This is my first post so here is my mandatory intro. I had participated in the ecosanres forum a number of years ago while i volunteered in Cambodia and have maintained an interest in sustainable sanitation ever since.

Im currently working as a process engineer in Brisbane with the wastewater service provider. Everyday im facinated by how the work in sustainable sanitation (such as that discussed in these forums) is so relevant to the challenges that continually arise in my day to day activities.

Im on a mission to educate my co-workers and executive management - so the questions of finance and economics is very relevant to them and therefore me. I beleive its only when developed countries adopt sustainable sanitation (a broad term i know) will it be easier to implement in developing countries.

Anyway back to Phillips question...

I have previously done some investigation into the operating "costs" of centralised wastewater treatment(developed world context)in Australia. As the discussion already highlights the costs are highly dependant on context and technology so i will reiterate the cautions already highlighted to you.

Trade waste fees and charges available from wastewater utilities will give you a reasonable idea of operation costs. These charges are often available on the utility website or by sending a simple request for information.

The trade waste charges are a very useful estimation/approximation, because these are often broken down into separate charges for nitrogen, phosphorous, suspended solids, BOD, volume, etc. These charges are also highly regulated (at least in Australia) to ensure there is no profiteering.

www.hunterwater.com.au/Resources/Documen...trade-waste-fees.pdf

www.melbournewater.com.au/content/about_..._sewerage.asp?bhcp=1


The above links should be a good start. But remember this is the Australian context and also take notice of the charges variations.

Regards

Mark

Dear Philipp / Elisabeth

Thanks to Philipp for taking the iniative on this and thankyou Elisabeth for highlighting the complexities involved which highlight very well the fact that collation of cost data about different sanitation options is easier said than done.

In my opinion, the discussion encapsulates the rationale for the focus of the Working Group to develop a standardised approach for collection and collation of data about sanitation systems. We need to find a way around the complexities so that we have a better understanding as to when it is valid to compare data sets and what factors we should take into consideration when making these comparisons.

As Elisabeth rightly points out, cost will depend - not just on technology type - but level of treatment efficiency and also size of treatment plant. So, it is therefore important to capture this information to enable a better intepretation of the data. She also questions the validity of comparing sanitation systems which perform different functions (e.g. pit latrines versus sewerage).

These points are valid and provide addition reason why we need to think this through what this means in terms of financial data collectiom and analysis. However, I see nothing wrong at this stage in proceeding with an initial scoping exercise to see what information is out there. We can then systematically work through it to see what we've got and how this influences our thinking about cost data collation.

So, anyone who has come across relevant information in the literature about costs of wastewater treatment, please send.

Comments/suggestions/responses from others would be most welcome.

best regards to all,

Jonathan

p.s. One note of clarification, I don't think economists are actually so much interested to acquire information on CAPEX and OPEX costs of wastewater treatment - it's more for sanitation programming and design where this information is required. But, clearly financial data is also central to economic analysis too.

p.p.s. I was going to respond to the technical point (raised by Christoph) about the use of constructed wetlands to treat fecal sludge. I see Florian has already responded to this on the Sanitation systems forum pages.
forum.susana.org/forum/categories/53-fae...constructed-wetlands

OK, just to clarify my point, sorry if I didn't make it clear before: it is absolutely pointless to compare the costs of an activated sludge plant with the cost of a pond system for a given situation where the effluent standard is for example only COD of 100 mg/L and SS of 50 mg/L (and no requirement for N and P removal). Of course the activated sludge plant will be much more expensive and one would only choose it if this superior effluent quality was a requirement, or if there was a lack of space for the ponds. Otherwise, the effluent quality from the activated sludge plant would be an overkill, as it achieves much better quality than that lower standard. (You may however compare an activated sludge plant with a trickling filter plant as they achieve similar effluent quality - if no requirement for nutrient removal).
This is the point I am trying to make.

So I am talking about the comparison aspect here. If you say, you simply want to collect costs of different treatment options (and not compare them), then fine. But this comparison is exactly what was in that graph - where the "biological filter system" was the most expensive and I would say "but this is obvious! It is designed to achieve better effluent quality and is therefore more expensive!".

