Emptying Technology, or MAPET.MAPET retains the positive featuresof each of the existing systems, com-bining new and old to make a moreappropriate technology.

Like the traditional method,MAPET uses only manual labour,both to empty the pit and to transportthe equipment. It also relies on theknowledge and experience of tradi-tional pit emptiers, because thesludge is disposed of by burying it onthe resident's plot. The essential ele-ments of the new technology are theexperienced emptiers' knowledge;both of how to deal with sludges ofvarious qualities by stirring and lique-fying, and how to estimate the size ofthe hole to be dug for sludge disposal.The practice of independent workerswho earn income by emptying pitlatrines has also been retained, modi-fied, and supported.

Recent innovations have contributedto both technology and methodology.The MAPET system uses modemhandpumps and vacuum techniques,while the requirement of public healthsupervision by a government agency(in this case the Dar es SalaamSewerage and Sanitation Department,DSSD) is the result of modem urbaninfrastructure.

The technologyThe MAPET equipment consists oftwo main components: a piston pumpwith flywheel, and a 200-litre vacuumtank, each mounted on a pushcart. Thepump and vacuum tank are connectedtogether with a 3/4-inch air hose. A4-inch hose-pipe - at least 4 metreslong - is clamped to the tank to drainthe sludge from the pit.

The MAPET has several attach-ments which are derived from tradi-tional emptying practice: a mixing rodfor stirring the sludge to improve itsviscosity, a hook for removing clothand other solid materials that block theflow of the sludge, and a spade and ahoe for digging the hole for sludgedisposal. A chisel and a hammer areuseful for widening the squatting holeor for making a hole in the latrine wallfor the sludge hose-pipe.

An important feature of the MAPETequipment is that it is all built inTanzania, and is based on parts,materials, and techniques readily avail-able in small workshops. The total cost

manually using a bucket, and disposingof it in a hole that is dug elsewhere onthe resident's plot. It is a time-consuming, unhygienic, and expensivemethod. Secondly, the Dar es SalaamSewerage and Sanitation Departmentoperates a pit-emptying service, whichuses large vacuum tankers. Theseconventional tankers, however, oftencannot get close enough to the latrinepits because of the limited spacebetween houses in the unplanned orsquatter areas. Dependence on im-ported fuel and spare parts also makesit difficult to operate a cost-effectiveservice with these tankers. For theseand other reasons the existing servicescould not cope with the demand for pitemptying, so a new system was devel-oped, called the Manual Pit Latrine

MAPEl: An appropriate latrine-emptyingtechnologyby Maria S. Muller and Jaap RijnsburgerIt is clear that it will never be possible for everyoneliving in the cities of the South, especially in therapidly growing mega-cities, to be connected toconventional water and sewerage mains. Thistechnology allows homeowners to have hygienicand convenient on-site sanitation.

IN MOST CITIES in Africa a largesection of the population relies onon-site sanitation. That is certainly thecase in Dar es Salaam, the largest cityin Tanzania, where 80 per cent of thehousing units have a pit latrine. Whena latrine pit in the city is full, there israrely enough space available to builda new one, so the pit must be emptiedand re-used. When pits are allowed tooverflow, they are not only an unpleas-ant mess for the neighbourhood, theyare also a threat to public health. Anumber of diseases, from diarrhoea tocholera, are common in areas withinadequate sanitation services.

In Dar es Salaam two systems areused to empty latrine pits. First, thereis the traditional method of scoopingthe sludge out of the latrine pit

The MAPET is designed for easy handling.

24 WATERLINES VOL.l3 NO.1 JULY 1994

The quarterly magazine of practical change in the developing world

Design criteria for the development of MAPET equipment.

The tricycle wheels also had disad-vantages, as the irregular-sized tyresare vulnerable and the ball bearings aretoo light for a loaded tank cart.Because of the lack of alternatives, the

olutionU e human-pow red equipment:• handpump for mplying• pu h art ~ r Iran portPump indirectl , realing v uumin Ihe tank which will draw up thludge.

In lall a gauge a gl . panel) 1control Ihe Iud Ie el.

e (appr xirnat dim n ion of:• flywheel diam ler: 800mm• r lali n peed: 40-60rprn• pump olum per tr ke: 2.0

litre• m of flywh I: 2 kgEquipm nl mu I have maximumwidth of mOl (relale to the\ h Ib e of the carts and I theflywheel diamet f).

pply locally a ailabltechn I gie ~ r:• drinking-wat r handpump and

piped water upplie• mOlor-v hide maintenan• bicycle maimenan eDe ign the tank 10 be lipped:coupling po ition 'up' for pumpingand m noeuvring, down' ~ rdi charge.

e 4-inch auer ho e-pipecoupling.Excavate the ludge thr ugh thequatting hoI by m an fa

ho -pipe.

APPROPRIATETECHNOLOGY

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Design criteriaR duc d pend nc on imp rt dfo il fuel.

Make optimal u e of human p werfor a pumping head f 3m.

Prevent 'Iudge from entering Ihpump 10 redu e both the ri k fbl kage and hea y wear.

