2013

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Turbulent Tube Flocculator – Fall 2013

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Felice Chan, Jonathan Christensen, Stephen Jacobs, Ana Oliveira

Abstract:

The purpose of our research is to design, build, and eventually test a lab scale turbulent tube flocculator. This is important because while the AguaClara plants in Honduras and India have flocculation that occurs in turbulent 􏰃ow, the prior AguaClara program research has focused on laminar tube flocculators. Thus, with the turbulent tube flocculator experimental apparatus, future AguaClara researchers will be able to more accurately conduct research to perfect the design of the full-scale plant. The prior literature that proved most relevant related to either the materials needed for the turbulent tube flocculator to be built or the size of eddies necessary for flocculation.

The 2013 summer semester AguaClara team's design for the turbulent tube flocculator was that the flocculator should be a vertical single coiled tubing configuration. The design used two pairs of pipes to constrict the tube in the coil to create turbulent eddies. The main goal of the Fall 2013 team was to perfect the initial design created in the summer of 2013 and then build the turbulent tube flocculator.

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Sand Source and Testing - Fall 2013

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Rebecca Schneider and Meghan Furton

Abstract:

The Sand Source and Test Methods sub-team is new to AguaClara this semester. Our main sources of research come from the known SRSF sand constraints, which dictate that no sand should be able to slide through the 0.2 mm slots in the PVC pipe, the sand should be hard and not prone to dissolution in acid, the backwash velocity required to expand the filter bed by 30% should be very close to 11 mm/s, and the sand bed must not have significant stratification after backwash. In addition to the constraints provided by the SRSF, the filter sand used must also satisfy American Water Works Association guidelines (AWWA). We are using American Water Works Association (AWWA) media constrains along with the American Society for Testing and Materials guidelines (ASTM International) to compile a series of test methods for filter sand. We intend to determine which of these constraints apply to the SRSF design. Furthermore, progress towards local sand acquisition is varied between the sites in India and Honduras as of September 2013. In India, sand is currently taken from the Barakar river and the only modifications made are sieving it for correct size on site, using two large rectangular mesh sheets that are shaken by two people. The two sieve sizes currently in use are No. 60 and 30, which correspond to particle sizes of 0.25 mm and 0.5mm respectively. There is also potential access to laboratories in the Universities and NGOs nearby. In Honduras, on the other hand, there is not an established sand mine industry and sand will likely be taken from river beds near the site. Transporting this sand from the river to the site is easy, but testing will be done in the apartments without the use of laboratory equipment that is difficult to transport.

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Chemical Dose Controller - Spring 2013

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Andrea Castro, Kent Chan, Saugat Ghimire

Abstract:

Accurate chemical dosing is an essential part of an AguaClara plant. Proper dosing is required for effective flocculation, sedimentation, filtration and disinfection. Coagulant (Poly Aluminum Chloride or Alum) and disinfectant (Chlorine) are chemicals used for dosing in an AguaClara plant. The linear chemical dose controller (LCDC) automatically maintains a linear relationship between the influent flow to the plant and the chemical dose. The plant operator therefore only adjusts the dose of coagulant based on the turbidity of the influent water. The Spring 2013 team has had two lever-arm assemblies fabricated by Hancock Precision based on the Fall 2012 design with additional improvements, such as having one end rod of the lever arm made up entirely of stainless steel instead of having a stainless steel rod placed over the aluminum rod and substituting anodization of the lever arm with powder coating, as the latter is more resistant to a corrosive environment. One unit has been sent to Honduras and the other is expected to be utilized in India. In addition to this, we have fabricated the manifold system out of PVC, a chemical resistant material. Through application of the orifice equation, we sized the constant head tank float valve orifice. Through application of a statics equation we determined that the 􏰄oat valve size could be reduced, allowing the use of a standard 5-gallon bucket for the constant head tank. We fabricated a constant head tank, suspended by a chain and attached to a turnbuckle, which can be easily adjusted during calibration. We have set up a fully functional unit of the coagulant dosing component of the dose controller in the lab, calibrated the unit, and tested the system at our maximum flow rate to compare how the system behaves compared to the model prediction and were below ten percent error. We created a detailed 3-D drawing in Google SketchUp of the current design of the linear chemical doser system including all appurtenances, in addition to creating a parts list, to facilitate future fabrications and assembly. This will not only be helpful for future groups to better understand the dose controller but also make it easier for the manufacturers to build it in the future. We also came up with ideas for protecting the entrance tank 􏰄oats as water enters the plants at some locations in Honduras, to reduce dosing error.

