scholarly journals Solid–liquid Separation of Activated Sludge by Flotation Using Microporous Ceramic Diffuser

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
S. W. Hong ◽  
C. Park ◽  
T. H. Chung ◽  
Y. S. Choi
Keyword(s):  
Activated Sludge ◽  
Porous Ceramic ◽  
Operating Cost ◽  
Experimental Results ◽  
Solid Loading ◽  
Dissolved Air Flotation ◽  
Pressure Water ◽  
Solid Liquid ◽  
Solid Liquid Separation ◽  
Dissolved Air

Dissolved air flotation (DAF) is the most widely used to separate particles from liquid. However, the main disadvantage of DAF systems is the increased operating cost due to the energy requirements for the high pressure water recycling and air compressing. In this study, alumina–based porous ceramic diffusers which can produce microbubbles at low pressure regions have been developed in order to separate and thicken activated sludge solids. No bubble was generated at lower pressure (< 0.2 bar), whereas too large bubbles were generated at higher than 2.0 bar. At 1.8 bar, more than 70% of the bubbles had a diameter ranged from 20 to 60 μm. According the experimental results, the separation and thickening efficiency was mainly dependant on solid loading rate (SLR) and air to solid (A/S) ratio. When the sludge with a concentration of exceeding 5,000 mg/L was continuously fed into the flotation tank, the thickened concentration was measured to be higher than 20,000 mg/L, while SS concentrations in the clarified effluent were ranged from 5 to 10 mg/L. The experimental results revealed that the use of microporous ceramic diffusers could provide an economical, easy and reliable means of separating suspended solids (e.g., biological flocs) from liquid.

Enhancement of microbubble generation in a pressurized dissolution process by packing the nozzle with porous ceramics

2012 ◽  
Vol 65 (1) ◽  
pp. 69-75 ◽  
Author(s):  
Hiroshi Yamashita ◽  
Hideki Aoyagi ◽  
Hisato Minagawa
Keyword(s):  
Activated Sludge ◽  
Suspended Solids ◽  
Porous Ceramic ◽  
Operating Cost ◽  
Porous Ceramics ◽  
Packing Material ◽  
Dissolved Air Flotation ◽  
Dissolution Method ◽  
Main Disadvantage ◽  
Dissolved Air

The pressurized dissolution method is often used for microbubble generation. However, the main disadvantage of this method is that a large amount of energy (more than 0.3 MPa) is required to generate many microbubbles, each of which have a diameter of several dozen μm. To overcome this problem, we investigated the effectiveness of porous ceramic when used as the packing material in the pressurized dissolution method. The results showed that when compared with the control (no porous ceramics), use of porous ceramics resulted in a 39% increase in the number of microbubbles. Furthermore, when this system was used for the flotation separation of artificial suspended solids and activated sludge, the level of separation achieved with porous ceramics at 0.15 MPa was the same as that achieved using no porous ceramics at 0.25 MPa. It was estimated that the use of porous ceramics led to a 40% reduction in the energy required for the dissolved air flotation, with subsequent decreases in the operating cost.

Solid/liquid separation behavior of alum and polyaluminium chloride coagulation flocs

2006 ◽  
Vol 6 (1) ◽  
pp. 87-93 ◽  
Author(s):  
B. Gorczyca ◽  
G. Zhang
Keyword(s):  
Liquid Separation ◽  
Dissolved Air Flotation ◽  
Gravity Settling ◽  
Mean Size ◽  
Air Flotation ◽  
Solid Liquid ◽  
Solid Liquid Separation ◽  
Separation Behavior ◽  
Polyaluminium Chloride ◽  
Dissolved Air

Properties of alum and polyaluminium chloride (PACl) flocs were analyzed in order to explain solid/liquid separation behavior of these aggregates in dissolved air flotation and gravity settling. PACl flocs settle better and are less sensitive to changes in water temperature than alum flocs. Therefore, PACl flocs may be more suited for gravity separation, especially in cold waters, and alum flocs may be preferred for flotation. At an optimum coagulant dose for dissolved air flotation the logarithmic mean size of alum flocs was close to the size of the air bubbles (30 μm) and the proportion of flocs smaller than 20 μm was about 30.5%.

