How to Design Wastewater Systems for Local Conditions in Developing Countries

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  • F H Mughal
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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

Dear Kevin,

That is a very interesting and useful report. It is sad that Punjab government did not take any action. It is, in fact, a guidance manual, specific to our local conditions. Because of some similarities, the report would be useful for friends in India, as well. I see, you have been to Sukkur, Larkana and other northern Sindh towns.

Where can I find the report of Indian Central Pollution Control Board, you have referred to?

Regards,

F H Mughal
F H Mughal (Mr.)
Karachi, Pakistan

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  • kevintayler
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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

A quick follow-up on Christoph's email. His basic calculations confirm the point about the pond being overloaded - there is no way that a facultative pond could work with such a short retention time. The sewage strength was probably slightly lower than assumed by his 54gm BOD per capita per day (for some reason Indian wastewater is very weak). However, this does not alter the main conclusions.

I have found a couple of pieces of information that may be interesting and am sending them as attachments. One provides a list of WWTPs constructed under the Yamuna Action Plan with design capacities. The second is one of the Japanese university reports that I mentioned. I do have some other relevant reports and will try to sort out the best ones
Kevin Tayler
Independent water and sanitation consultant
Horsham
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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

Dear All,
based on the data from Kevin I did a quick calc about the mentioned combination UASB and WSP in India which has a black effluent.
No wonder the effluent is black. please see this table



The actual load for the WSP is 4 !! times higher than the recommended load. Therefore the lagoon must by anaerobic, therefore presenting strong odour and black effluent. This seems not to be a problem of the technology but yes of dimensioning.
And I choose the values totally in favor a low load of the WSP.

Pawan and Kevin, could you check if my data are more or less correctly assumed?

Regards

Christoph
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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

Dear All

As requested by Mughal, I am trying to add the Punjab wastewater report as an attachment. I hope that it works - it is almost 2Mb and I am not sure whether there is a limit.

In answer to Christoph, I think that the UASB plants in India varied in capacity from about 5000m3/d up to 25000m3/d and above. I have another report which should provide details but will have to look for it.

A couple of points, first -responding to Pawan's point on the effluent quality of the Indian UASBs. The UASBs were followed by 'polishing' ponds that were meant to provide secondary treatment but they only had a bout 1 day's retention and only reduced perhaps 25 - 30% of the polluting load. UASBs are what I would refer to as enhanced primary treatment - they remove more BOD and SS than a conventional sedimentation tank but nowhere near the amount required to meet generally accepted effluent standards. This was a big flaw in the design and it would have been better to have provided proper secondary treatment.

With regard to Mughal's point about failure to provide maintenance for WSPs in Sindh - I saw the same thing a few years ago in Sukkur, Larkana and other North Sindh towns. Also, I designed a system for Kohat in the north that was built but never commissioned. I think that Mughal's point about the difficulties of getting staff to maintain ponds that require fairly simple maintenance is an important one. There is a good report by the Indian Central Pollution Control Board that examines the operation of a large number of plants throughout India. I looked at the findings to see whether there was any correlation between simplicity of process and successful operation, focusing particularly on WSPs. The result supports Mughal's point - hardly any of the WSPs were operating satisfactorily. I think that that report is available on the internet.
Kevin Tayler
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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

Dear Pawan,

very interesting to hear about the UASB use in India. Do you have an idea which is the typical size and how many are there? Do you have some more information or could you point me to a publication? This month we started a research project about the potential of biogas production in UASB. We will measure the COD influent + effluent, the volume, biogas volume and biogas quality. One task is as well to gather more operational information. As a first result I can say we saw quite a few UASB which had strong odor problems - but that is an indicator for not properly managed or build UASB, as the gas should not come out without burning = oxidizing = no smell any more.

As for the observation of black colour. We do see that only in UASB where sludge goes out with the effluent. Could you comment on that?

Such color remains at the outlet final pond of the WSP.

