Thanks Nicolas for sharing your thesis with us. I will share it with my graduate students if that is OK with you.

Hi,
we have made 1.05 mld dewats at our kesar city site located ahmedabad, india.
effluent goes to subsurface poras pipe irrigation in gardens located at site.
we are getting good growth of plants and lawn area.
Thanks
Jignesh Goyani

Dear Elisabeth,

My statement referred to anaerobic DEWATS effluent (AF effluent in most cases).
The thesis contains investigation results from only one DEWATS in South Africa (there are very few more): it’s the NewlandsMashu research site. There, in order to “fail-safe” and since the idea is to push the loading to investigate loading limits it was important to not depend on effluent regulations and have the effluent further treated before final discharge. Therefore the DEWATS effluent goes back to sewer-line and then to municipal treatment.
The other systems I referred to are located in India and Indonesia (mainly Indonesia). Indeed, aerobic post treatment of anaerobic DEWATS effluent is very much recommended. But of course it has to be seen in a context of incremental sanitation improvement as you mention. In the case of these systems in India and Indonesia space and financing requirements could not be met at the time of implementation which is why their treatment is only anaerobic.

Kind regards,
Nico

Dear Yovianus,
adding to what Sudhir wrote, granulation does not seem to be absolutely necessary for anaerobic treatment in ABRs when these treat communal (in other words: low concentrated…) wastewater. We observed no significant granulation in our reactors and intense hydraulic surges yet, the sludge retention appeared to be good. As to the concentration of sludge: it is generally assumed that ABRs should have > 30 cm sludge level to perform well. They should be desludged when too (> half) full.
Downflow pipes increase the velocity at which ABR chamber feed enters the chamber, therefore increasing turbulence. Also the compartments are generally only 70 cm long, whether angled baffles would be better in terms of mixing could in future be investigated. To bear in mind though: downflow pipes are generally cheaper to construct than baffles.
Kind regards,
Nico

Dear Nicolas,

This has been an interested thread, thanks everyone.

I am just puzzled about this statement of yours:

Concerning the effluents: most go directly to rivers, in one case (research-plant South Africa) back to the sewer-line.

Does this statement refer to the effluent from the ABR (i.e. without aerobic post-treatment) and does this refer to the situation in South Africa (are there many DEWATS systems in South Africa?)?

I would have assumed that the South African legislation would not allow this kind of effluent to be discharged directly into rivers. So perhaps your statement was more referring to the situation in Indonesia perhaps? I guess everything is relative ("better than nothing") but if someone has enough money to construct and operate a DEWATS plant perhaps the aerobic treatment step at the end should be pretty much mandatory? Or am I being too idealistic (you mentioned lack of space)?

Regards,
Elisabeth

Dear Yovi

According to your recommendations:
1. Although granulation is not a requirement for ABRs as would be the case in UASBs, it does benefit the system. I investigated the granulation aspects for the Foxon (20006) report. Better performance was attained when granulation occurred but the conditions needed to be right for that - upflow velocities cannot be too high as washout occurs. I know that BORDA has a PhD candidate investigating biomass activity in sludge beds of ABRs in DEWATS plants. He has also seeded a plant with brewery sludge from an UASB - Nicolas would be able to point you in right direction on how to obtain that data from the PhD candidate.
2. Agree angle baffles and promoting mixing. But usual option is to have downflow pipes instead of hanging walls. Maybe a consideration for future.

Kind Regards
S

Dear Nicholas and Forum,

Thank you very much for sharing this result. Your research provide useful information on how to design, construct, and operate the ABR. Achieve organic removal until 60% is a successful in community setting. As I work mostly in aerobic treatment, I am very interested to learn more from your recommendation. Your finding showed the lesser performance against the theory as you concluded “Field observations confirmed published laboratory investigations that most treatment occurs in the first two to three ABR chambers and little, if any, beyond” and from Schoebitz, I suppose part of yours, “generally can be seen that the reduction of soluble COD after compartment 3 is very low. A reason for the poor treatment could be that the contact time between microorganisms and the substrates is not long enough for a complete digestion”

So I would like to discuss more what we can do to improve the performance.
Here are some ideas which bearing in my mind:
1. The biomass formation in the form of granule or suspended solid must be occurred, so the ABR start-up should target it, but I think it is crucial. Similarly in activated sludge, the biomass should be kept in a certain concentration in accordance with the organic loading. While in the wastewater engineering handbook also mention the same requirement for anaerobic treatment, I am still not finding the explanation on it over some references in this forum, if any.

