Experimental research on river and lake silts adjusted by a low alkaline silt modifier using as planting soils for greening

To solve the high pH problem of the filter and the dewatered silt cake during the treatment and disposal of the river and lake silt, a low alkaline silt modifier was employed in this research. To contrast the performance, PAC, PAM and together with the fly ash, conventional silt modifier, and the low alkaline silt modifier were added in the silt sample. The silt was dewatered using a pilot-scale plate and frame filter press. It is found that the filter and the dewatered silt cake with the low alkaline silt modifier were weakly alkaline, TN and TP are also lower than the other groups. The internal mechanism and feasibility of the dewatered silt cake were analyzed and demonstrated by micro-tests (e.g. XRD and SEM). The results indicated the steel slag, phosphogypsum and cement in the low alkaline silt modifier can provide mineral framework, increase the porosity of the silt cake and improve the dewatering performance of silt as the fly ash and the conventional modifier, while the steel slag, phosphogypsum in the low alkaline silt modifier could improve the distribution of phosphorus in the dewatered cake, promote the transformation of bioavailable phosphorus, and improve soil fertility.