Comparative performance of an electrocoagulation/flotation system with chemical coagulation/dissolved air flotation: a pilot-scale trial

2002 ◽  
Vol 2 (1) ◽  
pp. 289-297 ◽  
Author(s):  
J.Q. Jiang ◽  
N.J.D. Graham ◽  
C.M. André ◽  
G.H. Kelsall ◽  
N.P. Brandon ◽  
...  
Keyword(s):  
Pilot Plant ◽  
Dose Range ◽  
Pilot Scale ◽  
Organic Content ◽  
Comparative Performance ◽  
Dissolved Air Flotation ◽  
Treatment Performance ◽  
Running Cost ◽  
Air Flotation ◽  
Dissolved Air

An electrocoagulation-flotation (ECF) pilot plant was designed, built and operated to evaluate its performance in comparison with a pilot scale conventional dissolved air flotation (DAF) system for treating lowland surface water in the UK. Treatment performance was assessed principally in terms of changes in dissolved organic content (DOC) and system running cost. On average, the decrease in DOC, UV-254 and colour was 10-15% with ECF at pH ca. 7.8 and current densities of 2-5 A m-2 (equivalent dose range of 1-5 gAl(III) m-3). Acidification of the influent (pH 8.4 down to 7.5) decreased only DOC and increased apparent current efficiencies for Al dissolution above unity. Passivation of the aluminium electrodes by Al(III) (hydrous) oxides caused difficulties in maintaining a steady dissolved Al(III) concentration and also increased specific electrical energy consumptions. Treated water quality with ECF was as good as that with DAF at lower equivalent coagulant doses (< 5 gAl(III) m-3), but was less so at higher coagulant doses. The pilot-plant DAF system appeared to be more expensive in terms of its running cost for the conditions used; the cost ratios of DAF to ECF were between 3:1 and 5:1, respectively, for an equivalent treatment performance.

Optimising dissolved air flotation/filtration treatment of algae-laden lagoon effluent using surface charge: a Bolivar treatment plant case study

2012 ◽  
Vol 66 (8) ◽  
pp. 1684-1690 ◽  
Author(s):  
Russell Yap ◽  
Michael Holmes ◽  
William Peirson ◽  
Michael Whittaker ◽  
Richard Stuetz ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Surface Charge ◽  
Wastewater Treatment Plant ◽  
Pilot Plant ◽  
Treatment Plant ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
A Charge ◽  
Dissolved Air

Dissolved air flotation (DAF) incorporating filtration (DAFF) is used at the Bolivar wastewater treatment plant (WWTP) to polish lagoon effluent for reuse. Elevated algal populations are frequently experienced and can lead to increased coagulant requirements and process control issues. Streaming current detectors (SCDs) and a charge demand analyser (CDA) were used to monitor the full-scale plant. This was followed by an optimisation study using a pilot plant with a CDA. It was found that the normal operational charge demand range for DAF at Bolivar was between −46 and −40 μeq L−1. Decreasing the pH of coagulation reduced coagulant consumption and facilitated more sensitive CDA responses to changes in alum dose.

High-rate dissolved air flotation for water treatment

2001 ◽  
Vol 43 (8) ◽  
pp. 43-49 ◽  
Author(s):  
M. A. P. Raeli ◽  
M. Marchetto
Keyword(s):  
Reynolds Numbers ◽  
Pilot Scale ◽  
Water Velocity ◽  
High Rate ◽  
Raw Water ◽  
Parallel Plates ◽  
Dissolved Air Flotation ◽  
Removal Efficiencies ◽  
Air Flotation ◽  
Dissolved Air

This paper presents the results of an experimental investigation about the performance of a horizontal flow high-rate pilot scale Dissolved Air Flotation (HRDAF) unit containing inclined parallel plates for treating a coloured and low turbidity raw water. Experiments were performed with the DAF unit in order to verify the influence on flotation of : (i) the water velocity (Vh) between the plates, in the range 18 to 96.5 cm.min−1 with corresponding Reynolds numbers between 240 and 1060; (ii) the supplied air (S*) value ranging from 2.2 to 8.5 g of air/m3 of water ; (iii) the angle of the plates (60° or 70°). The best pilot plant operational condition was obtained applying only 4.0 g/m3 (S*) with Vh around 18 cm.min−1 for treatment of water coagulated with a Al2(SO4)3 dosage of 40 mg.l−1. In these conditions, the unit presented very good removal efficiencies of colour (90%, residual of 10 uC), turbidity (88%, residual of 0.8 NTU ) and TSS (94%, residual of 1.8 mg.l−1). Furthermore, the unit could operate at higher Vh values up to 76 cm.min−1 and still present good results. The DAF unit thus behaved as a high rate unit presenting good performance with low air requirement.

