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<International Source Book On Environmentally Sound Technologies
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7.4 Reuse (Topic d)

Reuse of wastewater and sewage sludge in agriculture should be strictly controlled in order to avoid chemical and/or microbiological contamination.

In the AC10, but most probably in all transition countries, the reuse of sewage sludge from treatment plants as fertilisers in agriculture is not common. A lack of knowledge of the real health risks and the wide adoption of unenforceable standards have tended to encourage the belief that reuse of effluents for irrigation is a costly process requiring sophisticated treatment technology. This has resulted in a failure to plan for wastewater reuse where sewage schemes have been installed. Especially in arid and semi-arid regions it is of high importance to include the reuse of treated wastewater as source for irrigation water. To achieve this and to ensure health protection, more realistic water quality guidelines are needed, taking account of the improved knowledge on epidemiological implications of wastewater reuse. A cheap, simple and effective solution is for example proper designed wastewater stabilization ponds used for secondary sewage treatment. The produced effluents are suitable for the use in irrigation and aquaculture. Wastewater–fed fisheries is used for example in Hungary (WHO 1989).

Only a few transition countries use wastewater for irrigation purposes, i.e. Poland and Hungary. In these countries the amount of municipal wastewater used for irrigation is very small; only 4% of the total wastewater generation in the case of Hungary. Indirect reuse, i.e. the abstraction of irrigation water from rivers receiving wastewater, occurs everywhere as a result of freshwater scarcity and the need to increase local food production. The surveillance of health criteria is in most cases not assured because of the lack of equipped laboratories and often the lack of well trained staff.

Reuse of sludge as fertiliser is traditionally accepted only from livestock breeding. Very little sludge from municipal treatment plants is used as fertiliser, not only because of health concerns (high heavy metal concentrations), but also simply because of no transport capacity to bring it to the fields.

The situation in Romania might serve as example of most of the transition countries. There is no direct use of wastewater (treated or untreated) for irrigation systems, sprinklers or to re-charge the ground layers. Neither the treated sludge is recommended (or collected) as fertiliser for health and ethical reasons. Despite good experiences in scientific pilot studies, the agricultural use of wastewater or sludge was not promoted. The official reasons were the high fertility rate of the Romanian soil and the lower costs and higher efficiency of chemicals used as fertilisers.

In the case of animal farms, the situation is different. Wet or dry methods to collect animal dejection is widely used to produce biological fertiliser according to a traditional method of "stable garbage", specific to these places- creating compost in natural conditions (Rojanschi, 1999).


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