Governments have initiated wastewater treatment programs to solve the problem of water pollution. The goal is commendable, but the inevitable result is the production of sewage sludge which can be considered as waste. If it is buried, incinerated, or discharged in the sea, the problem is not solved and we are back to square one. Moreover, we have wasted a potentially useful substance. The only promising solution is the transformation of sewage sludge into fertilizers. This study shows that sewage sludge produced by water treatment plants can be used as an efficient forest fertilizer which increases the size and height of trees. The fertilization of larch tree samples in green houses using anaerobic sludge from the Valcartier Wastewater Treatment Plant resulted in a 300% increase in height and 210% increase in diameter. Key words: management, recycling, sewage sludge, anaerobic sludge, fertilization, water pollution, forestry. [Journal translation]