(also in my opinion, it makes little sense to plot this cost as a graph over a 25 year period; for comparison, it is sufficient to calculate the NPV over 25 years and for a given discount rate and then to simply compare NPV values).

For this constructed wetland example, yes, sure one could quote a concrete example. But so what? Our aim was to make a generalised statement that holds true in all cases. A collection of single examples would come to the same general conclusion.

Regarding the simplified sewer system comparison to a pit latrine, it is wrong to compare them 1 by 1. If someone builds a simplified sewer system, they do it in order to also take care of the greywater. A pit latrine does not fulfill this functionality - obviously it will be cheaper then. It all depends on the intended objective.

I haven't looked at the results from that WASHCOST project from IRC. Is that available online by now? If yes, doesn't it answer the question which you have, i.e. "I would like to collect the costs of different treatment options"? This is their website, it looks pretty comprehensive to me: www.washcost.info/ - would be great if someone from IRC could join this discussion here (are they active in Working Group 2? If not, could we attempt to activate them?).

OK, I will leave it at this, and hope that other people now also join here, so it is not just you and me discussing these cost aspects.

Is there a specific reason why you are asking? Does it have something to do with the situation in Zimbabwe? Or is it just in general for WG 2?

Regards,
Elisabeth

Dear Elisabeth,

as I mentioned before I just would like to collect the costs of different treatment options. The aim is to have a rough overview of different costs for different technologies. Why do you say that one should never compare technologies which achieve different treatment objectives? From the view of an economist or of a decision maker it is not so important if effluent quality is higher or less high as long as it meets the given standard (you can find more information on the effluent quality in the publication of Arthur 1983 for the chosen example). This should be a discussion of costs and not on effluent quality! Just ask yourself when you buy things: you always want to have a good cost-benefit ratio. Less quality means less interest in paying lot of money.

The example given by Arthur in 1983 is from my point of view an excellent example how different options for the same assumptions:

The following assumptions have been made in the system designs.
Contributing population 250,000
Wastewater contribution 120 lcd
Average daily wastewater flow 30,000 m3 /d
Per capita BOD5 contribution 40gcd
Average daily BOD5 load 10,000 kg/d
Controlling temperature 20 C
FC concentration in raw sewage 2 x 107FC/100 ml
Effluent standard for BOD5 25 mg/l
Effluent standard for FC 10,000 FC/100 ml
Pumping required to inlet works and for irrigation

It would be great to have a comparison of different technologies in the technology review i.e. on constructed wetlands where you calculate the costs for different solutions for one setting.

“For large scale treatment plants of more than 10 000 person
equivalents (p.e.) in areas where land is available cheaply,
ponds have lower capital costs than constructed wetlands.”

This is in my view, inaccurate, how about a concrete example?

Regarding your comparison of apples and apples It is not wrong to compare the costs of pit latrines vs simplified sewer systems as long as there are people who are planning to construction one of these options.

The concept note is from my understanding (Jonathan can tell you more about it) not a question of high- or low-tech solutions but more to support the process of decision making for different technologies:

“The purpose of this initiative is to improve decisions related to sanitation investments by the promotion of a standardised framework for collation of cost data and an analytical approach to support more robust financial and economic analyses. At one level, the initiative aims to raise awareness of the need to include financial and economic assessment as a core component of decision making processes. At a more specific level, it aims to establish a framework for collection and collation of financial costs and promote a least cost approach towards financial analysis of sanitation options to sanitation programming.”

Regarding your question on different costs you can find more information in the factsheet of WG 02 (the updated version will be available soon): susana.org/lang-en/library/rm-susana-pub...peitem&type=2&id=609


Looking forward to more contributions, ideas, questions and examples.

Cheers,
Philipp

Dear Philipp,

Sorry, I don't quite understand what you are getting at here? It is actually very difficult to compare costs of wastewater treatment plants across all sorts of different technologies, countries, treatment aims, project sizes, project constraints (such as availability of land), climates, etc.

