Demo Plant
Project Objectives
The goal of the Demo Plant team is to create a demonstration-scale version of the technologies used in full-scale AguaClara plants in several rural communities in Honduras. The Demo Plant is an important tool used to promote AguaClara in the Cornell community, at national conferences such as the EPA P3 competition, and for community workshops in Honduras. The previous Demo Plant effectively shows how water flows through the plant; however, there are technologies that have not been incorporated into the Demo Plant which would further aid the educational and outreach aspect of AguaClara.
Since many of the modules in the AguaClara plant are being updated and created anew, the previous Demo Plant was not reliable as a reference for the full-scale plant. New parts needed to be machined and tested based on the current AguaClara technologies. This semester, the demo plant team focused on creating a Linear Flow Orifice Meter (LFOM), a chemical dose controller (CDC), an updated sedimentation tank with an operable floc blanket, and a Stacked Rapid Sand Filter (SRSF).
Flow Control and Chemical Dosing 
Sedimentation Tank 
The purpose of the sedimentation tank is to remove large particles from the water. The demonstration plant achieves this by using two functional sections: the floc blanket and tube settler, which are corollaries of the large-scale sedimentation tanks with plate settlers used in the real AguaClara plants. Although a full floc blanket has yet to be achieved in a full-scale AguaClara plant, floc blanket theory is the driving factor behind sedimentation tank design, and thus the illustration of a floc blanket and its functionality in the demonstration plant is a useful way to educate the public about AguaClara technologies. At the scale of the demonstration plant, tube settlers are more practical, and fully analagous to the full-scale plate settlers from the point of view of solids in the water.
The purpose of the floc blanket is to grow flocs, making them easier to capture. The tube settler acts to capture flocs grown in the floc blanket, cleaning the effluent water and feeding flocs back into the floc blanket. The floc blanket works by preventing flocs from setttling out: water enters at the bottom of a vertical column, and flows upward, acting to counter the gravitational force on the flocs and fluidize them. The balance of the upward flow rate with the downward gravitational pull on the flocs means that flocs must circulate throughout the column, rather than simply passing through. This forced circulation causes increased particle collision, meaning that the flocs grow. Flocs that grow to the point where the gravitational force is strong enough to cause them to settle out are resuspended by the influent jet. The floc blanket thus consolidates particles in the water into large, capturable flocs.
The majority of those flocs are drained out by a floc weir at the top of the floc blanket column. The resultant, cleaner water then travels through the tube settler, an angled pipe of the same diameter as the floc blanket column. The angle of the tube settler's walls causes flocs traveling in the water to settle out on the sides of the tube. Gravity then rolls them back down into the floc blanket, where they will grow and be drained out. The combination of the floc blanket and tube settler effectively cleans water of a large portion of particles before it is processed by the stacked rapid sand filter.
Stacked Rapid Sand Filter 
The purpose of the SRSF is to remove small particles that did not settle out in the sedimentation tank. The advantage of a stacked rapid sand filter over a traditional rapid sand filter is that the backwash process is more efficient. Since backwash of the layers occurs in series, the SRSF uses significantly less water to clean the filter. During filtration, water flows into the inlet tubes, out slotted pipes and through the sand layers. The purpose of the slotted pipes is to allow water to flow out but prevent sand from clogging the pipes. Therefore, the slots have to be smaller than a grain of sand for this to work. As water flows through the sand layers, any remaining particles stick to the sand effectively filtering the water. The water then flows back into a slotted pipe and through outlet tubes. After a while, the filter performance decreases due to particle buildup in the sand. At this point, it is necessary to backwash the filter.
During backwash, water only flows through the bottom inlet tube, creating a backwash velocity equal to the filtration velocity times the number of layers with the same flow rate used for filtration. This high water velocity fluidizes the sand bed, washing flocs out of the sand and through the backwash outlet.
In order to reproduce the SRSF on such a small scale, we based our design calculations on the MathCAD worksheet used to design the full scale SRSF. Due to the size, several modifications were made, such as reducing the number of sand layers to four and using valves instead of a siphon system for backwash. Additionally, we had to find some alternative way to replicate the slotted pipes which are impractical to fabricate on this scale.
80/20 Aluminum Frame
A new frame was constructed out of modular pieces of aluminum from the company 80/20 to house the new processes. This frame is easily deconstructed, is simple to pack for transportation, and is easily modified to accommodate changes in the required relative positions of the unit processes. The new frame is shorter, lighter, and more professional looking than the previous frame, while continuing to be simple to operate.
Team Members
Muhammed Abdul-Shakoor
Thalia Aoki
Sahana Balaji
Miree Eun
Tim Hui
Diana Kelterborn
Meena Selvanathan
Documents
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Challenges |
Tasks |
Teach-In |
Presentation |
User Manual |
Final Report |
Spring 2012 |
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Fall 2011 |
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