Intermittent addition of external carbon to enhance denitrification in activated sludge

1998 ◽  
Vol 37 (9) ◽  
pp. 227-233 ◽  
Author(s):  
S. Hasselblad ◽  
S. Hallin
Keyword(s):  
Carbon Source ◽  
Activated Sludge ◽  
High Capacity ◽  
Pilot Scale ◽  
Denitrifying Bacteria ◽  
Activated Sludge Process ◽  
External Carbon Source ◽  
Long Term Effect ◽  
Ethanol Addition ◽  
On Line

Efficient nitrogen removal in a pre-denitrifying activated sludge process strongly depends on the amount and nature of the carbon source in the wastewater. If denitrification has to be supported at periods, the response to a supplemental carbon source should be immediate and substantial. The aim of this work was to study how intermittent addition of ethanol affects process performance and the denitrifying capacity of the biomass in a pre-denitrifying activated sludge process. The investigated intermissions simulated a possible operational situation with a short stop of ethanol addition or a strategy with addition only at weekends. The long-term effect of intermittent addition was also studied. Experiments were performed in a pilot-scale activated sludge plant. Effluent nitrate was measured on-line and potential denitrification rates were determined with the acetylene inhibition technique. Once the bacteria were adapted to the external carbon source, the studied intermission of 24 hours as well as an intermission of six days showed no severe effect on denitrification capacity of the sludge. In order to maintain process stability with intermittent addition, the denitrifying bacteria had to sustain a high capacity at each stop. Five weeks of intermittent addition of ethanol did not change the level of nitrate reduction in the system during periods of ethanol addition. Denitrification potential was, however, negatively affected. The results suggest that it is possible to use an intermittent strategy when adding ethanol as an external carbon source in a pre-denitrifying system and for instance only support the denitrifying bacteria during weekends.

Adaptive control of the nitrate level in an activated sludge process

2003 ◽  
Vol 47 (11) ◽  
pp. 137-144 ◽  
Author(s):  
M. Ekman ◽  
P. Samuelsson ◽  
B. Carlsson
Keyword(s):  
Carbon Source ◽  
Activated Sludge ◽  
Heterotrophic Bacteria ◽  
Activated Sludge Process ◽  
Nitrate Level ◽  
Anoxic Zone ◽  
Linear Quadratic ◽  
External Carbon Source ◽  
On Line ◽  
Anoxic Environment

In an activated sludge process for nitrogen removal, nitrate may be reduced to nitrogen gas by facultative heterotrophic bacteria in an anoxic environment. In order to guarantee sufficient supplies of readily biodegradable carbon compounds, an external carbon source often needs to be added. In this paper, an automatic control strategy for controlling the nitrate level using an external carbon source is presented. The external carbon source is added in the first anoxic zone to control the nitrate concentration in the last anoxic zone. Key process parameters are estimated on-line for a simplified Activated Sludge Model No 1. The estimated parameters are used for updating a linear quadratic controller. The strategy is illustrated in a simulation study with realistic influent data and is shown to perform very well.

Iterative design of a nitrate controller using an external carbon source in an activated sludge process

1998 ◽  
Vol 37 (12) ◽  
pp. 95-102 ◽  
Author(s):  
Pericles R. Barros ◽  
Bengt Carlsson
Keyword(s):  
Carbon Source ◽  
Activated Sludge ◽  
High Performance ◽  
Controller Design ◽  
Wastewater Treatment Plants ◽  
Design Procedure ◽  
Pole Placement ◽  
Activated Sludge Process ◽  
Suggested Approach ◽  
External Carbon Source

More stringent effluent and cost requirements are increasing the need for better control of wastewater treatment plants. In an activated sludge process, the nitrogen removal efficiency may be improved by adding an external carbon source. In this paper, automatic control of the nitrate level by regulating external carbon flow is discussed. More specifically, an iterative tuning procedure for the controller is outlined. Iterative controller design schemes aim at tuning high performance controllers of low complexity using closed loop data. The basic strategy used in this paper is an iterative pole placement controller design procedure. The suggested approach is compared with conventional design in a simulation study.

Respirometry for determination of the influents SS-concentration

1996 ◽  
Vol 33 (1) ◽  
pp. 311-323 ◽  
Author(s):  
A. Witteborg ◽  
A. van der Last ◽  
R. Hamming ◽  
I. Hemmers
Keyword(s):  
Experimental Design ◽  
Activated Sludge ◽  
Substrate Concentration ◽  
Full Scale ◽  
Activated Sludge Process ◽  
Respiration Rates ◽  
On Line ◽  
Large Measurement ◽  
Set Up

A method is presented for determining influent readily biodegradable substrate concentration (SS). The method is based on three different respiration rates, which can be measured with a continuous respiration meter which is operated in a cyclic way. Within the respiration meter nitrification is inhibited through the addition of ATU. Simulations were used to develop the respirometry set-up and decide upon the experimental design. The method was tested as part of a large measurement programme executed at a full-scale plant. The proposed respirometry set-up has been shown to be suitable for a semi-on-line determination of an influent SS which is fully based on the IAWQ #1 vision of the activated sludge process. The YH and the KS play a major role in the principle, and should be measured directly from the process.