Build and maintain unil 1 ally.

Mu I be narrow enough 10 n gOlialemall path and gates to inner

c uri .

ust not u xpen ive, vulnerablegate valv to mak localmaintenance po ible.

Reports from the field for anyone concerned with development inpractice. Plus the latest in appropriate technology applications,news from Intermediate Technology, Book Reviews, Foodlines,Resource Guides, Broad Brush, and a development diary.

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En ure C mpatibiJilY with D 0lanker ho e-pipes.

void dem liti n of quailing laband supe tructure, which in ce ary with tradilionalemptying.

Chinese tricycle wheels, however,meant that the tank could be betweenthe wheels, resulting in satisfactoryloading, discharging, and movingcharacteristics.

of the equipment is $US3000 (inTanzania in 1992).

At the start of the project, twoprototype hand pumps were built inTanzania, a diaphragm pump and apiston pump. Field-testing showed thatthe diaphragm pump was less suitablefor the local conditions than the pistonpump, because of the vulnerability ofthe rubber diaphragm. Even heavy-duty diaphragms began' to crack andleak after a few months, mainly be-cause of the sun and the tension in therubber resulting from the requiredlarge stroke.

A piston pump with a leather pistonin a 6-inch PVC cylinder made fromsewage piping is now the standardMAPET pump used in Dar es Salaam.

In order to ensure that the knowl-edge and skills to sustain the technol-ogy were available locally, all theconstruction and adaptations, and allthe equipment assembly have beendone in Dar es Salaam by three DSSDmechanics supervised by DSSD man-agement. As a result, the DSSD is fullyable to build and maintain MAPETequipment.

Vacuum tank The first MAPETunits were equipped with a 200-litreoil drum as a sludge tank. This drumwas too prone to corrosion, however,and was quick to implode undervacuum-pressure.

Now the standard vacuum tank is a200-litre tank welded out of 3mm sheetmetal. II has been carefully designedto get the best performance in trans-port, steering, and tipping. The currentdesign is known as the kibuyu, (Swa-hili for gourd), reflecting the shape ofthe tank.

An advantage of the kibuyu tank, asacknowledged by the pit emptiers, isthat its dimensions have a lower centreof gravity, resulting in easier handlingof the push cart on which it is mounted.Its better diameter:length ratio alsoallows the expensive sheet metal to becut more efficiently.

Handcart and wheels Differentmethods of transporting the MAPETequipment were also tested. First, theMAPET pump and tank were trans-ported on the type of hired handcartthat is used locally to transport heavyloads (mkokoteni). Later, separate cartsfor the pump and the tank weredeveloped.

The wheels of the first carts were thesame as those of the mkokoteni: usedcar wheels. Car wheels, however, areexpensive, heavy, and wide. Thismeant that the tank had to be mountedover the wheels, as locating it betweenthe wheels would have resulted in awidth larger than 800mm (see designcriteria box). Using imported

WATERLINES VOL.13 NO.1 JULY 1994 25

The use of tricycle wheels means the MAPET can be pushed down narrow alleys.

tricycle wheels are still being used, butgrease caps have been introduced toprotect the bearings from the omnipo-tent sand.

In the next project phase the tankload will be adjusted to suit theavailable wheels. A reduced tank sizeof 100 litres is expected to enable theuse of standard bicycle wheels and

tyres and still retain the maximumdesired width of 800mm.

Sophisticated machinery and tech-niques are not required for either theconstruction or the repair of MAPETequipment; common workshop toolsare sufficient. Now minor repairs arecarried out by fundis, artisans who runtheir own small workshops. Their main

jobs are spot-welding loosened partsand repairing tyre punctures. Major,expensive repairs are carried out in theDSSD workshop, and usually involvethe handpump (bearings and guides,piston leather, 'or valves) and thewheels (bearings or tyres).

Disposal and treatmentThe MAPET system disposes of sludgeby burying it on the customer's plot.This method is safe as long as twoconditions are met: there should be alayer of earth at least two feet deep ontop of the sludge, and groundwatershould be prevented from entering thehole and pushing the sludge up.

This disposal method assumes thatthere is sufficient space on the plot.Where this is not the case, as in denselybuilt-up neighbourhoods, the sludgemust be transferred to another site fordisposal and treatment. The site mustnot have a high groundwater table andmust be protected during the long rains.

In Dar es Salaam the MAPET serviceis based on semi-formal co-operationbetween the municipal DSSD and theprivate, self-employed MAPET empti-ers working in the informal sector. TheDSSD is the owner of the equipmentand is responsible for maintenance. Thepit emptiers lease the equipment andcharge their customers directly.

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THE OBJECTIVE of the course is to support the development of strong scientific management in the agenciesinvolved in the water and environmental health services.

The Diploma/M.Sc course is run by the Centre for Environmental Health and Engineering (CHHE) in the Department ofCivil Engineering at the University of Surrey and is a 6.5 month full-time course which commences each year in October.The course is aimed primarily at overseas students working in the field of environmental health and engineering. Studentsshould be graduates or practitioners with qualifications or relevant experience in science, engineering or environmental health.

