Field Testing of Sludge Digger and Related Tools

  • dandreatta
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Field Testing of Sludge Digger and Related Tools

In the past I’ve announced the development of pit emptying tools, the sludge digger (for thick or thin sludge) the sludge dipper (for thin sludge) and a trash picking tool developed by my students that was called “The Crabtrap”. These devices have now been tested in Malawi and Nairobi.

The sludge digger is a simple bucket-based device that can handle trash. Some pictures of the sludge digger are below, and a video of an early version is at:



The sludge digger has been improved considerably since this video, and a new video will be made soon. The sludge digger works in thick or thin sludge, deep or shallow pits.

The sludge dipper is a simpler lighter version of the sludge digger and works only in thin sludge. It was not tested in Africa, but the basic idea can be seen at:



The crab trap is to clear out the trash in a pit or septic tank before using a more complex machine such as a gulper or an evacuator truck. The crab trap will be covered in a later post. The original prototype can be seen at



Modification have been made since this video was made.

The conditions in Malawi and Nairobi are very different from each other. The sludge is usually thick in the pit latrines in Malawi, and thin in Nairobi. The pits in Nairobi are also not very deep, or in some cases they are only emptied down to a certain depth. Septic tanks in Malawi have thin sludge.

The testing was limited, as the prototypes tested were quick prototypes not meant to be durable. Still, the devices were used in many different pit latrines and septic tanks, and local pit latrine emptiers were involved.

The sludge digger worked as intended, however the reaction of the pit emptiers was very different, based on the different conditions. In Malawi, where the sludge is thick, the tool worked well and would be a useful tool where the sludge is too thick to use a gulper or evacuator truck. The emptiers liked the sludge digger. The fact that the trash does not need to be removed in a separate step is a big plus. After the sludge is removed from the pit or septic tank, it is disposed of in the normal manner.

In Nairobi, where the sludge is thin and they don’t go down very far in the pit, the sludge digger also worked as intended, but it is not as fast as the current device. The current device is shown below, and is typically the lower half of a 10-liter jerry can nailed to a pole or stick. The pit emptiers are very skilled in using this in the tight spaces of a Nairobi pit latrine, and under Nairobi conditions it works well. Not surprisingly, they are not interested in the sludge digger.

In the future I will put together documents on building sludge diggers, sludge dippers, and crabtraps, along with putting together videos showing their use. Look for future posts on these topics.

Many thanks to Sanergy in Nairobi, and the University of Mzuzu in Malawi, for their considerable assistance with this field testing.

Dale Andreatta
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this field testing.

Dale Andreatta, Ph.D., P.E.
Mechanical Engineer
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  • hajo
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Re: Field Testing of Sludge Digger and Related Tools

Hi Dale,

I had followed up your posts about the sludge digger for quite a while and have always wondered why the bucket needs to be hinged to the rod? What is the advantage of this construct compared to a bucket welded to the rod as we use it here in Lusaka?

ciao
Hajo

We can't solve problems by using the same kind of thinking we used when we created them.
Albert Einstein
Any intelligent fool can make things bigger and more complex... It takes a touch of a genius - and a lot of courage to move in the opposite direction.
E.F. Schumacher
Everything should be made as simple as possible, but not simpler. :-)
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  • dandreatta
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Re: Field Testing of Sludge Digger and Related Tools

There are at least 2 reasons for pivoting the bucket.

If the sludge is thick, the bucket must be pivoted down (open end down) to be pushed into the sludge. The pivot is offset from the center of the bucket so that gravity tends to pivot the bucket down, unless the user is pulling up on the rope. Once the bucket is pushed down into the thick sludge, then the rope is pulled to pivot the bucket up and scoop the sludge, and then the bucket and handle are lifted out of the pit.

The second situation would be for thick or thin sludge if the pit is deep and the handle is long. Without a pivot you have to tip the whole handle, which gets awkward inside the pit latrine. I did not appreciate until I went to Africa, that the horizontal dimensions of the pit latrine are small. The current version of the sludge digger has a telescoping handle that can be as long as 2 meters, and it would be more difficult to tip this long of a handle up and down with each stroke.

It sounds like the conditions in Lusaka are similar to Nairobi, shallow pits and thin sludge. Under these conditions, a simple handle welded (or nailed) to a bucket is fine, The handle can be tipped such that the top of the handle is out the door of the latrine, if necessary.

As I like to say, every tool works well somewhere, no tool works well everywhere.

Thanks,

Dale

Dale Andreatta, Ph.D., P.E.
Mechanical Engineer
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  • hajo
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Re: Field Testing of Sludge Digger and Related Tools

Hi Dale,

thanks for your reply.

I wouldn't imagine that the bucket needs to be tipped (open end down) in order to push it into the sludge. The upward thrust shouldn't be that large that it cannot be pushed in 'bottom first'. 1.5 kg/litre, Or? I can't judge from experience or observation because the pit emptiers I have observed in Lusaka open the pit from the side, just below the concrete platform and enter with their buckets from the side, not from the top. The squat holes are too small (15 cm) to enter with a bucket and the toilets are not high enough for their long handles (2.5m).

But as you say, different locations have different challenges.

ciao
Hajo

We can't solve problems by using the same kind of thinking we used when we created them.
Albert Einstein
Any intelligent fool can make things bigger and more complex... It takes a touch of a genius - and a lot of courage to move in the opposite direction.
E.F. Schumacher
Everything should be made as simple as possible, but not simpler. :-)
Albert Einstein
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