Knowledge based diagnosis of solids-liquid separation problems

1996 ◽  
Vol 33 (2) ◽  
pp. 219-226 ◽  
Author(s):  
Sven-Göran Bergh ◽  
Gustaf Olsson
Keyword(s):  
Suspended Solids ◽  
Dynamic Models ◽  
Treatment Plant ◽  
Sensor Calibration ◽  
Knowledge Based ◽  
Good Ability ◽  
Solids Concentration ◽  
Hydraulic Conditions ◽  
Process Failure ◽  
On Line

Often the suspended solids concentration in activated sludge treatment plants may display both large amplitudes and unnaturally fast changes. If the sensor calibration has been found satisfactory, the abnormal appearance has to be explained by the process itself. There may be three principal reasons for such a behaviour: severe hydraulic conditions, poor floc separation properties or very high sludge blanket. During these circumstances it is very informative to qualitatively examine the relationships between the suspended solids concentration variations and important influencing variables, such as the flow rates and the sludge blanket level. This kind of knowledge based diagnosis is superior to dynamic models for such odd behaviour. A simple on-line method to perform the diagnosis is presented. The method has been tested on a massive set of data from a full scale wastewater treatment plant in Sweden and shown unexpected good ability to supply early warnings. It is also shown that small hydraulic disturbances may purposefully be injected into the settler in order to analyse the risk for process failure.

Nitrogen Reduction – Volume Demand

1992 ◽  
Vol 25 (4-5) ◽  
pp. 233-240
Author(s):  
T. Palmgren
Keyword(s):  
Suspended Solids ◽  
Age Factors ◽  
Reduction Rate ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Aeration Tank ◽  
Nitrogen Reduction ◽  
Solids Concentration ◽  
Yearly Average ◽  
Nitrification Process

Due to the slow growth of nitrification bacteria at low temperatures, nitrogen reduction normally requires long hydraulic retention time during winter. Important for the nitrification process is the aerated sludge age. Factors influencing the sludge age are aerated volume, mixed liquor suspended solids concentration, organic loading and sludge yield. In an existing plant you cannot easily expand the volume and the load is difficult to decrease. But the suspended solids concentration can be increased by running the biological step with the contact stabilisation process. At the Käppala Association sewage treatment plant in Lidingö just outside Stockholm, one of the six aeration tanks has been reconstructed for full scale nitrogen removal experiments. In this tank the old aeration system has been replaced with rubber membrane diffusers. Further more there are several zones separated by walls in the tank. The tank can thereby be run with great flexibility. By running it with the contact stabilisation process, the sludge age has been improved by a factor between 1.5 and 2 and thereby it succeeds in keeping the nitrification bacteria in the system even during snow melting. At temperatures of about 9 °C and hydraulic retention times of less than 3 hours in the contact zone there has been a nitrification degree of up to 50 to 60 %. The experiment was conducted with a stabilisation zone of up to half the total volume of the aeration tank. The main purpose for the experiments during the winter seasons was to improve nitrification. Keeping the nitrifiers in the system had been a crucial problem during previous years. When the nitrifiers were lost with an increased flow and decreased temperature the nitrification process didn't restart until the temperature was increased and the load decreased. Usually this didn't occur until the middle of the summer meaning a loss of nitrification for up to six months. In Sweden there is a goal set for 50 % nitrogen reduction for the plants in the Stockholm region. At Käppala we manage to keep 60 to 70 % nitrogen reduction during the warm season, that is from July to December. If we can keep up the nitrification the whole year we can achieve 50 % as a yearly average under normal conditions even though we can't keep the nitrogen reduction rate as high during the cold season.

