Closing the nutrient cycle: why and how

A way to reduce waste water problems

A workshop on community management of waste water (treatment and disposal) in low-income, semi-urban communities in the Kathmandu valley, Nepal, 2-13 November 1998

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The participants, click for a bigger picture and more information

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map of the valley: 1 = Sidhipur, 2 = Thimi, 3 = Kusunti, 4 = Panga

In a two week workshop organised by Dutch and Nepali a study has been carried out to improve the sanitary and health situation of four communities near Kathmandu:

Sidhipur: a beautiful compact agricultural village with 7000 people in 1200 houses. Still a quite original Newari community

Thimi: one of the oldest places in the Kathmandu valley situated on a hill, surrounded by fields for agriculture and vegetable growing. About 3000 houses, 14.000 people at less than 30 ha. Along the main road diverse activities like garages, shops and a hospital. In the village potteries and other small enterprises like "wine making". Most of the community is connected to sewers, but still a lot of open defecation: "shitting fields"

Panga: like Sidhipur, but more influenced by Kathmandu. Everything even more neglected than Thimi and Sidhipur. Several sewers, a septic tank. Not maintained.

Kusunti: Still a rather open area close to the ringroad of Patan and Kathmandu. The last three years many houses have been built in the area, this development will continue. A 45.000 p.e. sewer runs through the community, due to monsoon rains a big part has been damaged leading to a huge flow of waste water through the community.

Drawings of the four communities involved in the workshop, click for descriptions of the villages
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Sidhipur Thimi Panga Kusunti


Detailed maps of the communities

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Health and economic benefits of a closed nutrient cycle

Why has the environmental and health situation changed in the four communities? It seems to be much worse then it used to be. Outbreaks of water and hygiene related diseases occur to often. Polluted water may contain pathogens (like viruses, bacteria, protozoa and helmints), organic waste, nutrients, suspended solids. In principle waste water treatment is very simple and economic benefit can be gained from treatment. Thermal pollution and acidification as were found in Kusunti and Maddhipur require different ways of treatment.

During the workshop it has been made clear "what happens if the environment gets polluted through uncontrolled discharge of waste water?" and "why would we need to do something about it?". Not only the risk of drinking polluted drinking water effects health in the villages, but especially the practice of "open defecation", leading to "shitting fields" are potential very dangerous for health (hookworms, larvae penetrate through feet while defecating).

Is it only maintenance of the technical infra-structure, are social aspects more important? Likely it is a disturbance of a total social structure, of absorbing western habits without taking in account the disadvantage of methods from the west. Introduction of chemical fertiliser made the use of manure less attractive, had a negative effect on soil structure. Introduction of water taps leads to waste water. Sewers are expensive and not easy to maintain. Treatment of waste water is very expensive and needs much energy.

During the workshop it became obvious that the solutions, only can have success in these agricultural. low income villages, when they are as close to the daily life of the people, are as cheap as possible, use as little energy as possible. It is important that the people can take part in the processes, not only by paying taxes but also with labour. Above this treatment of wastes should also lead to profits by reuse of nutrients.


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The nutrient cycle of a Nepali community (click for bigger figure (46k))


A sustainable agricultural society

The basis of the workshop was a sustainable agricultural society:

  • close the nutrient cycle (of food from the land and manure to the land) as much as possible. Important elements in that cycle are C, N, P, H2O and minerals.
  • Waste or disposal of wastewater has to be paid two times:
    • loss of minerals;
    • environmental problems to be solved.

Separation of flows

Solutions to solve the environmental and nuisance problems are based on the principle that mixing of black waste, grey-, and white water should be prevented as much as possible. These three flows should be handled separately. If done properly a good ecological system will emerge and money can be saved or even earned, because:

  • less expensive fertiliser is needed;
  • less water is needed, because faeces do no longer have to be flushed away;
  • expensive treatment can be avoided;
  • manure can be sold.

Traditional uses and customs

Another starting point was to make use traditional uses and customs. Only add new techniques or ideas that are close to the people. Be aware of adopting modern western technology in a developing country, especially one with a monsoon climate. Another advice: keep it simple (KISS).

Western technology with superfluous use of water in modern bathrooms, flushing toilets, mixed sewage systems, etc. leads to enormous waste water problems.

