Thanks Christoph,

After understanding step by step (very slowly... the simplicity and advantages of this "French" system, I am a fan too

In my opinion too, one centralized 100%-STROMLOSE "French" 500 pe CW plant is the right engineering solution, as we have enough slopes and an existing "mix-system", not "my" many (13x) little "German" CW's. Sand availability and existing soil conditions are favorable and always a prerequisite part of my usual preliminary "lump's".

I made purposely this strange comparison with my own lump netto prices (incl. little tanks + siphons), as I will very likely not be able to convince the well organized village people + mayor, having only very high "German pilot-prices" at hand for a much better and simpler "French solution".

Originally this above mentioned first French system in G. been planed for total 370.000 EUR:
7 CW-ponds, 860 m², 4,3 m2/pe
+ 100 m sewer DN 400 (I guess 450 EUR/m)
+ culvert;
+ storm water flow-dividing structure;
+ Pump station

After 800-1.000 French systems already nearby in place (in France), we can not talk or call it anymore a German "first pilot plant" just from the technical and economical point of view. But yes it can be just called an innovation for Germany.

I am asking for realistic French/European LUMP costs EUR/m2 for the "pure" CW plant incl. siphons, for a first rough budgeting + decision finding stage.

If you compare e.g. planing & constructing of large power-plants in France or in Germany, they would most likely have very similar costs...

Regards,
Detlef

Dear Detlef,
a) your calc example shows a difference of 866 €/pe. I don´t know which situation you have in mind, but for a lot of situations should this amount should be enough.
b) you are comparing 2 different situations. A plant for each household is not the same as a centralized plant for 500 p.e (I know you thought of 12*40 pe) but in my understanding the right solution would be one plant. At least we have been discussing a situation with one plant before.
c) Again - the plant you are basing your judgment of the costs has a special situation as ALL rainwater or the mixed system had to be treated. So you would have to add to your example the costs for a complete advanced stormwater treatment.
That is the aspect I based on my "it depends" comment. The costs are very much influenced on: availability of sand, type of underground /soil, rocks??, slope, requirements for frost protection, discharge conditions, total volume to be treated etc.
Therefore I think it is more than right to state "it depends" when you talk about a specific case.
I am not that much into the discussion what is best for Germany - I just wanted to make clear that the French system by no means is more expensive than a normal wetland under standard conditions. My limitation for the use of the French system is more on the psychological side of our clients - people do not accept the system as we apply raw water. It is always a long way to go.

Attached some impressions of a french system we did in Perú. I think it makes very clear why I am such a fan of the french system.

Regards
Christoph

Hallo Christoph,

Thanks for spending parts of your Sunday on this.

Yes, approx. 500 l/pe + "Party-Filter" for a septic tank.

ABR up-flow velocities:

Heinz-Peter MANG send me kindly last year on my questions on the "right" up-flow velocities [m/h] this:
EAWAG small ABR: 0.06 - 0.3
EAWAG big ABR: 0.15
EPUVALEAU (Belgien)ABR: 0.3
SEECON ABR: 2.0
Buckley Durban: 0.27 - 0.55
BORDA: 2.0 (aber seit 2007 bereits reduziert auf 1.0 m/h)
AKVOPEDIA: 0.6
grassrootswiki: 0.6
Ain Shams University, Department of Public Works Engineering, Cairo: 0.125

The rest of German text I will send direct to you,...

Most of this ABR's are in tropical areas.

Back in 2010, just on my own and by my educated guessing, but without know-how and experiences like yours I was choosing 0.3 m/h. I am not sure about your mentioned only settling in each camber, again my know-how is for very detailed science work and being just on my own not good enough.

Seeing it maybe for the time being as a "black box", winter time results of "cold" ABR's outlet, COD's and TSS's are very promising and following some how Mr. Sasses (BORDA's) results. Aldo I do not have enough numbers of test results from the ABR because of money constrains. I just tested during most critical winter time. Until a sciences based long-term test by an independent institute being done, maybe I still compare "apples with pears" through my wishful thinking


Costs for CW's...:
I regret, I do not like your ...all depends on circumstances ..., as I do hear this too often from others, but in reality often it boils down just to very simple lump rules of thumps, just following a red thread for doing rough budget calculations to make a first preliminary decisions on wwtp planing options.

In general by all German high prices circumstances in the small size "conventional" CW-area of 4-50 pe (DWA A 262), let me do a "lumpy" netto-calculation of two maybe extreme options, "using" a real 500 pe village (having already a mix-collection system), just as an lump example on CW's (not septic tanks included).

