Mulj izdvojen u postupcima pročišćavanja otpadnih voda potrebno je adekvatno obraditi i zbrinuti na ekološki prihvatljiv način i u skladu sa zakonskom regulativom. Zbrinjavanje mulja je skup i ekološki osjetljiv postupak. U velikom dijelu zemalja EU problem zbrinjavanja mulja do danas nije cjelovito riješen, a otežanu okolnost predstavlja i nedostatak jedinstvene legislative. Uslijed većeg broja različitih tehnoloških mogućnosti zbrinjavanja mulja i mogućih utjecaja na okoliš i zdravlje čovjeka, potrebno je iznaći dogovorno rješenje na razini znanstvene, stručne i šire javnosti. Među prihvatljivim i aktualnim rješenjima posebno se ističe spaljivanje mulja i korištenje nusprodukata (pepeo iz ložišta spalionica) u mnogim granama industrije. Budući da je industrija građevnih materijala značajan potrošač prirodnih resursa, a beton najčešće korišten umjetni materijal, upravo se u ovom području nalaze najveće mogućnosti korištenja dobivenog pepela. U ovisnosti o porijeklu otpadne vode i primijenjenim postupcima pročišćavanja te načinima obrade i temperaturi spaljivanja mulja, kao i kemijskom sastavu i fizikalnim karakteristikama generiranog pepela, u sklopu projekta „RESCUE“ istražuje se mogućnost korištenja pepela kao zamjene za dio cementa u betonu i mortu. Budući da pepeo pokazuje određena pucolanska svojstva, njegovo korištenje u cementnim materijalima čini se prihvatljivim i izvodljivim s tehničkog, ekonomskog i okolišnog aspekta..; The sludge separated in wastewater treatment procedures must be adequately treated and disposed in an environmentally friendly and legally compliant manner. Sludge disposal is an expensive and ecologically sensitive procedure. In the majority of EU member-states, the issue of sludge disposal has not been adequately solved, with the absence of uniform legislation being additional aggravating factor. Due to a large number of different technological alternatives for sludge disposal and potential impacts on the environment and human health, it is necessary to agree on the solution at the scientific and professional level, including the general public. Sludge incineration and the use of by-products (ash from incinerators) is dominant among acceptable current solutions in many different industries. Since the building industry is a significant user of natural resources and concrete the most commonly used artificial material, it is particularly in this field that potential uses of generated ash seem the most numerous. Depending on the origin of wastewater and applied treatment procedures, including methods of sludge treatment, incineration temperature as well as chemical composition and physical characteristics of the generated ash, the “RESCUE“ project investigates possible uses of ash as a partial replacement for cement in concrete and mortar. Since ash shows certain pozzolan characteristics, its use in cement materials seems acceptable and feasible from the technical, economic and environmental viewpoints.