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Emptying septic tanks/pit latrines in Kigali - Rwanda
3

Emptying septic tanks/pit latrines in Kigali - Rwanda

Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
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

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Nicolag

No matter what you use you are going to have up to 1000m of hose if that is how far away the truck is and the 2-300m vertical is going to be a problem.

The reality is i would expect, that if you want the liquid in that truck you are going to have to carry it.

So perhaps there has to be an alternative solution thought through.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
great - thanks for the feedback.

That's essentially what I'm trying to establish: will I ever be able to do this via a pump/series of pumps or do I need to get real and just keep planning around the container carrying system.

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Some camping trailer parks here, instead of providing a distributed underground sewage system, bring you a 30...200l tank on wheels, into which you discharge your accumulated waste water. Then the portable tank is pulled to a truck or a central drain. It's a nice system for level paved roads. For goat paths, not so much.

The thought occurs that maybe the buckets you're using are perhaps not optimal. Find a history of honey buckets and you might find a better shape than whatever you're using. Or do some experiments.

You can't pump honey that far up a hill with the pump at the top. Carrying the pump down to each latrine is impractical. Using a jet pump at the top increases the volume of what you have to deal with. Have you got the budget and the power source to put a pump at each latrine, and provide permanent piping up to the truck, or a holding tank?

Can you persuade the citizens to climb a hill to use a toilet, as in a nicely equipped modern latrine up high, accessible to the truck, or mounted on a trailer and towed away to discharge?

Mike Halloran
Pembroke Pines, FL, USA

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

What about a transfer tank either on a skid or aerial tram with the a winch powered by the transfer truck? You would then "only" need a reasonably straight path to raise or lower the transfer tank between latrine and truck. You should avoid liquid containers that are partially filled, since they are unstable from the sloshing free surface. Either completely fill a smaller container or perhaps consider an air bladder or something else to stabilize a partially filled container. Where there is a will, there is a way!

Walt

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

How about a hand operated or air operated Wilden pump (on a truck) to transfer this sewage ( from a discharge port at the bottom of these receptacles)?

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Hmmm. lets look at some basics here. 200 - 300 m vertical implies a pressure at the base of any pump or line to be approx. 30 bar. That's quite a lot and would need some reasonable wall thickness hose, even if was only 3 or 4" and then would still be full of "liquid" when you're finished, so might end up being as heavy as the current system.

You might be better off thinking along the lines of a small vacuum / pressure tank and a small air / vacuum pump and say 200m of hose. Then for the ones furthest away or steeper, pump into the same tank in a cascade system. This would reduce the pressure in your vessel to around say 10 barg.

You vacuum out the waste, then turn the pump around and pressure up the tank to blow the waste down your pipe either to the truck or to the next tank in line. You should be able to make it small enough to attach some wheels and be able to push / pull / carry the tank and hose.

This is a similar set up to what they do when spreading slurry on a farm, they vacuum up the slurry, then pressure the tanker to spray it out the back.

Something like this http://www.sswm.info/content/human-powered-emptyin...

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

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Gents,

Get on Google Earth and have a look at Kigali. Its going to be tough to do anything given the "specification".

My opinion is that pumping is not the answer, too far , too much lift, too much equipment to haul too many variables , and difficult terrain.

Therefore i would suggest that bimr is on the right track. Mechanize the hauling of the buckets in effect.

Maybe a tank and some small pumping equipment could be mounted on a small all terrain vehicle, so that it is relatively self contained and delivers its load of say 50 gallons back to a tanker.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Pumping is not a consideration even in your wildest dreams.
It will need to be manhandled as it was in my youth in Australia, the dunny-man called once a week to remove a full pan leaving an empty one in its place, worked well as there was no other alternative.
Google dunny-man Australia.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Another option may be a hand or air operated Moyno pump - for 200m vertical rise, break it up into a few intermediate pumping stages and holding tanks to suit.

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
Thank you - the above is really useful. Some are some thoughts I've had (I'm pretty familiar with all the low cost systems currently out there - these hills have just added a new dimension), some are new thoughts.

What Artisi has said about the data is really critical. I present you the worst case scenario; but we are really not sure if that represents 5% of the 'market' or 50. To understand this would be a fairly serious undertaking. The baseline everywhere is of course very dense but the distance/head to drive-able road is massively variable area to area.

