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Sedimentation Tank Hydraulics

Wiki Markup
h1. Inlet Manifold Research and PIV Measurements

h2. Team Members
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Rami Bechara
Gonzalo Caprario
Vanish Grover
Nicolas Pautassi
Julia Schoen
Arthur Shull

h2. Introduction

Currently, the design inlet to the sedimentation tanks to the AguaClara plants consist of an inlet manifold whose objectives are:

* keep the velocity of the water high enough to prevent sedimentation prior to the tank
* get an even distribution of the influent along the sedimentation tank
* re-suspend the flocs in the bottom of the sedimentation tanks
* prevent floc breakup

The inlet manifold consists of a PVC pipe with a row of drilled holes facing down. The jets coming out of the ports will prevent floc accumulation in the bottom of the sedimentation tanks and hopefully the velocity will keep the floc in suspension to create a floc blanket.

To read more about the inlet manifold design please refer to the [design|Agalteca Design] link. 

h2. Objectives

The objectives of this research are to experimentally test the inlet manifold recreating the same conditions that will face in a real AguaClara plant, and modify the design based on the results.

To begin with, we calculated the manifold dimensions which include:

* Pipe diameter
* Ports' diameter
* Ports' spacing

The calculations for this experiment were based on the Agalteca design flow and tank dimensions.

Based on [theoretical information about manifolds|Inlet Manifold Equations], the initial idea is to prove that to create an evenly distributed flow throughout the different ports of the manifold, we would have to taper the pipe to have the same velocity along the manifold and therefore the same flow in each port. 

To begin with the study, we should calculate a manifold with a constant diameter for the design flow. The results of that calculation proposed a 6" PVC pipe with 1" ports spaced 5 cm center to center (total 57 ports). [Drilling Process Images|Pictures]

These calculations assumed that the sum of the areas of the vena contracta of the ports should equal the cross sectional area of the pipe.

Refer to the following link to view the [calculations|^Agalteca Manifold Design 1.xmcd].

The next step is to recreate in the lab the conditions of that manifold in the Agalteca plant.   To do this, a submersible pump with the design flow will recreate the inlet flow and the whole manifold replica, will be installed in a flume to begin the flow testing. 

The velocities coming out of the ports will be measured using an ADV as shown in the following [image|Pictures|IMG_0462.JPG].

The results obtained by this measurements will be plotted and compared to the theoretical expected values.

Based on the obtained results, the manifold should be modified and the testing procedure should be repeated until even flow distribution is achieved. 
 
 
h2. Experimental Methods and Results
[Experiment 1: 10' Uniform Manifold Ap/Am=1|Inlet Manifold-10ft Manifold Test 1]
[Experiment 2: 10' Uniform Manifold Ap/Am=1, take 2|Inlet Manifold-10ft Manifold Test 2]
[Experiment 3: 20' Uniform Manifold Ap/Am=2|Inlet Manifold - 20' Manifold Test 1]


Stay up-to-date on this project by checking the [Meeting Minutes|Inlet Manifold Meeting Minutes], [goals|Inlet Manifold Goals] and [Challenges for Future Semesters|Inlet Manifold Future Challenges].

h2. Current Research Teams

[Spring 2010 Inlet Manifold Research Team|Spring 2010 Inlet Manifold Research Team]
* Redesigning the inlet manifold for the sedimentation tank in an effort to maintain constant flow out of all of the ports. !AguaClara Honduras Trip 2011 323.jpg|width=200, border=0!


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Introduction

A floc blanket is a dense, fluidized bed of particles that forms in the sedimentation tank below the plate settlers. A floc blanket works like a mesh to trap small flocs, thereby reducing effluent turbidity. As flocs are continually resuspended in the blanket, sludge build up on the tank bottom is reduced. The sedimentation needs to be drained and cleaned less frequently, reducing the amount of clean water wasted.

The latest working design of the AguaClara sedimentation tank consists of an inlet manifold with vertical diffusers to channel water into the tank as a line source. A semi-circular half-pipe beneath the diffusers serve as a jet reverser to resuspend flocs. Plate settlers placed above the inlet manifold that catch flocs while allowing water to flow past the settlers into exit launders. The flocs that settle out at the bottom of the sedimentation tank are removed regularly by a sludge drain. Implementing a floc blanket and a floc hopper in the sedimentation tank provide an additional method of filtration and will reduce sludge build up, instead allowing flocs to be wasted at a constant rate from the floc hopper. 

Current and Future Research

Excerpt

One of our main goals of the semester was switching our coagulant to PACl instead of alum and see how the change affects performance. The PACl seemed to be much stickier than alum and we had problems with it sticking to the glass and insides of the flocculator. We also conducted experiments switching energy dissipation rates in the jet reverser. We were expecting to find a point where the energy dissipation rate is too high and performance decreased. We didn’t find a point where the floc breakup caused a decrease in performance. During these tests we actually found that momentum can play a large role in floc blanket failure because if the momentum of the floc sliding down the incline gets too large it can overpower the pet reverser and cause it to fill up. We also looked at sludge consolidation depending on the depth of the floc hopper. We found that the depth can make a large difference in consolidation. 

More Information

Sedimentation Team Research Rationale
Sedimentation Team Research Rationale2
Sedimentation Team Research Report 1

Section
Column
Members

Casey Garland

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Sedimentation Tank Hydraulics Documents
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Past Research

Fall 2010 Inlet Manifold Team
Spring 2010 Inlet Manifold Research Team