, respectively [7], and specific gravity of sludge of 1.0 (kg/L), the total nitrogen concentration of the dewatered sludge at TS 5% is calculated to be 3.7 gN/L. At all temperatures, nitrogen degradation of the pretreated dewatered sludge was higher than that of the raw dewatered sludge.…”

“…Anaerobic digestion of sewage sludge without heating is under operation at several WWTPs in Japan [1]. Psychrophilic operation with less heating energy reduces operational cost, although longer retention time is required [7]. Pretreatment to increase biodegradability of sewage sludge can reduce required retention time or lower the operational temperature for obtaining the same performance.…”