I imagine we will need a range of systems and a pre job assessment will have to identify which system to use each time.

If we forget the transport for a second (re-inventing how to carry stuff up hills is difficult!), let me tell you about our current system closer to the pit. We use a Vane pump to build up a negative pressure in thick walled barrels, close the valve, and sludge is sucked in. We then pour to the 50l barrels (half full) so they can be carried. The thing we really need to avoid, is human exposure to sludge, so the pouring is not idea.

I haven't got good enough internet to upload a video of our process, but you can see an example of the machine here: https://www.youtube.com/watch?v=igy81IvqvR8 The most important thing to watch is the pouring of the waste. We don't pour into a nearby pit like these guys as the area we work is too dense - we pour into 50L barrels to carry to a road side.

Any idea how we can go direct to those smaller barrels (Even if we do need to make them smaller as suggested in a post above) to avoid the pouring?

Its also worth noting that the real 'exposure' part is at the start. These pits are full of solid waste, and we begin by fishing out rags with a hook. No matter what system we come up with, we're not doing well to overcome this. https://www.youtube.com/watch?v=6gbDNf1uybo

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Is this how the saying goes? To an optimist the barrel is half full; to a pessimist the barrel is half empty; to an engineer the barrel is the wrong size!

Walt

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Nope, just has a safety factor of 2.

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

These rags would get in the way of just about any pump you can throw at this service. Educating these people would be one amongst many longer term tasks. In the meantime, a blowcase would avoid the use of a pump, but you need high press compressed air for this..

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Gents

The rags i saw in the You tube were not really that much worse than what you get on the inlet screens of a municipal waste water plant in terms of size and nature. However in such a circumstance there is normally a lot more dilution ie: less rags and more water.

But the problem is not lifting out of the pit but getting it away somewhere to do something with the waste.

Nicolag

In general terms how often are pits pumped out? Weekly, monthly , yearly

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

The whole concept needs rethinking, commencing at the home level. Think about filling in all the pits and trenched and revert to a single pan system for each house, emptied weekly or as necessary. The weekly dunny-man calling in the early hours of the morning worked well in many areas of Australia - admittedly not an ideal method of disposing of human waste but probably streets ahead and manageable compared to the present system

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Artisi

I think you are right. Remember Brisbane had "night soil" well into the 70s and would be a real and workable solution. Only trouble might be how far the dirt collector might have to walk to get back to a truck. Most cities that were laid out with night soil in mind had lanes at the rear of the property.
Nonetheless i think it could at least be a partial solution.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

I have been trying to think through some totally alternative methods as well. I am sure that these would be problematic in some way but i am still going to float out these ideas for discussion, just to get the ideas flowing.

1) A portable latrine system with the outhouse built over a tanker trailer or as part of the tanker itself . When the tank is full you tow the trailer away. Obviously this wont work everywhere because vehicle access is a problem already, but may also offer a partial solution.

2) A system that uses a solar drier to dry the solids out after a short digestion period. This would require a site with some slope so that the sludge can flow under gravity to the solar drier which would be roughly something like a glass house only made out of a plastic clear film. The sludge would be substantially drier , therefore less volume to carry but would have to be dug out of the drier and carried in wheelbarrows. Still a better option than carrying a bucket. Likewise the heat of drying and the solar radiation would reduce the bacteria levels in the sludge. Lots of problems and some complexity and probably wont be suitable for a lot of sites

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
The wrong size barrels are pretty handy to be honest as it allows us to be a bit more sloppy with the pouring. Only other hope is to suck into some intermediate tank what releases precisely the barrel volume. Any barrels less than 50L do not come as standard here, unless you look at using the standard water jerry can.

Again of course I agree, its a complete re-invention of the system that is necessary. Particularly for us, because we have a waste-to-energy plant and the newer sludge has far greater value than the older stuff. That said, by the time you get to a latrine (in their current form), you might as well empty as much as you can when you get there because it's already been so much hassle to set up (and customers get pretty upset if sludge is still within sight). I would love to, as part of our current work, block off the depths of the pit and build it so that it can be emptier (a) more easily, and (b) more regularly as part of our current work; but that would be a huge social change for people who value a pit latrine as deep as physically possible to avoid emptying completely. Maybe I should revisit this thought.