Treatment of tunnel wash water and implications for its disposal

2014 ◽  
Vol 69 (10) ◽  
pp. 2029-2035 ◽  
Author(s):  
M. Hallberg ◽  
G. Renman ◽  
L. Byman ◽  
G. Svenstam ◽  
M. Norling
Keyword(s):  
Traffic Safety ◽  
Urban Areas ◽  
Suspended Solids ◽  
Treatment Plant ◽  
Particulate Material ◽  
Wash Water ◽  
Polluted Water ◽  
Solids Concentration ◽  
Low Concentrations ◽  
Road Tunnels

The use of road tunnels in urban areas creates water pollution problems, since the tunnels must be frequently cleaned for traffic safety reasons. The washing generates extensive volumes of highly polluted water, for example, more than fivefold higher concentrations of suspended solids compared to highway runoff. The pollutants in the wash water have an affinity for particulate material, so sedimentation should be a viable treatment option. In this study, 12 in situ sedimentation trials were carried out on tunnel wash water, with and without addition of chemical flocculent. Initial suspended solids concentration ranged from 804 to 9,690 mg/L. With sedimentation times of less than 24 hours and use of a chemical flocculent, it was possible to reach low concentrations of suspended solids (<15 mg/L), PAH (<0.1 μg/L), As (<1.0 μg/L), Cd (<0.05 μg/L), Hg (<0.02 μg/L), Fe (<200 μg/L), Ni (<8 μg/L), Pb (<0.5 μg/L), Zn (<60 μg/L) and Cr (<8 μg/L). Acute Microtox® toxicity, mainly attributed to detergents used for the tunnel wash, decreased significantly at low suspended solids concentrations after sedimentation using a flocculent. The tunnel wash water did not inhibit nitrification. The treated water should be suitable for discharge into recipient waters or a wastewater treatment plant.

The Infuence of the Depth of the Secondary Sedimentation Tanks on the Sedimentation Efficiency at Bromma Sewage Treatment Plant

1988 ◽  
Vol 20 (4-5) ◽  
pp. 143-152 ◽  
Author(s):  
M. Tendaj-Xavier ◽  
J. Hultgren
Keyword(s):  
Activated Sludge ◽  
Suspended Solids ◽  
Ferrous Sulphate ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Design Flow ◽  
Activated Sludge Process ◽  
Solids Concentration ◽  
Rapid Flow

Bromma sewage treatment plant is the second largest plant in Stockholm with a design flow of 160,000 m3/d. The wastewater is treated mechanically, chemically by pre-precipitation with ferrous sulphate, and biologically by the activated sludge process. The requirements for the plant are 8 mg BOD7/l, 0.4 mg P/l and 2 mg NH4+-N/l. The requirement for ammonia refers to the period July-October. In order to meet those rather stringent requirements, the biological step was expanded 3 years ago with 6 new sedimentation tanks. The 6 new tanks have the same area as the 6 old ones but they have only a depth of 3.7 m compared with the depth of the old tanks, 5.7 m. Experience from the first years of operation of the new tanks is that these tanks are more sensitive and less efficient than the older ones. It seems that the effluent suspended solids concentration from the old tanks is less influenced by rapid flow variations than the concentration in the effluent from the new secondary sedimentation tanks. During the nitrification period denitrification takes place to some degree in the secondary sedimentation tanks. This may cause loss of solids and it has been observed that the deeper old tanks usually produce an effluent of better quality and seem to be less influenced by denitrification than the new ones.

Increased performance of secondary clarifiers using dynamic distribution of minimum return sludge rates

2009 ◽  
Vol 60 (9) ◽  
pp. 2439-2445 ◽  
Author(s):  
A. Lynggaard-Jensen ◽  
P. Andreasen ◽  
F. Husum ◽  
M. Nygaard ◽  
J. Kaltoft ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Suspended Solids ◽  
Considerable Increase ◽  
Wastewater Treatment Plants ◽  
Treatment Plant ◽  
Total Flow ◽  
Equal Distribution ◽  
Solids Concentration ◽  
Hydraulic Load ◽  
And Control

Most wastewater treatment plants have several secondary clarifiers or even more sets of clarifiers including several secondary clarifiers, and in practice it is a well known problem that equal distribution of the load to the single clarifier (or set of clarifiers) is very difficult—not to say impossible—to obtain. If the problem is neglected, quite a big percentage of the total clarifier capacity—measured as the max. allowed hydraulic load—can be lost. Further, return sludge rates are seldom controlled by any other means than as a (typically too high) percentage of the inlet to the wastewater treatment plant—giving a varying and too low suspended solids concentration in the return sludge, which again can lead to an unnecessary use of polymer in the pre-dewatering of the surplus sludge taken from the return sludge. A control of the return sludge rate divided into two parts - control of the total return sludge flow and control of how the total flow shall be distributed between the secondary clarifiers - is able to solve the mentioned problems. Finally, as shall be demonstrated on full scale wastewater treatment plants, a considerable increase of the hydraulic capacity of the treatment plants can be obtained.

