Protection of Aquifers - Hydrogeology: Objectives, Methods, Applications - page 203

Figure 107 Seasonal variation in nitrate concentration in the Avignon alluvial plain (data from
the Société Avignonaise des Eaux).
The only solutions are to export the excess byproducts of livestock
farming into watersheds with a nitrogen defi cit, or, in the frequent case of
an entire region having a surplus, to incinerate the excess manure.
In areas of intensive farming, the spreading of ammonium nitrate,
a highly soluble fertilizer, causes increases in both nitrate and reduced
nitrogen likely to nitrify under aerobic conditions. Another problem is that
this input of mineral nitrogen occurs in addition to the inputs of organic
nitrogen in the major, already excedentary livestock farming regions,
without taking into account the doses already present due to this organic
nitrogen. This useless added nitrogen then serves only to contaminate water
resources even more.
Groundwater in every intensively farmed area is affected by this
pollution, which shuts down catchments or requires costly treatments
(nanofi ltration, reverse osmosis). In France, the aquifers of the Paris,
Aquitaine basins, of the Alsacian vinyards, and of the Saone or Valence
plains regions, are subject to this intense diffuse pollution.
6 DOMESTIC SEWAGE AND SANITATION
There are two collection methods for domestic pollution: on-site septic
systems, where sewage ends up being treated by an individual treatment
system, and town sewers, where sewage is brought to a treatment plant
that can be several kilometers away from the collection point. The hazards
to groundwater are different for each method: individual septic systems
present only a local pollution hazard from the sewage being treated, whereas
town sewer systems often have leaks, resulting in hazards due to the leakage
of untreated sewage as well as from the water exiting the treatment plant.