Traitement des eaux usées par coagulation-floculation avec recirculation des boues chimiques : Performance générale et stabilité du procédé

2000 ◽  
Vol 27 (4) ◽  
pp. 702-718
Author(s):  
Frédéric Monette ◽  
François G Brière ◽  
Michel Létourneau ◽  
Marc Duchesne ◽  
Robert Hausler
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plant ◽  
Treatment Plant ◽  
Normal Plant ◽  
Plant Operation ◽  
Load Variations ◽  
Sludge Recycling ◽  
The Stability ◽  
Chemical Sludge ◽  
Flocculation Process

Six series of tests were carried out to have a better understanding of the stability and efficiency of a coagulation-flocculation process with chemical sludge recycling. The tests consisted in sequential sludge recycling in 100-L pilot reactors. Other tests were performed to examine the stability following wastewater loading variations. Results showed that stability was reached immediately during the first recycling sequences. Furthermore, to obtain improved results compared with those of a classical coagulation-flocculation process, the flocculant concentration must be increased according to the sludge recycling load. Results also revealed that recycling sludge does not absorb wastewater load variations. Consequently, the implementation of sludge recycling in a wastewater treatment plant would not cause effluent degradation or entail major changes in a normal plant operation routine. The predominant coagulation-flocculation mechanisms that explained the increase in efficiency, in comparison with the classical process, were identified as enmeshment and sweep flocculation. Finally, the recycled sludge produced were conditioned and dewatered in a fashion similar to that of a classical process.Key words: recycling, sludge, preformed flocs, coagulation-flocculation, treatment, wastewater, stability.

Traitement des eaux usées par coagulation-floculation avec recirculation des boues chimiques : Influence des réactifs

2000 ◽  
Vol 27 (4) ◽  
pp. 719-734
Author(s):  
Frédéric Monette ◽  
François G Brière ◽  
Michel Létourneau ◽  
Marc Duchesne ◽  
Robert Hausler
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plant ◽  
Treatment Plant ◽  
Pollutant Removal ◽  
Sludge Recycling ◽  
Chemical Sludge ◽  
Flocculation Process

Three series of tests were carried out at laboratory and pilot levels to examine the functions of reagents (coagulant, flocculant, sludge) involved in a coagulation-flocculation process with chemical sludge recycling. Results showed that the recycled sludge participates favourably in the process. The gains in efficiency are particularely significant for lower coagulant concentrations when flocculant concentration is not limitative. The pollutant removal increases with the sludge recycling load but seems reversible and dependent on coagulant concentration. Results also revealed the advantages of recycling sludge before injecting coagulant. To decrease the total chemical costs at a wastewater treatment plant, the strategy must focus on diminishing the coagulant concentration and increasing the flocculant concentration while maintaining a sufficient recycling sludge load to ensure gains in efficiency.Key words: recycling, sludge, preformed flocs, reagents, coagulation-flocculation, treatment, wastewater.

Traitement des eaux usées par coagulation-floculation avec recirculation des boues chimiques : Évaluation et validation à grande échelle

2000 ◽  
Vol 27 (4) ◽  
pp. 735-753
Author(s):  
Frédéric Monette ◽  
François G Brière ◽  
Michel Létourneau ◽  
Marc Duchesne ◽  
Robert Hausler
Keyword(s):  
Wastewater Treatment ◽  
Treatment Plant ◽  
Water Tank ◽  
Small Particles ◽  
Recycling Process ◽  
Sludge Recycling ◽  
Work Done ◽  
Chemical Sludge ◽  
Flocculation Process

Two sequences of tests were carried out at the Centre d'épuration Rive-Sud wastewater treatment plant (Longueuil, Que.) to evaluate the performances of a coagulation-flocculation process with chemical sludge recycling. The tests consisted in following the evolution of the quality of the treated water when two flowsheets are supplied simultaneously in parallel with the same wastewater, one flowsheet incorporating the sludge recycling process. Results showed that the recycled sludge contributes significantly to water degradation compared with a classical coagulation-flocculation system. These results do not corroborate the previous work done by Monette et al. (F. Monette et al. Canadian Journal of Civil Engineering, 27: 702-718, 719-734, 2000). The problems observed are explained by inadequate plant installations for sludge recycling. High coagulant concentrations also limit the gains in efficiency associated with recyling. The process reacts rapidly to wastewater loading and reagent modifications. The recycled sludge conditioning is slightly more difficult because of the small particles created by recycling pump turbulence. Finally, turbidity measurements in the flocculator water tank could be used as an excellent indicator for sludge recycling load estimation.Key words: recycling, sludge, coagulation-flocculation, treatment, wastewater, full scale.

Research on Variable Metric Chaos Optimization Modeling for the Prediction of Wastewater Treatment Plants Performance

2012 ◽  
Vol 428 ◽  
pp. 169-175
Author(s):  
Guo Kai Fu ◽  
Yi Yue Hu ◽  
Zhi Zhang
Keyword(s):  
Neural Network ◽  
Wastewater Treatment ◽  
Wastewater Treatment Plant ◽  
Wastewater Treatment Plants ◽  
Treatment Plant ◽  
Treatment System ◽  
Variable Metric ◽  
Chaos Optimization ◽  
Actual Operation ◽  
The Stability

A reliable model for any wastewater treatment plant is essential in order to provide a tool for predicting its performance and to form a basis for controlling the operation of the process. This would minimize the operation costs and assess the stability of environmental balance. For the multi-variable, uncertainty, non-linear characteristics of the wastewater treatment system, a variable metric chaos optimization neural network (VMCNW) prediction model is established standing on the actual operation data in the wasterwater treatment system. The model overcomes several disadvantages of the conventional BP neural network. Namely:slow convergence, low accuracy and difficulty in finding the global optimum.The results of model calculation show that the predicted value can better match measured value,played a effect of simulating and predicting and be able to optimize the operation status. The establishment of the predicting model provide a simple and practical way for the operation and management in wastewater treatment plant,and have good research and engineering practical value.

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