Startup of Simultaneous Low Dissolved Oxygen Coupled with Low F/M System and the Prevention of Sludge Bulking by Acclimating Limited-Mineralization Sludge with Higher-Concentration

It is significant to realize stable operation of the simultaneous low dissolved oxygen coupled with low F/M system. Two acclimation modes including 1) reducing DO firstly and then adjusting the F/M , and 2)reducing the F/M firstly and then adjusting DO were conducted. The results showed that the first operation mode was prone to induce high-viscosity sludge bulking at the reaction temperature of 9~10°C and filamentous bulking under low F/M of 0.08~0.1kgCOD/kgMLSS•d at 20±1°C。However, good settling performance and effluent were achieved under the second operation mode. It is proposed to culture limited-mineralization activated sludge with higher-concentration to realize the prevention of sludge bulking.

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ComammoxNitrospiraare the dominant ammonia oxidizers in a mainstream low dissolved oxygen nitrification reactor

10.1101/504704 ◽

2018 ◽

Cited By ~ 1

Author(s):

Paul Roots ◽

Yubo Wang ◽

Alex F. Rosenthal ◽

James S. Griffin ◽

Fabrizio Sabba ◽

...

Keyword(s):

Dissolved Oxygen ◽

Activated Sludge ◽

Removal Rate ◽

Ammonia Removal ◽

Biological Nutrient Removal ◽

Ammonia Oxidizing Bacteria ◽

Ammonia Oxidizers ◽

Total Abundance ◽

Low Dissolved Oxygen ◽

Activated Sludge Processes

AbstractRecent findings show that a subset of bacteria affiliated withNitrospira, a genus known for its importance in nitrite oxidation for biological nutrient removal applications, are capable ofcompleteammoniaoxidation (comammox) to nitrate. Early reports suggested that they were absent or present in low abundance in most activated sludge processes, and thus likely functionally irrelevant. Here we show the accumulation of comammoxNitrospirain a nitrifying sequencing batch reactor operated at low dissolved oxygen (DO) concentrations. Actual mainstream wastewater was used as influent after primary settling and an upstream pre-treatment process for carbon and phosphorus removal. The ammonia removal rate was stable and exceeded that of the treatment plant’s parallel full-scale high DO nitrifying activated sludge reactor. 16S rRNA sequencing showed a steady accumulation ofNitrospirato 53% total abundance and a decline in conventional ammonia oxidizing bacteria to <1% total abundance over 400+ days of operation. After ruling out other known ammonia oxidizers, qPCR confirmed the accumulation of comammoxNitrospirabeginning around day 200, to eventually comprise 94% of all detectedamoAand 4% of total bacteria by day 407. Quantitative fluorescence in-situ hybridization confirmed the increasing trend and high relative abundance ofNitrospira. These results demonstrate that comammox can be metabolically relevant to nitrogen transformation in wastewater treatment, and can even dominate the ammonia oxidizing community. Our results suggest that comammox may be an important functional group in energy efficient nitrification systems designed to operate at low DO levels.

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