Nonlinear fuzzy control of the dissolved oxygen in activated sludge processes

2012 ◽  
Author(s):  
A. Zawadzki ◽  
R. Piotrowski
Keyword(s):  
Fuzzy Control ◽  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Activated Sludge Processes

Improving nitrogen removal in predenitrification-nitrification biofilters

2004 ◽  
Vol 48 (11-12) ◽  
pp. 419-428 ◽  
Author(s):  
L. Larrea ◽  
A. Abad ◽  
J. Gayarre
Keyword(s):  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Nitrogen Removal ◽  
Suspended Solids ◽  
Complete Removal ◽  
Cod Removal ◽  
Nitrification Rate ◽  
Removal Rates ◽  
N Removal ◽  
Activated Sludge Processes

The effect on NH4-N removal rates in nitrification biofilters of filtered biodegradable COD and particulate COD leaving predenitrification biofilters was studied in a lab scale plant configured with the separated system of biofilters for secondary nitrogen removal from urban wastewaters. Applying a typical COD load of 11 kg/m3.day to the predenitrification biofilter and maximizing its COD removal by adding nitrates or by operating an improved control of the internal recycle, only 60% removal of filtered biodegradable COD was found. This value corresponds to the complete removal of the readily biodegradable substrate (30% of influent filtered COD) and 36% of filtered slowly biodegradable substrate (50% of influent COD). The remaining 64% of the latter entered the nitrification biofilter, causing competition between heterotrophs and nitrifiers for dissolved oxygen in the inner layers of the biofilm. Consequently the nitrification rate had relatively low values (0.5 kgN/m3.d) at 14°C despite using dissolved oxygen levels of 6 mg/l. This behaviour may explain the lower nitrification rates obtained in some cases of nitrification biofilters compared to those in tertiary nitrification after activated sludge processes. The particulate COD entering the nitrification biofilter is associated with the suspended solids leaving the denitrification biofilter which are adsorbed by the external layers of the biofilm, increasing its thickness. The activity of the nitrifiers was affected because of a lack of oxygen when the thickness was left to grow considerably. Therefore no significant particulate COD effect is expected to occur as long as backwashing is carried out with the appropriate frequency.

Hierarchical dissolved oxygen control for activated sludge processes

2008 ◽  
Vol 16 (1) ◽  
pp. 114-131 ◽  
Author(s):  
R. Piotrowski ◽  
M.A. Brdys ◽  
K. Konarczak ◽  
K. Duzinkiewicz ◽  
W. Chotkowski
Keyword(s):  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Oxygen Control ◽  
Dissolved Oxygen Control ◽  
Activated Sludge Processes

Grey-Box Identification of Dissolved Oxygen Dynamics in Activated Sludge Processes

1996 ◽  
Vol 29 (1) ◽  
pp. 6804-6809 ◽  
Author(s):  
L.J.S. Lukasse ◽  
K.J. Keesman ◽  
G. van Straten
Keyword(s):  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Activated Sludge Processes ◽  
Oxygen Dynamics

Fuzzy model-based predictive control of dissolved oxygen in activated sludge processes

2014 ◽  
Vol 136 ◽  
pp. 88-95 ◽  
Author(s):  
Ting Yang ◽  
Wei Qiu ◽  
You Ma ◽  
Mohammed Chadli ◽  
Lixian Zhang
Keyword(s):  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Predictive Control ◽  
Fuzzy Model ◽  
Model Based ◽  
Activated Sludge Processes

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.

The optimal dissolved oxygen profile in a nitrifying activated sludge process – comparisons with ammonium feedback control

2013 ◽  
Vol 68 (3) ◽  
pp. 641-649 ◽  
Author(s):  
L. Åmand ◽  
B. Carlsson
Keyword(s):  
Feedback Control ◽  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Flow Rate ◽  
Air Flow ◽  
Average Concentration ◽  
Treatment Level ◽  
Air Flow Rate ◽  
Set Point ◽  
Activated Sludge Processes

Ammonium feedback control is increasingly used to determine the dissolved oxygen (DO) set-point in aerated activated sludge processes for nitrogen removal. This study compares proportional-integral (PI) ammonium feedback control with a DO profile created from a mathematical minimisation of the daily air flow rate. All simulated scenarios are set to reach the same treatment level of ammonium, based on a daily average concentration. The influent includes daily variations only and the model has three aerated zones. Comparisons are made at different plant loads and DO concentrations, and the placement of the ammonium sensor is investigated. The results show that ammonium PI control can achieve the best performance if the DO set-point is limited at a maximum value and with little integral action in the controller. Compared with constant DO control the best-performing ammonium controller can achieve 1–3.5% savings in the air flow rate, while the optimal solution can achieve a 3–7% saving. Energy savings are larger when operating at higher DO concentrations.

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