Effect of Contaminated Suspended Solids on Water and Sediment Qualities and Their Treatment

Abstract

Abstract Suspended solids (SS) have been discharged into water areas such as rivers, lakes, and ponds. The SS adsorb various contaminants such as heavy metals and nutrients and also form sediments by sedimentation. Therefore, contaminated SS will be able to influence not only the water quality, but also the sediment quality. In order to understand the effect of contaminated SS on the water and the sediment, SS and sediment samples were obtained from the des Hurons River in Canada. In addition, laboratory filtration tests were performed to develop a technique for removal of the SS. A downward filtration system was used with a nonwoven geotextile as a filter medium. The apparent opening size (AOS) and the thickness of the filter were 150 μm and 0.2 cm, respectively. For the investigation, the results showed that both SS and the sediments contained heavy metals with concentrations in the SS higher. In particular, zinc concentrations of the SS were approximately from two to five times higher than the Canadian guideline for sediments. In addition, it was found that SS concentrations were associated with chemical oxygen demand (COD) and total phosphorus (T-P) concentrations. Therefore, it was found that SS can play an important role in the water and the sediment qualities. The laboratory filtration tests showed the SS were reduced from 32 mg/L to 2 mg/L or less by the nonwoven filter. Thus, SS removal will improve not only the water quality, but also the quality of the bottom sediments.