Resource recovery of sludge as a building and construction material – a future trend in sludge management

Rapid urbanization in many areas of the world has resulted in an drastic increase of wastewater sludge. In highly urbanized cities, sludge disposal by landfilling may no longer be appropriate owing to land scarcity and increasingly stringent environmental control regulations. Therefore future trends in sludge management are towards minimization and reutilization as useful resources. Incineration is one feasible means of converting bulky sludge to practically inert, odorless and sterile ash. The disposal of this significantly reduced volume of sludge ash can be subsequently handled easily with much smaller scale. The disposal problems will be drastically reduced if sludge or sludge ash can be put to large-scale economic applications. This paper reviews current studies by various researchers in reutilising sludge as non-conventional construction materials. Properties of the innovative materials derived from sludge, the processing technology, and the suitability of the materials for construction purposes will be discussed. A summary of the research work carried out by the authors in the past ten years, specifically in the area of sludge reutilization as building bricks, lightweight aggregates, and cementitious material will also be presented.