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%.

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.

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

scholarly journals Evaluating Pre- and Post-Coagulation Configuration of Dissolved Air Flotation Using Response Surface Methodology

Processes ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 383 ◽  
Author(s):  
Emmanuel Kweinor Tetteh ◽  
Sudesh Rathilal
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Cost Effective ◽  
Post Treatment ◽  
Oil Refinery ◽  
Optimum Conditions ◽  
Dissolved Air Flotation ◽  
Air Flotation ◽  
Pre Treatment ◽  
Dissolved Air

The effects of coagulation-dissolved air flotation (DAF) process configuration was studied on oil refinery wastewater. The configuration was done in two ways: acid-coagulation-DAF (pre-treatment) and acid-DAF-coagulation (post-treatment). Two different cationic and polymeric organic coagulants were employed in this study to compare their treatability performance with the two aforementioned configurations. All the coagulants applied before the DAF were found to be effective, with over 85% more contaminant removal efficiency than their post-treatment. Alum, being the most cost-effective coagulant, was then employed with response surface methodology (RSM) to obtain the optimum conditions. These include a coagulant dosage of 100 mg/L, air saturator pressure of 375 kPa and air–water ratio of 10% vol/vol corresponding to a desirability of 92% for the removal of oily pollutants from a local South Africa oil refinery’s wastewater. With the response quadratic models that were developed, the optimum conditions were tested experimentally, which were consistent with the models predicted results at a 95% confidence level.

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.

Evaluation of flow hydrodynamics in a pilot-scale dissolved air flotation tank: a comparison between CFD and experimental measurements

2015 ◽  
Vol 72 (7) ◽  
pp. 1111-1118 ◽  
Author(s):  
B. Lakghomi ◽  
Y. Lawryshyn ◽  
R. Hofmann
Keyword(s):  
Pilot Scale ◽  
Solid Particles ◽  
Cfd Model ◽  
Two Phase ◽  
Dissolved Air Flotation ◽  
Cfd Models ◽  
Three Phase ◽  
Computational Fluid Dynamics Cfd ◽  
Air Flotation ◽  
Dissolved Air

Computational fluid dynamics (CFD) models of dissolved air flotation (DAF) have shown formation of stratified flow (back and forth horizontal flow layers at the top of the separation zone) and its impact on improved DAF efficiency. However, there has been a lack of experimental validation of CFD predictions, especially in the presence of solid particles. In this work, for the first time, both two-phase (air–water) and three-phase (air–water–solid particles) CFD models were evaluated at pilot scale using measurements of residence time distribution, bubble layer position and bubble–particle contact efficiency. The pilot-scale results confirmed the accuracy of the CFD model for both two-phase and three-phase flows, but showed that the accuracy of the three-phase CFD model would partly depend on the estimation of bubble–particle attachment efficiency.

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