Research has been carried out on the use of dehydrated and stabilized sludge as an organic fertilizer. The physical, chemical and microbiological composition of the sludge from Biological Treatment Plant (BTP) was evaluated, the optimal sludge doses as soil amendatory under different agricultural crops were determined, the soil suitability for the application of the sludge, generated in the domestic wastewater treatment, was evaluated. Methodologically, the works were carried out in accordance with the requirements of Directive 86/278 / EEC on the protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture. It has been established that the sludge accumulated in (BTP) contains sufficient amounts of organic matter and macronutrients (NPK) necessary for the development of plants, while the heavy metal content does not exceed the maximum admissible concentrations for sludge stipulated in the national and European regulations. The experiments demonstrated the effectiveness of the use of dehydrated and stabilized sludge from BTP as a fertilizer under different agricultural crops. Investigations have been carried out on the possibility of composting fresh sludge from wastewater treatment plants with various agricultural waste. The controlled composting technology of sludge with poultry manure contains original elements for the intensification of the composting process by activating the thermophile micro-flora, so that a fertilizer with high physic-chemical qualities and free from helminths and pathogenic microorganisms is obtained. Conducting composting in a controlled way allows the capture of ammonia, carbon dioxide, thermal energy and their use in greenhouses, which also diminishes the polluting impact on the environment