Are constructed treatment wetlands sustainable sanitation solutions?

Günter answers that question himself by saying that it's the whole sanitation system that counts and not the single technology that makes sth. sustainable or not.

I would like to expand this even further, by saying it's not the technologies or a system of technologies that matter, but the most important is the institutional set-up, the capacities of the people involved and the financial mechanisms. And for those people doing the projects, the project implementers, it's their working approach that matters for sustainability: that enough focus is given to these factors when providing support to a community.

Although this sounds very much like common place, it's unfortunately more the rule than exception that this is simply not done (enough). Just too many projects are done in the classical way: good engineers come, design a nice system with nice technologies, make sure that construction is done in good quality, give 2 days O+M training and that's it. A year later the plants are still unused or broken down, but then that's because "the local people did not take care". See quotes below, it just happens all the time.

MalRoyalE wrote: Reedbeds can fail, usually from the human activity, or inactivity, in keeping them working, doing the work they were designed to do.

F H Mughal wrote: Now, get this – since, there was nothing to do, the O&M staff became lazy and stopped attending to the O&M of the ponds. Over the years, there was heavy weed growth, mosquitoes breeding all around, dirty outlook and zero treatment efficiency. I happened to visit these ponds and, noted the reasons that allowed the staff to become negligent in duties, rendering the ponds almost discarded.

The last post of F H Mughal is very interesting!

I could observe very similar patterns in community operated water supply systems in several countries: systems that rely on pumping are often more sustainable (better payment morale of consumers despite higher tariffs, better organised operating committee, etc.) than systems that are entirely gravity driven.

This is because the first have to be well organised for ensuring the service to continue (if no one pays, the electricity bill for the pump can't be paid, etc.), while in gravtiy fed system, the water runs by itself to the houses and motivation of people to pay and take care is much less. Quite obvious, but also squarely against basic sustainability principles of a purely technical approach, where cheaper to operate is always better.

To summarize my point: one of the biggest threats to sustainability in sanitation is too much focus on technology.

Best regards,
Florian

PS: here a picture of the first constructed wetland in Kosovo. It was never put in operation.


PPS: I also think that CWs are a great technology with lots of potential for many situations. We are currently preparing the 2nd and 3rd CW of Kosovo, hopefully with more success and sustainability

we are using a combination of up flow anaerobic reactor + constructed wetlands in periurban areas of Cochabamba - Bolivia successfully since 2009 see aguatuya.org/?page_id=30 and related publications.
The reactors do 2/3 of the job (BOD remotion) and the CW 1/3... I believe CWs are reliable and very tolerant to fluctuations in organic load.

Dear Mr. Guenter,

Your paper is interesting and informative. Constructed wetlands (CWs) are, no doubt, popular wastewater treatment systems that are simple to operate and, can achieve significant BOD removals, provided they are operated properly. In general, they are suitable for small communities and villages. There are, however, no CWs in the Sindh province of Pakistan, both in rural and urban areas.

As regards the question: Are constructed treatment wetlands sustainable sanitation solutions; I would say that, it is a subjective question – they may be sustainable in some areas (as you say, there are 3,000 CWs is Austria), but not in all areas. And, this, in question, is highly dependent on the people’s perception.

I relate my experience here, which, I’m sure, you will find it interesting. In a rural town in Sindh province, Pakistan, oxidation ponds were constructed, decades back, for treating municipal wastewater. Oxidation ponds, as you know, are low-cost wastewater treatment systems that require relatively large land area, work on bacteria-algae symbiosis, and their O&M (operation and maintenance) costs are almost zero – so to say. They will get “struck-up,” biologically, if the raw wastewater contains toxic industrial constituents.

Now, get this – since, there was nothing to do, the O&M staff became lazy and stopped attending to the O&M of the ponds. Over the years, there was heavy weed growth, mosquitoes breeding all around, dirty outlook and zero treatment efficiency. I happened to visit these ponds and, noted the reasons that allowed the staff to become negligent in duties, rendering the ponds almost discarded.

In 1982, I was required to propose, design and construct a municipal wastewater treatment plant in Karachi, Pakistan. I proposed aerated lagoons wastewater treatment plant. I installed locally-fabricated cage rotors for aeration. I intentionally did that to study the psychology of the people.