Modules include:• Water resource protection • water and wastewater treatment • environmental impact assessment • public healthepidemiology • institutional development. international standards and guidelines. databases and data management.global monitoring programmes. bacteriology, ecology and biotic indices. ecotoxicology and toxicity testing. industrialwaste disposal and control.The M.Sc involves planning and carrying out a research project on a subject relevant to the student's home country.

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26 WATERLINES VOL. 13 NO.1 JULY 1994

New and ForthcomingTitles from Intermedia'eTechnology Publications

Maria M. Muller is a senior sociologist and laapRijnsburger is a senior physical planner!engineer. Both are with WASTE COl/sultants.Crabethstraat 3BF, 2801 AN Gouda, TheNetherlands. Fax: +31 182084885.

for example by conventional tanker.The introduction of sludge transfer

by means of fixed, concrete tanks hasnot been successful in Dar es Salaam,because of complex land-use proce-dures. In the proposed next projectphase the application of a mobiletransfer tank will be tried out. •

Subscription rates for 1995The individual ubscription rate f r Waferlines for 1995 will ta£ 15 ($2 ) but the rate for organizations or in tituLi n' will go up£20. Th price for organization ta the arne: 7. The changwill take en ct from 1 January 1995. Vou can avoid thi increase by payingy ur ub ription before the ew Year. and re d wh pay for twwill be able t pay for both yea at th Id price.

The am pric change apply t Appropriate Te fmology.

Water, Sanitation, Environment and DevelopmentEdited by John Pickford, Peter Sarker, Adrian eoad, Margaret'nee, Rod Shaw, Srian Skinner and Michael SmithThis book covers a wide range of current development issues such as communitymanagement, groundwater, health and disease, institutional development,irrigation, sanitation, solid waste management, water quality, water sources, watersupply and water treatment. It presents over forty papers from the 19th WEDCConference held in Accra, Ghana, in 1993 _ 162pp. ISBN I 853392405.£15.95.

Integrated managementMAPET equipment provides a usefulpit-emptying service in particular cir-cumstances: when the groundwatertable is low, when there is sufficientspace for sludge burial, and when thelocation of the latrine is inaccessiblefor the regular tanker services. If thereis equal accessibility for both theconventional tanker services andMAPET, it is more efficient to use thevacuum tankers of 2000 or 5000 litres.

The applicability of MAPET couldbe increased if a method of sludgedisposal was developed which did notrely on on-site burial. The haulingdistance of MAPET is limited to aboutlkm, as it is pushed manually. Itshauling capacity could be improvedby introducing neighbourhood sludge-transfer stations, from where sludge ishauled to a central treatment facility,

Traditional pit emptiers are selectedby the DSSD to become MAPET teamleaders, then each team leader selectstwo more people to form a team withhim. All the team members are trainedby the DSSD to operate the equipment,carry out small repairs, and perform theemptying service in a hygienic manner.

As the agency responsible for sanita-tion services, the DSSD supervises theservice performance of the pit emptiers.

A MAPET team empties, on aver-age, one latrine per day, removing 1m3

of sludge (five tank loads). The timespent on this varies considerably, anddepends on the soil conditions and theheaviness of the sludge.

The features of the MAPET equip-ment - its small size, manualoperations, and maintenance that iscarried out to a large extent by smallworkshops - make it suitable for usein a community-based pit-emptyingservice. The self-employed pit empti-ers can choose their own 'serviceterritory' or neighbourhoods, and cannegotiate with their customers onhow much sludge is to be removedand at what price. Requesting theservice becomes easy for residents, asthe pit emptiers can be contacted in theneighbourhood. In the next projectphase the organization of a communityservice will be developed.

Community Assessment: Guidelines for developing countries Dr Douglas StockmanUsing a qualitative community assessmentapproach, this book discussescommon contributors to ill health, with particular attentionto commonly overlooked non-medical causes. Topics explored include basic demographics, water and sanitation, foodpreparation, nutrition, community resources, health and endemic diseases, and an introduction to the growing field of RapidEpidemiological Assessment. l44pp. 'SBN I 853392243. £7.95.

Hill Irrigation: Water and development in mountain agriculture Linden VincentExamines the environmental constraints and socio-economic contexts to successfulmountain agriculture, and reviews the policies andtechnological approaches used to promote irrigation in different mountain regions. l44pp. 'SBN r 85339 r7r 9. £9.95.

Buried Pipelines for Surface Irrigation Robert van Senium and Ian SmoutA guide to the use of low-pressure pipelines instead of canals Forthe distribution of irrigation water. Highlights the local techniquesusing local industries, and the areas where these techniques are appropriate. 208pp. ISBN I 85339 1875. £15.95.

Order from Intermediate Technology Publications, 103/105 Southampton Row, Londonwe 1B4HH,UK.Tel:+44 714369761. Fax: +44 714362013. Please add 20% for p&p.

WATERLINES VOL.13 NO.1 JULY 1994 27