DAF Dissolved Air Flotation how to get Length ,Height and Width after input parameters 1

[sebastianS]

Hi folks,


I need help and it will be great from your experience to help me, I appreciate that.

I work on design DAF Dissolved Air Flotation product. I have input parameters and with input parameters I calculated A/S ratio, Air solubility, Solid loading ratio, Hydraulic loading ratio etc, the next step when I know calculations and what is required DAF plate area , I need to find what will be Length, Height and Width for my DAF plate pack (Dissolved air Flotation).

How do I find that informations ?
Also for Height of the DAF - is it standard height required for the air bubble motion upward.

King Regards,

Andreas

 

[sebastianS]

when you mention : linear vertical velocity of 10 m/hr - is that refers to water rise rates - which is 10 m/hr

 

[ashtree]

Yes

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[sebastianS]

Hi ashtree and other guys ,

I put this parameters from previous your suggestion here , and here is my DAF -Sketch.

Thank you ashtree for powerpoint, I am trying to understand all, and here is something what I need to know exsctly :

From Powerpoint you attached file, do I need calculate
this Contact zone or is that desired length.
Also for my DAF, I want DAF design without bottom skimmer or Auger.
Example of DAF is like this one : Huber-Siltb

Here on Picture My_DAF_ dimensions are : Length 4.5 m, Width 1.1 m Height 3.33 m

for this dimension do I need put also dimension Length for separation zone as on this picture Contact Zone is showed from Powerpoint you gave me.

All technologies inside for DAF I don't need that ,as I only need to design this DAF.

Please provide me with information for this Contact zone - : is that desired length ?

 

[ashtree]

You typically only need a bottom auger if there is a reasonable amount of heavy solids that settle out in addition to whatever comes up with the float. Given that you have chosen a hopper bottom even without the auger you may still require some sort of drain or desludging valve.

You have chosen a high recycle rate so your contact zone will need to be bigger than normal or your velocities and detention times lower.
With a flow of 50m3/hr 100m/hr contact zone vertical velocity you will need 0.5m2 of contact zone area or half that if you want 200m/hr.
Use a detention time of 1-2 minutes to work out the volume.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[sebastianS]

There will not be heavy solids

detention time : I don't know what is,
water rise rates : I can say it is 10 m/hr
but I don't know exactly how do I measure all this parameters, or get direct from commisioning engineer as they will not say (of course)

I am now on site this days .
How do I measure water rise rates, could I do that by stopwatch from start machine , /something like that.

As I am there this days,

they use

https://www.toroequipment.com/products/dissolved-air-flotation-anaconda-daf/

- FRC 10 Toro DAF

but material is different (our material - clean water , with low solid concentration, low chemicals, oil and grease) that is just what I hired for one month from them to use their DAF for testing materials.

I want to measure this parameters when feed materials ( liquid/solid) comming inside their DAF and how to behave in DAF ( to obtain : detention time, water rise rates). Can I do that with stopwatch anything or analysis from PLC monitor??

_________________________________________________________________________

you mention 100 m/hr , how did you get 100 m /hr

Total flow = Q + recycle flow: 25 + 25 = 50 m3/hr
and with assupmtion water rise rates (vertical velocity) 10 m/hr

how did you get 100 m/hr

Also here on this picture where lamlella packs start and hopper bottom - is that all one size for height of DAF or from lamella packs to top ;

Kind Regards,

Sebastian

 

[ashtree]

The contact zone is generally quite small with a velocity of about 100m/hr and detention time of 1-2 minutes.

Detention time= volume /flow.

If the volume of the tank is 100m3 and the flow is 100kl/hr(100m3/hr) the detention time is one hour.

In the contact zone you want a detention time of 1-2 minutes. At 50m3/hr the volume of e contact zone should be 0.8 to 1.6 m3. At 100m/hr velocity in the contact zone only the area will have to be 0.5m2 or less.

If you are going to put a lamella pack in the design is totally different. A lamella is for settling so if you have no solids you do not use a lamella pack in the DAF.



Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[sebastianS]

There are some solids but not in way to clog Lamella packs, they will be in some low percentage . I will know clearly what is percentage of solids after I collect samples of material for testing.

do you have fb or some other contact where we can talk private? and also you will have benefits of this ,as you can be in this project.

 

[ashtree]

No. I don't do facebook.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[sebastianS]

if I use detention time : 20 min ( in separation zone - am I right)
and detention time in contact zone : V/Q = in my case : 50/25 = 2 min.

