Rapid Mix Tube, Fall 2009

Karen Alison Swetland, Patience Ruijia Li

Abstract

During the fall 2009 semester, the main focus of the Rapid Mix Tube subteam was the development and design of a rapid mix tube system to provide adequate large and small-scale mixing of alum with the raw water source entering the plant. The system developed in the fall 2009 semester is designed for the Agalteca plant, but the ultimate design can be modified to fit into future AguaClara plants and even fit into existing plants to improve rapid mix . The design of the system evolved multiple times throughout the semester, and the current system was developed to improve upon the main problem of those initial designs: access to the small scale rapid mix orifice to clean it in case of clogging. The design of the tube was thus tailored to fix this problem, and a MathCAD file calculating orifice sizes and head loss through the system was developed. A built prototype model of the rapid mix tube was also constructed to provide a model for the construction of the rapid mix tube system, and a series of experiments (to be run using FReTA) was also designed to test the effect of the rapid mix tube system on the effluent water turbidity and to determine the need for the rapid mix tube system.

Computational Fluid Dynamics Flocculation Tank Simulation, Fall 2009

Abstract:

Computational Fluid Dynamics (CFD) is a tool used by AguaClara to obtain a description of the flow through a portion of the plant where particle formation and growth (flocculation) occurs. This part of the plant is referred to as the flocculator. In this section, dirty (turbid) water flows through a series of baffles that enhances turbulent mixing. Essentially, for particles (flocs) to grow and eventually settle out in the sedimentation tank, they first must collide. By increasing the level of turbulence, the flocculator is increasing the collision potential of flocs. However, if there is too much turbulence, the flocs will break up and not settle out. By running CFD simulations of the flocculator, AguaClara can analyze the parameters important to flocculation and use the resulting data when making design decisions.

Computational Fluid Dynamics Flocculation Tank 3D Simulation, Spring 2009

Abstract:

The flocculation tank simulation team works on building a stable and reliable numerical model to simulate the flow inside the hydraulic flocculation tank, and providing well-studied guidelines for design, construction and operation of the flocculation tank.

Gravity powered hydraulic flocculators are used by AguaClara small-scale water treatment plants due to their low cost, inherent simplicity and robust operation. However, their inflexibility of energy input into the water relative to mechanical flocculators requires well studied design based on the understanding of the flow field and relevant performance parameters.

An appropriate CFD simulation can provide detailed numerical solutions for all the variables in the flow field, and by varying parameters such as tank geometry and flow conditions, we could obtain predictions of each of the flow variables and thus optimize the design towards lower cost and better performance.

Currently, our effort is focused on depicting an accurate energy dissipation map inside the flocculator, describing the size and the shape of the region where most of the energy is dissipated and the formation and collisions of flocs happen, thus providing basis for more efficient and economical design utilizing geometries that dissipate energy as uniformly as possible.

Turbidimeter, Spring 2011

Emily Clamp, Rohiverth Guarecuco, Julia Morris

Abstract:

The goal of the turbidity team was to create a low-cost turbidimeter that measures water turbidity within the range of 5 NTU to 250 NTU. Thus far, the team has brainstormed various turbidimeter designs and created several prototypes for simultaneously testing different LED display patterns. Many patterns have been assessed, including a dual-range LED display pattern for measuring a broad turbidity range. The dual-range LED pattern was tested using an experimental setup that allowed turbidity measurement of water that was constantly mixed with kaolin clay using a water pump. The team determined that only the fine pattern of the dual-range pattern was necessary, since the pattern alone could accurately measure turbidities from 5-200 NTU. This approach is based on resolution of the fine pattern within the turbidimeter as opposed to the use of contrast when using conventional Secchi disk patterns. The fine-resolution pattern was used to create a low-cost turbidimeter prototype equipped with an NTU scale based on the power-law equation derived from experimental results.

Tubidimeter, Summer 2011

Jennifer Gass, Maxwell Petersen, Heidi Rausch

Abstract:

The goals of this summer’s Turbidity team were to:

• Finish the testing that the previous team had been working on in order to design a cheap (under $20) Turbidimeter that can easily be transported to potential AguaClara facility locations.

• Find a relationship between depth and Turbidity that is within 50% accuracy for a specific disk design based on line thickness and spacing.

• Fabricate and calibrate 10 turbidimeters that will be ready for shipment by July 28, 2011.

Thus far, the team has managed to improve the design of the original Turbidimeter while lowering cost and increasing portability. All ten prototypes were built, calibrated, and sent to Honduras by the specified date. The only shortcoming was that due to size limitations the Turbidimeter could not measure below 15 NTU, however, this does allow for greater ease of use. The final Turbidimeter design is just over 60 cm in height and costs $4.02 to make.

