Chris,

Just to let you know that we've developed a "recipe" for debris/solid waste to add to faecal sludge simulants on the basis of your team's work (MPFS - Interim Report A) plus a selection of debris considered a 'worst case scenario' such as lengths of rebar, rope and wire. We're producing a simple spreadsheet tool that can be modified to add new types of debris, or to change the proportions of each, and hopefully will be able to share it in the next month or so - the intention being that it starts to help standardise the material that people use for testing PETs (pit emptying technologies).

Best regards, Jamie

Sorry, I just noticed that the date was wrong in the above post: the correct date for this webinar is Tuesday, 29 April -- one week from now.

Dear all,

In case you have been following this thread and are interested in my research project, then the upcoming webinar number 7 on “Adding missing links in sanitation value chains” could be interesting for you:

My presentation in this webinar is entitled:

Is a power auger "Excrevator" a suitable tool to empty pit latrines in South Africa and septic tanks in India?


The webinar will take place on:

Tuesday 29 April 2014, 16:30 - 17:15
(CET - Central European Time; time converter to find your local time: www.timeanddate.com/worldclock/converter.html )

More details of the webinar, which has 3 presenters, are available here on the forum:
forum.susana.org/forum/categories/139-in...mit=12&start=12#8145

There is no need to download any software to attend (simply go to this website: seint.adobeconnect.com/seiwebinar/). However, you must obtain the password to enter the room. To obtain the password, please e-mail Elisabeth von Muench: This email address is being protected from spambots. You need JavaScript enabled to view it..

I look forward to meeting you at the webinar and answering any questions you may have. If you have questions about the content of my research before the webinar, please put them here on the forum.

Regards,

Francis

(just for people's information: if you want to obtain the e-mail address of another forum member, simply click on the "contact" button that is to the left of the person's post, below the person's profile picture - you can then send a short message of up to 360 characters; naturally, the contact function only works when you are logged in; enjoy!)

Hi Francis,

Thank you very much for the response. I look forward to meeting you and the team. As noted, I will be in North Carolina Oct 13-17, 2014 but can come early or stay late as needed. If you have certain dates around that time that work better for you, please let me know so I can be sure my schedule meets your availability.

If possible, can you please send me your email address so that we can take this conversation off the forum so as to save the other participants? My email address is This email address is being protected from spambots. You need JavaScript enabled to view it.

Thanks
Blake

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Note by moderators: This post was made by a former user with the login name BlakeMcK who is no longer a member of this discussion forum.

Greetings Francis

Thank you for your comments which were most useful.

Since my previous posting I have been pointed to a paper presented at the recent WWTmod 2014 conference (www.biomath.ugent.be/WWTmod2014/docs/pro...reliminary_final.pdf) entitled "Characterization and separation of unbiodegradable matter in WRRFs by Majdala Mansour-Geoffrion, Peter L. Dold, Alain Gadbois, Stéphane Déléris and Yves Comeau. The abstract of which follows:-
Abstract
The purpose of this paper is to present a critical review on the characterization of influent unbiodegradable organic (trash) and inorganic (grit) particulate matter, to propose a fractionation of particulate unbiodegradable matter and to how the fractionation can be used to evaluate trash and grit removal efficiencies of physical separation units.

This paper (and references) presents a good starting point for the quantification of non-faecal material in on-site sanitation systems.

Our intention is not to provide a table of particle size range and mass fraction, but rather a practical inventory of material to add to a given mass of sludge simulant.
While a whole pit will be analysed, it is intended to determine the material in manageable batches of 25 to 50 kg. In this a more granular view of a pit will be obtained, but still it will not be able to discriminate layers within a pit.

A PhD student is about to start a project to determine the mass and composition of the material in screenings and scum within septic tanks serving community ablution blocks. This will lead on to techniques for the better management of such residues.

Chris

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Note by moderators: This post was made by a former user with the login name ChrisBuckley who is no longer a member of this discussion forum.

Hi Chris,

As always, PRG is on the leading edge of fecal sludge

Trying to "standardize" sludge is an extremely important effort, and your group (PRG) is the best and most qualified to do this, particularly for South Africa VIPs. Initially, we tested on bentonite mixtures, and dairy manure, but as you pointed out, we need to consider sludge strength, viscosity, "stickiness", trash contents, etc. As you know, just using % solids is highly misleading, and I think we need to educate users (and funders) that it's not that simple.

A few quick comments on your proposed study:

1. Particle size can be measured in different ways (e.g., geometrical mean diameter). For the Excrevator, the "traditional" particle size distribution of soils/pure fecal material (say from microns to 50 mm) is probably not an issue: the auger can lift these. Larger particles up to 100 mm or higher may be the bigger problem, but I think the "shape factor" of particles may be the bigger issue. The "shape factor" would quantify whether it's a sphere or a rod, or some other irregular shape. For example, we have preliminary testing showing the Excrevator (in its current form) can lift 100 mm long pieces of rope of 10 mm dia. But how do we quantify paper (rolled vs flat), or plastic bags, or other trash? This would be very important for us as we try to think about "cutting", "shredding", or "screening" as part of the Excrevator operation.

2. I know that testing on actual pits is difficult and expensive, but i fear that one pit may not be enough to capture variability (even in Durban).