Pits can be up to 7/8 m deep - more typically 3m (people often tell us they are 10m but i think this is just because the builders charge them by metre, so they mis-quote them on how many metres they have really dug). We're finding that people empty ever 8-15 years (very variable numbers of users). Some of the settlements in town are so new that they have never needed to be emptied.

In the restaurants, pubs - we get nice sludge - not so much trash. But the households ....lets jsut say the pit yesterday had a mosquito net and a football + 200L of shit covered trash.....

Bear in mind this is the situation across ~ 50% of the population of most African cities - so its worth thinking about...but a bulldozer often comes to the fore as the better option winky smile

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
Clean Team in Ghana are a start- up enterprise reverting back to a night soil type activity: http://cleanteamtoilets.com/

Only problem for them is that they lose money as cleaning the barrel and disposing of the resultant waste water.

Nicola

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

You could build trailers on wheels with several toilets installed on each trailer. I would label these trailers "toilet" trailers. Once a trailer is filled up, it can be pulled by several members of the village to the downhill waiting truck. The trailer can then be towed by the waiting truck which in turn has an empty "toilet" trailer to be pulled/ pushed by up the hill by the same villagers. Manpower should not be a problem and you partially solve the problem of unemployment.

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

If it's feasible to always go downhill, why not use temporary-ish piping and use gravity flow to fill the trucks.

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

I was about to mention compoosting toilets, but the OP stated they know a lot of low cost systems and more crucially want to use the waste for a bioenergy plant. But given that, as you mention, some pits are emptied every few years, are you sure you get much energy from them?

I want to pick up Bimr's idea with the tricycle and combine it with the vaccuum system seen in the first video:
Build the vaccuum system as seen here, but build it from a section of fat pipe. The hose for waste and the air pipe will attach to a flange on the top. on the botton, you mount a knife valve. Mount the pipe on your tank, close valve, operate vaccuum until pipe is full. shut off vaccuum, open valve, waste drops into tank, close valve, repeat. The valve should have the full diameter of the pipe & and could turn out to be the most expensive part.

This way your tank can be any old ICB or even a bag and does not need to withstand any negative pressure.

The bucket in the video is translucent, I'm not sure how you'd see the filling level in a piece of pipe. maybe keep the barrel and see if you can attach a flange to the bottom (if PVC, glueing should be possible) to mount a valve.

Possible problem is rags or anything clinging to the walls where the valve closes, blocking the valve.

Edit to add: Would it be feasible to have a duck bill valve or similar on the lower end of the pipe? So the vaccuum closes the valve, eleminating some steps.
I'd also think that the large seal surface achieves a better seal when small solids cling to the surface.

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Although not very likely 'low cost', but along the same idea as Ashtree's solar drier:
waste zapper article
I wonder what ever became of this?

gbangs
TC 8.3.3
NX 8.5.3.3 MP11

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
Sorry for delay but thanks for these helpful posts.

Martin - you are coming closest to whats feasible here I think.

(and you raise the important question, is this old sludge even useful - we are taking samples and testing for calorific value periodically to try build up some data around this - we only have 15 pits so far so not the greatest data set; but thanks for bringing this back to top of my agenda).

Finally got a video of our process uploaded: https://www.youtube.com/watch?v=5S_8mLChMe4

We really need to drop the vehicle idea - no way to get any form of transport within 50m of all of these latrines (wheelbarrows included); and most often ~200m (though I do hope we'll work in easier areas where this is not the case).

What we really need to eliminate in the short run, is any visible sludge (to get us through an enviro health inspection) so the pouring is a no-no. Martin, I was thinking about what you were saying about the pipe or modification of the existing vacuum barrels to build a neater discharge system (not to a tanker as you suggest, but to the barrels that we carry to the road).

Possible to modify the existing barrels (though I'm reluctant to tamper with the one good thing we have). Only other thing I have found so far capable of withstanding such a pressure is some thick walled irrigation pipe that we could possibly try to mount a bottom end on and turn into a bit of a hopper system. Totally black so not ideal, but we'd find some way around knowing it was filling. We could try to use this upright and have a large valve to discharge direct to waiting barrels. Though I would fear for the valve (shitty locally made version) holding up through the repeated negative pressure build up.
[/u]

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

My thoughts are this: The shit will have to be carried between 50 and 200m, and every transfer of containers means you spread some around.