I would love to recommend to the village people and their mayor this French wwtp "Phragmifiltre" option, even not going for "my" small scale "conventional" German CW's, but I do not have correct rough budget costs for a "French connection"...

1. each family (approx. 125) all will get constructed by a company a small 4 pe CW approx. 338 EUR/m2 = 1.350 EUR/pe, pipe-network construction near "0".
2. 13 grouped CW's (each 10 families will get connected to a 40 pe CW) all CW's will get constructed by a company, approx. 117 EUR/m2 = 465 EUR/pe

On number 2, the pipe network costs will possible "kill" this option and a possible option 3 will be maybe a mixture of small and larger family groups/CW's, and yes it "depends on circumstances" (going down in detail) .

Just compare this roughly with existing "French Costs" in Germany, having an existing collection pipe-network and constructed by a company a 200 pe wwtp with 600 m² CW = 5 CW-ponds = 558,000 EURO (2009) = 930 EUR/m2 = 2.790 EUR/pe

I regret this nice French System option will have unfortunately a hard future in Germany, even if constructed by a lower 450 EUR/m2. Maybe tendering which inclusion of French companies for planing and construction will help to spread this nice wwtp's in Germany too.

Schau'm mal

Regards,
Detlef

Thanks Christoph for answering the questions much better than I can (I am not so much into details of designing).

For the costs, I also see no reason why the vertical flow systems in France should be more expensive than the CWs usual in Germany. When technologies are applied for the first time in an area, engineers often tend to do some over-engineering to be on the safe side. That's a good approach, but of course one should not extrapolate costs from such first pilot plants.

As for the discussed plant in Rusca, it is more result of experimenting than thorough desiging I think. As far as I know, the precedessors of our project at the time, when deciding to do something about wastewater, built the ABR at that prison first, and only later added the CWs. Looking at all components together, I'd say it would be more logical to transform the ABR in a pure settler and have the liquid part treated in the filter beds.

In Moldova, we don't invest much in wastewater treatment plants for the time being, not for technical difficulties but because of the challenges for haveing a reliable operation, and mainly for the low need for wastewater treatment in villages (we focus on rural areas there), where people produce very little wastewater.

Hi Florian and Detlef,
just some quick remarks about some questions of Detlef.

Do you have "normal" French civil engineering costs for this kind of wwtp's at hand?

"French systems" (raw water wetlands) are not more expensive than other wetlands. As always ...all depends on circumstances ....You can do your calcs based on your typical costs you know for €/m². But in order to compare on a equivalent basis you have to add measures for stormwater treatment - you see the results in a "normal" wetland - clogging as the pretreatment looses sludge. And you have to get to the same overall treatment quality - this is the total annual discharge load of BOD or nutrients should be equal. This means you an not solve the storm water problem just by bypassing. Which was exactly the main problem in the case of the two "expensive" french systems in Germany if I remember right. There cold not be any untreated discharge therefore any other system would have to be designed to the stormatwer conditions - and therefore be much more expensive. But coming back to costs in general… In Peru we are able to construed the french system for about 120 - 180 €/hab. in a size range of 80 - 200 pe - about the same costs as for a "conventional" wetland.
Concerning the discussion of odor in french systems - the "secret" is to load fresh wastewater. Than there are less odor problems than in VFW with pulse loadings after an ABR. But I agree that french systems are nothing for a private household.
Detlef you write:

I adapted the tropical design criteria of BORDA to our cold climate condition, ......and much slower up-flow velocity (max. 0.3 m/h) within the ABR-cambers

I agree with enhancing HRT time in cold climate that makes a lot of sense, but the upflow velocity max 0,3 m/h would result in having a series of settlers which is not the aim of an ABR. and THIS is the point why I do not see ABR as a good option for cold climates. You have to double ??? the retention time but have to maintain the upflow velocity - this means the double of baffles - expensive and strange. I as well would go for a larger settling volume - I agree the German 1,5 m³/p.e for households are maybe not the best choice, but something as 500 l/pe with three chambers seems to me as a good approach.

But I admit I am a long time away from cold climates.

Regards
Christoph

Dear Florian,

Thanks, this is very helpful.

The manual beds fed alternation is good solution, for our circumstances too.