2. The baffles/compartments configuration should be adjusted in order to achieve two operational conditions: the solid (sludge/biomass) remains in the system and the maximum contact between sludge and wastewater should occur in longer time. The baffle/compartment design, I see, adopt the settling theory and the mixing theory. For example, the up-flow velocity is designed between 0.5 – 1 m/h, parallel with what usually used for secondary sedimentation tank but in different term: surface overflow rate. Higher the number, higher the turbulence of the flow. As we want to have a maximum mixing, the turbulence flow is what we need. I see two document here, patent from McCarty (1992) and report from Foxon (2006), provide the example of such design, by make an angle baffle. Thus we don’t need so many compartments as current design, the first parts for mixing and the last part for settling.

Need opinion from other part.

Thank you,

Yovianus Toni Sakera

Dear F H Mughal,

Im glad you find the work useful.

I do not have such project-lists, anaerobic treatment is quite far spread, certainly in Indonesia and India there must be thousands of anaerobic systems implemented. Concerning the limiting factor of the anaerobic processes, the general view held for anaerobic reactors treating wastewater with high solid content is that hydrolysis is the rate-limiting degradation step. However, some of the results shown in the thesis suggest that this does not apply for solid accumulating systems such as the ABR. We don’t know yet for sure, but in such systems it is probable that methanogens play a limiting role.

As to the issue of anaerobic discharge: of course, I don’t think anyone would argue that this is the optimal situation, also because of the high ammonium. But one has to look at the context (limited land area, limited funds, no electricity, no skilled labour, very limited maintenance) and at the local situation without such systems (direct discharge to rivers or groundwater, uncontrolled anaerobic digestion in open sewer lines, unlined infiltration pits…). If the context allows, post-treatment (e.g. through planted gravel filters) is possible and in many cases implemented.

Kind regards,
NR

Dear Nicolas,

Your dissertation is interesting and useful. Since you have put in a lot of work, do you have a list (with brief details) of anaerobic wastewater treatment plants in India, Indonesia, South Africa, and possibly Pakistan?

Did you find performance of methane bacteria as an limiting factor?

Discharging anaerobic effluents in receiving streams might be problematic, as streams under tropical climates are, quite often, low in dissolved oxygen. Anaerobic effluents would further aggravate that condition. At higher temperatures, typical of tropical countries, streams will hold restricted dissolved oxygen. How do you handle that - discharging effluents with almost zero dissolved oxygen in receiving streams?

Regards,

F H Mughal

Dear Nico,

Yes, there is some problem with that link, but we hope it will get straighened out soon. Here is the paragraph I was referring to:

Another good reason to use the finished compost as cover material is that it filters odors much more efficiently than most other materials, removing and breaking down up to 99% of volatile organic compounds.
(search for: EPA Innovative Uses of Compost: Bioremediation and Pollution Prevention)
It has also been shown to eliminate 75% of the reduced sulfur compound emissions that most contribute to the characteristic aroma of shit (en.wikipedia.org/wiki/Feces#Odor) in a laboratory study of conditions similar to those of commercial composting operations (Büyüksönmez et al. 2012, www.ncbi.nlm.nih.gov/pubmed/23362761), and up to 97% of the stench from landfills (Hurst et al. 2005, cat.inist.fr/?aModele=afficheN&cpsidt=16548526). There have been a couple of isolated cases of dogs or rats being attracted by the odor and messing with the sack that is receiving the feces, but only when sawdust was being used as cover material, not when finished compost was being used (and this is another reason for the plastic bin mentioned above).

In other words, I make the air filter for the Waterless Urinal with 1.5-year-old decomposed ex-feces, which likely contain microbes that consume ammonia (given the occasional mixture of urine in the feces), for example Nitrifying Bacteria, which are known to exist in soil:

en.wikipedia.org/wiki/Nitrifying_bacteria
www.academia-net.org/news/soil-bacteria-...lf-cleansing/1208578

Another question that I would like to ask everyone with respect to the Waterless Urinal is
What studies can be cited to show that less odor is produced from pure stored urine compared to diluted urine or urine deposited on sidewalks, etc.?

Best wishes,
Chris Canaday

Hi Chris,
thanks,
yes, the stormwater issue is an important one and unfortunately not easy to solve on such small scale systems.
Normally one would design an overflow-weir in front of the plant, but these plants are designed for such low maximum design flows that any overflow-weir fitting such max flows would block with raw wastewater.
I propose an alternative solution in the thesis, which could work but still has to be field-proven.
Concerning the effluents: most go directly to rivers, in one case (research-plant South Africa) back to the sewer-line.
As Sudhir pointed out, research on agricultural reuse of such effluents is currently performed in South Africa

Saludos,
Nico

PS: I found your inodoroseco post very interesting, unfortunalty the link www.chekhovskalashnikov.com/water-sanitation/ did not work

Dear Chris

Mr Reynaud also worked on the Newlands Mashu DEWAT system in Durban, South Africa where there were doing agricultural re-use.