So why not use more of the white vaccuum barrels so that one is filled while the others are carried to the vehicle? Two people (4 with poles) can carry one vaccuum barrel. At the vehicle, you have hoist to ease lifting and tipping the barels into your tank. Something like a garbage truck uses to pick up waste. Still thinking how this can be enclosed, so you don't have a huge health hazard.

The barrels get lids for the trip. Possibly use smaller (=shorter) barrels.

I think it's unavoidable that some surface has shit on it after every trip and needs cleaning.
You can have vaccuum system similar to the one at the pit to empty the vaccuum barrels, then you move the dirt problem from the outside of the vaccuum barrels to the outside of the suction pipe/hose. This can be built with more enclosing (I actually have a rough idea how this would look like but no time to draw it now)





RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
Thanks Martin

Of course! I never thought of that - if we manage to bring in roadside tipping we could just work with 10 or so barrels coming back and forth - so if I can make a less clunky/hard to lift vacuum proof barrel then we eliminate a round of pouring (provided its not too heavy).

Ok - i have to have a think about this. I was thinking of an intermediate hopper type system but was not really enjoying the concept - this is much better.

Unfortunately getting anything made that is a total nightmare - but we would happily ship them in if there was anything we could find that withstood the vacuum but was relatively lightweight.

Nicola

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
Estimated pressure build up of 0.7-0.9 bar for the current ~50L barrels. So if we brought it down to 30 would only need to withstand ~0.5. No experience with these materials so I'm not sure what we could work with.

All i've managed to find here is some thick walled irrigation pipe (310mm with 20mm walls)- similar to original barrel diameter.

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

I was thinking something like the attached.

This would be a single vacuum container, but then you insert into it the plastic sealable container - you can see many examples where you have snap type lids used for paint, fertilizer, etc. Trick is to make it small enough to be able to lift it out of the vacuum container so really no more than 20 - 30 litres, then stack them on a trolley and wheel them to the truck.

Lifting the top with the pipe out does mean some dripping but much reduced.

You do need some sort of liquid trap on the vacuum line to stop the liquid going into the vacuum pump, but I kind of assume you have something like this already?

The advantage is you don't need vacuum capacity for the transportation buckets.

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

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
OK - I never even considered this as a possibility. You are saying I can have one strong tank which can withstand the vacuum and just insert my barrel for use inside? That would be fantastic if I could think of a way to get them out easily (perhaps via screw on lids with handles on?). Just lifting the lid would be a vast improvement over pouring.

I'll try and see if I can find something around the paint tub filling to get a better idea.

Yes - have a liquid trap.

Nicola

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Could your vacuum tank system be set up so the vacuum is only supplied to some kind of 'header tank' which you then empty into the non pressurized containers for transport to the vehicle?

Essentially take Little inches sketch but instead of the captive inner bucket have a suitable valve + outlet at the bottom?

Putting it up on a little portable tripod or similar may be enough of a head to get it to then poor down into your containers.

Work flow would be set up tank on tripod (or hang from tree or...), run vacuum pump to fill it, stop vacuum pump, open valve to poor the waste into transport container.

As to your containers what do use, literally buckets?

Might I suggest a more ergonomic container combined with a backpack type set up - backpack sprayers have this you just need to lose the pump & sprayer etc.



Or you might be able to just come up with a back pack harness for a '5 gallon' container or similar that may be more readily available.



Finally, is the terrain always so terrible you cant use some kind of cart to transport the containers? I'm not talking your typical red rider wagon but something like a game tote or deer hauler with two or even one large (almost mountain bike or dirt bike size) wheel. http://gametote.com/index.html



Might take 2 people but seems if you can avoid carrying the drums - even only at say 50% of sites - that would be a big plus.

Or, if you can get your header tank high enough relative to your vehicle could you use a hose part way?

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RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Basically yes.