Estimation of suspended solids concentrations in activated sludge settling tanks

1997 ◽  
Vol 35 (8) ◽  
pp. 127-135 ◽  
Author(s):  
Youngchul Kim ◽  
Wesley O. Pipes ◽  
Paul-Gene Chung
Keyword(s):  
Activated Sludge ◽  
Suspended Solids ◽  
Marked Effect ◽  
Treatment Plant ◽  
Accurate Method ◽  
Volume Index ◽  
Sludge Volume Index ◽  
Solids Concentration ◽  
Exponential Decrease ◽  
Sludge Settling

This is a report of a field study based on data from an activated sludge process in a wastewater treatment plant in Chester, Pennsylvania, USA. The objective was to develop an accurate method for estimation of the average suspended solids concentration (SSB) of the layer of sludge in the settling tanks (the “sludge blanket”). Plant operators estimated SSB by averaging the mixed liquor suspended solids (Sm) and the return sludge suspended solids (Su) concentrations. Measurement of SSB showed that averaging Sm and Su frequently overestimated SSB by a large amount. A different relationship between SSB and parameters which are normally measured for operational purposes was developed. The parameters are Su, the overflow rates and data from the sludge volume index (SVI) measurement. It was found that an increasing overflow rate will result in an exponential decrease in the ratio of SSB to Su. Also, the SVI has a marked effect on the ratio of SSB to Su and thus on the amount of suspended solids which can be stored in the settling tanks. The proposed estimation equation was found to be statistically superior to estimation by averaging the Sm and Su.

The use of dynamic BNR and two-dimensional clarifier modelling to investigate nitrogen removal at Eastern Treatment Plant, Melbourne, Australia

1999 ◽  
Vol 39 (6) ◽  
pp. 89-96
Author(s):  
J. R. Messenger ◽  
J. C. Smith ◽  
M. J. Tetreault ◽  
C. Vitasovic ◽  
S. Zhou ◽  
...  
Keyword(s):  
Transfer Rate ◽  
Suspended Solids ◽  
Oxygen Transfer Rate ◽  
Treatment Plant ◽  
Aeration Tank ◽  
Two Dimensional ◽  
Solids Loading ◽  
Solids Concentration ◽  
The Impact ◽  
Denitrification Process

The use of process and two-dimensional clarifier modelling to investigate the implications of upgrading Melbourne Water's Eastern Treatment Plant to a nitrification/denitrification process is discussed. Results indicate that the existing clarification capacity is sufficient for the increased solids loading arising from operation at a nitrifying sludge age but that the existing diffuser system may need to be replaced in order to achieve the required oxygen transfer rate. The impact of step feeding into unaerated zones to reduce the aeration tank suspended solids concentration and to achieve denitrification is discussed and the installation of baffles to improve the performance of peripheral feed clarifiers is suggested.

Validation and implementation of model based control strategies at an industrial wastewater treatment plant

2001 ◽  
Vol 44 (2-3) ◽  
pp. 145-154 ◽  
Author(s):  
D. Demey ◽  
B. Vanderhaegen ◽  
H. Vanhooren ◽  
J. Liessens ◽  
L. Van Eyck ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plant ◽  
Industrial Wastewater ◽  
Dynamic Models ◽  
Control Strategies ◽  
Treatment Plant ◽  
Practical Implementation ◽  
Industrial Wastewater Treatment ◽  
Model Based ◽  
On Line

