Hi Joe and Elisabeth

Lots of questions and comments! I try to address them.

It is correct that the hygienic risk from feces is much higher than from urine. However, it should also kept in mind that there are some risks from urine as well. This does not only concern the direct use as fertilizer, but also the collection of urine including spilling urine in a larger tank, and the discharge of untreated urine to the ground. Our data hopefully help to make a proper risk assessment.

Uncontrolled discharges to the ground, i.e. directly at the toilet and not for agricultural purposes is also critical due to the high nutrient loads. For the drinking water quality, this might be at least as critical as the pharmaceutical residues.

In the VUNA study, the urine was collected by municipal staff from UDDTs in peri-urban eThekwini but also brought by toilet users to a central collection point. We tried to provide safe conditions during collection. These conditions will also be provided by EWS for further collection campaigns.

The VUNA study was financed by BMGF. It was a joint project of Eawag and EWS.

There are other potential pathways than groundwater contamination - for example sideways leaking onto foodcrops. Lateral/sideways flow is a common thing in topsoils (which might be different to the issue of plumes from a latrine if the latrine is much deeper into the ground than a UDDT).

Or the pathogens/viruses might persist in the surrounding soil where the urine has generally percolated and disperse, to be picked up by small children playing with the soil.

Maybe it really is no risk at all, hence why I was asking the question.

Ah, OK, see what you mean, so you're referring more to the groundwater pollution aspect in this case? I thought you were referring to inexperienced (or careless) users/owners of UDDTs handling the urine from their UDDTs during reuse activities (which they are not in the case of eThekwini).

Groundwater pollution is a different matter but as far as I know this has also been researched in great detailed by South African researchers (see also this forum category here: forum.susana.org/forum/categories/193-gr...king-water-treatment). No generalised statements can be made on this but for this specific case of eThekwini I think the conclusion was no signficant risk because a) the groundwater level is extremely deep and b) the groundwater from that area is not used for drinking water (i.e. no local wells). (how the groundwater might interact with surface water somewhere else in the hydrological cycle of that particular area - i.e. with regards to pharmaceutical residues - I don't know)

But I look forward to Kai's response on this.

Did eThekwini really comission this research? I thought they were a research partner but the funding came from the Bill & Melinda Gates Foundation for the VUNA project (more on VUNA see here:
www.susana.org/en/resources/projects?search=VUNA) and it had also a rather fundamental research aspect, rather than perhaps responding to immediate questions from the municipality, let alone responding to situations of people falling sick from using UDDTs (?).

muench wrote: Hi Joe,

As far as I know the "regular" users of UDDTs in the eThekwini area do not reuse urine at all, but the urine is simply infiltrated. Reason being that they don't do any gardening activities (apparently). So no risks with respect to urine reuse there.
I think during the VUNA project there might have been some treatment and reuse work but that was done in a research context where it is much easier to provide the "perfect" conditions with regards to safety (?). Kai, please correct me or clarify? Thanks.

That's how I understood the situation in eThekwini too, but I assume this means that fresh urine is being released regularly into the surface-soil environment, so I don't know whether this actually means that there are "no risks with respect to urine reuse".

We know the potential for problems with latrine leaks into groundwater, which then comes around again in potable drinking water, but I think many have assumed as you have above that there is "no risk with respect to reuse" from UDDT urine infiltration and I'm trying to understand if that is actually now considered to be the case. Presumably eThekwini think it is a potential problem or they'd have not commissioned the research.

Hi Joe,

As far as I know the "regular" users of UDDTs in the eThekwini area do not reuse urine at all, but the urine is simply infiltrated. Reason being that they don't do any gardening activities (apparently). So no risks with respect to urine reuse there.
I think during the VUNA project there might have been some treatment and reuse work but that was done in a research context where it is much easier to provide the "perfect" conditions with regards to safety (?). Kai, please correct me or clarify? Thanks.

See also here for a related thread about the UDDTs in the eThekwini area:
forum.susana.org/forum/categories/34-uri...wini-in-south-africa

Overall (for other cases than the eThekwini case where people are not looking for fertiliser), as Kai pointed out, we need to balance the risks of urine reuse regarding potential disease transmission and pharmaceutical residues entering the environment (which is - as we all know - much less significant than with reused faeces or faecal sludge or partially treated wastewater), versus the potential benefits regarding a potential increase of crop yield. Nevertheless, I do think the research that you (Kai) and others have done and are still doing on risks of urine reuse is very important so that we gain more clarity over the risks and how to manage them. So I think it's good to discuss it in this thread here.

Regards,
Elisabeth

Thanks Kai, that is interesting.

Do you have a feel for the way that the UDDTs you've studied are actually being used? Are they storing the urine for long enough to be safe enough for reuse without further treatment? Should be still not be focussing on the risks from untreated faeces rather than the (far lower) risks from urine?

