# Revision history [back]

The Vacutug was designed by me for Graham Alabaster of UN-Habitat United Nations Centre for Human Settlements in Nairobi Graham.alabaster@unhabitat.org and is being manufactured in Bangladesh by the Mirpur Agricultural Workshop and Training Centre (MAWTS) in Mirpur, close to Dhaka.The "ex-works" cost was around US $5,000 last time I heard about two years ago. (Contact Hamidul Bari at mawts@bdonline.com. You can also contact Harrison Kwach at UN-Habitat in Nairobi < Harrison.kwach@unhabitat.org who co-ordinates things in Nairobi. It is also planned to manufacture it in Mozambique, South Africa and Kenya. It was designed specifically to reach into areas where other vehicles cannot reach and the initial trials were carried out in Kibera township, a peri urban settlement of around 800,000 people in an area of only 210 hectares on the outskirts of Nairobi. Its performance is limited to relatively short haul distances due to its small capacity (500 litres) and low travel speed (5 kph) but it can go where no other latrine emptying systems can reach. The wastes in pit latrines decompose with time with the heavier inorganic wastes settling to the bottom of the pits so that after about two years sedimentation these wastes are virtually unsuckable by any vacuum system. The wastes at the bottom of the pit may have a density as high as SG. 2.0 with a high viscosity and high thixotropy. The fresher organic wastes at the top of the pit will have SG 1.0 with a low viscosity and are easier to suck. The height of the top of the tank above ground level will determine the total suction head so that it gets progressively harder to suck the wastes the fuller the tank, the deeper the pit and the longer the wastes have been decomposing. However, you refer to "trench latrines" and presumably these are for emergency situations and refugee camps so that I assume that they will be quite shallow and the wastes will be relatively fresh. In situations such as this the Vacutug can be used effectively as a pump to push the wastes back up a pipe to a "mother" tanker" some distance away. This can be mounted on a truck or on an agricultural tractor trailer for transporting the wastes to the disposal area. The Vacutug has a top inlet valve and a bottom discharge valve so that a short length of vacuum hose can be used to suck in 500.l of sludge through the inlet valve. This valve is then closed and the tank is pressurised to a pressure of around 1.0 bar to force the wastes out through the discharge valve and through the transfer pipe to the mother tanker. In this way the Vacutug can pump as much as 10 loads (5,000. l) per hour when used as a pump and the size of its tank is not relevant. (Typically each person will produce between 35 litres and 50 litres of sludge per annum using a dry pit with a good leaching system. I don't know how far it is possible to pump the wastes in this way but I would expect at least 200 metres, depending on the waste characteristics and the gradients with perhaps the addition of a very small amount of water to reduce the viscosity of the wastes. We are presently working on a method of reducing the viscosity of the wastes in pit latrines so as to enable less frequent emptying and on the design of a latrine pit for mechanised emptying. I am working with Steven Sugden of LSHTM (London School of Hygiene and Tropical Medicine on this as part of a wider research project which will include his work on manual pumping of latrine wastes. I hope that this is of some help to you in your Haiti project. I did some work in Haiti about 25 years ago when MSF introduced a Micravac latrine pit emptier which I had developed. It is a very tragic country. Regards Manus Coffey  2 No.2 Revision The Vacutug was designed by me for Graham Alabaster of UN-Habitat United Nations Centre for Human Settlements in Nairobi Graham.alabaster@unhabitat.org and is being manufactured in Bangladesh by the Mirpur Agricultural Workshop and Training Centre (MAWTS) in Mirpur, close to Dhaka.The "ex-works" cost was around US$ 5,000 last time I heard about two years ago. (Contact Hamidul Bari at mawts@bdonline.com. You can also contact Harrison Kwach at UN-Habitat in Nairobi < Harrison.kwach@unhabitat.org who co-ordinates things in Nairobi. It is also planned to manufacture it in Mozambique, South Africa and Kenya.

It was designed specifically to reach into areas where other vehicles cannot reach and the initial trials were carried out in Kibera township, a peri urban settlement of around 800,000 people in an area of only 210 hectares on the outskirts of Nairobi. Its performance is limited to relatively short haul distances due to its small capacity (500 litres) and low travel speed (5 kph) but it can go where no other latrine emptying systems can reach.

The wastes in pit latrines decompose with time with the heavier inorganic wastes settling to the bottom of the pits so that after about two years sedimentation these wastes are virtually unsuckable by any vacuum system. The wastes at the bottom of the pit may have a density as high as SG. 2.0 with a high viscosity and high thixotropy. The fresher organic wastes at the top of the pit will have SG 1.0 with a low viscosity and are easier to suck. The height of the top of the tank above ground level will determine the total suction head so that it gets progressively harder to suck the wastes the fuller the tank, the deeper the pit and the longer the wastes have been decomposing.

However, you refer to "trench latrines" and presumably these are for emergency situations and refugee camps so that I assume that they will be quite shallow and the wastes will be relatively fresh. In situations such as this the Vacutug can be used effectively as a pump to push the wastes back up a pipe to a "mother" tanker" some distance away. This can be mounted on a truck or on an agricultural tractor trailer for transporting the wastes to the disposal area.

The Vacutug has a top inlet valve and a bottom discharge valve so that a short length of vacuum hose can be used to suck in 500.l of sludge through the inlet valve. This valve is then closed and the tank is pressurised to a pressure of around 1.0 bar to force the wastes out through the discharge valve and through the transfer pipe to the mother tanker. In this way the Vacutug can pump as much as 10 loads (5,000. l) per hour when used as a pump and the size of its tank is not relevant. (Typically each person will produce between 35 litres and 50 litres of sludge per annum using a dry pit with a good leaching system.

I don't know how far it is possible to pump the wastes in this way but I would expect at least 200 metres, depending on the waste characteristics and the gradients with perhaps the addition of a very small amount of water to reduce the viscosity of the wastes.

We are presently working on a method of reducing the viscosity of the wastes in pit latrines so as to enable less frequent emptying and on the design of a latrine pit for mechanised emptying. I am working with Steven Sugden of LSHTM (London School of Hygiene and Tropical Medicine on this as part of a wider research project which will include his work on manual pumping of latrine wastes.

I hope that this is of some help to you in your Haiti project. I did some work in Haiti about 25 years ago when MSF introduced a Micravac latrine pit emptier which I had developed. It is a very tragic country.

Regards

Manus Coffey