Turbidimeter, Fall 2011

Julia Morris, Andrew Gorodetsky, Heidi Rausch

Abstract:

This report will cover all the work that has been done by Cornell’s AguaClara program on turbidimeters. Research first started on creating a new, low cost turbidimeter at Cornell in the Spring of 2011. Since then several different prototypes have been created and ten turbidimeters have been sent to Honduras for use by communities who are considering building an AguaClara plant. The reason that a low cost turbidimeter needs to be developed is so that communities who may be in need of water treatment facilities can test their water without incurring the high expense of other turbidimeters currently on the market. The most current complete turbidimeter prototype can read NTU values down to 15 NTU. The research discussed in this report details new turbidimeter designs with which it may be possible to read NTU values down to approximately seven NTU. The most promising design includes the use of a blue LED light and a large HDPE block, which is used for diffusing the light. However, this design will need to be tested more thoroughly for accuracy before it can be fabricated for use in the field. In the future if research continues to be done to try to create a turbidimeter that can read turbidity values below 5 NTU the length of the lowering rod may have to be made longer than the current prototype, which is only 60 cm long. Without adding length to the lowering rod current research suggests that it may be impossible to read the turbidity of any water with an NTU value lower than seven.

Validation CFD in ANSYS Fluent, Spring 2010

Validation Studies of Fluent Turbulence Models for Fluent Simulations of AguaClara Flocculators

Travis Stanislaus

Introduction:

The AguaClara water treatment project uses ANSYS Fluent computational fluid dynamics (CFD) software to simulate and analyze turbulent fluid flow in idealized models of flocculators in AguaClara water treatment plants. The flocculator simulations in Fluent are used to obtain turbulent kinetic energy dissipation rate, ε, and energy loss coefficient, K, between baffle in the flocculator for AguaClara design equations that determine the height of the flocculator, H, the spacing between baffles, S, the quantity of baffles in the flocculator, and flocculation performance, Ѳε^(1/3) , Ѳ is the residence time between two baffles. The results from Fluent are used in the design of AguaClara facilities, so verification and validation of the Fluent flocculator model and simulation has been conducted continuously since the time AguaClara began using Fluent simulations. Verification is determination of the degree the model being simulated is an accurate representation of the developer’s description and solution to the model. Validation is determining if the model is an accurate representation of the real world physics and intended uses of the model.

Laminar Tube Flocculator, Fall 2010

Tami Chung, Alexander O’Connell, Karen Swetland

Abstract

The Fall 2010 Tube Floc Team of aimed to better understand the development of rapid flocculation through a series of experiments and data analysis. In previous semesters, we had focused on the variation of flocculator length and alum dose. With the completion of these studies, we encountered more questions regarding the fundamental mechanisms involved in the process. As a result we chose to focus on characterizing the minimum coagulant dose needed to initiate rapid flocculation for two difference coagulants, alum and PAC. We hope to use this data in the future to develop a theoretical framework describing the onset of rapid flocculation. In order to accomplish this goal and to ensure the accuracy of our data we made a number of improvements and modifications to the FReTA apparatus this semester. We are currently in the process of collecting data and hope to complete our planned experiments by the end of the Fall 2010 semester.

Laminar Tube Flocculator, Fall 2012

Patience Ruijia Li

Abstract

According to the predictive occulation model proposed by Swetland et. al., 2012, large ocs do not signicantly contribute to turbidity removal  only small colloids can collide eectively and aggregate to a size that will be removed by sedimentation. Based on the hypothesis that large ocs are useless, a oc breakup procedure was devised. Results obtained using a coiled tube occulator and occulation residual turbidity analyzer (FReTA) shows that higher turbidity removal was achieved after breaking the ocs, comparing to results using the same method but without oc breakup. Therefore breaking ocs at regular intervals to maintain continuous growth will promote better performance of occulation. This research nding provided a good reference for future hydraulic occulator design.

Low Flow Flocculator, Spring 2012

Ryan Anthony, Elyssa Dixon, Zac Edwards

Abstract

Open ow occulators, like those currently used in AguaClara plants, increase in cost for lower ow rates (less than 5 L s ). AguaClara must be able to meet the need of a wide range of community sizes, so scaling the design for low ow plants is crucial. This report specically analyzes three dierent scenarios that use obstructions within a pipe to remove the geometric constraints that cause the errors found in the current designs. Two scenarios include placing semi-circular baes (similar to those in open ow occulators) within the pipe and maintaining the spacing between and above the baes or maintaining the area between and above the baf- es. The last scenario involves placing balls on a string through the center of a pipe. A table is provided within this report comparing critical values for these occulators for a 3 L/s plant. An initial comparison of the three options shows that the scenario that maintains area above and between baes is the most eective with materials. However, discrepancies with calculations in the approach using balls as obstructions ultimately yields the results inconclusive.

