Technology brief

Urban pit waste
management
Introduction
All pit latrines and septic tanks will eventually become full ofaccumulated sludge. Before construction starts, good designers
will have made a decision as to whether or not the unit is
to be emptied or moved. With septic tanks the decision isstraightforward; they are designed to be emptied periodically.
The decision for pit latrines is not so simple. It will depend on
the latrine design, location and customs of the users. However,in urban areas it is likely that there is no land available todig a new pit, so it will be necessary to arrange for a pit to be
emptied as soon as it is full. The users need to be made awareof this requirement and to have formulated a workable methodof emptying and disposing of pit wastes during the projectplanning stage.
This briefing paper looks at the options available for urban pit
waste management, including various pit emptying methods
and options for sludge disposal.

How it works
Emptying full single pit latrines
can cause a serious healthhazard, as the freshly deposited
sludge at the top of the pit willcontain many faecal organismsthat may be pathogenic.
Twin pit latrines are designed tobe emptied without the need tohandle fresh excreta. Removalof dried sludge from a pit thathas been left undisturbed anddry for two years should be
relatively straightforward as thematerial will have decomposed

1 | Urban pit waste management

sufficiently and be relatively
safe to handle (althoughcare should still be taken tominimise contact).
The sludge and scum fromseptic tanks is relatively easy
to remove because of its highliquid content. A septic tankserving a communal latrine
will probably fill very quickly
so it is very important thatthe emptying method is welldesigned and can be repeatedat regular intervals.

Approaches
There are two parts to be considered ina pit waste management strategy: how
to empty the pit and how to dispose of
the material removed, including how totransport it.

Pit emptying
There are two choices for pit emptying:motorised emptying or human-powered
emptying.

Motorised emptying
A vacuum truck or tanker is a motorised
vehicle equipped with a pump and astorage tank. The pump is connected to ahose which is lowered down into a septictank or pit, and the sludge is pumped
up into the holding tank on the truck.
Generally the storage capacity of a vacuum
tanker is 3-10m3 so large septic tanks may
require a truck to return more than once tofully empty the tank.
Although smaller more mobile pumps havebeen developed, large vacuum trucks arestill the norm. Unfortunately, the large
trucks often have difficulty accessing
pits/septic tanks in areas with narrow or
nondriveable roads. Depending on thecollection or treatment technology, thematerial in the tank or pit can sometimes
become so compacted that it can not easily
be pumped.

In these situations it is necessary to thin
the solids with water so that they can flow
more easily, but this is inefficient andpotentially costly. If water is not available,
it may be necessary for the waste to be
manually removed.

Human-powered emptying
Manual emptying of pits is done either byhand using buckets and shovels or using a
portable, manually operated pump.
Some pits can only be emptied manually,for example, material left to decompose
and dry out in a twin pit system or Fossa
Alterna. These technologies require manual
emptying (with a shovel) because thematerial is solid and cannot be removed
with a vacuum pump.
Technologies that are water-based, forexample a septic tank can be emptied
with mechanical pumps. Water-based
technologies should generally not beemptied by hand because of the high riskof collapse, toxic fumes, and exposure to
the hazardous sludge.
Several alternatives to vacuum tankers
have been designed, such as: the Vacutug,
a small vehicle where the same engine
activates the pump and propels the tank to
the treatment plant (see photo below); the
MAPET (Manual Pit Emptying Technology),
with mounted on a pushcart and a manual
pump operated with a flywheel; and theGulper, a manual direct-action pump,useful for thicker sludge.

Septic Tank

Vacuum tanker
emptying a
septic tank

2 | Urban pit waste management

Many of these technologies are still
not widespread due to cost, speed
and institutional constraints that have
prevented their widespread acceptance. Itis critical then that locally-made, innovative
solutions are found that can be owned
and operated in the community. WaterAid
experience of pit emptying in Maputo,
Dhaka and Dar es Salaam with thesetechnologies has identified the need for analternative pit emptying technology withthe following characteristics:• Able to gain access without demolitionof property.
• Able to handle waste without requiring
direct contact by humans.
• Manufactured and maintained locally.
• Cost less than $2000.
• Sufficiently light weight that it can becarried across the shoulder.
• Operable by one man.
• Sufficiently robust to allow for neglect
and misuse.
• Capable of emptying at least the top
metre of the pit.

Sludge disposal
Removal and disposal of sludge frompits and tanks is a complicated issue. It isregarded as unpleasant, dirty work and thepeople who do it carry with them a negativesocial stigma. To compound the problem
they are often forced to work at night toavoid causing a disturbance to residents,
in crowded, unlit neighbourhoods pushingbarrows or manoeuvring vehicles throughnarrow lanes. Accessing suitable disposalsites nearby is also a major problem.
Consequently the sludge is often neglected
and illegal dumping of the waste iscommon. Alternatively the pits are not
emptied at all; they fill up, overflow andbecome unusable. Giving the matter
careful consideration at the system design
stage and planning a safe, practical,
affordable method of disposal will reduce
the likelihood of this happening.
Sludge that has been left undisturbed for
two years in a watertight pit or tank is not ahazard to the environment, and can safely
be spread on a garden or on a refuse tip.
Decomposed sludge can add humus andfibre to the soil which will promote plant
growth. Sludge containing plastic bags,stones and other solids will be less usefulas they will be environmentally intrusive
if spread on open ground; this material
should be buried.
Open disposal of fresh sludge into water oronto land is an environmental and healthhazard. One solution is to bury the sludgein pits so that it cannot come into contact
with humans or animals. Alternatives
are to mix it with the influent at a nearby
sewage works dry it on drying beds before
reuse, or compost it with domestic refuse.
Limiting the distance the sludge has to betransported to the disposal point will greatly
reduce costs and will increase the likelihoodof proper disposal being carried out.