How do I measure time for detention time to obtain 10 - 20 min , is there any possibility to find that as I am face to face with DAF system and every day looking on DAF. ( like on PLC monitor or stopwatch

Also for conventional DAF is 10 -20 min detention time( is that from experience, some standard for all DAF , or assumption from Engineers experience.

Here on my picture : I put orange colour - is that contact zone ?

- are they start from Lamella packs or from hopper bottom ( I can't find this informations in any book)


can I calculate detention time Separation zone like : Total flow / area , in my case 50 / 5 = 10 ?
Thanks

 

[ashtree]

Yes , the orange part is the contact zone. The 10-20mins detention time is required for the bubbles to adequately coalesce, cling to particles and rise to the top. In specialised cases you may be able to do this quicker but as a general guide that is the time required.

It will depend on a lot of variables but you will need to have the required detention time above the lamella. The lamella is really there to settle and collect heavier solids so is almost working independantly of the DAF. If you have many solids you may need to consider a collection auger because as soon as you open the withdrawal valve in the bottommm of the hopper you may cause all sorts of undesired flow paths.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[sebastianS]

Hi ashtree


What is difference between conventional and high rate DAF design -
Is it conventional DAF without Lamells packs?, and is it DAF with Lamella packs - related to high rate DAF ?



When you say water rise rates ( vertical linear velocity ) is that related to contact zone or in separation zone , and is it water rise rate same number for contact zone and separation zone.
and what is maximum velocity volume inside the tank
For calculation detention time for contact zone : total flow / Q

How do I find calculation detention time for separation zone? Is that: Total flow / area
Example if total flow is 50 m3/hr and area is 5 m2 - in that case : 50/5 = 10 , and use in case that height is 3 m , 10/3 = 3.33333 ( 60 min /3.33 = 20 min , is it about 20 min correct detention time

Or there is standard like for conventional DAF and High rate DAF , which you suggest me from powerpoint slide .
For conventional DAF : detention time is 10 – 20
And for High Rate 10 – 15 min



If you can put here email, or number on which I can call you for futher informations, that will be great

Kind Regards,

 

[ashtree]

The rise rate in the contact area is much higher than in the separation zone and they are not normally the same.
Detention time is : Volume/flow
Vertical velocity is : Flow (m3/hr)/area

There is no definitive separator between standard and high rate DAF units. High rate units are an evolution of earlier DAF units and then tend to have shorter detention times and higher vertical velocities.

It is against forum policy to post our email or phone numbers as this can attract nuisance spam etc.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[sebastianS]

IN CONTACT ZONE : detention time : Volume/Flow - 50/25 = 2 min

IN SEPARATION ZONE : detention time volume of separation zone)/(volumetric flow rate through separation zone.) Is that this : 50/25 = 2, ( 60min /2 = 30 min

what is maximum velocity volume inside the tank

Here on picture is data : if I use small area then that is big vertical velocity, big area then that is small vertical velocity.

Also what confuse me : Is it conventional DAF without Lamells packs?, and is it DAF with Lamella packs - related to high rate DAF ?

That is not in case important, but I have to see in what percentage is outlet sludge on bottom if is in high level then I will not use Lamella, is is not , then Lamella. Someone told me also If is to much sludge , then option is DAF should be bigger without lamella, but now I can find (thanks to you ) Area and understand that, ( area depends from Hydraulic loading rate ; Area = Q/Hydrauling loading rate (5 m3/m2h ) , 25/5 = 5 m2

Still I have problem how to find Height, if I have area,design loading rate, Hydraulic loading rate ( from table: from 5 to 15 ) . from your suggestion : If you assume 20 mins detention time and you have a linear vertical velocity of 10m/hr assumes that the liquid will travel upwards 3.33metres in 20 minutes. Using all these assumptions gives you a tank of 5m2 and 3.33 metres usuable depth.
- [highlight #EF2929]is that from calculation : 60 min / 20 min detention time = around 3 min , 3.33 metres [/highlight]


If I have from this calculation (if it is correct) 30 min detention time, and vertical velocity of 10 m/hr - liquid will travel upward : 60 min / 30 detention time = 2 min (so liquid will travel upward around 2 min in 30 min? , is this correct or not?? So Tank will be 5m2 and about 2 or more about 2.5-3 m usable depth from this calculation ?

