LEED GA, EI, Graduate Research Assistant Auburn University
Water quality treatment for agricultural, urban, and construction stormwater has become an increasingly important topic. Pollutants from these sources create adverse water quality impacts on receiving water bodies. Among these sources, suspended sediment has significant influence on water quality because it is also a media of pollutants. The treatment system for removal of suspended solids is important. Compared to other land uses, construction operations produce a large amount of sediment yield due to the earth disturbing the nature of land-grading activities. In addition to sediment, pollutants carried by soil particles create adverse water quality impacts to downstream receiving water bodies. This study determined the efficiency of sediment removal by developing and analyzing three passive treatment systems: a control tank, and two lamella settlers inserted with 18 plates, and 9 plates. In this study, five types of soils: A25, Snobrite 75, Pigment 60, Minex 4, and Kaolinite at 500 mg/L, 1000 mg/L, and 5000 mg/L were treated in system consisted of 18 plates, 9 plates, and no plates with 30 minutes, 1 hour, and 1.5 hour residence time. It was founded that all considered factors significantly influenced the turbidity reduction compared to the selected base conditions at 500 mg/L sample solution with 30 minutes residence time in the system without plates.
The main purpose of this research is to identify different design factors for the lamella settler and obtain the optimized design strategy. The numbers of plates inserted into the system always had the greatest or second greatest impact on turbidity improvement which recommended to insert more plates to increase system’s efficiency. Based on the results of multiple linear regression analysis, 18 plates inserted with 90 minutes residence time with 5000 mg/L sample treatment produced the most efficient turbidity removal rates. The calculated turbidity removal rates for different types of soils were reasonable corresponding to the calculated settling velocities. Minex 4 had largest settling velocity who created the largest turbidity reduction rate compared to other samples. Snobrite 75 was the most suspended samples with lowest settling velocity and turbidity reduction rates. The relationship between turbidity and TSS needs further study with variance of particle size distributions. The prediction of TSS after treatment of different systems is expected to accomplish correlated to studied relationship among particle size distribution, TSS, and turbidity in future. Based on the developed relationship curves, these bench scale experiments can predict the turbidity reduction rates and TSS removal rates for different system setup which will be correlated to the large scale system. The TSS removal rates were obtained by turbidity reduction rates, the turbidity measurements at effluent decreased a lot compared to the influent for each test, which might be caused by the change of particle size distribution as larger particles captured by the treatment tanks. The relationship between TSS and turbidity will be studied in future work to prove all the assumptions made in this study.
Understand the various components and concepts that are used in the design of water treatment system.
Learn about bench-scale systems used to effectively remove the suspended solids.
Guide the design of large-scale lamella settlers used for stormwater applications.