The Vacutug. Credit: WaterAid/Eva-Lotta Jansson

3 | Urban pit waste management

For human-powered emptying a travel
distance of no more than 0.5km isconsidered to be a practical guide.
Development of transfer stations can help
improve sludge management. Transferstations are discharge points for faecal
sludge and septage into conventional
sewers that are then connected to acentralised treatment plant. The transfer
station can either be directly connectedto
a sewer main, or can be a large storage
system that can be operated to release thewaste into the sewer main at controlledintervals. This will improve treatment
performance and reduce peak loads.
Transfer stations are especially appropriate

for dense, urban areas where there is
no alternative discharge point and may
help to reduce the incidence of illegal
sewage dumping. The location must be
carefully chosen to maximize efficiency,
while minimising smells and disturbancesto nearby residents. Furthermore, if theutility provider responsible for sewers andsewage treatment can be persuaded tobuild transfer stations near to low-income
communities and to offer incentives toincrease their use, then it may be possible
to significantly improve the health of acommunity by providing an inexpensive,
local solution to faecal sludge and septage
disposal.

Advantages and disadvantages
Advantages
Human-powered • U seful for serving
emptying
sections of thepopulation which would
otherwise go unserved.
•P otential for local job
creation and incomegeneration.

Disadvantages•T ime consuming: can take several days
depending on the size of the pit.
• Hard, unpleasant work.
•M APET requires some specialised repair(welding).
•R equires a disposal point or dischargearea; sludge transport over 0.5km isimpractical.
•S ludge must be carried/pushed offsite
which is difficult and time consuming.
•S pillage and bad odours are likely.

Motorizedemptying• Fast, and generally
efficient.

•E xpensive operating and maintenancecosts that are passed onto the customer;not all customers can afford the service.

• Minimizes risk of contact•C annot pump thick, dried sludge (thiswith unhygienic material.
must be manually removed).
• Depending on thepolitical/ economic
structure, vacuum truck
enterprises can benefit
a community and be asource of sustainable
income.

4 | Urban pit waste management• Very high capital costs.
•B ecause of access, location, oreconomics, not all trucks discharge to asuitable facility.
•P umps can usually only suck down to adepth of 2-3m and the pump must belocated within 30m of the pit.

Capital andoperational costs
A new Vacutug can cost anywhere from
$20,000 to $100,000, although new trucks
are rarely purchased. Used or self-modified
trucks are more common and cost in theregion of $8,000 to $10,000. A MAPET will
cost around $3,000 and a Gulper around$300. Both can be can be fabricated locally.
A shovel, drum and cart for hand-emptying
will cost about $150.
Operation costs of the Vacutug are very
high compared to the MAPET, Gulper andhand tools. These will will be mainly vehiclemaintenance, fuel and oil, but bribing/paying local authorities to obtain licenses
and permission to discharge contents will
incur large expense too.

5 | Urban pit waste management

Useful resources
Eawag and Sandec (2008) Compendiumof sanitation systems and technologies.
Available at:
http://ecompendium.sswm.info/
Fecal sludge management on Wikipedia
https://en.wikipedia.org/wiki/Fecal_sludge_
management
Stone Family Foundation, Experiencesof developing pit emptying businesses in
East Africa
http://www.thesff.com/resources/SFF_
Experiences-of-developing-pit-emptyingbusinesses-in-East-Africa-FINAL.pdf

Case study

GulperJulius Chisengo,
Group Operator
UMAWA, 48 years
old (right) andCleophas Shinga,
Group Operator
UMAWA, 49-years
old (left, empty
the contents ofa pit latrine, Dares Salaam City,
Tanzania

WaterAid/ Eliza Deacon
Since 2010, WaterAid Tanzania has
worked with entrepreneurs in Temeke,
one of the municipalities of Dar esSalaam. These entrepreneurs (oftenfamily-owned businesses) have ventured
in waste management and especially pit
emptying: they have used the Gulper
manual pump to extract the sludge fromfull pits, discharging it into barrels which
are transported on motorised tricycles
until reaching small treatment plants.
The small size of the tricycles means they
are adept at winding through the narrowlanes of unplanned settlements which do
not have a sewer network.
WaterAid teamed up with BORDA, a
German organisation that has promoted
decentralised treatment of human waste
in many countries. This had to be done ina manner that was safe, environmentallysound and also offered a commercial
return for those running the collection
business. The plan was boost returns byexperimenting with production of manureand biogas for sale.
6 | Urban pit waste management

For the business to be viable, it needed
to have the potential for scaling up. This
meant identifying an operational areawith a reasonable density of population.
Household and business rates were
fixed and management systems put inplace to ensure a service that responded
to the needs of their customers witha technically appropriate solution thatcomplied with local regulations.
Several years after, several businesses
are still thriving and one of them hasestablished an “excellence centre” totrain new entrants. The businesses havemore than 4,000 customers, in addition tohotels and restaurants. They have proventhat pit emptying is a viable operation,
to the point that the neighbouringmunicipality has included such pit
emptiers in its regular tenders

Part of a series of WaterAid
technology briefs available atwww.wateraid.org/uk/technology

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determined to make clean water, decent
toilets and good hygiene normal foreveryone, everywhere within a generation.
2018
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