In this paper, the practical implementation and validation of advanced control strategies, designed using model based techniques, at an industrial wastewater treatment plant is demonstrated. The plant under study is treating the wastewater of a large pharmaceutical production facility. The process characteristics of the wastewater treatment were quantified by means of tracer tests, intensive measurement campaigns and the use of on-line sensors. In parallel, a dynamical model of the complete wastewater plant was developed according to the specific kinetic characteristics of the sludge and the highly varying composition of the industrial wastewater. Based on real-time data and dynamic models, control strategies for the equalisation system, the polymer dosing and phosphorus addition were established. The control strategies are being integrated in the existing SCADA system combining traditional PLC technology with robust PC based control calculations. The use of intelligent control in wastewater treatment offers a wide spectrum of possibilities to upgrade existing plants, to increase the capacity of the plant and to eliminate peaks. This can result in a more stable and secure overall performance and, finally, in cost savings. The use of on-line sensors has a potential not only for monitoring concentrations, but also for manipulating flows and concentrations. This way the performance of the plant can be secured.

Prediction of Suspended Solids in Urban Sewers by Transfer Function Model

1994 ◽  
Vol 29 (1-2) ◽  
pp. 171-179 ◽  
Author(s):  
J. W. Delleur ◽  
Y. Gyasi-Agyei
Keyword(s):  
Transfer Function ◽  
Suspended Solids ◽  
Remote Access ◽  
Transfer Function Model ◽  
Concentration Data ◽  
Function Model ◽  
Main Trunk ◽  
Solids Concentration ◽  
On Line

There is increasing concern about the sediments transported in urban storm sewers. Progress has been made on the measurement of suspended solids, and telemetry systems have been installed that permit remote access to flow, temperature and suspended solids concentration data. Using observations obtained in the main trunk sewer in Brussels, Belgium, a transfer function model for the prediction of suspended load concentration from temperature and discharge measurements was developed. This model is based on the transfer function methodology developed by Box and Jenkins. It is shown that the transfer function model correctly tracks the suspended solids observations and makes reasonable forecasts. It provides a valid alternative for the determination of suspended solids in urban sewers from discharge and water temperature observations which are more easily measurable on line than suspended solids.

On-line determination of sludge settling velocity for flux-based real-time control of secondary clarifiers

2006 ◽  
Vol 54 (11-12) ◽  
pp. 249-256 ◽  
Author(s):  
A. Lynggaard-Jensen ◽  
L. Lading
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plant ◽  
Control Algorithm ◽  
Suspended Solids ◽  
Settling Velocity ◽  
Treatment Plant ◽  
On Line ◽  
Sludge Settling ◽  
Settling Characteristics

The state diagram for operation of secondary clarifiers is used to design a control algorithm for the return sludge pumping and determination of the actual hydraulic capacity of the biological step of a wastewater treatment plant. On-line input for the control algorithm is derived from a sludge volume sensor and a suspended solids sensor in the form of software sensors giving values for the sludge settling characteristics – settling velocity, sludge volume index, initial settling velocity and the exponent in the Vesilind equation – allowing the control to accommodate the ever changing settling characteristics and thereby keep the suspended solids flux in the clarifiers in balance for both dry weather flows and during rain events. The control algorithm has been implemented, tested and set into normal operation on a full scale wastewater treatment plant.

Field Verification of On-Line Instrumentation at a Municipal Wastewater Treatment Plant

1987 ◽  
Vol 19 (3-4) ◽  
pp. 669-680 ◽  
Author(s):  
Gordon W. Speirs ◽  
Robert D. Hill
Keyword(s):  
Wastewater Treatment ◽  
Suspended Solids ◽  
Municipal Wastewater ◽  
Wastewater Treatment Plants ◽  
Treatment Plant ◽  
Municipal Wastewater Treatment ◽  
Flow Rates ◽  
Control Loops ◽  
Field Verification ◽  
On Line

As part of a full-scale project to demonstrate the advantages of using automated process control in wastewater treatment plants, on-line sensors used in various control loops were calibrated and/or verified during control system commissioning and startup. The on-line measurements included liquid flow rates, air flow rates, suspended solids concentrations, and dissolved oxygen concentrations. The methods used to confirm instrument performance are presented along with results that show that several instruments were found to operate outside the manufacturers' written specifications. In addition, on-line methods which can help determine when recalibrations are required, and thereby help to reduce maintenance costs and ensure reliability, are also presented.

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