BOD on dehydration toilets efluents

  • RodrigoBIS
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BOD on dehydration toilets efluents

Dear Susana partners:

In BIS Chile, we are making a full technical analysis for evaluating users, designs, opertaing mechanisms and aditives. In my country, we don't have anything similar to laws and technical norms that regulates waterless toilets.

Having that, we are fixing sanitary parameters using norms like the compost law (NCh 2880 in case you are in my same situation and what to have further reading), in the solid finishes product. The norm gave us a few tests in how to measure the compost maturity, understanding that is an equivalent way to say how diminished is the 'putrid potential'. Definitely composting makes a good work on this... and what about dehydration???

Dehydration kills pathogens effectively, that means higyenized, not stabilized. In dehydration the stabilization mechanism is different, the mineralizatin works with phisical-chemical oxidation, but my common sense tells me this mechanism is slower.

I haven't found a reference that measures the mineralization level on dehydration not-composting toilets, maybe a DBO * reporting in a sudy case can be enough. All this bla-bla is for answering one simple question:

Is it possible that a sanitized efluent in a dehydrating unit, gets putrid and stinky if gets wet? Probably not, but I need the DBO content or a equivalente measure on stabilizatin level, for having a full engineer answer


* Note by moderator (EvM):
DBO is Spanish for BOD which is biological oxygen demand ("demanda biologica de oxygeno" in Spanish)
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  • Florian
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Re: DBO on dehydration toilets efluents

RodrigoBIS wrote: All this bla-bla is for answering one simple question: Is it possible that a sanitized efluent in a dehydrating unit, gets putrid and stinky if gets wet?


I think the simply answer is yes. The materiel is dried but not mineralised or transfored in stable organic matter (humus). If moisture is added, it still can be composted or digested anerobically.

Also, dehydration does not provide for complete hygienisation. It does reduce pathogen content considerably, but does not remove all pathogens completely, in particular not persistent pathogens like parasite eggs. Post-treatment (e.g. prolonged storage) is needed for comple hygienisation.

Best,Florian

Florian Klingel
Water and Sanitation Specialist at Skat Consulting Ltd.
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  • RodrigoBIS
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Re: BOD on dehydration toilets efluents

Thanks florian, but I need a reference, experiment, or mathematical equation who said that, and that was the question. In the technology evaluation I'm making (where composting, dehydration and incineration toilets are being technically evaluated), I need to know if the efluent is gonna give any problem after being disposed on soil as conditioner.

And I kinda disagree about the helminth egg die rate on dehydration toilets. Accoding to the paper I'm including in this post, and references like Schönning and Stenströmin EcoSanRes 2004-1 report "Safe use of urine and faeces in ecosan systems (I have the file in spanish and traslated the title, maybe the actual title in english it's different)", that with pH 9 total innactivation of helminth eggs and viruses it's achieved in 6 months, if one to two cups of ashes are added after each defecation.

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  • RodrigoBIS
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Re: BOD on dehydration toilets efluents

sorry dude, I didn't read the prolonged storage as post-tratment... in that case I totally agree with you. But the lack of oxidation in faecal matter in higienized, pathogen free, finished product, causing putrid conditins after moisturizing using it as soil conditioner it's still a concern for me now... because if that happens, it would be right to say that dehydration toilets are not sanitary apropriate because of this oxidatin lack, but for saying a that HUGE affirmation, you (or we) have to be completely sure, and I'm not jajaja. Thanks everybody again!!
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  • joeturner
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Re: BOD on dehydration toilets efluents

Some of the numbers you are asking for might be found in David Hawksworth's work on the eThekweni (South Africa) urine diversion toilets - see here
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