Contributions to the Discussion

Contributions September 9-15, 2000

UPA, Health and Environment
Contributions received in the second week of session 2 (september 11-17)

From: Ruben Rodriguez, CEPIS
Date: 11-9
Subject: waste water and sewage sludge for re-use in agriculture (summary of paper by the moderator)

The authors stress the need for an integral and practical approach to waste water management and reuse in agriculture, that combines four different strategies:
1. Treatment of the waste water and sewage sludge.
The authors stress that a treatment technology should be used that is effective in eliminating pathogens but low in management and maintenance requirements (like the stabilisation pond system). The level of treatment needed to allow safe productive re-use, depends a.o. on the degree of dilution of the waste water after treatment, as well as the type of crops cultivated and the irrigation techniques applied.
Sewage sludge can be used without treatment if stored during a year (or shorter if processed under elevated temperatures), injected in the subsoil or inserted in furrows and covered before sowing.
2. Restriction of crops cultivated. Where treatment of waste water is not available or insufficient the types of crops grown have to be restricted. Three groups of crops are distinguished: a. crops where use of untreated waste water does not have risks for the consumers, but may have for the workers involved if no proper protection is taken (non-food crops, crops that are processed by heating or other process that eliminates pathogens, fodder crops that normally are sun dried before consumption, parks not accessible by the public); b. Crops that have certain indirect risks for the consumers (green fodder crops, food crops that do not in direct contact with the waste water or that cooked before consumption) and c: all products that are eaten fresh and have been in direct contact with the waste water, public areas.
The authors stress that crop restriction is an effective method only if certain pre-conditions are met: effective control of the crops cultivated, sufficient supply of alternative products at an acceptable price, low market demand for the prohibited crops.
3. adequate irrigation methods. Depending the category of crops cultivated, irrigation methods like gravity and sprinkler irrigation are less desirable and localised methods of irrigation are preferred. The latter are more efficient in water use but require also a much higher capital investment, often not available among the users of untreated waste water.
4. protection of human beings from infection by using protective clothing, washing and cooking food, good hygiene during harvesting, processing and marketing, information to farm workers and consumers about the risks of the
use of untreated waste water and protective measures.
From: Leo van den Berg (Alterra)
Date: 12-9
Subject: re-use of waste water and sewage (reaction to Rodriguez)

Thank you for this valuable information. I have two questions about it:

(1) you write: "a treatment technology should be used that is effective in eliminating pathogens but low in management and maintenance requirements (like the stabilisation pond system)": yes, but one often hears that stabilisation ponds take up too much space in an urban environment. What techniques are used that meet the same requirements but need less space?

(2) you write: "Sewage sludge can be used without treatment if stored during a year (or shorter if processed under elevated temperatures), injected in the subsoil or inserted in furrows and covered before sowing": yes, but as you state yourself afterwards, there are still many risks. In The Netherlands we experiment with 'land-farming' techniques (involving micro-organisms that decompose many pollutants) and the issuing of "clean soil certificates" by an official agency. Do you know of cities that have more experience with this?

Leo van den Berg

From: Jo Lines (LSHTM)
Date: 13-9
Subject: malaria and maize

Two "matters arising".

1. Maize plants are NEVER breeding sites for malaria or any other kind of mosquito. The reference that confirms this is: Watts, T., and Bransby-Williams W.R. (1978) Do mosquitoes breed in maize plant axils? Medical Journal of Zambia 12, 101-102. I would guess that this study was also the source of the newspaper article refered to earlier.

As far as I know, there is no mosquito that breeds in maize axils. But the axils of some other (larger) plants can breed some other mosquitoes. For example, the axils of banana and Pandanus can be breeding sites for Aedes aegypti mosquitoes. [This species is important in West Africa as a vector of Yellow Fever, and it is also important as a vector of dengue in Asia and Latin America.] There is only one Anopheles malaria vector that breeds in plant axils; this species specialises in living in bromeliads and like this group of plants, it is only found in the New World.

2. Kaspar Wyss reported that urban agriculture does not create suitable conditions for the breeding of Anopheles malaria vectors in Ouaggadougou, and suggested that the same goes for the rest of the Sahel. Well, I don't know Ouaggadougou, and I can easily believe what Kaspar says about it, as long as no-one grows rice or sweet potato in Ouagga. The same applies to African towns in general: as long as there is no rice and no sweet potato and no yam, then people may well be cultivating urban crops without any associated contribution to the malaria problem. But in any town where people ARE growing rice or sweet potato or yam, or any crop grown in deep cultivation ridges of clay soil, then urban agriculture almost certainly does contribute to the malaria problem. The "instructions" for growing rice - i.e. the conditions in which rice will thrive - are virtually identical to the instructions for growing Anopheles gambiae. You can't grow rice in Africa without growing Anopheles gambiae. For example, ouake is a town in northern Cote d'Ivoire, not so very far from Ouaggadougou. Urban agriculture is common: there are small plots with rice. These are, without any doubt, a major source of malaria mosquitoes. In fact as I suggested before, my guess is that that urban cultivation is the main source of malaria mosquitoes in that town. Does Bouake count as part of the Sahel?

