Introduction
The sedimentation tank is a critical component of the AguaClara design. Since AguaClara does not yet utilize filtration, the sedimentation tank is the location where virtually all of the suspended material removal occurs. Moreover, the important goal of minimizing construction costs means the tank should be as small as possible. Because of its relatively small surface area and the lack of a redundant or back-up removal mechanism, optimization of the sediment tank is a critical design goal.
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The specific design challenge for the Inlet Manifold Research Team is to design an optimal inlet manifold for the sedimentation tank. Past AquaClara designs have evolved to inlet systems that currently feature PVC pipes with multiple holes (exit ports) creating vertical (downward) flow along the bottom of the pipe. The intent of the design is to create a smooth, quiescent influent condition that creates slow, upward flow through the sedimentation tank, ideally with the flocculated inflow initially traversing through a settled floc "blanket" that aids in removal. Some performance issues of past plants (lack of settling floc in one area of the tank, for example) have suggested that there may be non-uniform flow conditions in the sedimentation tank, leading to non-optimal performance.
The goal of an optimal influent design is to investigate and correct any discovered unbalanced flow conditions, thereby creating the following optimal inlet conditions:
• Sufficient inlet velocity to prevent sedimentation prior to entry into the tank
• No excessive velocities anywhere in the pipe, outlets, or in the tank that might result in a high energy dissipation rate causing floc breakup.
• An even distribution of the flocculated influent along the length of the sedimentation tank without horizontal circulation or other non-uniform flow patterns that will create non-uniform rising flow and/or non-optimal sediment tank performance. Optimal flow is vertically upwards until reaching the lamella plates.
While our team is specifically looking at the inlet manifold, some other aspects of the sedimentation tank may also be considered for an overall optimal design. For example, the behavior of the effluent launders and overall geometry may create interactions with the flow from the inlet manifold and may be considered.
Below is a video that exhibits the current behavior of the inlet manifold using a simple dye test in a home-made miniature sedimentation tank, according to current AguaClara design. One can observe that the dye is highly concentrated at the far end of the sedimentation tank, revealing an uneven flow distribution through the pipe.
Members
Past Research
More Information
Future Research Goals
Future research goals will be developed as the semester advances.
Past Research Teams
The Fall 2010 Inlet Manifold Team has focused on the theory that pressure recovery may be responsible for uneven distribution of the influent. Pressure recovery is the effect caused by the energy of forward motion in the pipe. This velocity is converted to static pressure as the velocity slows toward the end of the pipe, as dictated by Bernoulli's equation. In addition, the forward motion created a horizontal component to the discharge, as discussed in our results.
From our Fall 2010 Team Page you can find the theory behind our work as well as our experimental set-up in the lab.
Also on our team page you will find the results of our team's experiments. Our scale models demonstrate both a pressure recovery effect and horizontal flow components; we will continue to explore these behaviors and model corrective designs as the semester progresses.
Spring 2010 Inlet Manifold Team
The Spring 2010 team used an ADV, or Acoustic Doppler Velocimeter, to measure the velocity at the ports of both a 10' and 20' manifold model. Their data proved inconsistent with expected theoretical values and pointed towards technical difficulties with the mechanics of the ADV.
Spring 2010 PIV Research Team
The AguaClara flocculator design is based on Computational Fluid Dynamics (CFD) models. Velocity measurements, using particle image velocimetry (PIV show that the minor loss coefficient predicted by the CFD models over estimates head loss. Incorporation of these results into the CFD models will eventually make flocculator design more efficient and cost-effective for future Honduran communities.
Capstone Design Projects
The course CEE 4540, Small-Scale Water Supplies, was challenged to develop creative solutions to the uneven flow distribution of the inlet manifold. Projects included MathCAD files and power point presentations.