I found that, because there were lots of things to do at the plant (running rotors; operating main pumps and secondary pumps; manual removal of scum; maintenance of cutely-designed lawns; operation of control panels, etc), the staff did their duty properly and kept the plant in neat and tidy condition. Biologically, the plant achieved over 90% BOD and SS removals. I closely watched the staff and, can see why they are working hard – because there were lots of things that required attention.

I’m attaching some publications, which I hope, you and other colleagues would find them interesting.

Regards,

F H Mughal

Dear CW-Colleagues,

FYI: We are adding, as a kind of improvement to our CW-constructions, always an Effluent-Filter (we call it "Party-filter" in the outlet of pre-treatment (inside septic tanks or ABRs), like the US-Americans do it with their "Zabel-Filter" since the 1950's, to protect their leaching fields against clogging too.

large: www.aqua-verde.de/page4.php?view=preview&image=30&category=6
www.aqua-verde.de/page4.php?view=preview&image=63&category=6
small: www.aqua-verde.de/page4.php?view=preview&category=7&image=65

We call it Party-filter, because as during parties much beer is consumed and much more use of toilets is going on and many particles within the pre-treatment tanks have no time to settle to the bottom. Over 5-10 years big "party-animals" who own a CW without part-filter clogging their CW.

Only since 2009, our CW-system is "Enkeltauglich" = "Grandchildren proven" too, like Mel's.

Independent research may has shown Effluent-Filter decreases TSS by 50-90% and CBOD5 by 20-40%. If this is real and not only a "marketing" tool, we might abolish any CWs after Party-Filters ? We are planning to check on this "reductions" by our own little research.

Good Luck with your own CW-projects.

Detlef

DEar all
Interesting topic thanks for sharing Gûnther et all
We celebrated 20 years with Constructed Wetlands in Sweden in May this year! www.swedenviro.se/wrs/documents/Wetland%...y%2022-24%202013.pdf
Wetlands are regaining terrain in Sweden and you can see them constructed in many municipalities. The company in Sweden spearheading R&D in the field adn appplication is WRS Water Revival System www.swedenviro.se/wrs/index_en.html
Kind regards
madeleine

Er ... Yes they are
Reedbeds I built 15 to 17 years ago still work as well as they did all those years ago. Of course they continue to do the work they were designed to do, and this has been important.
Equally, an older gentleman wrote to tell me his reedbed was 120 years old and out Environment Agency are still happy with the outflow quality.
Reedbeds can fail, usually from the human activity, or inactivity, in keeping them working, doing the work they were designed to do. But the main structure remains, and getting it back into working order requires gardening technology. Once the flow rate is re-established, then in a short time ( 1 week ish )the whole system will recover well.
So the answer to the question is a big fat YES.
So give your reedbeds a good cuddle and thank them for all the work they do
Mel

Dear Joe,
in Austria we have more than 3000 CWs installed, mainly for treating domestic wastewater.
Most of these CWs are small, starting from CWs for single households.
The Autrian design standard requires a specific surface area od 4 m² per person for vertical flow CWs with intermittent loading.
Best reagrds,
Guenter

First of all, thank you Guenter for sharing the article. It is very interesting.

For Joe and his answer of “How small the CW can be constructed?” I would say it depends on the quality and quantity (flow) of the raw water and the space you have available. All these factors together will give you a hint for which type of CW you need.

Thanks Guenter, that is interesting. In the past I worked on some wetland bird reserves which have been operating reed treatment beds for some decades, it would be interesting to see how they compare to those constructed for human sanitation.

As a general question, is is possible to tell me how small these things can be constructed? The examples you give in the paper seem to be fairly large, would you say there is a minimum size below which they are ineffective?

I recently published a paper with this title discussing CWs in relation to the SuSanA criteria and that the systems point of view is important for sanitation.

Langergraber, G. (2013): Are constructed treatment wetlands sustainable sanitation solutions? Water Sci Technol 67(10), 2133-2140, doi: 10.2166/wst.2013.122.

I do hope that the paper is of interest for you.
Best regards,
Guenter Langergraber