SuSanA - Forum

Re: Biogas production from digested sewage sludge - by: AquaVerde

Fri, 24 May 2013 13:30:01 +0000

I came across a good presentation on

Biogas technology

a key technology to adjust fluctuating renewable energy sources and to recycle scarce resources from bio-wastes and residues
by Prof. Jens Born

See developments on ABR technology: Fermenter Technology - M-ABR (combination of fermentation and biofilm)

1. Biogas ABR-technology has a lot of innovative potentials:
◦ Simplicity and robustness
◦ Maximize efficiency
◦ Substrate invariance

2. Promising ABR-technologies are already introduced in waste-water treatment, but have to be adapted to the prerequisites in agriculture (dry matter content, .

I hope the presentation is of interest to you too.

Best regards,
Detlef SCHWAGER

Re: East Africa now switches to Biogas - by: JKMakowka

Thu, 25 Apr 2013 11:40:00 +0000

Thanks for linking that comprehensive article. It's nice to hear that food processing industries in EA are discovering bio-gas on a larger scale and that there is some success at a institutional and house-hold level too.

Personally I doubt the relatively expensive fixed done HH biogas units will ever take off though. What is really needed, is a affordable, durable and mass-produced plastic bag biodigester for that to ever scale up at rural HH level.

I recently talked to the Ugandan representatives the novel rain-water harvesting "bags" called BOB: drwh.enterpriseworks.org/ which is pretty similar in design to what an ideal plastic-bag biodigester would look like too. Maybe I can convince them to look into bio-digesters too.

East Africa now switches to Biogas - by: Doreen

Thu, 25 Apr 2013 07:35:10 +0000

Dear Colleagues,

I came across this article in the East African newspaper about the rising interest in Biogas in the region.

Please follow the link to read the article: www.theeastafrican.co.ke/news/EAC-switch...hou97kz/-/index.html

They even mention Umnade Trust biogas units and the Naivasha Bus Park Public Toilet with a biogas plant which was funded by GTZ (now GIZ), EU and SIDA.

Best regards,

Doreen

Re: Biogas Sanitation Systems and DEWATS in schools. Any best practices? - by: christian.rieck

Wed, 10 Apr 2013 22:14:24 +0000

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

Re: Chinese Technical Code for Application of Anaerobic Digestate Fertilizer (Bioslurry) - by: muench

Tue, 09 Apr 2013 10:31:29 +0000

And I had one more question about pathogen kill in anearobic digesters:
I had asked (above):

From my understanding, biogas digesters are not particularly strong on destroying pathogens. The helminth eggs may settle well but wouldn't you still find them in the slurry? By which mechanism would they get killed in a digester?

Answer by Heinz-Peter Mang (thank you!!):
++++++++++++
The question with the helmith egg was answered already in the GIZ-ecosan-Technology review "Biogas sanitation" (www.susana.org/lang-en/library?view=ccbk...mp;type=2&id=877). "Helminth" means parasitic worm, including : Ascaris lumbricoides (sometimes called just "Ascaris"), and hookworm (Anclostoma duodenale and Necator americanus). In the table "Effects of anaerobic sanitization on selected pathogens and parasitic ova as well as on E-Coli indicator (source: Zhang Wudi, BRTC, China 1985)" it is explained that these ovas (eggs) have 98.8 to 100% fatality after 10-36 days in mesophilic conditions and 53-90% fatality after 30-100 days in ambient temperature fermentation.

As we have in conventional simple biogas sanitation systems a separation of a long sludge retention time through sedimentation and scum formation vs. a short liquid retention time, settled ovas are treated. This differentiation of the hydraulic rentention time does not happen in Completely Stirred Tank Reactors (CSTR). And as explained in the Technology review: "Chinese, and Dutch as well as German studies showed that there is a complete inactivation of the pathogenic test organisms through aerobic post composting process." See also some confirming new research work from Nigeria (attached) and from SANSED.
+++++++++

Most basic digesters that I know of in developing countries operate at ambient temperatures or at the most mesophilic (35 °C). This means we get some helminth egg kill (according to the above 53-90%) but not total. It would in fact be better to quote the log reduction, I guess. That's fine by me, it means that the WHO multi-barrier approach still needs to be applied.

