Physicochemical characteristics of a new organic soil conditioner from composted sludges from a pulp deinking process

A new organic soil-conditioner from composted sludge produced from a newspaper deinking process was examined compared with raw uncomposted sludge, its physical and chemical characteristics tested in order to study its effectiveness. The water-holding capacity of the conditioner was almost 7.6 and 1.8 times higher than that of the pure soil and the raw sludge, respectively, and remained stable at temperatures between 9 degrees C and 27 degrees C. The composted sludge had a 53% organic matter content and 35% in humic substances which was 3.5 and 2.0 times lighter than the pure soil and the raw sludge. Incorporation of this material into the soil in concentrations of up to 25% resulted in a 1.7 times increase of the water-holding capacity of the mixture, whereas 90% of the water-holding capacity was achieved in less than 10 min. The apparent density of the mixture was decreased and was not affected by the residence time of the samples into the water. The pH of the mixture's eluates was shifted to higher values (pH=7.0). The specific conductivity of the eluates was increased. Due to this parameter, a limit was observed in the use of this conditioner. The amount of ammonium-nitrogen (NH -N), phosphorus (P), calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu)(4), and manganese (Mn) in the eluates increased, while the amount of potassium (K) and iron (Fe) decreased in comparison to what would be expected from the separate contributions of soil and conditioner. Therefore, there exists an interaction between this material and soil that occurs when the conditioner is incorporated into soil.