New sewage treatment plants in Indian cities: could dry toilets have been a viable alternative? - and Bengaluru wastewater reuse example

  • StevenHorn
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  • Process engineer, worked in wastewater treatment sector in South Africa, Australia, UK, the Netherlands, Germany
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Re: Sewage Treatment in India: "We are making collection, transportation, treatment and finally reuse of sewage mandatory"

To answer Mughal’s questions from 29 May in this thread (and in way of introduction: I am the mentioned husband of Elisabeth von Muench; I am a process engineer by training, currently working for a company (contractor) building wastewater treatment plants worldwide ( ); I was area manager for India for one year in 2014):

1. What types of wastewater treatment plants are preferred in the rural areas of India – activated sludge, trickling filters, aerated lagoons, anaerobic filters, waste stabilization ponds, etc?

What is your definition of rural here? I only have experience in urban India. If rural areas are quite dispersed then there is little point in building a sewer system and treatment plant, as it would not be cost effective. Or do you mean rural areas with small towns of say 100,000 people? I would say for rural areas with lots of space, the waste stabilization ponds are probably still the most common at present, but this is just my guess.

For the urban areas, we mostly build conventional activated sludge treatment plants and SBRs (sequencing batch reactors), a variant of the activated sludge process.

2. Is funding for the O&M (operation and maintenance) of the plants a problem, in rural areas in India?

From the viewpoint of a contractor, we are more and more seeing contracts where the company that has built the plant is also paid to do the O&M for 5-15 year periods (with the budget as set out during the tendering process). Where the funding for the O&M comes from, I am not totally sure but I would expect the same sources where the funding for the capital came from, i.e. from Indian tax revenue but also from JICA, Asian Development Bank (ADB) and Worldbank.

In the past, the O&M was usually done by the municipality itself, not by the contractor. For example, in a recent project in Jordan where we built a treatment plant, it was done like that. After the plant was built and handed over, there were problems with the O&M being carried out by the wastewater treatment authority (client). In my opinion, the model of the contractor both building the plant and subsequently operating it for some years is usually a good one.

3. Are the plant’s components like aerators, screw pumps, sludge scrappers, large vertical non-clogging pumps, etc, etc, manufactured locally in India, or, are they imported?

These days, all this standard equipment is manufactured in India. Only specialized equipment is sometimes imported, like CHP units (combined heat and power units) or high efficiency blowers.


Steven Horn
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  • JKMakowka
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Re: Sewage Treatment in India: "We are making collection, transportation, treatment and finally reuse of sewage mandatory"

muench wrote: I don't know... Doesn't sound very appealing to me to have millions of lowly paid sanitation workers moving containers of excreta around a big city [...] - adding further to all the cities' traffic jams (and odors?) if nothing else. And for a country like India that is pulling itself out of poverty and slowly leaving "developing country" status behind, I don't think politicians would be thrilled to push for that option.

If you put it that way... but yet this is the way it is done everywhere when it comes to regular solid waste (if a solid waste disposal system exists).

I think for dry sanitation to succeed, it needs to hook into such existing and generally looked on favorable solutions. Urine based fertilizer production might then be a great way for municipalities to do some cost recovery on their solid waste disposal systems, similar to how it is done with land-fill gas for example.

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  • F H Mughal
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Re: Sewage Treatment in India: "We are making collection, transportation, treatment and finally reuse of sewage mandatory"

Dear Steve,

First off, many thanks for your informative post. That was my request and, I highly appreciate.

Yes, you are right – with rural areas I mean small towns. The choice of wastewater treatment systems in India seems to be similar to that of Pakistan. Here too, WSPs would be preferred in rural areas, and systems with extended aeration in urban areas.

In 1966, Dorr Oliver designed 2 large trickling filters plants in Karachi. Another foreign firm came in 1980s and converted them to primary treatment only.

Of interest is the point of O&M you mentioned, for India and Jordon. As you say, in India, you had to do O&M for 5-15 years – that is a very large O&M period!! In Jordon, there was none. You had to hand over the plant immediately after construction to the client n Jordon. These are two opposite perspectives.

I designed aerated lagoons wastewater treatment plant in Karachi in 1982. The contractor operated the plant for one year. That was the clause in the tender documents, and the contractors quoted their tendered amount accordingly.

Before I sign off, I have one small request: keep up writing those posts. Not only you write nicely (and in the process, you churn out useful information), your wife is desperate to increase the membership of this forum – - we can then have 5,001 members (if there are already 5,000 members)!!