From: Tanya Bowyer-Bower
Date: 14-9
Subject: Policies in Harare regarding UPA & Environment

Contribution to the questions set for this Part 2 of our UPA Health and Environment discussion based on the Harare case study:

What UA policies are implemented in your area and the extent to which they consider environmental impacts?The answer to these questions for the case study of UA in Harare is explained in a short paper of mine published in the Geographical Journal of Zimbabwe in 1997 (?The potential for UA to contribute to urban development in Africa – dilemmas of current practice and policy?), a copy of which is about to be placed in the planning section of the infomart for this e-conference.

How do UA policies attempt to balance the conflict between positive and negative effects?
The traditional answer to this in Harare has been – to ban UA (as explained in the above mentioned paper). Under pressure from urban residents, the municipal authorities have now backed down from implementing the plan. However has not yet got to the stage / cannot yet reach consensus on completing guidelines for an effective management of UA such that it is undertaken for fulfilling agreed goals (the goals have not yet been agreed either). Hence the output of a global discussion of this nature could be very useful in guiding cities like Harare as to what viable options could be.

Which policy measures were implemented in your city to prevent and/or diminish the environmental risks of UA? So far none because UA has always been technically illegal and so agricultural extension services have had no mandate to assist urban farmers. Obviously this should change with UA no longer being prevented, and even more so should it become technically legal.
I hope these contributions to the questions are useful. Feedback welcome.

From: Pay Drechsel
Date: 14-9
Subject: Municipal by-laws

Dear Tanya, Your statements are in fact very generic and match also our experience and point of view. Thanks.

It would be nice to get more feedback from participants familiar with municipal authorities and their bye-laws etc. There are cities like Accra, where the Metropolitan Assembly (AMA) has somehow recognized the value of food production in the city. AMA supports through the decentralization policy of the Government of Ghana the institutionalization of urban and peri-urban agriculture through a related Department and Sub-Committee in the Assembly. There is a Director for Urban Agriculture, and every year at the National Farmers Day this official recognition is expressed in awards for the best urban and peri-urban farmers per city (besides best farmers at district/regional/national level). But there are also a range of bye-laws, which however mostly restrict UA, e.g. to protect the urban consumers (one says that no crops shall be watered or irrigated by the effluent of a drain from any premises or any surface water etc.). However, these bye-laws are seldom enforced, accompanied by no or weak structural and s rategic planning with respect to UA. Positively speaking, the UA policy situation appears complex but it is developing. Currently it is a mixture of yes and no, and the authorities are in need of much advice and decision support.

From: Paul Calvert (Ecocolutions)
Date: 14-9
Subject: ecological sanitation

Dear discussion group

I wonder why you do not appear to be considering the tremendous potential of ecological santation in these debates. (Much of the debate centres around mosquito menace, this approach can have a significant effect of reducing mosquito breeding sites - see below)

Half of the problem we are dealing with stems from the wrong approach to sanitation. Current approaches to sanitation create sewage. Engineers and public health authorities, agriculturalists etc are then faced with what to do with this less than ideal product that did not need to be made in the first place. Why take good nutrients and contaminate water with them and add indutrial effluent to spoil them....? In many cases the nutrients in urine are transported to where they need to be by the people who need to use them!

With urine diversion at source and composting of faeces on site at a family scale there are huge benefitss to urban agriculture. Much of the urine can be piped subsurface to growing beds on site or to local growing areas and is an excellent fertiliser. The composted faecal matter is safe and a good soil improver. Urine and faeces are kept out of industrial waste water so the contamination of urine and compost with chemicals and heavy metals is avoided and the contamination of industrial effluent with pathogens is avoided. The products of ecological sanitation are infinitely better than septic tank and pit latrine sludge, aesthetically, nutritionally, and from a health standpoint. The families themselves do the processing (no sewage and therefore no sewerage installation and maintenance costs, or leaks to pollute and contaminate water bodies, groundwater or water pipes).

Emptying a compost toilet for the compost is not an unpleasant or dangerous task - the same cannot be said of septic tanks and pit latrines. Large volumes of water that would have been used for flushing are saved for much more useful (and sensible) purposes. Families can derive nutritional and or economic benefit from these products (urine - ie liquid fertiliser, compost, the products they grow with them, and the savings they make from not purchasing commercial fetiliser) The urine from one person can be adequate to fertilise 50 to 200 sq m of cultivated land.

There are other benefits too such as the energy savings in reduced commercial fertiliser production and transport of that product and its constituents to/from the centres of production and use. Another benefit is that unlike septic tanks and pit latrines which very often are a significant source of mosquito breeding compost and dessicating toilets do not provide sites for this.

There are clearly different scales that this reuse of ecological sanitation products can be developed on. In Sweden urine is now being used on trials by farmers to fertilise their fields after being collected from eco-communities and stored. There are numerous examples of ecological sanitation now working successfully in the world, China, Vietnam, Mexico, India - where I am working, Sweden, Bolivia, parts of Africa, etc.

Reuse close to home by families themselves can surely be a significant benefit to famuily and community health and well being, saving expenditure on commercial fertilisers, preventing pollution of water bodies and ground water with pathogens and placing nutrients in the wrong place, saving water, improving soils, providing income and nutrition. All this being done right in the families and homes that the most need these benefits...