To attain and maintain the water-quality objectives described above, strict methods must be used to reduce pollution caused by certain dangerous substances discharged into the European aquatic environment, i.e. inland surface water, groundwater, internal coastal waters and territorial sea waters. Some toxic substances discharged into the water are, of course, chemically or biologically diluted and decomposed until their toxicity disappears, but others are persistent, i.e. they retain their chemical composition, and therefore their danger to the environment and to man, for a lengthy period, which can, in some cases, be several years.
For this reason a European Directive contains provisions on the collection, processing and discharge of urban waste water and biodegradable water from some industrial sectors, and on the disposal of sludges [Directive 91/271]. In particular, the Directive stipulates that as a general rule, waste water which enters into collection systems must, before disposal, be subjected to secondary treatment in accordance with a timetable adjusted to the size of the population covered and the type and situation of the collection water. Another Directive concerns the protection of waters against pollution caused by nitrates from agricultural sources [Directive 91/676].
A Framework Directive on pollution caused by certain dangerous substances discharged into the aquatic environment of the EU is directed towards curbing the process of the deterioration of that environment by prohibiting or restricting the discharge of toxic substances [Directive 2006/11]. The latter are divided into two lists: a "black list" grouping particularly toxic, persistent and bioaccumulable substances, and a "grey list" which mainly concerns substances whose harmful effects are limited to one locality and depend on the properties of the receiving waters. Whether substances from the first list or the second list are involved, the Directive provides for authorisations granted for all discharges into European waters, issued by the competent authority of the Member State concerned for a limited period.
The growing use of chemical compounds in industry, agriculture and in products of household use poses ever-more serious dangers to the environment and human health. Hence, detergents are a significant cause of pollution of the European aquatic ecosystem. The formation of foam in waters into which detergents are discharged in large quantities limits the contact between water and air, makes oxygenation difficult, jeopardises the photosynthesis necessary for the life of aquatic flora, has an adverse effect on waste water purifying processes and constitutes a risk of the transmission of bacteria and viruses. For those reasons and in order to prevent technical barriers to trade the EC/EU has harmonised the laws of the Member States relating to the placing on the market and the use of detergents [Regulation 648/2004, last amended by Regulation 259/2012].
One very dangerous industrial sector for the aquatic environment is that of the manufacture of titanium dioxide, which is a pigment used for the manufacture of paints, varnishes, plastics, inks, etc. Untreated waste from factories which produce titanium dioxide is known as "red sludge". The alteration of the colour and transparency of water which it causes leads to the reduction of photosynthesis and phytoplankton and, in the most serious cases, to the disappearance of all life from estuary waters and the waters of the receiving sea. Hence, a Directive on waste from the titanium dioxide industry, provides for the control by the Member States of the operations for treating such waste and sets procedures for harmonising the programmes for the reduction and eventual elimination of pollution caused by waste from the titanium dioxide industry [Directive 2010/75].
In addition to its own work to combat the pollution of the aquatic environment, the European Union participates in the work carried out in the framework of international cooperation, including: the Berne Agreement of 1963 concerning a Commission for the Protection of the Rhine against Pollution [Decision 77/586], the Convention on the Protection of the Rhine [Protocol of signature and Decision 2000/706]; the Convention for the Protection of the Marine Environment of the North-East Atlantic [Convention and Annex V]; the Convention on the protection and use of transboundary watercourses and international lakes [Convention and Decision 95/308]; and the Convention on cooperation for the protection and sustainable use of the Danube [Convention and Decision 97/825].