3. The concept of "layers" - hard layers and soft layers, thickened scum and watery layers, compacted bottoms - it may be hard to simulate that. Layers can be revealed by field penetrometers, but in our lab, we've tried to think about how to simulate these layers, and it's difficult.

4. Any thoughts on septic tanks? These may be more a South Asia, SE Asia problem, where vacuum trucks take out the watery upper layer but leave the bottom compacted layer untouched. In addition to VIP sludge, perhaps quantifying septic tank sludge might also be in the works?

As always, it's refreshing to discuss FS with you. My hope is that in the near future we will have a clearer idea of which desludging techniques/equipment are best for different pits/regions. I'm not sure we will find one that will work for all types.

-Francis

Hi Blake,

We would be glad to meet with you in October. We have a lot of trips scheduled at this point (India, Malawi, South Africa), and we intend to iterate on the design, so the Excrevator may look a little different at that time. I think we may end up with different designs for South Asia's septic tanks and ZA's VIP sludge.

Francis

Hi Francis,

Like so many other people, I am very excited about the potential of this technology. Cheers to you and your team for all the great work so far.

iDE implements sanitation marketing projects in 6 countries around the world (www.ideorg.org). Many of the latrines we promote are pit latrines. In Cambodia, we Facilitate the adoption of the Easy Latrine - a pour-flush off set pit latrine. We are starting to hit scale there, as more than 225,000 of these latrines have been purchased and installed by rural households in the past 3-4 years. We are brainstorming around how to create hygienic latrine emptying businesses to service rural households with these latrines and the pit excrevator could be an enormously important technology innovation.

I am going to be attending the Water and Health Conference at UNC from Oct 13-17, 2014. Would it be possible for me to come visit you and the team to meet in person and see the technology? I think working together could be really beneficial for both of us.

Best,
Blake

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Note by moderators: This post was made by a former user with the login name BlakeMcK who is no longer a member of this discussion forum.

Greetings Francis,

I was very impressed with the demonstration in Delhi. To assist you and other developers of desludging devices the PRG will undertake a complete particle size analysis (from +100 mm to 20 micrometer) of one full VIP. The purpose is to provide a recipe of non-faecal material that can be added to a homogeneous sludge such as the bentonite which you used. In this way we will try to establish a "Durban standard VIP sludge". In parallel with the particle size analysis we will measure viscosity in a number of different ways (shear rheometer and lab and field penetrometers)and a stickyness index (to describe the clearing of the material from the pump material. Your or other pit emptying device developer's thoughts on other appropriate tests will be appreciated.

Chris

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Note by moderators: This post was made by a former user with the login name ChrisBuckley who is no longer a member of this discussion forum.

The paper on the power extraction auger (The Excrevator) has been published in the Journal of Water, Sanitation, and Hygiene for Development.

The link is here: www.iwaponline.com/washdev/004/washdev0040072.htm

Journal of Water, Sanitation and Hygiene for Development Vol 4 No 1 pp 72–80 © IWA Publishing 2014 doi:10.2166/washdev.2013.183

Power earth auger modification for waste extraction from pit latrines

Tate Weston Rogers, Francis L. de los Reyes, Walter J. Beckwith and Robert C. Borden

Department of Civil, Construction and Environmental Engineering, North Carolina State University, Campus Box 7908, Raleigh, NC 27695, USA E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

ABSTRACT
The extraction auger was developed to meet the need for a low cost, effective method to empty pit latrines in difficult to access locations. The basic design consists of a motor that rotates an auger inside a pipe, lifting waste from a pit and depositing it into containers through a wye fitting at the top of the device. Laboratory testing of the auger showed increases in flow rates with increasing auger rotational speed and waste viscosity. An auger with an external hydraulic drive was capable of lifting dairy waste over 2.5 m, at flow rates of over 125 liters per minute. Field-testing showed the equipment was effective at lifting medium viscosity wastes containing a mixture of liquid and solid material. However, the auger was not effective in removing low viscosity, liquid waste that would flow backward down the auger reducing lifting efficiency. The auger was capable of drilling into dense solid waste, forming a ‘posthole’ in the waste. However, since the dense solid waste would not flow towards the auger intake, actual waste removal from the pit was limited. Improved methods are needed to mix liquid and solid waste in pits prior to removal with the extraction auger or other technologies.

Keywords: auger; pit emptying; portable

I had the pleasure of interviewing Francis last week at the Reinvent the Toilet Fair in Delhi, India (see here for more info on this fair: forum.susana.org/forum/categories/139-in...lhi-21-22-march-2014)

Here is the short interview (3 min.) with Francis, the project leader, to give the overall project story and current status:



And here is a demonstration of the "excravator" on fake faecal sludge (bentonite-water mixture) at the fair:



Francis told us that he met an Indian manufacturer at the fair who has expressed an interest in trying out one of his units.

Enjoy.

Photos from the exhibit in this Flickr set:
www.flickr.com/photos/gtzecosan/sets/72157644247686635/

The team from North Carolina State demonstrating their modified power screw auger for emptying pits. by Sustainable sanitation , on Flickr

Engine used for the Excrevator by Sustainable sanitation , on Flickr

Regards,
Elisabeth