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.

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.

Flocculator Efficiency, Fall 2015

Mallika Bariya, Tanvi Naidu, Chae Young (Flora) Eun

Abstract

The Fall 2015 Flocculator Efficiency subteam worked on designing, developing, and testing a flocculator model that optimizes the vertical­flow flocculator used in AguaClara water treatment plants. The team addressed the accumulation of low­shear regions of water above the top of the lower flocculator baffles, a phenomenon that creates a “dead” region in which collision potential for the creation of flocs is very low. Dead zone formation occurs due to a decrease in fluid velocity as water transitions from the bottom of the flocculator to the top and as it flows over the lower baffles. The team hypothesized that compressing the water flow would increase the fluid velocity and, as a result, allow the water to flow at a higher trajectory over the lower baffles and reduce the formation of dead spaces. Furthermore, the addition of an extra contraction and expansion would create more turbulence in the region above the lower baffle and increase collision potential. This issue was addressed by installing obstacles in the form of slit pipes at the tops of the lower baffles. Test results with these features showed that the obstacles were able to compress the flow and consequently increase the fluid velocity and turbulence in the ‘dead zone’ region. The team measured and observed the results of this design feature by testing the model through flow visualizations using a red dye tracer. Among the variables tested, the best desired effect was observed with a restriction of 78% of channel width, for both laminar flow and potentially turbulent flow (Re= 3000). With a 60% restriction, the formation of a circulating region was observed, although this eventually cleared up. There is a need for further research on how the geometry of the obstacle might be impacting this phenomenon.

Turbulent Tube Flocculator, Spring 2014

Felice Chan, Jonathan Christensen, Stephen Jacobs, Ana Oliveira

Abstract

Since the Summer of 2013, the Turbulent Tube Flocculator team has been developing and optimizing a design for a lab scale turbulent tube occulator to better mimic the processes that occur at full scale plants. From this, a vertical occulator of approximately 1.5 m was constructed with 30 coils of exible tubings connected with pieces of metal pipe. Currently, the team is working on the rest of the experimental setup, which involves pumps, turbidimeters, pinch valves, clay stock, temperature and pressure sensors, Settled Water Turbidity analyzer (SWaT), rapid mix, and Process Controller software. Clay will be added directly to the head tank to keep the suspension stable in absence of coagulant. The coagulant, injected immediately following rapid mix, is responsible for aggregation of suspended particles present in the solution. Experiments will measure turbidity reduction as a function of coagulant dosage.

Turbulent Tube Flocculation, Summer 2014

Shreya Jain, Tanya Peifer, Nadia Shebaro, Luke Zhu

Abstract

Over the summer of 2014, the turbulent tube flocculation team has worked to implement and test a SWaT system for analyzing residual turbidity from the flocculator. The group is also working to implement PID control for the turbulent tube occulator to regulate the amount of clay added to the system. The team made minor physical adjustments to the turbulent occulator through the shortening of tubes and the tube settler position. By the end of the summer research period, the team has established a working occulation system to facilitate experiments done by future teams.

Turbulent Tube Flocculator, Fall 2014

Felice Chan, Mingze Niu, William Pennock

Abstract

Over the fall semester of 2014, the Turbulent Tube Flocculator Team improved the turbulent tube flocculation apparatus in terms of flow control, turbidity control and general structure. The objective of this improvement was to prepare the apparatus by the end of the semester for experimentation. The team made a number of updates this semester, including building a support structure for SWaT and the effluent line. In addition, two air releases were installed as well as a diffuser system in the constant head tank to eliminate air from the flocculator. In addition to the structural modifications of the apparatus, the team updated the process controller method file for experimentation. The experiments performed on this apparatus will be used to validate the equation derived by Dr. Monroe Weber­Shirk based on the experimental work of Dr. Karen Swetland.

Fluidized Bed Flocculator -Spring 2014

Felice Chan, Jonathan Christensen, Stephen Jacobs, Ana Oliveira

Abstract:

Novel methods of water treatment, that do not use electricity and only require basic construction materials, are in demand worldwide in remote regions without established centralized water treatment. Gravity-driven unit processes must be developed for these water treatment facilities. Current hydraulic flocculators use baffles with dimensions on the order of meters to generate turbulence and achieve particle aggregation. An alternative approach is to use sand grains, rather than large solid sheets, as flocculator baffles. A fluidized sand bed flocculator occupies much less plan view area, but generates much more head loss. Implementation will depend on a balance of the cost of land and materials against the available hydraulic head.

