PULP MILLS (JUDGMENT) 88 (b) Question of the production technology used in the Orion (Botnia) mill 220. Argentina maintains that Uruguay has failed to take all measures to prevent pollution by not requiring the mill to employ the “best available techniques”, even though this is required under Article 5 (d) of the POPs Convention, the provisions of which are incorporated by virtue of the “referral clause” in Article 41 (a) of the 1975 Statute. According to Argentina, the experts’ reports it cites establish that the mill does not use best available techniques and that its performance is not up to international standards, in the light of the various techniques available for producing pulp. Uruguay contests these claims. Relying on the CIS, the second Hatfield report and the audit conducted by AMEC at the IFC’s request, Uruguay asserts that the Orion (Botnia) mill is, by virtue of the technology employed there, one of the best pulp mills in the world, applying best available techniques and complying with European Union standards, among others, in the area. 221. Argentina, however, specifically criticizes the absence of any “tertiary treatment of effluent” (i.e., a third round of processing production waste before discharge into the natural environment), which is necessary to reduce the quantity of nutrients, including phosphorus, since the effluent is discharged into a highly sensitive environment. The mill also lacks, according to Argentina, an empty emergency basin, designed to contain effluent spills. Answering a question asked by a judge, Argentina considers that a tertiary treatment would be possible, but that Uruguay failed to conduct an adequate assessment of tertiary treatment options for the Orion (Botnia) mill. 222. Uruguay observes that “the experts did not consider it necessary to equip the mill with a tertiary treatment phase”. Answering the same question, Uruguay argued that, though feasible, the addition of a tertiary treatment facility would not be environmentally advantageous overall, as it would significantly increase the energy consumption of the plant, its carbon emissions, together with sludge generation and chemical use. Uruguay has consistently maintained that the bleaching technology used is acceptable, that the emergency basins in place are adequate, that the mill’s production of synthetic chemical compounds meets technological requirements and that the potential risk from this production was indeed assessed. 223. To begin with, the Court observes that the obligation to prevent pollution and protect and preserve the aquatic environment of the River Uruguay, laid down in Article 41 (a), and the exercise of due diligence implied in it, entail a careful consideration of the technology to be used 78