Post-Treatment of Effluents from Anaerobic Reactor Treating Domestic Sewage by Dissolved-Air Flotation

1999 ◽  
Vol 40 (8) ◽  
pp. 137-143 ◽  
Author(s):  
R. G. Penetra ◽  
M. A. P. Reali ◽  
E. Foresti ◽  
J. R. Campos
Keyword(s):  
Scale Up ◽  
Oxygen Demand ◽  
Pilot Scale ◽  
Domestic Sewage ◽  
Uasb Reactor ◽  
Dissolved Air Flotation ◽  
Operational Conditions ◽  
Apparent Color ◽  
Air Flotation ◽  
Dissolved Air

This paper presents the results of a study performed with a lab-scale dissolved-air flotation (LSDAF) unit fed with previously coagulated effluent from a pilot scale up-flow anerobic sludge blanket (UASB) reactor treating domestic sewage. Physical operational conditions for coagulation (rapid mix) and flocculation/flotation were maintained constant. Chemical (FeCl3) dosages ranged from 30 to 110 mg.l−1. The effect of pH was also verified in the range of 5.1 to 7.6 for each dosage. Best results were achieved for 65 mg.l−1 of FeCl3 and pH values between 5.3 and 6.1. For these conditions, the removal efficiencies obtained in the LSDAF unit were: between 87% and 91% for chemical oxygen demand (COD), between 95% and 96% for total phosphate (TP), 94% for total suspended solids (TSS), between 96% and 97% for turbidity (TU), between 90% and 93% for apparent color (AC) and more than 96% for sulfide (S). For the UASB-DAF system, global efficiencies would be around 98% for COD, 98% for TP, 98.4% for TSS, 99.3% for TU and 98% for AC. The stripped gases treatment is desirable.

scholarly journals Automation and Control of a Dissolved Air Flotation Pilot Plant

2017 ◽  
Vol 50 (1) ◽  
pp. 3911-3916 ◽  
Author(s):  
Rodolpho R. Fonseca ◽  
José P. Thompson, Jr. ◽  
Ivan C. Franco ◽  
Flávio V. da Silva
Keyword(s):  
Pilot Plant ◽  
Dissolved Air Flotation ◽  
Automation And Control ◽  
Air Flotation ◽  
And Control ◽  
Dissolved Air

The feasibility of electro-osmotic belt filter dewatering technology at pilot scale

2000 ◽  
Vol 41 (8) ◽  
pp. 137-144 ◽  
Author(s):  
H. G. Snyman ◽  
P. Forssman ◽  
A. Kafaar ◽  
M. Smollen
Keyword(s):  
Applied Voltage ◽  
Feed Rate ◽  
Cost Effective ◽  
Pilot Scale ◽  
Filter Press ◽  
Digested Sludge ◽  
Dissolved Air Flotation ◽  
Anaerobically Digested Sludge ◽  
Air Flotation ◽  
Dissolved Air

Sewage sludge is typically dewatered using drying beds, belt filter presses or centrifuges. Mechanical dewatering of sludge is costly in terms of capital and running costs, especially the flocculent. In an attempt to address the need for more cost-effective dewatering technologies, electro-osmotic belt filtering was developed by Smollen and Kafaar in 1995. Themechanical equipment resembles a belt filter press but the belts are stainless steel, woven belts, which act as the electrodes. In this study, thefeasibility of the technology was tested at pilot scale using wasteactivated-, anaerobically digested- and dissolved air flotation sludge. The parameters which were investigated includes the applied voltage, polyelectrolyteusage and sludge feed rate. Applied voltage of between 15 and 25 volts increased the dewatering significantly in the waste activated- and anaerobically digested sludge. Applying a voltage in dissolved air flotation sludge could not enhance the efficiency of dewatering, unless stored to de-air. The technology was found as sensitive to polyelectrolyte dosages as belt presses. The performance of the electro-osmotic belt filter was sensitive to feed rate, but performed well with non-thickened waste activated sludge (0.61% solids), resulting in cake solids above 20%.

