The Effects of EPS, Clay Minerals, and Sand on the Flocculation Process

• Alyssa Wentzel, Marine Science, University of Delaware

• Tian-Jian Hsu, Civil and Environmental Engineering, University of Delaware
• Jorge Penaloza-Giraldo, Center for Applied Coastal Resources, University of Delaware

In estuarine environments, bio-secreted cohesive materials such as extracellular polymeric substances (EPS) and cohesive clay particles, generate a considerable diversity of flocs due to flocculation process. However, non-cohesive materials, such sand, may also participate in floc formations. In addition to sand, these flocs are vehicles of pollutants and their transport plays important role in water quality and ecosystem. The objective of this research was to provide quantitative analysis on how sand interacts with EPS and Bentonite particles in the flocculation process. The specific research questions that were studied are: (1) What are the behaviors that sand experiences when interacting with EPS and Bentonite? (2) Is there a correlation between the number sand contained in EPS-Bentonite flocs and stickiness? To answer these questions, six flocculation experiments with different ratio concentrations of Bentonite and EPS were carried out by a regular jar test. Since the sand was the response variable, its concentration was established by the difference between 500 mg/L and the total sum between bentonite and EPS. The results show that as sand increases in concentration and EPS reduces in concentration, there are less sand particles contained in flocs. A similar trend is also observed when replacing EPS with Bentonite. Ultimately, by studying bentonite, EPS, and sand in the flocculation process, a more comprehensive understanding of the complimentary role between mineral cohesion and bio-cohesion can be established.