Laminar Tube Flocculator - Spring 2015

Luyan Sun, Tanvi Naidu, Kevin Shao

Abstract:

Research on the Laminar Tube Flocculator in Spring 2015 aimed to validate the results obtained by Karen Swetland with the FReTA system and to further investigate factors that affect the overall turbidity removal. The past semester’s team worked to test the new residual turbidity monitoring system, SWaT, in comparison to the FReTA system and to verify that the new system can obtain similar results to those obtained with the old system. However, the actual coagulant tubing size used in the previous SWaT experiment was different from that in the pump control method file. Because of the incorrect input in tubing size, the PACl dosages were not accurate. The Spring 2015 research derived correction factors that would make the previous date usable. Then experiments were conducted in the SWaT system to finish verifying Karen Swetland’s results. Future works includes experiments to determine if there is an optimal floc size which is small enough to combine with small clay particles yet large enough to be separated in the sedimentation tank. Also, future teams should study how dissolved organic matter (DOM) affects the performance of the flocculator and sedimentation tank. These findings will improve the performance of the flocculator and make it more effective for use in water supply.

Grit Removal Innovation Technologies - Spring 2015

Annie Ding, Mary Millard

Abstract:

The current AguaClara plant design requires a large entrance tank to settle out grit particles prior to the flocculator. Grit removal by horizontal flow sedimentation prevents the settling of these larger particles in the flocculator (a phenomenon that has been observed in several AguaClara plants to negatively affect plant flow and operation). The purpose of the Grit Removal Innovation Technologies (GRIT) team is to redesign the current grit settling system by introducing plate settlers prior to the flocculation unit. In doing so, the plan-view area needed to settle out the grit will be greatly reduced, decreasing construction costs and overall AguaClara plant size. This paper outline the GRIT team’s process exploring plate settler design options that act either as sedimentation units only, or as combined flocculation and sedimentation units.

There is no other literature on the topic of designing such grit removal systems, and not all of the relevant parameters are well understood. The team’s design process has therefore been based on a series of reasonable assumptions and equations currently used in flocculator and sedimentation tank design. Many constraints (detailed in this report) were found to impact the design of the grit removal unit, including grit particle “roll-up” effect, optimal head loss, optimal unit length. In addition to the design of the grit removal unit itself, this team explored the corresponding designs of rapid mix, linear flow orifice meter (LFOM) placement, and coagulant dosing, in order to create a fully integrated system.

Over the course of the Spring 2015 semester, the GRIT team has developed three potential grit removal designs, created visual mock-ups of each, and even sent a detailed design of the best iteration to Honduras for implementation in a small-scale plant. The first iteration, a combined grit removal and flocculator system, integrated grit removal capabilities into the flocculator baffles, but it was rules out early in our design process due to the potential loss of coagulant to grit (as coagulant would be dosed before grit would be removed), inefficient use of space, and construction and cleaning impracticalities. The second and third iterations were both based on the idea of creating a tightly packed series of plate settlers (we call this a Grit Removal Unit, or GRU), analogous to the ones used in current sedimentation tank design, used before the flocculation process and designed to settle out grit specifically. The second iteration placed this GRU inside the entrance tank, while the third iteration placed it within the first flocculator channel. After analyzing space need, flexibility of design, and capacity for rapid mix/coagulant dosing integration, the third iteration was chosen as the optimal grit removal design and is well on its way to being constructed in Honduras!

Fabrication: Floc Hopper Probe - Spring 2016

Miguel Castellanos

Abstract:

The floc hopper probe is a devise that is meant to locate the height of the sludge blanket in the floc hopper of AguaClara water treatment plants. Teams in the past have conducted research and eventually fabricated a working probe prototype that was transported down to Honduras in January 2016. The probe was tested at different treatment plants in Honduras and showed promising results with minor complications. This semester, one of the main objectives is to re-size the probe in order to ensure that it is able to enter the PVC pipe port that is in the sedimentation tank channel system. Furthermore, the team will look into making the design more professional while keeping it cost effective.

Note: The final report for this subteam for this semester was not available and the final presentation is linked instead.

Floc Size and Count App - Spring 2016

Christian Rodriguez, Anthony Verghese, Deniz Yilmazer

Abstract:

Turbidity measurements provide the primary source of performance monitoring at many water treatment plants. However, turbidity readings of floc suspensions do not provide any insight into the performance of subsequent treatment processes. The Floc Size and Count App team’s aim is to create and easy-to-use personal computer application that could measure floc size distribution using a digital camera with appropriate magnification. The app will be written in LabVIEW. The aim for this semester is to develop coding expertise in the LabVIEW environment and start working on the app that will be used in the AguaClara labs and eventually in AguaClara drinking water treatment plants.

