Emptying septic tanks/pit latrines in Kigali - Rwanda 3

[Nicolag]

Hello

I am an engineer working in Kigali to design systems for emptying pit toilets. Some key facts:
- 90% of Kigali (1 million people) have no sewer
- Instead of a sewer, people have 'on-site' sanitation - either a septic tank or pit latrine (basically a 2-5 m deep pit in the ground that you squat over)
- Many of these pits are not accessible by road, Kigali is incredibly hilly, and the more informal areas are extremely densely populated.

We have some basic equipment at the moment that is allowing us to pump waste from the toilet/pits. However, due to the nature of the roads/hills -we then load the waste into 50L buckets (half full so they are lighter) that are carried up to a waiting truck on the road side. This can be over 100 barrels, 2.5 tonnes, meaning 100 round trips up steep hills with a bucket of sludge on your shoulder.

Is there another way?

The distance to the truck is 500-1000m; obviously sometimes the nearest road is downslope; but it is often 200-300m (vertical) distance up-slope.

Bear in mind that getting a large pump beside the pit is very difficult due to the narrow access paths and terrain.

All help appreciated. Is the reality that we'll have to stick to the carrying?

Nicola

 

[HEC]

For container and transport solution look at

http://www.qdrum.co.za/

a rolling drum!

Mark Hutton

 

[Nicolag]

I am pursuing your ideas above
(i) the intermediate hopper
(ii) the barrel within a vacuum proof container

having some prototypes made up and I will keep you informed of developments - we should be giving them a test next week

On a side note - a colleague was suggesting that rather than do the walking to the roadside with the barrels, that we collect in a holding tank and use an air compressor to boost to the road (useful for 200m horizontal, 50m head for a portable compressor- we need to get slightly more than that for this to be useful). Any thoughts on this concept?

 

[LittleInch]

I'm glad you came back - this has been an interesting set of posts and feedback is always good. Please come back to us with the odd picture and whether it works or not.

The problem with any pressurized system in places like you are, especially if the system is portable, sectionalized or reelable is the high potential for failure, especially as you will not be able to easily judge height. The instinct will be if you get to 60,70,80m height is to screw down the air pressure relief valve and then BOOM. Spraying liquid Sh1t over the population will rapidly diminish your very admirable ability and desire to clean up these latrines....

Any gas driven / air systems will contain a reasonable amount of stored energy, which means that any incident will continue to flow until that pressure is released.

In places like Rwanda, labour is generally available and mechanizing things is sometimes seen as taking work away from people.

The second main difficulty with any pipe system is how do you clean out the material in the pipe as you move form place to place. Really quite difficult in those locations so unless you can somehow reliably seal off each section of pipe as you go from place to place, then it becomes very heavy and the potential for leakage is very high.

Keep up the good work.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Nicolag]

Hmm - interesting feedback - thank you. Plenty of risks there.

We are testing the hopper system tomorrow so I'll send some pics of how this is materializing.

 

[Nicolag]

Just wanted to provide some update

the hopper system is not the perfect solution but it sure is a good one. This is not the best video, but we now build up a vacuum in this black barrel and when it fills with sludge we release via a tap.

Obviously this tap is too complicated (will hopefully replace with a gate valve of sorts) and we have since added a splash plate to avoid the operators coming into contact with sludge...but overall its a great improvement comapred to the old pouring system we had

https://www.youtube.com/watch?v=SIYiasjZvVk

https://www.youtube.com/watch?v=4dZ44nZeqgk

The lid has been improved since the video too so someone doesn't need to stand there, and we have eliminated a labourer from our operations through having one person operating the valve at the top of the barrel and the tap below.

baby steps, but good ones! Thanks for the help.

 

[EdStainless]

We really appreciate the feedback.
Good progress.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[LittleInch]

Agree great to get feedback.

So does the metal barrel have two nozzles? one for filling and one for emptying? I couldn't quite work it out from the video but definitely looks better than pouring it out or indeed moving the inlet pipe from one container to another.

For this type of operation the quarter turn valves are probably still best. They might need cleaning and lubricating to stop them sticking (they seemed to be a bit stiff sometimes on the video), but are much faster to open and close than gate valves in those sort of sizes.

Keep up the good work.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[KENAT]

Thanks for the update and glad it's working for you.

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