Modeling and optimizing of coagulation-flocculation process by response surface methodology for rehabilitation of tannery wastewater treatment plant

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.

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Optimization of coagulation–flocculation process for papermaking-reconstituted tobacco slice wastewater treatment using response surface methodology

Journal of Industrial and Engineering Chemistry ◽

10.1016/j.jiec.2013.04.033 ◽

2014 ◽

Vol 20 (2) ◽

pp. 391-396 ◽

Cited By ~ 40

Author(s):

Yufeng Wang ◽

Kefu Chen ◽

Lihuan Mo ◽

Jun Li ◽

Jun Xu

Keyword(s):

Response Surface Methodology ◽

Wastewater Treatment ◽

Response Surface ◽

Flocculation Process

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

Canadian Journal of Civil Engineering ◽

10.1139/l00-047 ◽

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.

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