  • the old stormwater discharges for recharge groundwater resources (eventually by using ponds surrounding the village) has been beautiful designed. Try to prevent erosion.
  • use toilets for production of black waste (private or communal), and start composting for making manure
  • grey water must be kept as white as possible. Use a small sewer for grey water discharges to simple treatment plants (e.g. reed bed wetlands or oxidation ponds/ditches)

General points

  • a good design is important, based on detailed maps indicating pipes, gutters, wells, ponds etc.;
  • local knowledge, traditional customs and uses need to be taken into account and built upon where possible;
  • awareness raising and education are needed;
  • people need to be informed about implications for capital costs, maintenance and management, they should be left the choice and be assisted in developing their own maintenance and management system!! Plan the whole lifecycle of every aspect.
  • many improvements can be brought about through self-help.


Some remarks during the workshop:

  • money doesn't stink

  • do not throw money away

  • chemical fertiliser is expensive and not good for soil structure

  • waste water is a waste of nutrients

  • adopt polluter pays principle

  • every positive action has its negative effects

  • no drinking water supply without waste water treatment

  • do not mix wastes

  • the most important: KISS - keep it simple stupid

  • maintenance is as important as a good design

Separate the waste streams as much as possible:

White water:

It is important to prevent rain to get mixed with wastes, the monsoon climate leads to severe rainstorms (often > 100 mm/day = 100 l/ during the summer months. Average rainfall in the valley is 1900 mm/year, of which 80 % during monsoon. More information. Old Newari villages like Sidhipur, Panga and Thimi are wonderfully built for wet monsoons with wide gutters for a quick discharge from the village and use in agriculture or in ponds for recharge of ground water. But the old structures are poorly maintained.

Black wastes

The western practice to use flush toilets is comfortable in the households, but expensive. It induces an enormous waste water flow. Per capita about 50 l faeces and 500 l urine is flushed away with around 15.000 l water leading to a yearly flow of over 15.000 l waste water.  It is much more wise to adopt a system of black waste collection, combined with animal manure composting, leading to production of manure:
  • keep black waste as dry as possible (night soil) by using private (double vault) latrines or communal latrines.  Or make sure it gets the right moisture content for digestion to use the carbon in the waste to produce biogas for heating.
  • if possible collect the urine for reuse of nutrients in agriculture. Keep using the practice of mixing ash and urine for use in agriculture or adopt the 'Mexican or Vietnamese practice' of composting urine.

Grey water

Construct separate sewer lines for water from washing, bathing and kitchen water. The nutrients in this waste water should be reused by growing products in constructed wetland systems or in (fish)ponds. These treatment systems should be run by organisations or private persons who will have the benefits of the products. Only when the waste flows become to big, or when not enough space is available treatment systems, like oxidation ditches should be considered.

Mixed flows of waste water

When it is not possible to separate the wastes completely separate the black waste and the settable wastes from the grey water as close as possible to the sources by building septic tanks: settled sewerage. These septic tanks should be emptied regularly. The sludge can be treated as black wastes, the water from the septic tank as grey water.

Technical options

For sorting out technical solutions we used the SANEX computer model, developed by T. Loetscher . Additional information and a review of the technical solution can be found in "SANEX during the workshop"

Short and long term solutions

It pointed out that the communities can do a lot on their own, therefore we introduced short (or self-help) and long term solutions.

short term solutions

long term solutions

Some of the long term solutions for the four villages:

For Kusunti the above principles imply that, unless huge amounts of money, land and water for flushing become available, the general use of sewage pipes and the construction of a big treatment plant are not encouraged. Kusunti is a growing community with more and more "outsiders" settling there in a seemingly uncontrolled manner. Proper town planning should be encouraged, so that infrastructure such as septic tanks connected to small bore sewers and drainage channels can be planned also. External finances will be needed to realise the infrastructure bringing waste from the houses to a place for treatment and disposal. The possibility of a sewer connection to the treatment plant in Dhobigath is to be explored.

A dying factory causes quite some chemical and thermal pollution. Research on how to bring this under control is needed.

In Thimi two different problems can be distinguished: i) the environmental pollution as a result of open defecation and ii) the pollution caused by the industrial area (car-workshops) close to the main road. Thimi has a lot of tourist potential, which could serve a motivational factor for realisation of improvements. There is a big need for double vault toilets that allow for separation of black waste and subsequently for composting by mixing the black waste with other organic material. Oxidation ponds around the village could treat grey water. If black waste is mixed, a first pond should be a covered, anaerobic one. The existing treatment plant could possibly be used for treatment of grey water and black water. However, given the water scarcity, creating a black water flow to the treatment plant is discouraged. For the industrial area discussions could start about having polluters pay for treatment.