Toxic metals removal from dilute solutions by biosorptive flotation

1995 ◽  
Vol 32 (9-10) ◽  
pp. 211-220
Author(s):  
A. I. Zouboulis ◽  
P. Solari ◽  
K. A. Matis ◽  
G. A. Stalidis
Keyword(s):  
Toxic Metal ◽  
Separation Process ◽  
Dissolved Air Flotation ◽  
Metals Removal ◽  
Dilute Aqueous Solutions ◽  
Flotation Technique ◽  
Solid Liquid ◽  
Solid Liquid Separation ◽  
Digested Sewage Sludge ◽  
Dissolved Air

Toxic metal ions (cadmium, nickel and zinc), considered as priority pollutants, were removed from dilute aqueous solutions by sorption onto non-living (sterilized) anaerobically digested sewage sludge. The desorption of cadmium from metal-laden sludge was also examined. Flotation was subsequently applied as an effective solid/liquid separation process. The dissolved-air flotation technique was applied for the generation of fine bubbles and, in parallel, electrokinetic measurements were carried out. Promising results were succeeded from the combined process of biosorption/flotation (termed biosorptive flotation).

Flotation efficiency of activated sludge flocs using population balance model in dissolved air flotation

2006 ◽  
Vol 23 (2) ◽  
pp. 271-278 ◽  
Author(s):  
Heung-Joe Jung ◽  
Jae-Wook Lee ◽  
Do-Young Choi ◽  
Seong-Jin Kim ◽  
Dong-Heui Kwak
Keyword(s):  
Activated Sludge ◽  
Population Balance ◽  
Balance Model ◽  
Population Balance Model ◽  
Dissolved Air Flotation ◽  
Sludge Flocs ◽  
Air Flotation ◽  
Dissolved Air

Nocardia effects in waste activated sludge

1998 ◽  
Vol 38 (2) ◽  
pp. 49-54 ◽  
Author(s):  
Krishna R. Pagilla ◽  
David Jenkins ◽  
Wendell Kido
Keyword(s):  
Activated Sludge ◽  
Foam Stability ◽  
Anaerobic Digester ◽  
Waste Activated Sludge ◽  
Dissolved Air Flotation ◽  
Anaerobic Digesters ◽  
Primary Sludge ◽  
Mixed Liquor ◽  
Dissolved Air ◽  
Batch Foaming

Two effects of Nocardia in waste activated sludge (WAS) were investigated: (i) the influence of WAS in the solids treatment recycle streams on Nocardia persistence in the activated sludge, and (ii) the effect of Nocardia in WAS on anaerobic digester foaming. About 4% of the Nocardia present in the mixed liquor was due to seeding from the WAS solids in the dissolved air flotation thickener recycle stream recycle. Nocardia filaments in WAS at levels of between 104 to 106 intersections/g VSS resulted in Nocardia levels of approximately 104 to 105 intersections/g VSS in anaerobic digesters that treated both WAS and primary sludge. The effect of disinfecting these Nocardia filaments in the WAS with Cl2 was investigated at Cl2 dose ranges of 20-60 mg Cl2/l WAS and 100-200 mg Cl2/l WAS on a lab scale using batch foaming tests to assess success. Chlorination with 20 - 60 mg Cl2/l WAS approximately doubled both sludge foaming potential and foam stability. At Cl2 doses of 100-200 mg Cl2/l WAS, foaming potential was increased almost 10-fold, and foam stability was increased by 2.5 times. These results indicate that chlorination of WAS feed to an anaerobic digester for inactivation of Nocardia should not be practiced.

Upgrading performance of an activated sludge process through addition of talqueous powder

1996 ◽  
Vol 34 (5-6) ◽  
pp. 75-83 ◽  
Author(s):  
J. Cantet ◽  
E. Paul ◽  
F. Clauss
Keyword(s):  
Activated Sludge ◽  
Control Unit ◽  
Physical Structure ◽  
Experimental Models ◽  
Volume Index ◽  
Liquid Separation ◽  
Floc Structure ◽  
Rapid Effect ◽  
Solid Liquid ◽  
Solid Liquid Separation

This study is intended to induce better performance of existing activated sludge wastewater plants without modifying the physical structure of the plant. The process consists in injecting a specific mineral powder into the aeration stage with two precise purposes: firstly to improve floc structure and thus facilitate solid/liquid separation in the clarifier, and secondly to reduce nitrogenous pollution. By means of two experimental models the indisputable and rapid effect of talc/chlorite blend on the solid/liquid separation was established (with a sludge volume index improvement by a factor of 2 to 3 within a few days) compared with a control unit. The increase in nitrification capacity of the system is also clearly shown with nitrification yields being increased by 30%. These results lead us to believe that it is possible to use this process of enhanced nitrification for running a plant reliably without dysfunctioning. Problems linked to hydraulic or biological excess loading can be solved this way. Moreover, the addition of talqueous powder improves sludge dewaterability.

Sign in / Sign up

Export Citation Format

Share Document