Mutual boost of granulation and enrichment of anammox bacteria in an anaerobic/oxic/anoxic system as the temperature decreases when treating municipal wastewater

Low temperature is an important factor affecting the municipal wastewater treatment systems. The aim of this study was tracking the variations in the abundance of anammox bacteria (AnAOB) and the sludge form as the temperature decreased. Mutual boost of granulation and enrichment of AnAOB was achieved even though the temperature dropped from 20.4 ?C to 12.9 ?C. The average particle size of the sludge increased from 128.5 mu m to 245.6 mu m. With low dissolved oxygen (DO) aeration (0.2-0.5 mg/L) and short oxic hydraulic retention time (HRT) (5 h), nitritation in the anaerobic/oxic/anoxic (AOA) system was stable enough to provide NO(2)(- )for AnAOB. Ca. Brocadia, a type of typical AnAOB, was enriched from 0.03% to 0.24% in the suspended sludge and reached 16.09% in the granular sludge. Overall, this study presents the prospects of anammox and granule technologies when treating municipal wastewater at a low temperature.

Automated summary

This study investigated the variations in the abundance of anammox bacteria (AnAOB) and sludge form in municipal wastewater treatment systems as temperature decreased. The findings showed that granulation and enrichment of AnAOB were achieved even at low temperatures. The study highlights the prospects of anammox and granule technologies for low-temperature municipal wastewater treatment.