Ponts to finalize the treatment aspect
Liaqat Hayat
Dear All,
1. I have reviewed my earlier planned layout for the CWL units as per attachment for your comments to finalize this discussion.
2. The comments in respect of following aspects may be given in particular.
- Size of CWL cells no. 1 & 2 which is 60′ into 50′ and 30′ into 50′.
- Addition of row of vetiver plant for say 200 meters length to process the effluent from CWL - 2 to stream through a row of vetiver as done in hotel beach. I am not clear if the effluent should pass through these vetiver plants or first it should be ponded there are some time and then disposed off to the stream. This is an optimal addition and may be needed when the effluent from setic tank has to be passed direct to stream for cleaning / maintenance operations for CWL cell 1 & 2. The rock stone layer can also get plugged with solids and may have to be cleaned.
- The row of beds/ponds is now 5 with one having no plants to act a "control bed". Also I am still thinking of providing some ventilation to this layer through separate pipe.
- Regarding Dr. Paul Truong, to make it 20cm the depth instead of 12cm, I feel that we may increase this at effluent distribution and collecting locations in the bed to reduce fear of clogging while keeping the rest at same 12cm depth. Your comments please?.
- We shall also cover top of stone layers with 3″ mulch to avoid odor. How I will clean this stone layer if it is choked. Have to re-excavate or can embed any pipe for blowing air back? Any comments please?
- The 5 beds/ponds to be alternated filled to give same drying time to the other? To what extent the drying process in beds can be helpful in the treatment?
- The plants used in CWL -1 is vetiver and in CWL -2 it is sorghum crops for availability reason and also to try two options to see their performance in field in this climate. These plant varieties (can be further modified may be after a visit to M.P singh nursery )
- What is finally the life of a CWL and how it can be maintained for a longer time? When rock bed/stone beds are to be cleaned and how?
- The stream is mostly dry except rainy season. Can we use its bed for growth of vetiver also? Can a small lake with a small wall in the stream flow can help by creating a small pond and extra water just overflows. This over flowing will also give aeration to the flow in the stream. Like to share with you on these points.
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With Best Regards,
Liaqat Hayat
Jacky Foo
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Points to finalize the treatment aspect
Submitted by Jacky Foo on Fri, 27/07/2007 - 11:02.
Liaqat Hayat [liaqat...@gmail.com]wrote:
>The stream is mostly dry except rainy season.
thus is new information to me !!
this means that when effluent is directly discharged into the stream
when it is dry, the stream is like a sewer !!
How many months is it dry ?
-----
Jacky Foo
http://www.iobbnet.org
Jacky Foo
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CWL design
Submitted by Hanns Pitot on Fri, 27/07/2007 - 11:12.
Dear Liaqat,
I think you mean 12 and 20 inches rather than cm!
A properly constructed wetland does not need any cleaning except, in
some designs, regular cutting of the above ground growth. So, it can
last for decades, and has to be rebuilt, when it doesn't work anymore.
That's the beauty of it. The plant roots, which grow and regrow, will
keep up the permeability of the system. That actually highlights the
importance of the proper choice of plants. Phragmites tends to have a
horizontal root system, about 60 cm deep, and in that way, it keeps up
the permeability of a CWL with horizontal flow.
The second cell in your design looks more like a plot of land with
subsurface irrigation. Sorghum is surely not a plant growing in
wetlands? Could you explain that part of it to me?
Otherwise, I like your design, but I would still try several species
of plants in the first cell. Just to be sure you picked the right one.
Have a look at local water bodies and see whether any of the mentioned
plants are growing there. Phragmites certainly will, and rushes or
bulrushes, too. Apart from papyrus, there are other plants in that
same genus, that my be growing in Pakistan and may be suited. Pick
only those plants that grow truly submerged.
Regards, Hanns-Andre
Hanns-Andr Pitot
Member of the AT-Association
Am Steinacker 42
38723 Seesen
Germany
Tel./Fax: -49-5381-5468
E-mail: hap...@yahoo.com
Jacky Foo
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water holding capacity of the 2 cells
Submitted by Jacky Foo on Fri, 27/07/2007 - 11:16.
with reference to the diagram
Q: what is the total water holding capacity for the 2 cells ?
