The objective of waste water treatment is to prevent large quantities of substances to reach and impact the environment in high doses and concentrations. Areas of high population densitiy naturally are areas were production of sewage sludge is high (see Figure 1-1). Presently about 8 million t of sewage sludges (MAGOAROU 2000) are produced each year in the EU member states (Table 1-1). Its high content of organic materials, of nitrogen and phosphorous suggest their use as soil conditioner and fertilizer in agriculture. Consequently it is one of the EU policies to enhance sludge use in agriculture (MARMO 2000). .