Floc App - Fall 2016

Christian Rodrigues, 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 does not provide insight into why the water treatment plants are performing well or poorly. The floc size and count app team’s aim is to create and easy-to-use desktop application that would measure floc size distribution and potentially provide insight as to why a plant is performing well or not. The app will be written in LabVIEW and made available for easy use as a stand alone executable application. The aim for this semester is for the team members to finish the LabVIEW program, integrate the program with a camera system, and have other teams test the camera system and software. By the end of the semester, we hope to have a functional prototype than can be tested by other AguaClara Teams in their experiments.

Contact Chamber - Fall 2017

Cheer Tsang, Yeonjin Yun, Ben Gassaway

Abstract:

The introduction of coagulant into turbid water causes collisions of suspended particles with coagulant nanoparticles, which promotes the growth of flocs. However, a large portion of the coagulant dose adheres to pipe walls rather than influent particles, requiring a higher than necessary coagulant dose to account for this effect. In order to minimize coagulant waste, an apparatus called the contact chamber was fabricated to increase collisions between influent particles and coagulant. The Fall 2017 Contact Chamber team analyzed the performance of the contact chamber by comparing influent and effluent turbidity in experiments with and without a contact chamber. After several trials, it was concluded that the contact chamber did not improve the effluent turbidity. In fact, the effluent turbidity with the contact chamber was significantly greater than the effluent turbidity without the contact chamber.

High G Flocculation - Fall 2017

Roswell Lo, Tanvi Naidu, Luna Oiwa

Abstract:

The High G Flocculation team this semester designed an experimental set-up to test the effects of velocity gradient (G) in a flocculator and to determine the optimal G value based on flocculator performance in terms of effluent turbidity. The G value was varied in different trials by varying flocculator flow rate while controlling for coagulant dosage, influent turbidity, flocculation tube length, and upflow velocity through the sedimentation tank. G_theta was kept constant as around 20,000. The constant sedimentation tank upflow velocity was achieved using a waste stream between the flocculator outlet and sedimentation tank. It was found that for a standard coagulant dose, lower G values were associated with lower effluent turbidity, with 100 Hz being the lowest value tested. The same general relationship was observed for a higher coagulant dose, except that the lowest G values resulted in higher effluent turbidity due to floc blanket collapse. Data from this study will be used in the future to inform the geometry of the flocculator, i.e. the optimal distance between baffles in a full-scale water treatment plant.

Sensor Development - Fall 2018

Dana Owens, Lawrence Li, Lois Lee

Abstract:

The objective of the Sensor Development subteam is to develop sensors to monitor water quality during the water treatment process in Aguaclara plants. In previous semesters, the subteam developed a working prototype for an in-lab fluidized bed solids detector and also made progress towards prototyping a submersible sludge blanket detector. This semester the subteam also worked on finalizing a product-level version of the in-lab fluidized bed solids detector with a more intuitive user interface.The subteam will also work on finishing and determining the best prototype for the sludge blanket detector.

Sensor Development - Spring 2019

Lois Lee, Lawrence Li, Srilekha Vangavolu, Sonu Kapoor

Abstract:

The Sensor Development subteam’s goal is to develop low-cost sensors with readily available materials to monitor and report water quality in the water treatment processes in AguaClara plants and labs. In Spring 2019, the subteam worked on four different projects. The subteam started developing a calibration curve for the Fluidized Bed Solids Detector that was fabricated in the previous semester, and also prototyped a Sludge Blanket Detector for the upcoming Honduras trip. Additionally, the subteam began developing the Mobile Application-Processed Endoscope. The subteam also started designing a low-cost turbidimeter that would measure both the transmittance and absorbance of light.

Sensor Development - Fall 2019

Sonu Kapoor, Saul Bernaber, Rishik Zaparde

Abstract:

Sensor Development's goal is to develop affordable sensors with readily available materials to monitor and report water quality in the water treatment processes in AguaClara plants and labs. In Fall 2019, the subteam worked on two different projects that were slight modifications from the previous semester. The subteam worked on a second prototype of the submersible Sludge Blanket Detector. Additionally, the subteam also started designing a low-cost turbidimeter that would measure the amount of dissolved organics as well as turbidity.