Thanks




Sebastian (Jasmin Babic)

 

[sebastianS]

IN CONTACT ZONE : detention time : Volume/Flow : 50/25 = 2 min

IN SEPARATION ZONE : detention time : (volume of separation zone)/(volumetric flow rate through separation zone.) Is that this : 50/25 = 2, ( 60min /2 = 30 min


If I have from this calculation (if it is correct) 30 min detention time, and vertical velocity of 10 m/hr - liquid will travel upward : 60 min / 30 detention time = 2 min (so liquid will travel upward around 2 min in 30 min? , is this correct or not?? So Tank will be 5m2 and about 2 or more about 2.5-3 m usable depth from this calculation ?




Kind Regards,

Sebastian

 

[ashtree]

Your flow is 50m3/hr because you have 25m3/hr plus 25m3/hr recycle.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[sebastianS]

Yes, it is, I mess all this with numbers. (sorry)

So Flow is 50 m3/hr



Flow Q = 25 m3 /hr
Recycle Flow = 25 m3 / hr
_______________________________
Total Flow through unit = 50 m3/ hr
TSS = 120 mg/L
Efficiency factor, f = 0.5
Recycle Temperature T = 10 – 12 C
Hydraulic loading rate = 10 m3/ m2h
Solving for the tank area for separation zone, A = Flow/Hydraulic loading rate , A : 50/10 = 5 m2
Design loading rate = Q/A , Design loading rate : 50/5 = 10
Detention time for contact zone = volume / flow , Detention time : 5 m2/50 m3hr = 0.1 min

IN SEPARATION ZONE : detention time volume of separation zone)/(volumetric flow rate through separation zone.) Is that this : 5/50 = 0.1
Contact zone Area : 0.8 to 1.6 m3 ( your suggestion thanks)
The Contact zone is generally quite small with velocity of about 100 m/hr and detention time of 1-2 minutes (your suggestion thanks so much)
Contact Zone : velocity about 100m/hr, detention time 2 min
Water rise rates (vertical velocity) for separation zone = total flow / area , 50m3 per hr / 5 = 10 m/hr
Water rise rates (vertical velocity) for contact zone = total flow / area , 50m3 per hr / 0.8 = 62.5 m/hr , 50 m3 per hr / 0.5 = 100 m/hr




The only problem is Hydraulic loading rate : m3/m2h - this m2h - is that mean separation area , or all tank, and how to calculate area of plates, is that refer to area of plates - m2h?

From table : conventional DAF 5 - 15 m3/m2h( That is ok, but what that refers to



Also If I have Solid loading rate : 3 kg /hr , is it same calculation for all of this , using flow 50 m3/hr


I think I am confused little bit, it is this ok , please

 

[ashtree]

Your solids loading of 3kg/hr comes from 120mg/l of TSS x 25m3/hr flow rate.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[sebastianS]

yes I found how to obtain 3 kg , but I saw one post they said : you can get DAF design on Solid loading rate too :

Calculation process is it same as for hydraulic loading rate like :
Solving for the tank area, A = Flow/solid loading rate
Design loading rate = Q/A , Design loading rate
Detention time for contact zone = volume / flow
Water rise rates (vertical velocity) for separation zone = total flow / area


Or is it everthign different with Solid loading rate

http://frcsystems.com/daf-system-design-plate-pack-vs-open-tank/

So including all information ( thanks to you) and Hydraulic loading rate 10 m3/m2h, Area : 5m2
Height : from your assumtion , but I am type of Engineer who's going in detail how to find exactly all that, and air bubble motion upward ( but I think it's not possieble to obtain that information direct on site, how measure their start from start point to top, This Version on picture 1 :

Hydraulic loading rate : m3/m2h [m3/m2h - this m2h is that refer to area of plates?


Sorry I was confused, probably tired as I work on this without break all day all night ,

when they say : Detention time = volume / flow , so Volume is in m3 ( in that case all time I was wrong? that is not area m2 in my case 5 m2 ?

Volume = L x H x W in this case is it , height where is assumption 3.33 m


What is volume (m3) of this separation area
If area is 5 m2 = L x W
Is it Volume whis = L x W x H ?
Volume = 4.5 x 1.12 x 3 = 15 m3

Just to be clear


In that case from your calculate : If you assume 20 mins detention time and you have a linear vertical velocity of 10m/hr assumes that the liquid will travel upwards 3.33metres in 20 minutes

So Volume for tank area V = L x W x H , V : 4.5 x 1.12 x 3 = 15 m3
Detention time = Volume/Flow , Detention time : 15 / 50 = 0.3 , 0.3 x 60 min = 18 ( around 20 min) and 60 min / 18 (around 20 min ) = 3.33 m is this correct ?

 

[ashtree]

Yes you are correct.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"