For example, in the graph which you posted, treatment technologies are being compared which produce quite different effluent quality (although I can see that in the original publication of 1983 they are pretty vague about this point). E.g. in Germany, if you have a biological nutrient removal activated sludge plant, then for sure it will be much more expensive than a pond system in Ghana. But the effluent quality from the former plant is also much higher, and this is because the discharge standards set by the regulating agency are much higher. Same goes for advanced treatment plants, where the discussion is now in Germany to remove also micropollutants from wastewater via technologies like ozonation, adsorption with activated carbon and so forth. Hence, one should never compare technologies which are designed to achieve different treatment objectives (but this is being done in that paper and in the graph, as far as I can see).

Another example is that sometimes you have to go for a more expensive, compact technology if there is a space limitation (e.g. in the extreme case, use of a Membrane bioreactor if there is no space, versus a pond system when you do have space).

The other point is that when it comes to centralised treatment plants, then the cost per person connected (or per m3 treated) will almost always come down the bigger the treatment plant is. You can find ample publications for this, it is logical due to economies of scale. A quick google search will bring up such results. So when people compare published costs of treatment plants, make sure they are talking about the same size of the plant.

For the specific example of constructed wetlands for developing countries, we made some qualitative statements in our technology review on constructed wetlands where we compare them with ponds (even though again the question of differing effluent quality pops up) - maybe this is useful to recall here.

You can find this publication here in the SuSanA library:
www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=930

On page 11 you find this qualitative information:

2.7.4 Cost considerations
The capital costs of subsurface flow CWs are highly
dependent on the costs of sand since the bed has to be filled
with sand. Secondly the capital costs are also dependent on
the cost of land.
Financial decisions on treatment processes should not
primarily be made on capital costs, but on net present value
or whole-of-life costs, which includes the annual costs for
operation and maintenance.

The following points can be made when comparing costs for
constructed wetlands and high-rate aerobic treatment
processes:
· Constructed wetlands do not exhibit economies of scale
to the same degree that high-rate aerobic treatment
plants do. For small plants of up to 500 p.e., constructed
wetlands are usually cheaper to build than high-rate
aerobic plants but for larger plants, they are usually more
expensive in terms of capital costs.
· Constructed wetlands have significantly lower operation
and maintenance costs compared to high-rate aerobic
processes for energy use and operator time.
For large scale treatment plants of more than 10 000 person
equivalents (p.e.) in areas where land is available cheaply,
ponds have lower capital costs than constructed wetlands.

But there is a range of other aspects which have to be taken
into account when making the decision between the two
different treatment processes, as shown above.

We argue that the capital costs argument should be less
important than the reliability and long-term sustainability of
the treatment plant, including its financial sustainability which
is strongly influenced by annual operation and maintenance
costs.

In our other technology review on UDDTs (currently under completion; draft version also in SuSAnA library), we are comparing costs of different UDDTs. So in my opinion, cost comparisons are only valid within one technology or within a set of technologies that are comparable (even ponds and constructed wetlands are not comparable in all aspects). There are horses for courses - as the Brits would say.


I have seen graphs where people compare costs of pit latrines versus simplified sewer systems. To me, this is so wrong, as one is not comparing apples with apples. A sewer system also takes care of greywater, whereas a pit latrine is not. Etc.

So overall, it would be useful if you and/or Jonathan Parkinson (IWA) could clarify what sort of cost data is meant to be collected here? I read the concept note by Jonathan (which you had attached) but am still confused; I thought he was not actually referring to centralised wastewater treatment plants but rather to basic sanitation systems.

Regards,
Elisabeth

I found an interesting publication from 1983 by Arthur & Worldbank comparing different treatment options. Even if the value of the dollar has changed over the past years it gives a good overview on the costs. I created an graph including the investment and operational costs over 25 years for waste stabilization pond system, aerated lagoon system, oxidation ditch and biological filter.

[img]www.susana.org/images/documents/05-working-groups/wg02/cost-overview-treatment-options.jpg[/img]

You can find the publication in the SSWM library:
ARTHUR, J.P. ; The World Bank (Editor) (1983): Notes in the Design and Operation of Waste Stabilization Ponds in Warm Climates of Developing Countries . Washington: The World Bank.
www.sswm.info/sites/default/files/refere...ping%20countries.pdf

Dear Christoph,

thank you for the clarification. I move this threat to the WG 2 section, because in this case I am only interested in the costs and not in the technologies. I agree with you and changed the subject to wastewater.