I am not aware of any experiments using UV for urine treatment, but there is a study on using ozone. The purpose of the study was rather the removal of pharmaceutical residues:

Dodd, M.C., Zuleeg, S., Von Gunten, U. and Pronk, W. (2008) Ozonation of source-separated urine for resource recovery and waste minimization: Process modeling, reaction chemistry, and operational considerations. Environmental Science and Technology 42(24), 9329-9337.

pubs.acs.org/doi/abs/10.1021/es800560r

The doctoral thesis of my former Ugandan colleague Charles Niwagaba also has some urine storage experiments with results considerably shorter than 6 months:
pub.epsilon.slu.se/2177/

Edit: This might be also relevant to our previous discussion, but sadly behind a pay-wall:
www.sciencedirect.com/science/article/pii/S0925857498000743

@ Joe or Kai: any idea if UV treatment of source separated urine was tested before? I can only find studies for lifestock "waste-water", but with pure/transparent urine it should work even better.

Edit2: Regarding virus die-off in urine storage (also behind pay-wall):
www.sciencedirect.com/science/article/pii/S1093019101000570
(note the huge difference between storage at 5°C and 20°C, which I suspect also makes for the difference of the WHO figure and the tests done in Uganda for example).

Hi Joe

Storage can strongly reduce the number of pathogens in urine. WHO recommended a storage time of six months before urine can be used as fertilizer. This number was based on studies b Höglund et al., see e.g.

Hoglund, C., Stenstrom, T.A. and Ashbolt, N. (2002) Microbial risk assessment of source-separated urine used in agriculture. Waste Management and Research 20(2), 150-161.
www.scopus.com/inward/record.url?eid=2-s...996c9037613bf2e3c84a

However, six month storage requires very large storage vessels and might not always be a suitable method.

Best, Kai

Kai, I was wondering if you could comment on the role of storage. Do you think (or have you considered in any of this research) whether storing the urine reduces the activation of these pathogens?

For anyone who is interested and following this discussion, these are the links to the papers mentioned above:

Formation of Chlorination Byproducts and Their Emission Pathways in Chlorine Mediated Electro-Oxidation of Urine on Active and Nonactive Type Anodes by Hanspeter Zöllig, Annette Remmele and others.
Environ. Sci. Technol., 2015, 49 (18), pp 11062–11069
link

Inactivation kinetics and mechanisms of viral and bacterial pathogen surrogates during urine nitrification by Heather N. Bischel, Ariane Schertenleib and others.
Environ. Sci.: Water Res. Technol., 2015,1, 65-76
link

Dear all

I would like to reply to the discussion of our paper on hazards from urine collected from UDDTs.

Our study shows that source-separated urine has to be handled with care. This urine is not sterile, it contains pathogens, which are hazardous for human health, and also pharmaceutical residues, which pose a risk to the environment. However, urine is also a major nutrient source, which should be used for fertilization. Thus, we need some treatment.

All methods using chemical oxidation are hampered by the fact that urine contains a lot of organic substances, which scavenge the oxidants. Furthermore, oxidation of organic substances can also produce disinfection by-products, which can be very hazardous as well. This is also the case for electrochemical urine treatment. We recently published a paper (open access) on this topic:
Zöllig, H., Remmele, A., Fritzsche, C., Morgenroth, E. and Udert, K.M. (2015) Formation of Chlorination Byproducts and Their Emission Pathways in Chlorine Mediated Electro-Oxidation of Urine on Active and Nonactive Type Anodes. Environmental Science & Technology 49(18), 11062-11069.

The treatment we chose in eThekwini is, first, stabilization of urine by nitrification and, second, water removal and disinfection by distillation. Stabilization means that volatile ammonia is converted to stable ammonium nitrate and 90% of the organics are oxidized. However, during nitrification only some of the pathogens are inactivated as we reported in another study (open access):
Bischel, H.N., Schertenleib, A., Fumasoli, A., Udert, K.M. and Kohn, T. (2015) Inactivation kinetics and mechanisms of viral and bacterial pathogen surrogates during urine nitrification. Environmental Science: Water Research & Technology 1(1), 65-76.

However, distillation at 80°C for several hours will ensure that the pathogens are killed.

We also looked at the removal of pharmaceuticals during storage and nitrification of urine. Some pharmaceuticals are removed, but enhanced treatment (e.g. adsorption on activated carbon) is required to reduce the concentration of all pharmaceuticals to tolerable low levels. We are currently preparing the paper on this study. Some results are summarized in the final report of the VUNA project:
www.eawag.ch/fileadmin/Domain1/Abteilung...inal_Report_2015.pdf

Best regards, Kai