In this case I would imagine the WSP is overloaded? I not I don´t understand as the black color should disappear when the sludge settled in the lagoon.

I am very curious to hear more about the Indian experiences, as we in Brazil do have a lot of UASB, a lot of problems as well, but mainly due to errors in design, operation or maintenance - not due to the system itself.

Regards
Christoph

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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

Dear Kevlin

You are very right that under Ganga Action Plan several UASB plants were constructed in states like Uttar Pradesh in late 1980s. For the treatment of effluent from UASB, WSP system has been implemented in most of the cases. It requires more land space. Odour problem is continuous. In some cases it has been observed that effluent from UASB turns in deep blackish colour ( like coke colour) when comes to settling chamber of WSP. Such colour remains at the outlet final pond of the WSP. People do not use such effluent for agriculture purpose. Its disposal remains a problem. Quality of treatment is also very low, it is regarded as the secondary treatment only. Therefore, UASB is not commonly used now in Indian cities.
regards
pawan jha
Pawan Jha
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Foundation for Environment and Sanitation
Mahavir Enclave
New Delhi 110045, India
Web: www.foundation4es.org
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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

Thanks Christoph

This is good information especially for the agencies that are planning to implement or implementing WSP. Here in Uganda under the ministry of Water and Environment we designing and planning for the construction of Faecal Sludge management. This is to be done in Urban centers where the sanitation coverage (mostly pit latrines) in urban areas in Uganda is estimated at 81% (SPR, 2012). According to the 2010 MDG progress report on sanitation and drinking water by WHO and UNICEF, access to improved sanitation in urban areas in Uganda is estimated at 34%, but this does not include 50% of the urban population which uses shared facilities. Despite the relatively high sanitation coverage figures, faecal sludge management (collection and treatment) in most small towns is poor.

For the sake of poor management, we plan to use the public private operators to run the system with subsidies from the government like zero taxes on Cesspool emptier. This can make it cheaper to empty lined pit latrines hence increase on the volume.

Anybody with information on Feacal Sludge treatment Plant design, construction and operation and maintenance can share with me.

Thanks

Arnold

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  • F H Mughal
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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

Dear Kevin,

I was delighted to see your interesting comments. Much like Fasialabad, in Tando Muhammad Khan (in Sindh), ponds were constructed, back in 1980s, because a large of land was available. Few years back, I visited the site, it was a picture of total neglect - weed growth all around, stagnant sewage in ponds - all suggesting that nobody is paying attention.

Since, you are familiar with the people here, I'm of the view that, when there is nothing to do in wastewater treatment plants, like ponds, people become unresponsive to their duties, and tend not to attend to the work. The TM Khan ponds gave that picture.

Could you kindly send me that report, you sent to the Punjab Government? I'm sure, it will be useful to me.

Regards,

F H Mughal
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Karachi, Pakistan

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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

Dear Mughal and Christoph

This is an interesting subject. I agree with Christoph that finding space for WSPs is difficult even when the first ponds are anaerobic. There are some examples in South Asia. The ponds in Faisalabad, Pakistan, built with ADB support in the late 1980s are very extensive and could only be built because a large tract of Agricultural University land was available. They treat perhaps 20% of the total sewage flow from Faisalabad. The original plan was to build other similar treatment plants but land acquisition would be prohibitively expensive. The IWMI did quite a lot of work to monitor the pond performance - it was less than optimum, partly because of poor maintenance but also because winds created short-circuits in the large ponds.

Dhaka has a large area devoted to a WSP system but again the system serves only a small proportion of the total flow from the city. Consultants recently produced proposals to gradually replace the ponds with anaerobic ponds followed by trickling filters, a system that they had used successfully in Vietnam.

This ties in with Christoph's argument for anaerobic treatment followed by secondary aerobic treatment and seems compatible with Mughal's emphasis on secondary aerobic treatment. I prepared a report on this for the Pakistan Punjab Government a few years ago, which unfortunately was never made public. This drew on operational experience with treatment plants in India, where I had been working immediately before the Pakistan work.