You say this French CW system is a CW without pre-treatment of sewage. In my opinion this first step of "aerobic soilification" is a clever pre-treatment system and could be used for other wwtp too, especial after sewage collection systems where a mix of storm water and sewage is flowing through and not much space for CW's as second stage is available. This is a good pre-treatment system to reduce from the beginning the sludge volumes going through any wwtp. It is in my opinion an "automatic" sludge treatment option as first stage of wwtp. It could be as well a simple technological choice for treating storm water overflows of (mixed) sewage collection system, which are up to now going not treated straight towards rivers.

In Germany (eastern part) two of this French CW systems (for mixed water= Mischwasser) in place. Unfortunately currently this system involves very high costs, e.g. 200 p.e., original planed for approx. 370.000 EUR and build in 2009 for approx. 550.000 EUR, for a total of 600 m2 CW-surface. This makes me wonder about any great future of this excellent wwtp system in Germany. "Normal" costs of CW's are never high like this. "Normal" CW construction costs (in general civil engineering) in Germany in general not much different to France. In France 800-1.000 of this wwtp's already been build over the years.

Do you have "normal" French civil engineering costs for this kind of wwtp's at hand?

ABR's are not a good choice for this "mixing"-circumstances, they are good for "pure" sewage. In "my" little three numbers (experiences) with ABR's (6-30 p.e.) in Germany I adapted the tropical design criteria of BORDA to our cold climate condition, this means in general they have much longer HRT (hydraulic retention time, min. 3 days) and much slower up-flow velocity (max. 0.3 m/h) within the ABR-cambers, in general having a larger volume them original tropical BORDA's design. They work under cold conditions very fine and sludge accumulation is not surprisingly very small.

Still "my" calculated total settler- + ABR-volumes are smaller them DWA A262 and DIN (German standards) demanding for "normal" septic tank volumes and "my" following vertical CW been planed/build "too big", just by calculating the COD-load to CW! But German authorities (having less and less own engineers) sticking without much thinking only to existing guidelines/standards (1,5 m3/p.e. for septic tank & 4 m2/p.e. for vCW) and being not flexible based on proper engineering calculation, which is in the end costly to the costumer and "nice" for the construction industry. In the end a waste of resources!

In my educated guessing an ABR is a good technological choice for first stage treatment of large scale wwtp's, for "pure" sewage collection systems, generating energy instate of using a lot of energy to produce more sludge and high follow-up costs and burdens, see AS (Activated Sludge Systems).

How about adding a storm water divider in front of now existing "small" RUSCA's ABR and increasing just the settler capacity (x2)? To keep the following CW's free of clogging again. Additional having a kind of police-ing within the last camber of ABR, placing in the outlet an "AFS-Filter" (AFS, Abfiltrirbare Stoffe = TSS, total suspended solids), I call it "Party-Filter", you may call it as well "Police-ing-Filter".
BORDA added later this kind of "Party-Filters" (a simpler version a "tuf-tite Filter" 1,6 mm slots, Made in USA) to "their" cold ABR's in Afghanistan too.


"Zabel-Filter" 0,4 mm slots, Made in USA

A sewage overflow by a "Police-ing-Filter" of ABR is better them slowly bud surely clogging CW. The first 2-3 overflows will have a kind of teaching to the O&M manager and workers too, to really operate and maintain this wwtp. If "only" over a longer period a final clogging of CW occurred, the "normal mental reaction" of local wwtp-workers and engineers are: "ABR's or/and CW's are in general a bad technological solution..."

text becomes lengthy...

All the Best
Detlef

Hi Detlef,

most of the plants I've seen do not function automatically, the alternation is done manually with simple replacing the tubes like in this pic: www.flickr.com/photos/gtzecosan/64380165...et-72157628237934383. The only automated systems I've seen were with "electronic gadgets" e.e. magnetic valves. For municipal plants I don't think the manual operation is a bad thing, it means the operator has to go to the plant 2-3 times per week, the obligation for such routine visits can be helpful for good maintenance in my opinion.

As for the smell problem, no, I did not notice any bigger problems than with other type of wwtp. Rather to the contrary I'd say. The pictures in my slide-show may give a little wrong impression, because most pics are of plants that were only recently put in operation, where reed has not yet grown and thus wastewater and sludge is visible on the surface (I chose these pics, because you can see how the thing works, with older plants, you see just reed). The wastewater normally infiltrates quite quickly, after a few minutes, no more wastewater remains on the surface. Also the dense reed growth helps to protect from wind drift of smell I guess.

I think the treatment is also mostly done by biofilm inside the filter in this type of CWs, the function of the reeds is to maintain the hydraulic conductivity of the filter.

