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presents also a risk, particularly in warmer climates, because of its invasive potential; indeed,
water lilies have become a pest in water courses, lagoons and reservoirs throughout the world.
In fertirrigation, by contrast, partly purified water is returned to agricultural lands and
reused (Rismal, personal communication). Besides watering the soil, fertirrigation serves to
recycle nitrogen, phosphorus and organic matter in a cultivation environment (accordingly,
elimination of nutrients from sewage in this instance would be illogical and counterproductive).
Naturally, the risk of contamination from bacteria or other pathogens (viruses, fungi) must dictate
caution in the use of any such procedure for crops like salad and fruit; on the other hand there
is practically no health hazard in applying fertirrigation for others crops destined to be stored and
processed (cereals in general, sugar beet, etc.).
10.3 Other courses of action
Alternatively to full sewage treatment, lagooning and otherwise, there is the option of
discharging urban and/or industrial sewage effluents by way of pipelines laid on the sea bed out
to deeper offshore waters. This arrangement is not recommended for shallow inshore waters
and sheltered bays, where the discharged waste can resurface, or accumulate progressively
by reason of insufficient dispersion. A further often used but questionable procedure is to
transport solid and/or liquid waste by tanker out into the oceans, far from land, where the risk to
contaminate the coastline appears attenuated.
10.4 Monitoring programmes
As an essential complement to interventions, monitoring programmes should be
established.
Monitoring programmes are in fact an essential prerequisite for the assessment and
the control of the evolution of phenomena as well as of assessment of the effectiveness of the
interventions.
For their establishment the following point should be considered:
- Monitoring objectives must be reformulated in a more coherent way in order to
make planning more comprehensible and effective (Reuss, 1990);
- It is necessary to reaffirm the crucial role of the monitoring of pollution sources
(UNESCO, 1988);
- The first essential phase is to establish beyond the shadow of doubt the baseline
contamination levels, before establishing permanent programmes for certain areas
of special concern;
- A biological effects monitoring programme must be devised and implemented
within the MED POL framework (UNEP, 1992);
- The quality assurance programme for results must not only be continued but
reinforced as well;
- At the same time, all research efforts which might add to the general knowledge
of the marine environment must be encouraged in order to promote the
optimisation of monitoring programmes.