F H Mughal

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  • christoph
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Re: Sewage Treatment in India: "We are making collection, transportation, treatment and finally reuse of sewage mandatory"

Dear all,

actually I missed this very interesting discussion up to now as I thought (from the title) it is about India – in reality it is about concepts for all non served sanitation areas. Although all of what I am writing here I wrote in other posts here and there, I would like to put it together a bit (I apologize to all who read Susana since a longer time for repetitions)

I am a classic wastewater treatment engineer in my daily work. Our company (Rotária do Brasil) in Brazil is making the living from activated sludge plants, wetlands, anaerobic treatment (UASB, BAFFLED reactor) and biogas projects. We do everything from design, to construction, Electric and Automation, plant operation, septic tank emptying (trucks), sludge treatment. The sizes vary from 10 pe. to 200.000 pe.

We worked a lot in Peru (Rotaria del Perú, today AKUT Perú) with UDDT (Elisabeth mentioned it in a post above) – working on implementation with public utilities since 2008 in order to get models going, where the public utility takes up the responsibility for non sewered areas (which offer the possibilities to implement dry sanitation).

So I know both sides (the classic wet and the dry) very well.

Kai – although I am totally with you on a view that – if we want we could do dry concepts – I had to learn over the years that “we” (seen as the majority of society) apparently do not share the view – or knowledge – or conviction about dry sanitation that we (you and me) have.

For the defense of those who are not convinced about dry sanitation – there are no large scale business models (business as in public utility business) implanted to prove the viability. I did the theoretical numbers to prove the viability of dry sanitation concepts already in 2007 (it is in the Susana library) and we (company) repeated the calcs for several situations, nevertheless no rollout up to now. We (Heike and me) have been in discussion with SEDAPAL since 2009 repeatedly to implement in an area dry sanitation with no results (they are open if a doner would be open – they think they can not “risk public money on the concept). Lima is the perfect place for this and there is a VERY high need for that. We (company) did lately focus groups for the World Bank with the users of UDDT in Lima, ALL of them said that this would be the solution for a larger scale. We tried to convince several times various donors, that with only 2-4 Mio U$ a prove of concept would be possible. Nothing! I don’t understand why – but it is as it is. Dry sanitation is not seen as the solution by us (the society).

To me it is clear that container solutions with fresh feces as proposed/used by X-runner or Soil really are no viable solution. All our ( company) calcs show that the costs for a frequent recollection (weekly) are way too high and the recollection of urine as proposed by Elisabeth is interesting may be in the future…when P has an adequate value, but right now not viable. I would have to look up the exact number, but from the head more than 50% of the monthly costs of a model we (company) developed for GIZ (which is in the video) are from the urine recollection.

I do see a really LARGE possibility for areas without sanitation to go for dry concepts, as the bathrooms have to be constructed as well and a storage for at least 6 month could easily be integrated (at least in our (company) bench designs)… but again those who agree with me are too few. And apparently non are donor organizations. BMFG is not concentrated in South America even though Lima could be a good example. Those who are there, still are not convinced.

But I see it very important to get definitions straight as Steve pointed out. Some talk of rural but mean settlements, which leads to a large difference in concept.

So closing this lengthy post I would like to propose the use of clear definitions. For me three definitions are clear:
  • A) Rural – lots of space between houses
    B1) Densely populated areas –multi-story houses - absolutely no room, land is very scarce = valuable
    B2) Densely populated areas – 1-2 story houses - absolutely no room, land is very scarce
  • Everything else is between A and B depending on the size of the town – city. There can be made many classifications, they are all overlapping.


    P.S. Mughal – I don’t agree in using extended aeration for WWTP above 50.000 p.e (or even less). Too much energy, there should always be an anaerobic step (UASB or digester) if possible and a classic activated sludge process (5-10 days sludge age depending on the purpose). As well in order to get the possibility for energy production (viable in Brazil > 100.000 pe)
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    • Marijn Zandee
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    Re: New sewage treatment plants in Indian cities: could dry toilets have been a viable alternative?

    Dear all,

    All few observations from my side.

    1.) In the context of India, or any other nation with a large Hindu population, I think it would be very difficult to set up a functioning system which requires handling of semi-fresh human wastes. To many of the poor unemployed who may be compelled to work in this sector it would probably feel like a time machine going backwards.

    2.) I think the model where the contractor takes on at least 10 years of O&M after building a waste treatment system is a very sensible one. Of course, one still needs to guarantee that the client has sufficient income (tax revenue) to keep paying for the service all this time.

