2021 Volume 57 Issue 3 Pages 43-53
To assess the performance of an Excess Sludge reduction system using Carriers based on Acrylic PilE fabrics （ESCAPE） process, synthetic wastewater was treated using lab-scale continuous-flow activated sludge reactors. Bacteria and oligochaetes were presumed to settle on the pile carriers, thereby reducing excess sludge in the food chain. Each reactor consisted of an aeration tank （5L） equipped with the pile carrier （3cm pile length, 35/cm2 density, 7.5 × 25.5cm） and a settling tank （2L）. A control reactor and a test reactor were, respectively, uninoculated and inoculated with oligochaetes （50g-wet）. A 14-day operation period was repeated 13 times in all to evaluate the mass balance in the reactors. In eight operation runs at a low loading rate of 140 mgTOC/L・d, the net sludge reduction occurred with observed yield of －1.50 to －0.28 gVS/gTOC for the control reactor and －2.45 to －1.45 gVS/gTOC for the test reactor. In five operation runs at a high loading rate of 420 mgTOC/L・d, low excess sludge production occurred with observed yield of 0.31－0.62 gVS/gTOC for the control reactor and 0.07－0.56 gVS/gTOC for the test reactor, which were only 4－42% of the typical theoretical sludge yield of 1.46 gVS/gTOC. The test reactor removed organic matter from synthetic wastewater effectively with no negative influence on the effluent quality by introduction of the oligochaetes. Monophyephorus rubroniveus, a predominant oligochaete species, survived for 190 days, maintaining its reproductive ability on the pile carrier. The oligochaete recovered from the carrier laid cocoons on plate media, hatching 5－9 juveniles per cocoon. The oligochaete needed 9－18 days for hatching and 32－60 days for growth to 15 mm length. Providing efficient and stable operation conditions, the ESCAPE process will contribute to resolution of sewage sludge treatment difficulties.