Floc Recycle Venturi, Spring 2012

Ryan Anthony, Elyssa Dixon, Zac Edwards

Abstract:

The purpose of a venturi is to create a low pressure zone in the contraction of a pipe that can be used to pull􏰄fluid from another location into the existing 􏰄ow against the force of gravity. AguaClara can use this technology to implement floc recycle and decrease the necessary size of the flocculator. A pipe will transport heavily flocculated and turbid water from the floc hopper in the sedimentation tank to the horizontal section of the rapid mix pipe that leads into the flocculator. A venturi constructed in this horizontal portion of the rapid mix pipe will pull this turbid water from the floc blanket into the incoming plant flow and thereby increase the incoming turbidity. The flow of the turbid water transported from the floc blanket to the rapid mix pipe is dependent upon difference in head at the end of the system compared to the head in the throat of the venturi. By recycling the turbid water, a greater floc volume fraction will be present at the beginning of the flocculator to increase collisions and thereby reduce the amount of time that the water must spend in the flocculator; this, in return, will reduce the size of the flocculator and reduce material and construction costs.

Turbulent Tube Flocculator – Summer 2013

Felice Chan, Brooke Pian, Amanda Rodriguez, Greta Schneider-Herr

Turbulent Tube Flocculator – Fall 2013

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.

Floc App - Spring 2017

Christian Rodriguez, Anthony Verghese, Deniz Yilmazer

Abstract:

Turbidity measurements provide the primary source of performance monitoring at many water treatment plants. Turbidity provides an excellent way to measure overall plant performance, but it fails to provide insight into the specific processes that make up the plant. The earliest reduction in turbidity in an AguaClara plant occurs after the sedimentation tank with a time delay of 30 to 45 minutes. This delay makes feedback control challenging especially when raw water turbidity varies rapidly. The floc size and count app comes in to fill this shortcoming by providing an easyto-use desktop application to measure floc distribution in various parts of the plant. The floc app can measure floc size distribution of the flocculated water to characterize flocculation efficiency. Flocculation residence time is expected to be less than 5 minutes in the next generation of AguaClara plants and this will significantly reduce the feedback time to provide guidance for setting the plant coagulant dose.

Laminar Tube Flocculator - Summer 2013

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.

Laminar Tube Flocculator - Spring 2013

Margaret L. Fleming, Patience Ruijia L

Full Scale Floc Breakup - Spring 2013

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.

Countercurrent Stacked Floc Blanket Reactor, Fall 2016

Surya Kumar, Christine Leu, Amlan Sinha, Cindy Dou

Abstract

Floc blankets, which are suspended layers of highly concentrated flocs, have the potential of being a more efficient option for removing arsenic, fluoride, and certain dyes in terms of energy and water consumption than currently employed techniques. For floc formation, a coagulant needs to be added to the water, allowing particles to adsorb to each other when they collide. Previous research has shown that the coagulant, polyaluminum chloride (PACl), has properties that allow arsenic, fluoride, and certain dyes to adsorb to its surface. The first iteration of this research used three floc blankets in series with a counter-current flow of contaminated water and flocs. By feeding flocs from the last reactor into the second, and from the second into the first, the PACl’s surface area can be saturated. To test this theory and apparatus, a dye, Remazol Brilliant Blue R (RBBR), was chosen to be the contaminant due to its less toxic nature and visual component. With this apparatus and contaminant, this semester’s goals were to test dye removal efficiency from water with varying concentrations of clay, PACl, and dye. With a 1:1 ratio of PACl to dye, a dye removal efficiency of roughly 80% was achieved. However, the transportation of flocs from the third reactor to the second and first was not sustainably achieved.

Laminar Tube Flocculator - Summer 2014

Shreya Jain, Tanya Peifer, Nadia Shebaro, and Luke Zhu

Abstract:

Over the summer of 2014, the laminar tube flocculation team has worked to test AguaClara's new residual turbidity monitoring system, SWaT, as compared with prior teams that used FReTA. The group has also implemented PID control for the laminar tube flocculator to regulate the amount of clay added to the system. In order to achieve these goals, the laminar tubing system was simplified and reconfigured to eliminate the feedback loop with the turbidimeter. The team plans to continue optimizing the system and confirming the self regulating controls were working before starting experiments using varying dosages of coagulant.

Laminar Tube Flocculator - Spring 2014

Victoria Chou and Yining Dai

Abstract:

Flocculators are an integral part of the water treatment process. The􏱕focculation process turns the colloidal matter within water into flocs that will eventually be removed through the sedimentation process. The creation and eventual settling of flocs formed in the flocculator results in cleaner, clearer water. According to Swetland et al.'s hypothesis, flocs that reach a certain size are no longer effective in removing colloids be- cause the shear on the surface of the flocs becomes too high for the colloids to attach. Thus, by breaking large flocs, they may regrow and scavenge additional small colloids that were not able to settle out from the suspension. The purpose of this series of experiments is to continue testing the Floc Breakup Theory and, if valid, to determine the most effective way to break up flocs in order to have the highest removal rate of colloidal particles. The settled water turbidity analyzer (SWaT), a new turbidity measurement system, was designed and implemented for the Spring 2014 research, in which the effluent water first travels through an angled tube settler with continuous 􏱕ow before being analyzed by the effluent turbidimeter. A base case test was run to serve as a control showing residual turbidity with the new turbidity measurement system. Adjustments to the new setup were made to accommodate for issues that arose from the new turbidity measurement system.