    3.) I think the best "non-classical" solution that could be made to work for dense cities in the near future would be a system separation of urine, grey-water and black water. With different treatment systems on different scales. For example, the scale of large buildings or sections of streets for grey water and urine and something more like traditional WWTPs for the black-water. If the WWTPs are designed correctly, surprisingly high levels of energy and resource recovery are possible.

    4.) I think that pioneering new sanitation solutions for formal urban areas in the developing world is not realistic. People aspire to the standard set by the developed world. For me this means that we should try to have dry-sanitation towns or cities, with optimized recovery facilities, first in the developed world. I feel that until you have such examples (and evidence of voluntary take up by wider communities) it will be very hard to convince people and policy makers in the developing world to embrace such technologies.



    Marijn Zandee

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    • zenrainman
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    Re: Sewage Treatment in India: "We are making collection, transportation, treatment and finally reuse of sewage mandatory"

    I guess it is difficult to explain a large country in India in simple terms :) .*

    1. What did you mean by: "these are the best of times and the worst of times for waste-water in Bengaluru"?

    This is a quote from a famous English novel describing the early days of the French revolution.

    2. Is there any talk in your city about reducing the amount of wastewater generated? E.g. via reduction of water use (demand management)?

    The city is constrained for the supply of water which stands at about 80 lpcd right now. There is no question of reducing demand any further for the moment.

    3. What fraction of the 10 mio people are connected to the sewer system presently and will the connection rate be rapidly expanded?

    About 70 % of the people would be connected to underground sewerage system.

    4. Would people really drink the treated wastewater in that appartment building, and which treatment process is being used there? Must be something with membrane filtration? But in any case people don't tend to drink tap water in Indian cities but drink only bottled water, I thought? (my husband recently had an Indian water engineer visiting here in Germany and it took him about 20 minutes to convince him that drinking from the tap in Germany is safe...)

    People are already drinking the treated waste-water after blending it with fresh water . People do tend to drink tap water in India , depends on which city you are from . In my city Bengaluru tap water is absolutely safe to drink, for an Indian.

    5. When you are saying "One experiment we are assisting in is to use treated waste-water for artificial recharge of the shallow aquifer.", then who is "we"?

    We is my NGO Biome Trust and a resident society with 360 plots / households called Rainbow Drive in close discussion withe State Pollution Control Board.

    6. Are you agreeing with this trend of building more and more large treatment plants or would you argue for other alternatives? Like those decentralised treatment plants, would you say they are inherently better or it depends? (I guess dry toilets are out of the question for a densely populated city like this one)

    There is always a combination which would be reality. Is a 10 million litres per day plant large ? in the context of 1500 millions of waste-water being needed to be treated? In Bengaluru there will be 25 large treatement plants (MEASURED IN MLD) and about 6000 small treatment plants (measured in KLD)

    Finally it is Bengaluru now not Bangalore.


    * Note by moderator: The sentences in italics were the questions raised by Elisabeth in this post on 26 May (scrol up in the thread):

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    • zenrainman
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    Re: An example of an Integrated Urban Water Management process from Bengaluru,India

    The city of Bengaluru in South india has a population of 10 million. It is supplied with 1400 million litres of water every day from a river called the Cauvery. It is estimated that about 1100 million litres of waste water is generated every day which needs to be collected and treated. The city has three major valleys through which the storm-water and now the waste-waters flow. The water utility called the Bangalore Water Supply and Sewerage Board BWSSB has set up 14 sewage treatment plants and is in the process of setting up an additional 11 sewage treatment plants to treat all the 1100 miliion litres of waste-water generated. one such small plant is located at a lake called Jakkur in the North of the city. This is designed as an Upflow Anaerobic Sludge Blanket (UASB) with an anoxic tank and Extended Aeration system to treat 10 million litres of sewage per day. The system then releases the treated waste-water to a constructed wetland where it is polished and the enters a 50 hectare lake. The lake is always full throughout the year and recharges the shallow groundwater aquifer to the extant of 7 million litres per day. Fish is also reared in the lake and a daily average harvest of 100 kilogrammes of fish is collected by fishermen. The lake is full of birds including the weaver bird, cormorants, pied kingfisher and pelicans. In an interesting way using ecosystem services waste-water is used to enhance bio-diversity , fill a lake , recharge aquifers and provide drinking water through the shallow and deep bore-wells nearby. More details and photographs in the attached Facebook post

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