One potential problem with anaerobic systems is that they do not work so well with weak influents and sewage in South Asia is often quite weak. Several UASBs were built along the Ganga and its tributaries from the late 1980s onwards and these did not seem to work too well - as a consequence the Indian Government has moved towards Sequencing Batch Reactor and other relatively high-tech treatment options. The problems with the UASBs may be as much to do with poor operation as inherent weaknesses in the technology but I think that this is an area that needs more research. (There are some good papers by Japanese universities on operational experience with some of the UASBs, for instance those in Karnal,Haryana - but I think that more work is needed on this.

I quite favour trickling filters for secondary anaerobic treatment as they use much less energy than artificially aerated systems such as activated sludge. I think that possible problems with flies can probably be overcome by using relatively high-rate filters with plastic media
Kevin Tayler
Independent water and sanitation consultant
Horsham
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  • F H Mughal
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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

Dear Christoph,

I appreciate your views. The disinfection aspect you mentioned will raise many eyebrows.
In a megacity like Karachi, the drinking water do not get adequate disinfection. We had many deaths in Karachi due to Naegleria fowleri - result of inadequate disinfection. So, if disinfection of wastewater is mentioned here, that person will be called as "living in fool's paradise."

I prefer aerobic systems, midway between oxidation ponds and activated sludge.

Regards,
F H Mughal
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Karachi, Pakistan

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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

Thanks for the link Mughal,
personally I always appreciate Duncan Maras very high knowledge on lagoons and his clear view on "what is possible in developing countries".
I don´t share his VERY lagoon orientated interpretations. Almost every comparison ends with .... a lagoon is better, if this is wetlands, UASB or aerated lagoons... therefore his "critical discussions" are not very critical.
Just one example when he discusses disadvantages of lagoons
Pag. 93

Land
WSP do require much more land than conventional treatment processes such
as oxidation ditches (Chapter 20) or activated sludge. The choice is between
buying land (which is an investment – see earlier in this chapter) or spending a
large amount of money each year on electricity. It is quite straightforward to
determine where inexpensive land is available and how much it costs to
(a) convey the wastewater there and (b) construct WSP – is this cheaper than
an activated sludge plant nearer the city? If these cost calculations are done
correctly and honestly, the answer to this question is almost always Yes.

At least here in Latin America (even in 2003) lagoons had a severe problem of space. a) it is hard to get so large areas even if you go far. b) it is hard to get so large areas without a lot of earth movement c) there is a severe problem, that poor people rapidly tend to settle around a WWWTP.
These problems have to be addressed and made clear - in another chapter he could discuss the operational costs vs. land use aspect.
But this is a characteristic of his presentations/publications, he is always defensive (or aggressive) to everything which is not lagoons. Having that in mind the book is very helpful.

Although he does not like UASB instead of anaerobic lagoons, I would like to point to a combination I favor very much. UASB combined with facultative /maturation ponds (if you have the space, if not - just facultative and disinfection). UASB in the beginning - to do the “hard work” (~70 % BOD removal) with a clearly defined area, with the possibility (and need) to maintain a sludge removal - by that easier to maintain (in my understanding) as the typical situation, where the lagoon after start up is forgotten for years until the lagoons are full of sludge and the (than close) neighbors are revolted due to odor problems. The plant by that can be much smaller as well, diminishing the disadvantage of large areas. Furthermore it is much easier to control the methane emissions (and by that the odor as well) Obs.: I know many UASB have odor problems = not hermetically closed reactors – construction problem.

Yours

Christoph

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Re: How to Design Wastewater Systems for Local Conditions in Developing Countries

Dear Christoph,

The attached publication on Wastewater Treatment in DCs, by Duncan Mara, should interest you. But, first, please check it from copyrights' point of view.

Regards,

F H Mughal
F H Mughal (Mr.)
Karachi, Pakistan

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