In Panga, the existing collection tanks could be improved and cleaned up for use as sedimentation tanks, to be followed by treatment facilities for the effluent. But also here it would be better not to create a black water flow and to have human excreta collected using dry latrines or septic tanks and to only have the effluent and grey water go into the tank. A wetland, possibly with reed, can be constructed for treatment of grey water.

When properly cleaned, by diversion of waste inflow and removing water plants, the pond outside the village can be used for recharge of groundwater through rainwater collection.

In particular in Panga many dead rats are seen. These rats, being sources of infection, should be removed.

The situation in Sidhipur seems least complicated. Existing gutter systems could be restored for discharge of stormwater, which could then be fed into a pond for recharge of groundwater. Composting and reuse of black waste could be encouraged and coupled to wetland systems for the treatment of grey water. In order to improve drinking water quality a (natural) simple filter system can be built close to the storage tank.

Workshop evaluation

As an evaluative exercise participants were given a case for which they were asked to suggest short and long term solutions. The case was about a hypothetical village where open defecation is common practice. People are predominately farmers and the village has a dairy factory discharging waste water without treatment and a hotel with flush toilets. The various groups were asked to present their thoughts and it was striking to see how much they had incorporated of what had been discussed the previous days. For details about the case and the solutions of the participants

Participants were also asked to indicate in a few words how they appreciated the workshop. The main things mentioned were: I learned a lot about the management of waste water, it was good to exchange ideas and to see each other’s situation, it’s a pity that we were not given concrete solutions, there is still a gap between the workshop classroom situation and field reality.

Since some guests were expected for the afternoon session, participants prepared a brief presentation. Unfortunately, and probably as is often the case, the presentations only partially reflected what had been done and what had been discussed during the workshop. One of the resource persons therefore added on to it.

During a formal closing of the workshop participants were handed a certificate of attendance.

Research proposal

A research proposal has been formulated by workshop facilitators and participants and will be submitted to potential donors. Should the reader be interested in getting to know more about it, please contact IRC International Water and Sanitation Centre. Eveline Bolt, Programme Officer, IRC International Water and Sanitation Centre,

Summary of the research proposal

The workshop provided quite some ammunition for the development of a proposal for applied research. The proposal does not only focus on the testing technical options, but also on the testing of options for sustainable maintenance and management. In this respect it will also look into the interface between local authorities, the private sector and the community. The objectives of the research proposal have been defined as follows:

The total duration on the project is estimated to be three years.

For the workshop we used the SANEX computer model, developed by T. Loetscher

Additional information of the use of SANEX during the workshop

Source: Free Water and Sanitation News Service,

A pdf-file with full text of the workshop report is available through

The workshop has been organised by:

logo_small.gif (1143 bytes) IRC International Water and Sanitation Centre, The Hague, The Netherlands

Eveline Bolt, , homepage:

enpho.gif (2174 bytes) ENPHO Environment and Public Health Organisation, Kathmandu, Nepal

Amresh Karmacharya

newahsml.gif (1862 bytes) NEWAH Nepal Water for Health Organisation, Kathmandu, Nepal

Homnath Acharya

frieslan.gif (3412 bytes) Waterboard Friesland, Leeuwarden, The Netherlands

Theo Claassen

us.gif (3114 bytes) Waterboard Uitwaterende Sluizen, Edam, The Netherlands

Ruud Kampf

a list of addresses

the participants of the workshop

page compiled by Ruud Kampf, Email


page last edited: 20-04-04

A workshop on how to close the nutrient cycle to reduce waste water problems in four communities close to Kathmandu in Nepal, November 1998

Please give your comments and remarks on the workshop

ICFON - The Netherlands

Stichting ICFON: International Council of Friends of Nepal


Winblad, U. Towards an ecological approach to sanitation: summary, WHO Sanitation Promotion Kit, 1997

International Conference on Environment and Agriculture, Abstracts of an international conference, organised by the Ecological Society, ECOS, P.O. Box 6132, Kathmandu, Nepal, November 1-3, 1998. See also