Q: what is the intended retention time for cell 2 (the one with
plants)
Q: what is the current effluent volume (11 m3 (2500 gallons))from the
houses into the new Septic tank ?
Q: how much outflow do you anticipate from the CWL of 2 cells ?
Jacky Foo
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design criteria
Submitted by Hanns Pitot on Fri, 27/07/2007 - 12:41.
Jacky, in CWL construction, the area is the decisive design factor
(reflecting the amount of energy collected from the sun). In the fist
cell, which would be the pretreatment portion, 1500 square ft. give
about 130 m2 of active area. With 9 houses at the moment, that's about
45 persons, or roughly, 3 m2 per person. 1,5 m2 per person should be
ok, so the village can double in size if it comes to it, as initially
suggested by Liaqat.
The size is thus ok, only, I would follow Paul's suggestion and make
the depth of the first cell 20 in. (50 cm) deep). The second part with
sorghum would have to be constructed so that the sorghum takes up all
the nutrients that are coming out of the first cell. It's a
calculation for an agronomist. Liaqat, why didn't you design this
portion as described by Jacky, i.e. like a ridge and furrow irrigation
system?
I also like the last portion with Vetiver grass in the design.
Pakistan has periods with heavy rain, and the system would have to
accommodate for that. The vetiver row at the end would allow to
prevent runoff to pollute the creak during the rains (and would have
to be designed accordingly). In that light, I think the tank after the
second cell is probably superfluous, depending on how heavy the rains
are. May-be, there should be several parallel rows of Vetiver.
Greetings,
Hanns-Andr
Jacky Foo
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sizing cell two
Submitted by Hanns Pitot on Fri, 27/07/2007 - 15:08.
Out of curiosity, I have scaled the size of section 2 (I'll call it
section rather than cell because it comes out very big) in Liaqat's
design for banana, for which I happen to have some figures (based an
US, Indian and Vietnamese figures):
Nutrient requirements of banana: 500 - 600 Kg/ha of N, 100 - 150 Kg/ha
of P, and 600 - 675 Kg/ha of K;
Nutrients from human excrements: 5,2 Kg/person of N, 1,26 Kg/person of
P, and 1,08 Kg/person of K.
These are all annual figures.
You can see from the figures that the excrements of 90 people would
fertilize almost one hectare of banana plants. And I would suggest
that the removal of nutrients in the septic tank and the CWL (cell one
in the design) is set to zero and used as a safety margin, so that the
actual size of section (cell) 2 would be in the order of one ha (2,5
acres) of banana and possibly other fruits (papaya?).
What you also see from the figures, that's that there would be a
deficiency of potassium with banana, and that would mean that some
fertilization in that regard would have to take place. I think compost
made from dead banana trees and organic solid waste would do.
For other crops, like sorghum, the figure of one ha land area may be
lower, but fruit trees are a pretty safe bet as the fruit doesn't
touch the surface and thus offer an additional margin of safety with
regard to the possibility of getting contaminated by pathogens. Fruit
trees also are permanent plants and thus remove nutrients throughout
the year.
Hanns-Andre
Jacky Foo
+++++++++++++++
design criteria
Submitted by Hanns Pitot on Sat, 28/07/2007 - 10:31.
Q: How many people (9 houses in the drawing at the moment) would there
actually be in that village?
Hanns-Andr
Jacky Foo
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sizing cell two
Submitted by Hanns Pitot on Sat, 28/07/2007 - 14:22.
Noticed I should have written excreta in my previous posting, as the
term 'excrements' doesn't include urine. You never stop lerning!
Hanns-Andre
Jacky Foo
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design criteria
Submitted by Hanns Pitot on Tue, 31/07/2007 - 10:09.
It is saying at the beginning: some 50 persons in 15 to 16 houses - I
am sorry I overlooked it. With 45/90 person-equivaltents in my
calculation, it's about right, considering that small children don't
count.
Of course, if some form of dry sanitation (composting toilets) were an
option, the water treatment facility could be reduced in size. That
would concern the size of the septic tank in particular, which would
be working more like a grit removal chamber and not be accumulating a
whole lot of sludge.
Greetings,
Hanns-Andre