Which kind of experiences have you done in Brazil or other places and what can you tell us about the costs. Do you know good documents giving more information on the cost side?

Thank you and best regards from ZIM,
Philipp

Dear Phillip, you are mixing up two subjects which should be treated seperately.
Do you refer to fecal sludge treatment or to decentralized treatment?
Fecal sludge treatment cannot be done in a wetland (it would clogg) – it is possible in sludge mineralization beds but it has to be done very carefully and there is a lack of experience in proper design.
If you do it in a stabilization pond you will get an anaerobic lagoon – not very recommendable in terms of methane, odor and as well handling.
Fecal sludge certainly should not be put in a baffled reactor. The Baffled reactor is a pretreatment for wastewater, not a sludge treatment.
I agree with you that it is very important to have new ideas for the fecal sludge treatment. But before referring to costs, we would have to have good and proven solutions. Currently I know the following options:
• Sludge drying beds
• Lagoons – as I mentioned before…. a lot of problems
• Treatment in a large wastewater treatment plant – often not sufficiently thought threw as sludge has high DBO concentrations and normally LOTS of litter.
• ATADS (see other treat in this forum)
• Anaerobic treatment
• Sludge mineralization beds
Treatment in regard to helminth eggs is complicated, so use in agriculture is not recommendable beside the ATADS (which currently is still to expensive and energy consuming) and maybe (lack of data) sludge mineralization beds.
If somebody has more ideas about how to treat fecal sludge it would be nice.
Yours
Christoph Platzer
Brazil

I would like to start with an example from Nepal by our colleagues from ENPHO:

"At the request of the Municipality, in 2005, ENPHO, with support from ADB, UNHABITAT and WaterAid Nepal, initiated the construction of a community-based wastewater treatment plant at Siddhikali, where there was an outfall of a large sewer line and wasteland.

The constructed wetland at Sunga consists of a coarse screen and a grit chamber for preliminary treatment, a 42 m3 anaerobic baffle reactor (ABR) for primary treatment, horizontal flow followed by vertical flow reed beds for secondary treatment and two sludge drying beds for treating sludge. The total area of the constructed wetland is 375 m2. The treatment plant has a capacity to treat wastewater from 200 households, but it is currently treating wastewater from 80 households. The plant receives an average daily flow of 10 m3 of very high-strength wastewater (average BOD5 of raw wastewater is 1,775 mg/l).

Monitoring of the performance of the system over its first year of operation shows that it removes organic pollutants highly efficiently (up to 98% TSS, 97% BOD5 and 96% COD). It was also found that the ABR was very effective in removing organic pollutants and could remove up to 74% TSS, 77% BOD5 and 77% COD (Singh et al., 2007).

The total cost of the treatment plant was Rs. 2.5 million and the municipality has agreed to provide Rs. 50,000 per year for operation and maintenance costs.

The total construction cost of the wetland amounted to NRs. 1,800,000 (US$ 26,000) at NRs. 2,900 (US$ 40) per m2 of the wetland. The average O&M cost of the wetland is about NRs. 20,000 (US$ 290) per year."

Source:
www.wateraid.org/documents/ch7_decentral...tructed_wetlands.pdf

Dear all,

the treatment of faecel sludge as well as the management of faecel sludge became an important issue in the field of sustainable sanitation over the past years.

Just think about the different treatment solutions available for decentralized or semi-centralized options like Constructed Wetlands, Stabilization Ponds or Anaerobic Baffled Reactor (ABR).

From the point of view of an economist it is very important to get more information on investment costs as well as on costs for O&M to support the process of a decision making.

I would like to refer to the concept note by Jonathan Parkinson (forum.susana.org/media/kunena/attachment...iccosting-180811.doc):
Project design - Sound financial analysis is fundamental for good project design. To be able to appropriately cost a project within a given budget, sanitary engineers need to base estimates on accurate unit costs with a clear understanding of the uncertainties surrounding data sets.

I would like to encourage everyone to collect and to share all known projects to get an overview of the actual costs. The aim is to learn from each other. Please always refer to the original author/document for further questions.


Looking forward to your contributions.

Cheers,
Philipp