Hi

Would regards to your first point, I have not experienced complete phase separation in an ABR treating domestic wastewater. I played with 3 systems (lab to field-scale) and hydrolysis was always rate-limiting step. In the 3000L system, we used settled sewerage pumped to an 8-chamber ABR. For the lab-system, we used faecal sludge slurry in a lab system with a settling tank at the front. In the field system treating around 40 m3/d, we had a square settler/digester upfront to an ABR.

I think they use digester upfront because it is easier to harvest the gas. My experiences with square-type design is that we had leaks - the round shape is easier to make gas tight.

Regarding the cold weather, BORDA has an impressive plant built in Afghanistan. The digesters were built below ground level to keep it warm. It would be best to contact someone from BORDA for more info.

I have attached an old report (2006) from the WRC. Might be useful.

Kind Regards

Kind Regards

Dear Susmita,

We had a discussion about Biogas from ABR (DEWATS) started by Anthony. May you come in in this discussions with your know-how?
forum.susana.org/forum/categories/35-bio...5213-biogas-from-abr
and
started by WG8:
forum.susana.org/forum/categories/61-wg-...y-sanitation-operati

two of my points:
1. In my opinion the DEWATS of BORDA are two biogas plants one after the other. The ABR by it self is basically a proper but simplified multi-stage biogas plant with permanent hydraulic mixing of substrate with very stable anaerobic phases. Because, in relation to the 4 phases: hydrolysis; fermentation; acetogene; methanogene, been more or less made to "work" separated one after another in each of the 4 ABR-compartments.

This intended separation by compartments creates stability and opportunities to steer via different geometry of cambers, pH's and temperature the whole process. E.g. giving to the first ABR-camber more volume will give more time to the hydrolysis. The following 3 phases will "work" better, See 2012 research from Malaysia: scialert.net/fulltext/?doi=jas.2012.2586.2591

I am not sure why this proper "multi-stage biogas plant" is only used as a wwtp after a less stable "single tank biogas plant". Florian do you know more about? I am guessing the reason is to simplify the whole DEWATS system and to have after biogas production a simple but stable COD reduction "only".

2. By my guessing + under our "cold" conditions, the use of biogas will be "possible" starting by 200 p.e.. The Engineer from BORDA Mr. Sasse said 1998s min. 20 m3/d and COD 1000 mg/l. What is your experiences under "our" cold conditions? The anaerobic treatment steps (Hydrolysis/Acidogenesis/Acetogenesis/Methanogenesis) need different pHs, Temperatures and HRT/SRT, How you "steer" this (keeping all systems simple as possible, by intention), just by different camber geometries and probably different heating temperatures for each camber?

Anthony and Florian had queries too on related subjects.

All the Best
Detlef

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