Optimum Dosage and Product Selection Guidance for Flocculant Usage in Construction Stormwater Treatment

Implementing proper methods and techniques for construction stormwater management brings numerous benefits in protecting the environment, maintaining social justice, and enhancing sustainability within the construction industry. Flocculants improve construction stormwater management on active job sites by enhancing the function of temporary sediment control practices by facilitating the capture of fine-sized soil particles that are otherwise difficult to settle. The performance of flocculants is dependent on specific soil properties, dosage, and application techniques. Proper product selection and identification of adequate dosage rates is an arduous task for practitioners given the soil variability across job sites and a lack of implementation guidance. This study investigated the performance of various commercially available flocculant products on 15 soil samples collected from construction sites across Alabama through bench-scale testing methods. Experiments focused on providing guidance on product selection and identifying optimum dosage rates through soil assessment, match tests, and dosage experiment phases. The performance of polyacrylamide, sodium montmorillonite, chitosan, agricultural gypsum, and alum-based products was investigated across all soil samples for product selection. Dosage of selected products was evaluated by ranging manufacturers' dosage recommendations from 0% to 200% to evaluate settling performance across a range of dosing conditions. Results indicated that increasing recommended dosage rates negatively affected the turbidity reduction performance of tested products. In general, dosages lower than 40% manufacturer recommended rates showed a statistically significant improvement in turbidity reduction at a 95% confidence level. The study provides insight for practitioners and future research agendas on the proper usage of flocculants in the construction industry.