Dear Colleagues,

I would like to know whether you have any best practices of Biogas Sanitation Systems and DEWATS in schools around the world, particularly when it comes to operation and maintenance of the facilities.



Best regards,

Doreen

I recently visited a small fixed-dome bio-gas system in a primary school in Kampala/Uganda originally build as a pilot project by the Makarere University and SSWARS ( www.sswarsuganda.org ). Due to its size (only two toilets are connected) it does not produce sufficient gas for all the cooking needs, but they added a (school owned?) cow that feeds on the school grounds that also supplies manure to the system.
One of the reasons this was added, is that during the long Christmas school holidays the toilets are not in use and the digester thus had problems (didn't get further details on that).
It also seems like the government of Uganda has recently become interested in pushing Biogas technology in schools specifically... lets see what comes out of that.

Returning to the forums after quite a long hiatus!

As JK alluded to, I can't imagine biogas for schools being a useful idea at any size, unless livestock are involved or there is continual student presence at school all year round - the seasonality of most schools would kill any decent gas production. (As well, school wastewater is fairly low strength and, alone, doesn't really need biogas pre-treatment in most cases.)

This seasonal (and even weekday/weekend) flow variation makes schools a challenging topic for DEWATS - flow equalisation tanks are recommended to even out the flow passing to the treatment units. Constructed wetlands or aerobic filter units are likely the better bet for secondary treatment following a septic tank. BORDA and RTI have some good examples in Asia that I previously reviewed and can send if you're interested! I will be interested, though, to hear if there are any successful examples of biogas for schools, and what principles or special circumstances have made them successes!

Cheers,

Julian Doczi
Research Officer - Water Policy
Overseas Development Institute

Dear Doreen,

BORDA has experiences with this in Asia, for example in Indonesia. We recently added some more presentations from BORDA from the Nagpur conference to the SuSanA library and going by the title, these presentations from that conference could be relevant for you:

Campbell, Alex - Cambodia
School Based Sanitation (SBS) in Cambodia - Multi-Stakeholder involvement in decision making processes for sustainable decentralized school WASH infrastructure

Eales, Kathy - South Africa
The limits of community management: Some flndings from Indonesia's experience of implementing community-managed DEWATS at scale

Ekasanti, Prawisti - Indonesia
Pre-fabrication of DEWATS in Indonesia with RFP

Reynaud, Nicolas - Germany
Monitoring results of 108 DEWATS in Indonesia

Zifu Li, China
Prefabricated biogas reactor based system for community wastewater and organic waste treatment in developing regions of Asia

You can access all these presentations here:
susana.org/lang-en/library?view=ccbktype...p;type=2&id=1660

I agree with the others that you shouldn't expect too much biogas from a school-based biogas plant. The biogas might be a nice bonus but don't expect loads and loads of free energy...

Could you expand a bit on the background of your question? Why exactly did you ask?

Dear Julian: can you add the link(s) to those cases which you mentioned? Are they those which we have already in the SuSanA library? (better than sending by e-mail)

Regards,
Elisabeth

Hi Elisabeth,

Nothing new to add on BORDA - The case studies I did during my time at CAPS were already uploaded back in 2011 (see my post history for a reminder)

As for RTI, where I previously consulted, they have an entire website now on best practices for DEWATS planning and design (very useful!), which you can check out at: watsanexp.ning.com/

On this site you can also find info about a school DEWATS case study that RTI did in the Philippines, with secondary treatment provided by a cocopeat biofilter, for which RTI previously received Gates Foundation funding to develop. I personally think it's a really neat technology and very useful in countries with lots of coconuts!
watsanexp.ning.com/page/cocopeat-biofilter-for

Cheers,

Dear all,

I guess what you would end up with at a school is more a "biogas septic tank" which is a septic tank that is made gas-tight, so that methane is captured. The main aim of this device would not be gas production but COD/BOD reduction. The gas would just be a nice extra, and have a very positive ecological impact, because methane is not escaping into the air. As Elizabeth and others have mentioned, the gas production would be quite low, but may help light a few lamps at the school grounds at night.

The slurry of such a device would be very liquid and definitely require a form of secondary treatment, such as a wetland.

