Dear Dean,

I totally agree that the term should be "Decentralized wastewater treatment system".
The whole purpose of the system is to Treat the wastewater.

Also I wish to add that the effluent being discharged need to be applied for re-use,
It is best to have 3 process as indicated :
1. Waste- water Treatment, 2. disposal and 3. re use for secondary purposes.

When the water is used for reuse, then the community feels satisfied and good that the treatment system is doing its work etc..
Also the community gets information, as to how fast the filters are getting dirty and when are they required to be cleaned
After safe time, they would clean the filters etc..

It would be ideal to remove solid sludges for co-composting and creation of manure,

Well wishes,
Prof Ajit Seshadri, Vels University, Chennai

Dear Dean.
I will write in detail the points for DEWATS..
Treatment and Re use are impotrant practices which need to be propagated.
I am fan of this process DEWATS happening naturally in nature at all times.. some call it Autolysis ..
Pl bear with me.
Well wishes.
Ajit Seshadri .

Onsite sanitation can mean as little as digging a hole and crapping in it... or crapping in a bucket with a lid, for removal later. Thus "a sanitation system in which excreta and wastewater are collected and stored or treated on the plot where they are generated".

Dewats is about treatment and only treatment. In contrast, "on-site wastewater management systems", "on-site sewage treatment systems" and "on-site wastewater treatment systems" are all terms describing treatment systems that use "on site" land disposal of the treated effluent. This includes the humble septic tank.

"Wastewater treatment" is a term used for "a process used to convert wastewater into an effluent that can be returned to the water cycle"... i.e. this is about water recovery and can even include disposal to waterways after treatment. On-Site Wastewater Systems are more than just a wastewater treatment system, they also dispose the effluent on-site.

I don't believe the term "Decentralized wastewater system" should be used, this should always be "Decentralized wastewater treatment system". The whole purpose of the system is to TREAT the wastewater. Thats all. Although this is usually to a level suitable for the effluent to be discharged on-site, dewats don't actually need to be on-site wastewater treatment systems because they can (and sometimes do) discharge to a pipe that takes the treated effluent somewhere else... perhaps even to a waterway. They are only the treatment stage.

Introducing the term on-site means the effluent is not discharged off-site. Of course a dewats can be an on-site dewats! Two stages, treatment and disposal.

cheers
Dean

Dear Rainer,

Thanks for your response which prompted me to take another look at the text in Wikipedia about onsite sanitation. You're right about the aspect of treatment, i.e. that the degree of treatment may be highly variable.

I couldn't use your proposed definition 1:1 as I always need a reference for everything I write on Wikipedia (well, at least, I should). So I took another closer look at the EAWAG compendium and used their definition exactly now but clarified the aspect about treatment. I also thought your point about piped water supply was important so I have added that as well (without a reference at this stage but it could be seen as a common sense statement).

So now it looks like this:
en.wikipedia.org/wiki/Sanitation#Onsite_sanitation

Onsite sanitation
Onsite sanitation (or on-site sanitation) is defined as "a sanitation system in which excreta and wastewater are collected and stored or treated on the plot where they are generated".[27]:173 The degree of treatment may be variable, from none to advanced. Examples are pit latrines (no treatment) and septic tanks (primary treatment of wastewater). On-site sanitation systems are often connected to fecal sludge management systems where the fecal sludge that is generated onsite is treated at an offsite location. Wastewater (sewage) is only generated when piped water supply is available within the buildings or close to them.

A related term is a decentralized wastewater system which refers in particular to the wastewater part of on-site sanitation. Similarly, an onsite sewage facility can treat the wastewater generated locally.

What do you (and others) think?

Elisabeth

Hi Roumiani and Elizabeth, decentralized waste water treatment (SEWERAGE) systems are one technology (out of several) possible to be applied within on-Site Sanitation approaches and DEWATS (Decentralised Wastewater Treatment Solution) is a term developed by Loughborough University, Leicestershire, UK. The German NGO BORDA (Bremen Overseas Research & Development Association) has been promoting and implementing DEWATS systems in many countries in Asia and Africa. Several DEWATS were implemented jointly with WAZAZA in Zambia under the DTF.

