Effect of organic loading rate and fill time on the biohydrogen production in a mechanically stirred AnSBBR treating synthetic sucrose-based wastewater.

Abstract

This study investigated the feasibility to produce biohydrogen of a mechanically stirred anaerobic sequencing batch biofilm reactor (AnSBBR) treating sucrose-based synthetic wastewater. The bioreactor performance (30 °C) was evaluated as to the combined effect of fill time (2, 1.5, and 1 h), cycle length (4, 3, and 2 h), influent concentration (3,500 and 5,250 mg chemical oxygen demand (COD) L(-1)) and applied volumetric organic load (AVOLCT from 9.0 to 27.0 g COD L(-1) d(-1)). AVOLs were varied according to influent concentration and cycle length (t C). The results showed that increasing AVOLCT resulted in a decrease in sucrose removal from 99 to 86 % and in improvement of molar yield per removed load (MYRLS.n) from 1.02 mol H2 mol carbohydrate(-1) at AVOLCT of 9.0 g COD L(-1) d(-1) to maximum value of 1.48 mol H2 mol carbohydrate(-1), at AVOLCT of 18.0 g COD L(-1) d(-1), with subsequent decrease. Increasing AVOLCT improved the daily molar productivity of hydrogen (MPr) from 15.28 to 49.22 mol H2 m(-3) d(-1). The highest daily specific molar productivity of hydrogen (SMPr) obtained was 8.71 mol H2 kg TVS(-1) d(-1) at an AVOLCT of 18.0 g COD L(-1) d(-1). Decreasing t C from 4 to 3 h decreased sucrose removal, increased MPr, and improved SMPr. Increasing influent concentration decreased sucrose removal only at t C of 2 h, improved MYRLS,n and MPr at all t C, and also improved SMPr at t C of 4 and 3 h. Feeding strategy had a significant effect on biohydrogen production; increasing fill time improved sucrose removal, MPr, SMPr, and MYRLS,n for all investigated AVOLCT. At all operational conditions, the main intermediate metabolic was acetic acid followed by ethanol, butyric, and propionic acids. Increasing fill time resulted in a decrease in ethanol concentration.