Newsletter and Technical Publications
<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>
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
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).