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Laminar Tube Flocculator - Summer 2013

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Allan Brooks, Rivu Dey, William Pennock

Abstract:

Over the Summer of 2013, the Tube Flocculator team's overall goal was to further the understanding of floc breakup in order to heighten flocculator performance. Specifically, this was done by examining a single clamp's effect on flocculation, as well as finding the optimal orifice size while using multiple clamps. The effects of the clamps were predicted to increase overall colloid aggregation which would prove beneficial for the next step in AguaClara's process: sedimentation. Based on the results found over this summer, some conclusions can be made. One conclusion based on the end-clamp experiments is that larger orifice sizes display lower mean residual turbidities. Another is that, for a 28-meter-long flocculator, an evenly-spaced sixteen-clamp configuration appears to be better than using no clamps, depending on the clamp size used. The the eight-clamp configuration appears to not be any more effective than a no-clamp control, while a four-clamp configuration appears to show improved flocculator performance for certain clamp sizes. In future work, these findings can be applied to the full scale flocculator in hopes that floc breakup will prove useful for plant performance.

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Full Scale Floc Breakup - Spring 2013

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David Buck and Meg Fitzgerald

Abstract:

The objective of this research was to design a floc break up device to test the concept of floc break up at full-scale and improve flocculation performance of the AguaClara plant located in Atima, Honduras. Recent research suggests that using 􏰅ow constrictions to break up flocs improves performance and reduces settled water turbidity. Using this hypothesis, we designed a device to cause floc break up. We used a perforated plastic sheet which constricts 􏰅ow and creates many jets, which dissipate energy and break flocs. The proposed design for the prototype for Atima includes 21 orifices and an orifice diameter of 5.1 cm (2􏰃), which results in approximately 9.3 mm of head loss per device and 40% open area. We also determined that the devices should be optimally placed in the flocculator so that water flows upward through them. We plan to attach the devices between the baffles and walls of the flocculator with foam blocks. Our design can be fabricated in Honduras with locally sourced materials, so although the fabrication will require local labor, it does not rely on shipping materials from the United States. We will send our design to Drew Hart in Honduras who will fabricate the perforated plates and test them at full scale.

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Foam Filtration - Spring 2013

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Jenny Guan, Monica Kuroki, Lishan Zhu

Abstract:

Originally, the foam filtration system was designed to provide clean water to small-scale communities. The system was also designed to provide water in emergency situations such as a refugee camps. The system was ideally powered by gravity and the optimal filtration rate was made to be 3 L/min. For the Spring 2013 semester, the foam filtration team began fabricating a new system and recording the process of the new system. The previous filtration system was designed and shipped to Honduras in January 2013. The current design focuses on pieces readily acquired in-country. This allows feasible construction in Honduras and, potentially, other developing countries. Products such as 8020 steel, clear PVC piping and flexible tubing have been removed from the design because they cannot be easily found outside of the US. The foam filtration team this semester is also working on making the design more compact for easy transportation. Additionally, the foam filtration team designed a new compact stand of PVC piping to hold the filtration system. The team included a larger collection tank to allow for the incorporation of a linear dosing system.

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Fall 2013 Chemical Dose Controller

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Zeyu Yao, Saugat Ghimire

Abstract:

The Chemical Dose Controller is an important of component of a AguaClara plant. The CDC delivers the coagulant (Polyaluminum Chloride (PACl) or Aluminum sulfate (Alum)) to the influnt water and disinfectant Calcium hypochloride to the effluent filtered water. The Chemical Dose Controller is a simple mechanical response device which maintains a linear relationship between the plant flow and the chemical dose. It consists of a calibrated lever arm which the operator can use to adjust the dose of the chemical based on the turbidity of the influent water. The Fall 2013 team started off by putting together three half size doser units for stacked rapid sand filters constructed in India. All the parts were shipped to India with a detailed instruction manual to aid the assembly. The dosers sent to India contained CPVC ball valves with flouroelastomer seals that are more resistant to cholrine than the previously used PVC ball valves. The ball valves in all the AguaClara plants will now be replaced with these CPVC ball valves. Similarly, a lock-and lock container will now be used as the Constant Head tank for both chlorine and coagulant suspended with a chain and a turnbuckle for height adjustment. Although the lock-and-lock container degrades when in contact with chlorine, it is locally available and can be easily replaced. In addition to this, the design of a new half-size doser with single arm which only doses chlorine has been completed. A 3D sketchup file has been created and sent to Hancock Precision for fabrication. This new doser will primarily be used in low flow plants in India which only require chlorine delivery

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