Chemical oxygen demand and nitrogen removal in disgested blackwater by Feammox process

Abstract

Digested blackwater is characterized by a low chemical oxygen demand (COD) to nitrogen ratio. It requires external organic carbon to fully remove nitrogen in digested blackwater by conventional biological nitrogen removal. Feammox is a new biological process that has the potential to remove nitrogen from wastewater that has a low COD/N ratio. This research utilized two parallel anaerobic sequencing batch reactors, each with a capacity of 40 liters and a 14-day operational cycle, to treat digested blackwater. Iron-rich sludge and ferric were added in the Feammox reactor, whereas anaerobic sludge and no ferric were utilized in the control reactor. The result showed that the Feammox reactor removed 93.06 % COD, 85.19 % total nitrogen (TN), and 88.65 % ammonium, while the control reactor removed 95.85 % COD, 10.89 % TN. The COD removal efficiency of the Feammox reactor was comparable to that of the control reactor, suggesting that the addition of ferric did not significantly influence the COD removal rate after 14 operational days. The mixed liquor volatile suspended solids (MLVSS)/mixed liquor suspended solids (MLSS) ratio of Feammox sludge ranges from 0.3 to 0.35, much lower than that of the control reactor (0.7–0.75). Microbial communities in the Feammox reactor include Pseudomonas, Geobacter, Alicycliphilus, Geoalkalibacter, and Ohtaekwangia. This study demonstrates the Feammox process has great potential for digested blackwater treatment.

Keywords

• Feammox process
• Digested blackwater
• Nitrogen removal
• COD removal