Tapered vs. Uniform Baffle Configuration
Abstract
The vertical flow hydraulic flocculator has been used to test tapered and uniform baffle configurations during previous semesters, but the two configurations have never been compared with similar raw water conditions. For this reason the Fall 2008 Pilot Plant Flocculation team focused on determining which flocculation configuration is optimal. The tapered flocculation configuration model is based on the G-theta Model, while uniform configuration is based on the energy dissipation model. In our final results, the tapered baffle configuration produced marginally better turbidity than the uniform baffle configuration. However, due to low temperature conditions, the incoming turbidity was too low in order to produce conclusive results.
Introduction and Objectives
Recently development in Aguaclara technology have shown that the Gtheta model may be inappropriate to describe flocculation. A main goal of the pilot plant flocculation team was to determine the optimal flocculation configuration: Tapered or Uniform Baffle Spacing. Using the Gtheta model a tapered configuration would expose flocs to high shear initially and as flocs grew they would be exposed to less shear. Using an energy dissipation model the uniform configuration would be optimal. The tapered flocculator
The Pilot Plant flocculation team approached this problem by first determining the optimal spacing for the tapered flocculation configuration. It was then determined that the two configurations would only be comparable if the uniform spacing was equal to the last section of the tapered spacing. The tapered and uniform spacings were compared consecutively. The tests were then run in the same day to ensure similar environmental conditions and comparable data.
An important aspect of the vertical flow hydraulic flocculator is the alum dosing One of the main issues of this semester was determining appropriate alum dosing in the cold. This problem was approached by inquiring the staff at the Water Filtration Plant about their Polyaluminum Chloride dosing. Their dosage was then converted so that the Pilot Plant can insure proper dosage with a simple equation based on the plant's dosage.
Sampling Method
Overview
A sampling method for testing raw water at the Pilot Plant has been used for several semester's research. Alum is used as a coagulant and the dose can be set using process controller. Raw water running through flocculation tank can be sampled at any desired location. Sampling lines run to turbidimeters from three mobile tube settlers. The tube settlers mimic sedimentation. Additionally a sampling line runs from the raw water inlet to a turbidimeter. Turbidity data is stored in a excel spreadsheet using process controller.
Because the pilot plant takes water directly from the stream, environmental conditions change all the time and affect the incoming turbidity to the plant as well as the chemical composition of the particles causing turbidity. It is incredibly important to determine the best alum dose for each day of testing to ensure the formation of good flocs and collect appropriate data. The alum dose can also be related to the plant's PAC dosage using the relationship 1 part per million is equivalent to 0.182 mg/L.
Tube Settlers are used to mimic sedimentation before the turbidity of water in the flocculator is measured. They can be moved to different locations along the flocculator in order to examine effluent turbidity at various stages of flocculation.
Data is collected using process controller. It is stored in process controller and then analyzed.