Kind regards

Marijn

Dear Doreen and all,

Interesting discussion and thanks Elisabeth for pointing out the various presentations from Nagpur conference. I have had quite some struggeling experience with DEWATS in schools in Kenya, thus I want to contribute to this discussion abit. I agree with most of the points the previous speakers have raised except some issues on biogas (I would skip it) and secondary treatment.

In the school environments of Kenya (at that time it was my first time being in a developing country) I have noticed that school management is weak and thus expectations on proper O&M of DEWATS should be not be too high. It was especially obvious that the intial incentive of using the "cost-free" biogas for cooking did not pull the strings at the end. Once it got obvious that the biogas production is low and would only serve one or two cookers (out of many more) for 2 or 3 hours (required for a school day are 6 hours or more of cooking) the interest declined dramatically. It was easier for the schools to stick to cooking with wood which cooks faster and can be run continuously throughout the day. If using biogas it would mean to either stop using the cooker after the biogas has finished (not possible as they need all the cookers) or switching the cookers back to woodfuel (removing the biogas cooker from the stove which is cumbersome). See some pictures below. At the end the schools have mostly abandoned the use of biogas. Also small maintenance issues had quickly put off the schools in using the gas. Moreover it is quite expensive setting up such a digester and biogas system. One of the projects I am referring to is Gachoire Girls High School www.flickr.com/photos/gtzecosan/sets/72157625843400102/

Demonstration of biogas cooker in big stove von Sustainable sanitation auf Flickr

Biogas flame von Sustainable sanitation auf Flickr

I would find it most appropriate for schools to set up a simple settler and Anaerobic Baffled Reactor to reduce BOD/COD, no biogas capture/use and than infiltrate the effluent. This will keep the system simple with no major requirements of O&M, similar to a septic tank. The advantage is that the wastewater in DEWATS is treated better than in a septic tank thus reducing pollution risk of ground- and surface water. Key in schools would be to try to organise a regular de-sludging of DEWATS. This could be maybe done through a required contracting of local service providers like water utilities by the schools. Costs would need to be firmly included in the schools budget and a monitoring system set up with the Ministry/Department of Education (or other most suitable institutions) to check on a yearly basis the sludge level in the system or some other indicator for proper performance of DEWATS.

The semi-treated wastewater could also be re-used in wood lots or fruit planations e.g. Bananas via shallow underground infiltration trenches. The sludge could be deep-trenched within the school ground during long school holidays.

It would be great to hear more feedback from others on their experiences with DEWATS in schools.

Cheers
Christian

Hallo everyone,
this is my first time in this forum. I am currently working as an independent consultant for BORDA and WSUP on FSM -Projects and School sanitation. The last two years I worked intesively on DEWATS solutions in Sub-Saharan counries focusing on biogas technology.
Due to a contact with Christian, I was asked to join this discussion.
First of all the discussion is great and importnat, thanks.

Biogas for school sanitation is first of all a participatory case. If the school really involved in the assessment they need to decide if biogas makes sence for them with all pros and cons.
+gas (bi-product-cooking of relish for examaple)
+anaerobic treatment(more efficient than septic tank, (there is always airation in septic tank lids))
+bio degradeable waste disposal
-maintenance

From my experience biogas works in school sanitation...one major point though is maintenance!
If this is not covered the technology fails. We do need a service provider model for school sanitation maintenance or the school does it them-selves which is not very likely to happen from my experience except they really want it.
Furthermore DEWATS are quite expensive, therfore it will make sence to develop upgradable technology which can at first be applied at many places and later be upgraded to higher treatment efficiency (a little bit treatment is better than no treatment).
However, this is over streching the discussed topic.
Attached you can find a DEWATS handbook which BORDA has designed in Indonesia.
For any further questions on that please contact me.

Thanks


Regards
Thomas

Dear Thomas,

Great that you joined the discussions and thank you for attaching this very useful manual of DEWATS. I was always searching for something like that. Perfect!

With regard to the use of biogas in schools it always depends on providing the school with the expected data on operation and maintenance costs, time and personnel demand in order to make informed decisions. I am not sure if a school will choose biogas if they calculate the O&M costs against the savings on woodfuel or similar for cooking. If there are any economic analysises out there on cost effectiveness please post them here. My gut feeling says it wont make a business case, unless maybe the schools have sources of animal manure and kitchen waste to sufficiently boost biogas production.

Cheers,
Christian