Elisabeth

Re: Chinese Technical Code for Application of Anaerobic Digestate Fertilizer (Bioslurry) - by: muench

Tue, 09 Apr 2013 08:41:24 +0000

Meanwhile, I got some replies from Heinz-Peter mang about the bioslurry use in China (see my questions above), which I have translated into English and copied below:

+++++++++++++++
From Heinz-Peter Mang:

a) IDCOL = Infrastructure Development Company Ltd.
NDBMP = National Domestic Biogas and Manure Programme

b) Anaerobic digestate consists of (i) BIOL = Bioliquid and (ii) BIOSOL = biosolids (see chapter on the GTZ biogas film from 1992, it has been scientifically developed in Peru, then first applied in Bolivia, China, Nigeria), separation occurs by post-composting (leachate of the compost pile = BIOL), by sedimentation or filtration or drainage beds (subject to the requirements of further reuse application). BIOL will normally be further diluted with water for foliar fertilization, seed treatment, and used as biopesticides in the corn and fruit or flowers in the production. BIOSOL is used mostly for soil improvement or for fungal cultures.

c) The Chinese standard GB7959 requires that for the (co-) treatment of human faeces in biogas plants, a post-composting (which is usually the standard applied) or thermophilic fermentation is used. A non-authorised translation of the Chinese standard GB into English is attached below.

Sanitary Standard for the non-hazardous treatment of night soil
GB 7959-87

This standard is formulated in order to prevent the potential hazards, effective dispose the night soil, optimize the city environment, and protect the health of the people.

This standard could be used in the assessment of the non-hazardous disposal of urban waste and night soil, and provide suitable design parameters for the treating structures.

+++++++++++++

For the mentioned video see here:
www.susana.org/lang-en/videos-and-photos...mp;type=3&id=130

Or direct link:

I know it seems a bit odd to watch a biogas movie from 1991 but the funny thing about biogas technology for human and animal excreta is that it was peaking in the 1990s and the publications from then are still pretty valid (I am told)!

Regards,
Elisabeth

Re: Biogas Sanitation Systems and DEWATS in schools. Any best practices? - by: ThomasHoffmann

Mon, 08 Apr 2013 09:01:56 +0000

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

Re: Biogas Sanitation Systems and DEWATS in schools. Any best practices? - by: christian.rieck

Mon, 18 Mar 2013 23:37:51 +0000

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

Re: Biogas Sanitation Systems and DEWATS in schools. Any best practices? - by: Marijn Zandee

Tue, 05 Mar 2013 08:06:44 +0000

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

Re: Biogas Sanitation Systems and DEWATS in schools. Any best practices? - by: jdoczi

Sat, 02 Mar 2013 22:45:56 +0000

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,

Re: Biogas Sanitation Systems and DEWATS in schools. Any best practices? - by: muench

Fri, 01 Mar 2013 10:47:03 +0000

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

Re: Biogas Sanitation Systems and DEWATS in schools. Any best practices? - by: jdoczi

Tue, 26 Feb 2013 21:57:03 +0000

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

Re: Biogas Sanitation Systems and DEWATS in schools. Any best practices? - by: JKMakowka

Mon, 25 Feb 2013 10:36:35 +0000

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.

Biogas Sanitation Systems and DEWATS in schools. Any best practices? - by: Doreen

Mon, 25 Feb 2013 09:23:31 +0000

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

Chinese Technical Code for Application of Anaerobic Digestate Fertilizer (Bioslurry) - by: muench

Fri, 15 Feb 2013 19:39:48 +0000

Dear all,

I got the attached presentation sent by Heinz-Peter Mang and thought it could be useful for people working with biogas digesters and reuse of digestate in agriculture. It is not so easy to geld hold of such information from China.

The ppt is about the application of the digestate as fertiliser.

It is a short version of USTB/CSES training ppts which were used in a IDCOL-NDBMP training seminar on digestate utilisation in Bangladesh in 2012 (with support by KfW).
Before anyone asks: I also don't know what IDCOL-NDBMP is...
But USTB/CSES is epxlained in the ppt: Centre of Sustainable Environmental Sanitation
University of Science and Technology Beijing , P.R.China

I have two questions for Heinz-Peter:

(1)
The presentation talks about digested effluent and shows a slide (number 12) where people are spraying something that looks like water but the slide says "anaerobic digestate". I thought what comes out of such a digester is a slurry that is difficult to settle - so how can it be sprayed through such nozzles?

(2)
Secondly, the presentation mentions on slide 8:

Hygienic standard for the anaerobic digestate fertilizer should meet the requirements of Table 2 of GB 7959-1987, see Annex B.

What are the required hygienic standards? From my understanding, biogas digesters are not particularly strong on destroying pathogens. The helminth eggs may settle well but wouldn't you still find them in the slurry? By which mechanism would they get killed in a digester?

Regards,
Elisabeth