T
re
M
SUMMARY
D
U!
il
In order to improve urban waste water disposai into the Coastal zone, IFREMER bas
developed, since 1986, a multidisciplinary program on this topic.
>
ai
The main objectives of this program were to détermine the fates and effects of urban waste
water, by considering spécifie processes in the Coastal zone.
d
These studies were conducted, in collaboration with the Agence de Bassin Rhône- S
Méditerranée-Corse, on two characteristic sites (Morlaix on the English Channel and Toulon *
on Mediterranean Sea).
The main results of this program, presented during this workshop, confirm that in biological
and physical-chemical treatment plants, there is a good élimination of organic and
suspended matter.
By contrast, the élimination of nitrogen (in physical-chemical treatment plants) and of
phosphorus (in biological treatment plants) is generally weak. The phosphorus inputs front
urban waste water could be of the same order as river inputs during the summer ; foi
nitrogen, the main input to the Coastal zone generally cornes from farming activities oi
watersheds ; in the Mediterranean sea, because of the oligotrophic status of Coastal waters
nutrient inputs are not a real problem, except in enclosed areas like lagoons. If it i
impossible to transfer waste water disposai to a less sensitive area, spécifie technologies ol
nutrient dépuration should be used.
In the two treatment plants at Morlaix and Toulon, the rate of élimination of inorganii
pollutants varies between 75 and 80 %, except for iron in physical-chemical treatment. Th
rate of organic pollutant dépuration is higher in biological treatment plants (80-90 %) tha
in physical-chemical treatment plants (40-70 %) ; this lower value causes deterger
disposai of several ten tons per year at Toulon. Some organic compounds that are poorli
biodégradable, non-volatile and not adsorbed on suspended matter, are poorly eliminate
during treatment.
The micropollutant levels in the Coastal zone are generally lower than léthal concentrations
but bioassays using urchin or oyster larvae, show sublethal effects, if waste waters are ni
diluted enough.
Waste water treatment also reduces the concentration of bioaccumulable pollutants becaus
they are adsorbed on organic suspended matter and easily removed during treatment. Tb
réduction of fecal micro-organism inputs by classical waste water treatment is low, becaus
of very high concentrations in raw waste water, and of frequent use of by-passing.
8
re
M
SUMMARY
D
U!
il
In order to improve urban waste water disposai into the Coastal zone, IFREMER bas
developed, since 1986, a multidisciplinary program on this topic.
>
ai
The main objectives of this program were to détermine the fates and effects of urban waste
water, by considering spécifie processes in the Coastal zone.
d
These studies were conducted, in collaboration with the Agence de Bassin Rhône- S
Méditerranée-Corse, on two characteristic sites (Morlaix on the English Channel and Toulon *
on Mediterranean Sea).
The main results of this program, presented during this workshop, confirm that in biological
and physical-chemical treatment plants, there is a good élimination of organic and
suspended matter.
By contrast, the élimination of nitrogen (in physical-chemical treatment plants) and of
phosphorus (in biological treatment plants) is generally weak. The phosphorus inputs front
urban waste water could be of the same order as river inputs during the summer ; foi
nitrogen, the main input to the Coastal zone generally cornes from farming activities oi
watersheds ; in the Mediterranean sea, because of the oligotrophic status of Coastal waters
nutrient inputs are not a real problem, except in enclosed areas like lagoons. If it i
impossible to transfer waste water disposai to a less sensitive area, spécifie technologies ol
nutrient dépuration should be used.
In the two treatment plants at Morlaix and Toulon, the rate of élimination of inorganii
pollutants varies between 75 and 80 %, except for iron in physical-chemical treatment. Th
rate of organic pollutant dépuration is higher in biological treatment plants (80-90 %) tha
in physical-chemical treatment plants (40-70 %) ; this lower value causes deterger
disposai of several ten tons per year at Toulon. Some organic compounds that are poorli
biodégradable, non-volatile and not adsorbed on suspended matter, are poorly eliminate
during treatment.
The micropollutant levels in the Coastal zone are generally lower than léthal concentrations
but bioassays using urchin or oyster larvae, show sublethal effects, if waste waters are ni
diluted enough.
Waste water treatment also reduces the concentration of bioaccumulable pollutants becaus
they are adsorbed on organic suspended matter and easily removed during treatment. Tb
réduction of fecal micro-organism inputs by classical waste water treatment is low, becaus
of very high concentrations in raw waste water, and of frequent use of by-passing.
8