Dear All- Gunilla, Elizabeth, NityaJ, and others.

Having dealt with conventional natural process of sewage disposal system applying Dewats type of process for treatment of sewage and septage, wish to offr my comments on costing for capital - making of facility, maintainance daily and annually Etc..

The base design value for urban areas is taken of the flow data per day ... in kl/cbm per day at around 300-500 ppm BOD,
And if from poor or slum communities with lesser flush water at levels 1500-2500 ppm BOD.

In some OD areas, nght soil data is assessed accodingly for safe disposal.

Now we consider the base value of volume flow say 150 l gpcd per day per person, @ for 100px / 20 HH.. is 15000 l. ie 15 kl / cbm.

For natural primary process, at best it is done in sewer pipes, septic tanks, next for secondary process have baffle tnks with stone / pebble filters and in last- tertiary stage has phyto- remediaion using plants and greens.

Usually a HRT of 8 - 10 days is given.. ie for a day flow of 15 kl per day.
Total cubics or volumetriccally 15 0000 l, 150 kl/ cbm is held.

As a thumb rule for guidance have:
1. 5 -10% of 150 ML as pre process
2. 30% as primary- septic..
3.30% as scndry wth fltrs
4. 30% as tertiary wth plants Etc
5. 5-10% as polishing/ finishing process.

Accordingly the masonary work is progressed.. keeping say depth of each tank at 2-2.5m deep.
Exception phyto tank to be less at 1- 1.5 m ..
Hence surface land area can be assessed giving also working space kept at 50- 80% more.

Costing can be worked out applying the specs as given above vis a vis costs.. say at Delhi use Delhi Schedule of Rates..DSR.

For maintainance:
Daily ensure apt O & M practices. Electric power needed to draw out water for recirculation in phyto process and for re- use flow to community areas Etc.

6 mthly or annually each tank bottoms are excavated, filter stones flushed and cleaned
And all the matter is taken for co composting Etc.

Pipes are planned and fitted in each tanks for pulling out bottom sludges before implmntation of flows Etc.

Yearly the tanks are inspected any failure in structures are attended as required.

When re use water is used in communities , the gains to the extent of 50% cost of new water is realised.

With well wishes.
Prof Ajit Seshadri
Vels University. Chennai.

Hi Elisabeth,
Thanks for these tips. Very helpful!

best, Gunilla

Hi Gunilla,
After reading through your post again, some older discussions come to mind for me which might be useful for your literature research (maybe you already found them by searching through this forum):

There was a tool called WASHCost Calculator - we talked about it here:
forum.susana.org/forum/categories/164-fi...cost-calculator#2538
and here:
forum.susana.org/forum/categories/164-fi...proach-to-sanitation

Two interesting aspects from that:
- Make sure you don't just look at capital costs but also at the annual operation and maintenance costs (these can be high and difficult to finance for conventional treatment plants, e.g. for electricity costs of activated sludge plants). IRC was advocating using an LCA approach here (life cycle analysis).
- Make sure you compare systems that give you the same result. E.g. you cannot compare a sewer with a pit latrine because the sewer treats much more than just the excreta - it also takes greywater and possibly stormwater. The pit latrine plus fecal sludge managements only collects excreta, and sometimes only gives it partial treatment (so no wonder it's much cheaper).

Also Christoph Platzer from Brazil/Peru has posted quite a lot about the costs of dry sanitation versus conventional sanitation in the earlier years of the forum (2011 to 2015). If you put "Platzer" and "costs" into the search field you find some of his posts. E.g. I found this one which I think will be of relevance to you:
New sewage treatment plants in Indian cities: could dry toilets have been a viable alternative? - and Bengaluru wastewater reuse example
forum.susana.org/comparisons-of-various-...ewater-reuse-example

See also this paper that he authored in 2008:
Platzer, C., Hoffmann, H., Ticona, E. (2008). Alternatives to waterborne sanitation - a comparative study – limits and potentials. IRC Symposium: Sanitation for the urban poor - partnerships and governance, Delft, The Netherlands
www.susana.org/en/knowledge-hub/resource.../library/details/961

It's 11 years old now but I think the approach and methodology are still valid.

Please do let us know what you find and how you get on.

Regards,
Elisabeth

Dear Elisabeth,

Thank you for your thorough response, which made me realize that I did not sufficiently explain the background to my request. I am fully aware that a lot of people question the conventional sewer system as 'the gold standard' as there seems to be sufficient evidence to suggest that the linear-end-of-pipe solution (water toilet to sewer to treatment plant) is unfeasible particularly in rapidly growing urban areas because it is too inflexible, too costly and too slow to implement. Even so, governments and funding agencies such as the World Bank, hold it as the 'gold standard'. This is true pretty much across the world. For example, a recent paper suggests that 20 times more funding is made available in India for development of conventional sewer systems than for other potential solutions such as FSM (Hutchings et al., 2018). *

To give more weight to the argument that we need to find other solutions, we started to look for 'hard' numbers behind the claims that the conventional system is too slow, too inflexible and too costly for rapidly growing urban areas. We do have data from local consultants - what we are looking for is data from other locations, particularly under-serviced areas with high population growth, as this is where it intuitively feels as if it would be futile to invest in the conventional system.

Sorry for the 'jargon'. My understanding of these terms is that 'build-out-time' is the time it takes to 'build-out' the system from the work starts until the entire system is built. It is used in relation to the construction of conventional sewer systems (connections, sewers and treatment plant). The 'build-out-rate' is the time it takes per person or per household.

