ABR-CW quick sizing tool

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  • Marijn Zandee
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ABR-CW quick sizing tool

Dear colleagues,

Does anyone have a quick and dirty sizing tool (or reference to some simple formulas) for an ABR and a Constructed wetland to treat approximately 8 m3 of waste water per day? The BOD is probably around 250 mg/L.

At this stage I need to give people some idea of the size of units we would need for this option. If it becomes a serious project, we will do actual BOD/COD analyses and hire a waste water engineer for the design of the unit.

Thanks

Marijn Zandee
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  • JKMakowka
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Re: ABR-CW quick sizing tool

Will this help for the ABR?
www.sswm.info/sites/default/files/refere...nd%20Tecnologies.pdf

And maybe this for wetlands:
www.sswm.info/sites/default/files/refere...ucted%20Wetlands.pdf

( www.sswm.info is a good resource for finding such documents)
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  • christoph
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Re: ABR-CW quick sizing tool

Very quick and dirty :dry: :silly: ... just to have an idea about volume and space.
  • 12 h detention time for the ABR
  • 1,8 m²/hab. for a vertical flow sand filter wetland, 3m²/hab. horizontal flow.
correction. hab. = pe (person equivalent)

For warm climates
CP
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Re: ABR-CW quick sizing tool

Kris and Christoph,

Thanks, this will give us some general idea to start a discussion.

Christoph,

The figure of 3m2/hab does this mean per inhabitant/user?

Regards

Marijn
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  • jankn
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Re: ABR-CW quick sizing tool

The DEWATS in Developing Countries book by Sasse gives Excel based calculations in chapter 13 for ABRs and horizontal flow planted gravel filters:

http://www.sswm.info/sites/default/files/reference_attachments/SASSE%201998%20DEWATS%20Decentralised%20Wastewater%20Treatment%20in%20Developing%20Coun
Jan Knappe

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  • Elisabeth
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Re: ABR-CW quick sizing tool

Hi Marijn,
Just to answer your question from 19 April quickly: yes "hab." is the abbreviation for habitant or user. Let me add that to our list of abbreviations: en.wikipedia.org/wiki/Wikipedia:WikiProj...iations_and_acronyms
:-)

Hi Jan,
Are those Excel files available for general use? I guess not, as perhaps in the hands of non-experts they do more harm than they do good? (I think this was one of the reasons for BORDA in the past to not make such Excel files available). Just wondering.

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  • jankn
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Re: ABR-CW quick sizing tool

Hi Elisabeth
Exactly, the formulas are there in the book, but the Excel files are not available for general use (as far as I know).
I have seen those Excel files being used by BORDA colleagues; but you are right, a word of caution might be advised. Given that the original book has been published nearly 20 years ago now, I am certain that these calculations have been updated based on more recent findings and regional experiences with different design parameters. However, they can still serve as a starting point (!) for dimensioning DEWATS modules (namely Settler, a modified septic tank or ST; Imhoff tanks, biogas settlers or BGS, ABR, AF, PGF, and polishing pond or PP - to add some more abbreviations to the list), but final design should be reviewed by experienced regional experts.
Best
/Jan
Jan Knappe

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  • Marijn Zandee
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Re: ABR-CW quick sizing tool

Dear Jan,

Thanks, I was aware of the DEWATS booklet by Sasse, et al. I find a bit unfortunate that they presented the formulas used in the spreadsheets as EXCEL code, rather than as the formulas they used to base the Excel code on.

Probably, a lot of the formulas that were used for this booklet are still valid. Though for colder climates some parameters (such as up flow speed)may have to be adjusted.

Regards

Marijn
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  • AquaVerde
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Re: ABR-CW quick sizing tool

Dear Marijn,

Keep your self on very conservative side, e.g. use average temperature of colder season of possible location to design an "improved pre-treatment" (ABR) in front of CW.
Keep Up-flow velocity in ALL ABR-cambers less them 1 m/h!!! Especial if you do your first ABR-trail, do not reduce 40% CW-m2 as recommended in a GIZ/GTZ-paper. You may start very conservative with max. 10% reduction... without "wishful thinking" ;-).

I have all different versions of BORDA's Excel used, I found them very cumbersome. They need further developments in my opinion. By the way, Prof. Otterpohl developed this "tropical"-Excel together with Mr. Sasse many years ago! E.g. in Moldavia one ABR for 30 m3/d been designed, I regret 1/2 the size necessary with BORDA's "tropical"-Excel without real practical ABR-experiences! I by my self ended up using just "common sense" & only pocket calculator ;-) for our cold climate conditions in Germany, just to keep on the save side...
see picture in German language:




Good luck
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  • dmrobbins10
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Re: ABR-CW quick sizing tool

Here are two toolkits that you may find useful:

The first is a simple Excel tool that provides some rough design ideas. In this tool the strength of the wastewater is adjusted by adjusting the storage factor (see instructions at the bottom of page 1 of the tool). It uses 1.35 for a storage factor for residential strength wastewater, 1.8 - 2.4 for medium strength wastewater typical of a public market or hospital, and 2.5 - 3.5 for high strength.

The second is a constructed wetlands toolkit developed some years ago by the Bohal Environmental Management Office (BEMO) in the Philippines. This one is modeled using Reeds method. Pay special attention to the hydraulic conductivity of the media, as this has a big impact upon the overall sizing.

To my knowledge both of these have not been vetted by "professional" engineers and should be used with caution, and for discussion only, and not as a substitute for real engineering. It would be good to know if you find these useful or at least interesting.

Best,

Dave Robbins
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David M. Robbins
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