Regarding costs of the syphon, we bought some in a project for Kosovo, I think about 3-5000 Euro for the mechanism and transport, without the concrete tank. In the Moldovan projects, the motivation for copying was less costs than the desire to do everything locally. But as I said, I think it's better to buy key elements like this syphon, at least in wwtp that are the first of its kind in a country. I can't say about copyright issues, not sure if the syphons are patented, I think they are offered by various french suppliers.

As for the Rusca facility, interesting that you seem to know more details about it's history than myself

The wwtp there has an ABR and 2 stages of horizontal CWs, not vertical. The main problems of the plant were over-loading (or designed too small) and bad mainteance. The ABR was desludged not often enough, because of costs. So a lot of sludge went over to the filter. Also there is actually no good option for sludge disposal available, hardly any operating urban wwtp in the country. So we decided to build drying beds on the site and buy a sludge pump. This aleviated the situation quite a bit, sludge ist not carried over to the filter as much any more. But the filter may have become clocked partly in the last years of operation, effluent values are still not really good.

I was also not so convinced about the ABR in cold climate, and proposed to take out the baffles (except one or two) to have a simple settling tank with better settling capacity, but this was not done so far...

The absence of sludge treatment options is a strong argument of the vertical flow CWs without pretreatment, and we built also some of those in Moldova. Biggest challenge in all the facilities is to set up reliable maintenance.

Best wishes,
Florian

Hallo Florian,

Thanks for the "French connection"

I like the simplicity of this French pre-treatment system via an aerobic soilification (pre-treatment).

Do you know, how the beds fed alternations is AUTOMATICALLY functioning by hydraulic means? I guess, without sophisticated electronic gadgets.

Seeing the splashing of untreated raw (black) waste water and later pre-treated to the vertical CW, I guess you are experiencing great smell problems. Maybe this wwtp should be some hundred'S meter'S away from settlements!? What is your "smelly experiences" on that?

"My" little (up to 50 p.e.) black water CW's for pre-treated waste (for small hydraulic loads, only 5 mm each, 4-5 times the day), have small distribution HT-pipes (grey) with holes at underside and is laying direct on top of 10 cm 2..8 mm gravel. Additionally, only by hand 2..8 mm gravel been pushed from right and left on top of all distribution pipes (layer of 2-3 cm), leveled pipes resting more or less on small gravel ridges. No roots entering the 6 mm distribution holes. No smell at all, furthermore "my" CW's (just a "hydro-pot" with DRY gravel surface) are often "misused" as flower garden direct in front of houses in densely urban settlements. The use of reed becomes more and more seldom, as the bio-film is doing 95% of the "job" within CW's.

Do you know costs of this French siphons? I guess their high costs been the reason to just copy them!? Using HT110 pipe fittings for making a simple siphon copy is a great idea. The French colleagues do not declared this siphons as "Open Design", do the Moldova colleagues have legal Copyright problems by creating self-made copies of the French systems?

On the mentioned RUSCA system (prison + settlement), I know they use an "cold" ABR + "normal" vertical CW for pretreated waste water, using "German" CW design regulation (DWA A 262). Unfortunately they have storm-water intrusion to waste water collection system. Therefore sludge been pushed out of ABR on a regulate base and CW been already clogged. Additional this ABR have in my opinion a rather small volume. Only 1/2 of necessary for cold climate condition! Do you know maybe, how this ABR & CW problems been some how rectified by Moldova/Swiss engineers by now? I take this positive, as I like to learn from my mistakes and from other mistakes too.

Thanks in advance.

Regards,
Detlef


CW = Constructed Wetlands
ABR = Anaerobic Baffled Reactor
DWA = German Water Engineering Association
wwtp = waste water treatment plant

Note by moderator (EvM): This post was originally in this thread:
www.forum.susana.org/forum/categories/36...adgets-qopen-designq

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Thanks Detlef for these links! I've seen this system already, it's quite common in France with vertical flow CWs without pretreatment. I've not yet come across other syphon systems for unsettled wastewater...

Here some pics of some of the CWs I've visited in France a few years ago, including some of the syphon in use: www.flickr.com/photos/gtzecosan/sets/72157628237934383/

Here also a presentation of CWs that were build in our project in Moldova, the last slides show the syphons, which are self-made copies of the French systems: apasan.md/files/img/site/doc/ZUC_Prezentare_Generala.pdf
I'd recommend to rather buy the syphons from France, its not that easy to get the balance right...