However, tons of documents were written about the topic Sanitation, but even the (latest) 2010 update of the 1992 WHO Guide to the Development of on-Site Sanitation doesn't give much info about latest developments .
You are the experts and know better than me that the term sanitation covers more than sewage treatment. Sanitation covers livelihoods and sustainable (re)use of natural resources.
As you rightly said, Roumiana, our biggest concern with onsite sanitation is that we have a definition problem. WHO calls it on-Site Sanitation.
Permit me to disagree with the Wikipedia sentence: "On-site sanitation is defined as a sanitation system in which excreta and wastewater are collected, stored or treated at the same location (or on the same plot) where they are generated. Examples are pit latrines and septic tanks".
Only septic tanks (3 or 5 chamber), frequently used all over the world before centralized sewerage system got en vogue), qualify for sewage treatment as well as other technologies like ABR (unaerobic baffeld reactor) and unaerobic filters.

Pit latrines are mainly poorly build simple concrete bloc underground tanks and used for collection of all liquides from dwellings, i..e. black, grey and rainwater mixed, thus causing serious hygienic problems during rainy seasons contaminating close by hand dug wells. Most people call pit latrines wrongly septic tanks beeing misleaded by the supporting beams of the top cover.

@Elizabeth: this is my proposal, how to rewrite the text:
On-Site sanitation (OSS) ususally used to describe a decentralized wastewater system which collects, conveys and treats waste water (called sewage or black water) in rural areas and underprivileged urban communities mainly in developing countries from:
a) private houses, (dwellings or wards),
b) public toilets, and
c) individual public places
and thereafter is infiltrated into the ground or disposed into an affluent or reused for irrigation acc. to WHO standards depending on the outflow quality.
Wastewater flow is generated when appropriate drinking water supply is available within the buildings or close to them since it requires a poor flush or full flush toilets.
OSS is part of a sanitation system were wastewater and excreta are collected by small bore pipes, stored or treated in septic tanks at the same location (or on the same plot) where they are generated.
On-site sanitation systems are often connected to fecal sludge management systems (FMS) where the fecal sludge that is generated onsite is treated as an offsite location.
EEWAG (Swiss Federal Institute of Aquatic Science and Technology) developed a second revised edition of a Sanitation Compendium which describes in detail “improved” sanitation technologies that provide safe, hygienic, and accessible on-Site Sanitation. It includes the whole range of urban, peri-urban and rural technologies (e.g., from single pits to conventional sewers).

Hope that helps a little bit to sort out the definitions problem.

Best, Rainer

Rainer Sibum, Msc. (Eng.)
Wet and Green Engineering

(this post was originally in this sub-category: forum.susana.org/229-dewats-decentralise...er-treatment-systems)

Hi Roumiana,

I think the term DEWATS is somewhat a creation of BORDA, even though it just stands for "Decentralised wastewater treatment system" which could be any technology.

Whenever we talk of definitions, I refer to Wikipedia to check if things make sense there.

If I put DEWATS into Wikipedia, it is redirected to here:
en.wikipedia.org/wiki/Decentralized_wastewater_system

Decentralized wastewater systems (also referred to as decentralized wastewater treatment systems) convey, treat and dispose or reuse wastewater from small communities, buildings and dwellings in remote areas, individual public or private properties. Wastewater flow is generated when appropriate water supply is available within the buildings or close to them.

Decentralized wastewater systems treat, reuse or dispose the effluent in relatively close vicinity to its source of generation.

If I search for "on-site sanitation", it takes me to here:
en.wikipedia.org/wiki/Sanitation#Onsite_sanitation

there it says:

Onsite sanitation (or on-site sanitation) is defined as a sanitation system in which excreta and wastewater are collected, stored or treated at the same location (or on the same plot) where they are generated.[27] Examples are pit latrines and septic tanks. On-site sanitation systems are often connected to fecal sludge management systems where the fecal sludge that is generated onsite is treated as an offsite location. A related term is a decentralized wastewater system which refers in particular to the wastewater part of on-site sanitation. Similarly, an onsite sewage facility can treat the wastewater generated locally.

That sounds pretty good to me. Do you think it requires changing?

Regards,
Elisabeth

Hi Elisabeth,

its me again .

So now we have DEWATS to be only these wastewater systems, which are serving a community (usually poor and underdeveloped). On-site sanitation is not a decentralized wastewater system??

Of course the DEWATS system offered by BORDA is the only one, which can do the work. So, is it DEWATS about any decentralized system, or is it the BORDA one?

Well, I think we have a terminology problem here.

Best regards,

Roumiana