If you search "Quick opening closures" you should be good - the advantages here is that the vacuum applied will help seal the lid - all you really need is some locating lugs and a bit of a weight - some bricks or a person would probably do it if the seal is good enough. The trick is to get the sealing surfaces flat and the lid pretty strong.

Or a simple G clamp - there's bound to be a few of those hanging around

Something like this attached.

And a bin like this

Remember - More details = better answers
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RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

In case it helps, schematic of my suggestion.

Header tank Schematic

It's approximately to scale assuming 6 ft poles for the tripod, location and types of valves I've indicated may not be ideal but I'm not a pump or sewage guy (yeah I know I may be full of it but that don't make me an expert in handling it).

Rough work flow after setting up.
  • Close container fill valve.
  • Open waste extraction valve.
  • Run vacuum until header tank is full.
  • Close waste extraction valve.
  • Turn off vacuum (may not be essential)
  • Open container fill valve & fill container.

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RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

KENAT - Pretty good - I would put the fill line at the bottom of the bucket but otherwise OK, Just add a vacuum release valve to allow the SH1T to flow out and that could work a treat.

Remember - More details = better answers
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RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

LittleInch - sadly if I put the poop pipe down to the bottom of the poop barrel it obscured the poop text.sad

Good point on the vacuum release valve, simplistically perhaps add manual override to the vacuum relief valve.

Or put separate release valve in equivalent location in the system i.e top of tank equivalent - could be anywhere on the line from the tank to the vacuum pump for instance - maybe the vacuum pump controls already have one in?

So work flow becomes:

  • Close container fill valve.
  • Open waste extraction valve.
  • Run vacuum until header tank is full.
  • Close waste extraction valve.
  • Turn off vacuum (may not be essential)
  • Open vacuum release valve (not shown in schematic)
  • Open container fill valve & fill container.

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RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Refined per LittlInch.
  1. Ensure container fill control valve closed.
  2. Ensure vacuum release valve closed.
  3. Ensure waste extraction control valve open.
  4. Run vacuum until header tank is full/pit emptied whichever comes first.
  5. Close waste extraction control valve.
  6. Turn off suction pump (may not be essential depending on power source etc.)
  7. Open vacuum release valve.
  8. Open container fill valve
  9. Fill container to desired level.
  10. Close container fill valve.
Repeat steps 8-10 until header tank is empty.
Repeat steps 1-10 until pit is empty



Detail design may be able to come up with more elegant valve and piping arrangement or even introduce interlocks or similar to force correct process but I'm an ideas guy not details. winky smile

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RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
Damn I wrote a response but it got lost in the Rwandan internet.

Header tank
i have considered this and i have had the tank itself made (just 50L since the workmanship is poor, so I don't want too much negative pressure in there).My issues was
(a) how to safety control air valve on top of header tank (this could be 1.8-2m high by my calcs)
(b) what kind of valve to put connecting to the transport barrel. We have to have a 3" opening here so that it doesn't block. I was looking at ball valves as the most likely readily available option to withstand the vacuum but they are so clunky and difficult to use, certainly not something that you can easily just open and close for discharge. is there something better I can do here for fast discharge?

Little Inch, I fear I may be an idiot.

I'm not getting how the lid works in that system. My understanding is attached, but I feel like you're telling me it can happen inside...I totally don't understand how I can fill the barrel yet get a lid on it. Am I going mad?!

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

Valves don't have to be on top of tank - anywhere in that pipe/hose between pump and header should work. 'Id think where the pipe connects to the pump may be Good idea for ease of use.

What level of vacuum are you running?

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RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

No, you seem to have got the idea.

The only change from what I think you have now is that instead of filling the vacuum pot and pouring it out, you fill a container which you them lift out of the vacuum pot after putting a lid on it.

It's better if the filling tube goes to the bottom of the inner container to avoid splashing and the suction tube has a float which stops the "liquid" from flowing into the vacuum pump and also tells you when the container is full.

3inch full bore ball valves are normally very simple and easy to use with a quarter turn bar type operator

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

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

For container and transport solution look at http://www.qdrum.co.za/ a rolling drum!

Mark Hutton


RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
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?

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

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.

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
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.

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

(OP)
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.

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

We really appreciate the feedback.
Good progress.

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

RE: Emptying septic tanks/pit latrines in Kigali - Rwanda

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.

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