Aeration optimization through operation at low dissolved oxygen concentrations: Evaluation of oxygen mass transfer dynamics in different activated sludge systems

2017 ◽  
Vol 55 ◽  
pp. 224-235 ◽  
Author(s):  
Haitao Fan ◽  
Lu Qi ◽  
Guoqiang Liu ◽  
Yuankai Zhang ◽  
Qiang Fan ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Oxygen Mass Transfer ◽  
Low Dissolved Oxygen ◽  
Activated Sludge Systems ◽  
Oxygen Concentrations

Lethal Low Dissolved Oxygen Concentrations for Postlarvae and Early Juvenile Penaeus setiferus at Different Salinities and pH

1998 ◽  
Vol 29 (2) ◽  
pp. 221-229 ◽  
Author(s):  
Evenor Martínez ◽  
Miguel Aguilar ◽  
Limber Trejo ◽  
Isaac Hernández ◽  
Eugenio Díaz-Iglesia ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Early Juvenile ◽  
Low Dissolved Oxygen ◽  
Penaeus Setiferus ◽  
Oxygen Concentrations

scholarly journals Fish Rescue during Streamflow Intermittency May Not Be Effective for Conservation of Rio Grande Silvery Minnow

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3371
Author(s):  
Thomas P. Archdeacon ◽  
Tracy A. Diver ◽  
Justin K. Reale
Keyword(s):  
Water Quality ◽  
Dissolved Oxygen ◽  
Fish Assemblages ◽  
Sublethal Effects ◽  
Rio Grande ◽  
Quality Data ◽  
Water Quality Data ◽  
Low Dissolved Oxygen ◽  
Rio Grande Silvery Minnow ◽  
Oxygen Concentrations

Streamflow intermittency can reshape fish assemblages and present challenges to recovery of imperiled species. During streamflow intermittency, fish can be subjected to a variety of stressors, including exposure to crowding, high water temperatures, and low dissolved oxygen, resulting in sublethal effects or mortality. Rescue of fishes is often used as a conservation tool to mitigate the negative impacts of streamflow intermittency. The effectiveness of such actions is rarely evaluated. Here, we use multi-year water quality data collected from isolated pools during rescue of Rio Grande silvery minnow Hybognathus amarus, an endangered minnow. We examined seasonal and diel water quality patterns to determine if fishes are exposed to sublethal and critical water temperatures or dissolved oxygen concentrations during streamflow intermittency. Further, we determined survival of rescued Rio Grande silvery minnow for 3–5 weeks post-rescue. We found that isolated pool temperatures were much warmer (>40 °C in some pools) compared to upstream perennial flows, and had larger diel fluctuations, >10 °C compared to ~5 °C, and many pools had critically low dissolved oxygen concentrations. Survival of fish rescued from isolated pools during warmer months was <10%. Reactive conservation actions such as fish rescue are often costly, and in the case of Rio Grande silvery minnow, likely ineffective. Effective conservation of fishes threatened by streamflow intermittency should focus on restoring natural flow regimes that restore the natural processes under which fishes evolved.

Aerobic Sludge Digestion under Low Dissolved Oxygen Concentrations

2004 ◽  
Vol 76 (5) ◽  
pp. 453-462 ◽  
Author(s):  
Ravi Sankar Arunachalam ◽  
Hemant K. Shah ◽  
Lu-Kwang Ju
Keyword(s):  
Dissolved Oxygen ◽  
Low Dissolved Oxygen ◽  
Sludge Digestion ◽  
Aerobic Sludge ◽  
Oxygen Concentrations

scholarly journals Specific Oxygen Uptake Rate and Mass Transfer Coefficient in Activated Sludge System

2019 ◽  
Vol 4 (2) ◽  
pp. 24-32
Author(s):  
S.H. Tan ◽  
◽  
Jamaiatul Lailah M.J. ◽  
Aida Isma M.I. ◽  
◽  
...  
Keyword(s):  
Mass Transfer ◽  
Oxygen Uptake ◽  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Uptake Rate ◽  
Oxygen Transfer ◽  
Oxygen Uptake Rate ◽  
Specific Oxygen Uptake Rate

Activated sludge process is one of the effective methods in biological wastewater treatment and the impact of oxygen transfer through aeration process has the most important breakthroughs as it served as the largest consumer in the treatment. Aeration is an energy demanding process. Oxygen transfer into an activated sludge is a very challenging issue in the field of multiphase flows. Apart from the physical mass transfer phenomena between gas, liquid and solids phases, the transport mechanisms are also overlapped by time and temperature, varying microbial activity, impurity loads, adsorption and desorption processes. Oxygen uptake rate (OUR) for microbial population in the activated sludge system is important parameter to determine the amount of oxygen consumed during aerobic heterotropic biodegradation in the system. Evaluation of specific oxygen uptake rate (SOUR) and the volumetric mass transfer coefficient (KLA) of oxygen for three different wastewater treatment processes, namely conventional activated sludge (CAS), oxidation ditch (OD) and sequencing batch reactor (SBR) treating municipal wastewater in Kuala Lumpur have been carried out. In-situ and ex-situ measurement of pH, dissolved oxygen (DO), temperature, MLSS and MLVSS were carried out. In the activated sludge treatment, very low concentration of dissolved oxygen may cause the wastewater to turn septic resulting in death of bacteria or in active due to unstable anaerobic conditions. Conversely, an excessive dissolved oxygen may result to high energy and high 25 operating cost. Higher flowrate may also cause dissolved oxygen to rise, reducing the quality of sludge and slowing the denitrification process in the system. Results revealed that the OUR for SBR, OD and CAS were 9.582 mg O2 /L/hr, 10.074 mg O2 /L/hr and 13.764 mg O2 /L/hr, respectively. Low oxygen uptake rate indicates a low rate of microbial respiration. By computing the OUR, the mass transfer coefficient could be evaluated. It should be noted that among the treatment system in this study, the conventional activated sludge shows the highest mass transfer coefficient and specific oxygen uptake rate of 2.038 hr-1 and 15.605 mg O2 /g MLVSS/hr, respectively. Improving the oxygen transfer rate and reducing aeration in the system could achieve a cost-effective aeration system.

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

2018 ◽  
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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