ADVANCED TREATMENT OF PAPER MILL EFFLUENTS BY A TWO-STAGE ACTIVATED SLUDGE PROCESS

1994 ◽  
Vol 30 (3) ◽  
pp. 173-181 ◽  
Author(s):  
L. Knudsen ◽  
J. A. Pedersen ◽  
J. Munck
Keyword(s):  
Activated Sludge ◽  
Treatment Plant ◽  
Paper Mill ◽  
Pilot Scale ◽  
Activated Sludge Process ◽  
Two Stage ◽  
Paper Mills ◽  
Paper Mill Effluents ◽  
Scale Test ◽  
Oxygen Requirements

The work presented in this paper concerns the application of a two-stage aerobic activated sludge process for treatment of effluents from paper mills in Denmark. The paper describes both pilot-scale test results and fullscale experience with the process. The treatment process is characterised by a bigh-load first stage (2-4 kg COD/kg MLSSxd) followed by a low-load second stage to secure full nitrification and denitrification of remaining nitrogen compounds. The results of continuous pilot-scale tests show that it is possible to obtain a reduction of more than 85% of the incoming COD,01 and a 99% reduction of the incoming BOD5, resulting in an effluent quality of 230 mg CODsol/l and less than 10 mg BOD5/l. As indicated, practically all the biodegradable organic substances are removed by the process. The remaining fraction of soluble organics measured as COD is considered to be non-biodegradable by conventional biological treatment systems. The results produced in the pilot-scale tests are confirmed by the effluent qualities obtained in a full-scale treatment plant at another paper mill, involving an identical process concept. During the pilot-scale tests, special attention bas been paid to the removal of organic compounds, organic nitrogen as well as nutrients and nitrification. In addition, the sludge characteristics and the oxygen requirements have been considered.

Dimensioning of Aerated Grit Chambers and Use as a Highly Loaded Activated Sludge Process

1989 ◽  
Vol 21 (4-5) ◽  
pp. 13-22
Author(s):  
Jorg Londong
Keyword(s):  
Activated Sludge ◽  
Pilot Scale ◽  
Air Injection ◽  
Activated Sludge Process ◽  
Cross Section Area ◽  
Section Area ◽  
Degree Of Separation ◽  
Highly Loaded ◽  
Adsorption Stage

The aerated grit chamber has long been used to separate sand from sewage. Nevertheless, there are no definite and uniform recommendations for dimensioning, and there is little information in the literature about the degree of separation attainable. Thus, principles for dimensioning and the possible degree of separation are derived from measurements of large pilot scale plants, two-dimensional models, and existing aerated grit chambers. The following values for dimensioning were found in this work: a detention period of about 20 minutes; a width to depth ratio (w/d) of about 0.8; a minimal and maximal cross section area between 1 and about 7 m2; a flow velocity of 20 cm/s at the bottom of the aerated grit chamber. Simple formulae for the determination of the required amount of air can be given in relation to the w/d ratio, the depth of air injection and the kind of aeration used (fine or coarse bubble). The simultaneous use of an aerated grit chamber as an adsorption stage (highly loaded activated sludge process) is possible without additional air being required to maintain the velocity at the bottom of the grit chamber. For purely aerobic operation, however, the amount of air has to be increased.

scholarly journals Optimizing external carbon source addition in domestics wastewater treatment based on online sensoring data and a numerical model

2017 ◽  
Vol 75 (11) ◽  
pp. 2716-2725 ◽  
Author(s):  
Qibin Wang ◽  
Qiuwen Chen ◽  
Jing Chen
Keyword(s):  
Wastewater Treatment ◽  
Numerical Model ◽  
Carbon Source ◽  
Wastewater Treatment Plants ◽  
Pilot Scale ◽  
Fixed Dose ◽  
Carbon Addition ◽  
External Carbon Source ◽  
Wastewater Quality ◽  
Denitrification Reactor

The removal of total nitrogen in wastewater treatment plants (WWTPs) is often unsatisfactory for a variety of reasons. One possible measure to improve nitrogen removal is the addition of external carbon. However, the amount of carbon addition is directly related to WWTP operation costs, highlighting the importance of accurately determining the amount of external carbon required. The objective of this study was to obtain a low nitrate concentration in the anoxic zone of WWTPs efficiently and economically by optimizing the external carbon source dosage. Experiments were conducted using a pilot-scale pre-denitrification reactor at a Nanjing WWTP in China. External carbon source addition based on online monitoring of influent wastewater quality and a developed nitrification–denitrification numerical model was investigated. Results showed that carbon addition was reduced by 47.7% and aeration costs were reduced by 8.0% compared with those using a fixed-dose addition mode in the pilot reactor. The obtained technology was applied to the full-scale Jiangxinzhou WWTP in Nanjing with promising results.

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