Looking forward to continued input and discussion about this topic

Gunilla

Refs

* Hutchings, P., Johns, M., Jornet, D., Scott, C., & Van den Bossche, Z. (2018). A systematic assessment of the pro-poor reach of development bank investments in urban sanitation. Journal of Water, Sanitation Hygiene for Development, 8(3), 402-414.
iwaponline.com/washdev/article/8/3/402/3...he-pro-poor-reach-of

Hi Gunilla,

I am not familiar with the term "build-out rates" or "build-out times". What do you mean with those? Also, I think it is problematic to generalise these statements about "gold standards" over the entire world. I think you need to distinguish what kind of countries or regions you are talking about. E.g. if it's Western Europe then true, sewers are the "gold standard" and more or less the only standard for cities (it can be different in remote rural areas). But when it comes to developing countries, it's a different story. Here it seems that the central business district might have sewers and perhaps some affluent areas - although even they might be on septic tanks if it was deemed at some point that there is enough space for septic tanks - and the rest is not connected to a sewer.

The new buzz word in any case is FSM - Fecal Sludge Management. See here on the forum: forum.susana.org/53-faecal-sludge-management
Nasir recently pointed out in this thread that FSM can co-exist with sewers: forum.susana.org/53-faecal-sludge-manage...-question-from-india

So it's not a matter of "one or the other", it can be a matter of both - depending on which part of the city has which needs.

Have you read some of the very good FSM publications that the Bill & Melinda Gates Foundation has put out? I think in there you would find some information on costs, also in relation to sewer systems. Take a look in the SuSanA library and search for BMGF (results: www.susana.org/en/knowledge-hub/resource...title=&author=&year=). Also we recently received publications by NIUA which you might find useful (NIUA is the National Institute of Urban Affairs). They talk a lot about fecal sludge and septage management: www.susana.org/en/knowledge-hub/resource...title=&author=&year=

With regards to costs of sewers, have you contacted any consultants in your town about this? Civil engineers with a few years exerience in the local water utility will be able to give you rule of thumb figures for their towns, e.g. X $ per km of sewer, or X $ per household to treat their wastewater at a treatment plant etc. And don't just look at capital costs. Often it's the ongoing O&M costs that will "break" a project in developing countries... Capital costs being financed by a donor, O & M costs not....

I wonder if you've browsed through these threads in the forum yet in the category of financing, tariffs and fees:
forum.susana.org/164-financing-taxes-tariffs-transfers

I hope some of this is helpful and let's continue the conversation!

Regards,
Elisabeth

Dear Rochelle,

Thank you for your advice. At this stage we are looking specifically for information about the costs and build-out times for centralized sewer systems. The reason being that this is commonly perceived as 'the gold standard'. Intuitively, it feels as if the conventional waterborne toilet-sewer-treatment plant solution is unrealistic in rapidly growing urban areas because it is too expensive, too slow and too inflexible. Many claim that this is the case, but we had not been able to find any 'hard data' on costs or build-out times for sewer systems and treatment plants, which is why I turned to SuSanA for advice.

many thanks,
Gunilla

Dear Ajit,
Thank you for your advice. We will keep those caveats in mind.
best,
Gunilla

Dear Gunilla.

The data given by Nitya is a convenient data to work out your estimate +/- 10%.

Also in local Indian scenario the work is semi labor- machine driven oriented. But a basis can be worked out.

Well wishes.
Prof Ajit Seshadri.

Dear Nitya,
Thank you, this looks like it might be the kind of data we need for our analysis. I'm very grateful for all of your efforts. May I get back to you if I run into difficulties in interpreting the information?

best,
Gunilla

Dear Prof Oberg
I found a link that may help your case - gmdwsb.assam.gov.in/portlets/jica-assist...ati-sewerage-project. Its about a sewerage project in Guwahati, Assam.

Location of the Project (Zone-I) Guwahati Kamrup Metropolitan District
(South Central and South East Area) Assam
Target Population (i) 2020 : 10.10 lakhs
(ii)2035: 14.95 lakhs
(iii)2050: 23.32 lakhs
Project Implementation Period 7 (seven) Years
Construction of Capacity Treatment Plant
on ASP technology 187 MLD
Trunk Sewers 201 Km
Lateral Sewers 501 Km
Laying of Pumping Main Station 16.915 Km
Gravity Main 184.198 Km
Number of Pumping Stations 5 (five) Nos.
Number of Lifting Stations 18 (eighteen) Nos.
Number of House Connections,
Power Connections and Road Restoration 101058 Nos.
Trenchless Pipe Laying 880 metres
Total Project Cost JICA Portion: INR 1001.28 crore
State Share: INR 177.47 crore
Total: INR 1178.75 crore
(1 crore = 10 million, the current rupee exchange rate is about 70 to a US dollar)
Regards
Nitya

Dr. Ms. Gunilla Oberg, Professor, UBC, Vancouver, Canada

Respected Madam,

A few years back (2012- 13) for preparing costing for laying sewer lines, in communities and planning for Decentralized Treatment and Re use system, had used prevalent rates as per DSR- Delhi Schedule of Rates for civil and other works.
This data in table form would be available in website and on search under that title, please.
You should be able to get a fair idea on the rates, and can be compared and your area- rates can be arrived at.

with well wishes.
Prof. Ajit Seshadri, Vels University, Chennai, India.

Dear Prof.Oberg,

I attaching a recently collected data on the STP construction cost and sewer (UGD) cost from Hubli and Dharwad.

All costs in INR (Cr is Crore = 10 million)

I am not sure of the exact length of the sewer lines installed (should not be too hard to find out). Hope that helps