Turbidity and water clarity improvement processes in marine environment

• Main Author: Goh, Xue Ping.
• Other Authors: Tan Soon Keat
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Civil engineering::Water resources
• Online Access: http://hdl.handle.net/10356/39604
• Institution: Nanyang Technological University

Turbidity in marine water is largely due to total suspended solids in the marine environment. Turbidity removal is done to improve the quality of the marine water to protect aquatic life and human health. Standard jar tests were used to conduct coagulation and flocculation on the raw seawater samples collected. Results obtained indicated that for similar dosage of coagulant, alum generally produced higher turbidity removal efficiency than ferric chloride. This is most likely due to the “fluffy” nature of the alum flocs that facilitated the trapping of microflocs, bringing about more rapid settling and thus higher removal efficiency. Synthetic seawater in the form of kaolinite suspension was used as a substitute to raw seawater for all experiments. The first order reaction kinetics, C = Coe-kt, is a valid assumption and is representative of the flocs’ settling rate and removal efficiency. The greater the magnitude of k, the more rapid the settling of the flocs which in turn implies higher removal efficiency. Repeated attempts showed that turbidity measurement using the turbidimeter, instead of the conventional mass measurement method, should be used on the synthetic seawater to obtain observable results. Results showed that the optimal working range of alum coagulant is between 30 to 50 mg/L. However, the optimal range of ferric chloride could not be determined as its optical nature disallowed the use of turbidimeter. Specific gravity bottles tests proved to be ineffective for ferric chloride coagulant either. Different amount of sodium chloride added to the kaolinite suspension produced synthetic water with salinity ranging from 0 to 100 ppt. Results showed that the salinities of the water samples had little or no effect on the removal efficiency of total suspended solids. Experiments on synthetic seawater with varying temperature (13 to 97oC) showed that at significantly higher temperatures (above 63 oC), removal efficiency of total suspended solids were increased. The standard procedures for the jar tests and turbidity measurement method experimented in the laboratory were inferred to be largely effective when put into a real life situation of clarifying turbid seawater around a land reclamation site.