Effect of Biosurfactant Addition in a Pilot Scale Dissolved Air Flotation System

2014 ◽  
Vol 50 (4) ◽  
pp. 618-625 ◽  
Author(s):  
Fernanda C. Padilha da Rocha e Silva ◽  
Nathália M. Padilha da Rocha e Silva ◽  
Alex Elton de Moura ◽  
Rodrigo Almeida Galdino ◽  
Juliana Moura Luna ◽  
...  
Keyword(s):  
Pilot Scale ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Dissolved Air

Counter-current dissolved air flotation/filtration

1995 ◽  
Vol 31 (3-4) ◽  
pp. 173-178 ◽  
Author(s):  
Andrew Eades ◽  
W. J. Brignall
Keyword(s):  
Water Treatment ◽  
Pilot Plant ◽  
Volume Flow Rate ◽  
Scale Up ◽  
Particulate Material ◽  
Water Utilities ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Counter Current ◽  
Dissolved Air

Thames Water Utilities has developed and patented a Counter-current dissolved air flotation/filtration (COCO-DAFF) process as a compact water treatment system designed to remove particulate material from traditional water sources. In particular it has been developed to overcome operational problems with primary filters caused by seasonal blooms of filter blocking algae such as Melosira sp., Aphanizomenon sp. andAnabaena sp. The process can be run without flotation during periods when algae are not a problem, giving operational cost savings. This process differs from co-current dissolved air flotation in that the recycle water is introduced after the inlet structure, but above the filter media. This generates an even depth bubble blanket in the flotation tank through which all the flocculated water must pass. The advantages are that in moving the recycle inlet away from the flocculated water inlet the potential for floc damage by the recycle is eliminated. Also since the entire sludge blanket is supported by a deep, even, bubble blanket, on de-sludging any fall-out of sludge that occurs near the de-sludging weirs will have to go back down through the process, leading to subsequent re-floating, and a reduced potential for spiking of the floated turbidity. Process validation experiments have been carried out on a 1.4 Ml/d pilot plant based at the Kempton Advanced Water Treatment Centre, London. These tests have identified a required flocculation time of 15 minutes prior to counter-current flotation, and insensitivity to the depth of the air injection below top water level. Dissolved air distribution is achieved using a special high volume flow rate DAF nozzle designed to lower the number of nozzles required per unit area, and to maximise the spread of the bubble cloud for optimum bubble/particle contact. Computational fluid dynamics (CFD) has been used in the scale-up of the pilot plant experience into the first full scale of this design plant to be built, by PWT Projects, at the 200 Ml/d Walton AWTW, for Thames Water Utilities.

Evaluation of dissolved air flotation process for water clarification and sludge thickening

1995 ◽  
Vol 31 (3-4) ◽  
pp. 137-147 ◽  
Author(s):  
Harish Arora ◽  
James R. DeWolfe ◽  
Ramon G. Lee ◽  
Thomas P. Grubb
Keyword(s):  
Pilot Study ◽  
Algal Blooms ◽  
Water Source ◽  
Complete Removal ◽  
Organic Content ◽  
Dissolved Air Flotation ◽  
Flotation Process ◽  
Air Flotation ◽  
Sludge Thickening ◽  
Dissolved Air

Dissolved air flotation was evaluated using pilot and bench tests for water clarification and sludge thickening. A DAF pilot study was conducted on one water source with low turbidity, high color, high organic content and algal blooms. For this water, coagulation with alum, cationic polymer and pH around 6.1 resulted in removal of turbidity, color and algae. THMFP and TOC were removed by approximately 25 and 50 percent, respectively. A river water source was used in another pilot study to identify limits on source water turbidity for the DAF process. Tests conducted with induced high turbidity values resulted in filtered water quality with low turbidity and complete removal of color. TOC was removed by approximately 35 percent, however, inconclusive results were obtained for THMFP removal. Based on these pilot test, DAF is a viable clarification process, especially for source waters with low turbidity (infrequent spikes upto 100 NTU), high algal blooms and high color. Bench-scale DAF assisted sludge thickening resulted in performance similar to gravity thickeners. High recycle ratios (around or greater than 100 percent) were required for effective sludge thickening.

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