EStaRS, Fall 2012

Mihir Gupta, Kris LaPan, Rachel Proske

Abstract:

The use of filtration units for the treatment of drinking water is a common practice in engineering design. However these units are generally used for the treatment of large volumes of water. To improve upon this limitation, a stacked rapid sand filter was designed for low 􏰃ow rates. Work for the semester began with an existing filtration unit which did not contain sand, due to predicted failure from large head losses in filtration and backwash. The existing design was modeled in AutoCAD 2013 to provide an illustration of the system. Updates to this drawing were completed and will continue to be as fabrication phases occur. One of the primary tasks was to develop a mathematical model in MathCAD to calculate the flows and head losses throughout the system. The model was completed for filtration and backwash, and includes calculations for both cycles with and without sand present. Hydraulic testing was completed to determine the head losses in filtration and backwash, risk of sand transport through the backwash pipe, and 􏰃ow rates. These measurements and observations were compared with the mathematical model to determine its validity. According to head loss values obtained from the mathematical model, several changes were made to the filter prototype. Such fabrications included complete reconstruction of the backwash pipe, changing of valve types, and installation of NPT fittings and ball valves. Finally performance testing was completed to determine the effectiveness of the prototype in regards to decreasing effluent turbidity. Overall, it was determined that the filter prototype is highly effective at decreasing turbidity for several influent concentrations at the designed flow rate.

High Rate Sedimentation - Fall 2016

Ziwei (Vanessa) Qi, Aimee Owens, Ruizhe He

Abstract:

The Fall 2016 High Rate Sedimentation team investigated the effect of high upflow rates on maintaining a dense floc blanket and functional plate settlers. The team built a small-scale flocculator and tube model of the sedimentation tank in order to simplify the many experiment variation configurations.To analyze variables that effect effluent turbidity at an up- flow velocity of 3 mm/s, which is roughly triple the standard AguaClara rate. Experiment 1 varied length of the tube settlers, Experiment 2 varied length of the floc blanket, and Experiment 3 attempted to increase the density of the floc blanket by adding mass. Experiments have verified that longer tube settlers and longer floc blankets improve sedimentation tank performance.

Fluoride - Spring 2018

Philip Akpan, Tigran Mehrabyan, Desiree Sausele, and Victoria Zhang

Abstract

The Fluoride subteam seeks to develop a sustainable, inexpensive fluoride removal system for implementation in upcoming AguaClara plants located in India. Using the apparatus developed by previous semesters, the team continued running experiments testing how various concentrations of PACl affect fluoride removal. However, complications with the ability to measure fluoride concentrations required the team to shift its goals to designing a lab scale, gravity-powered system. The team finalized a design and completed construction of the new, electricity-free apparatus. The team plans to run experiments to test its fluoride removal capabilities after ensuring that there are no remaining water leaks.

Fluoride Floc Blanket - Spring 2017

Fluoride Auto — August Longo, Briana Li-Vidal, Michelle Cheng, Victoria Zhang

ABSTRACT:

The Fluoride subteam seeks to develop a sustainable, inexpensive fluoride removal system for implementation in upcoming AguaClara plants located in India. After earning an EPA Phase II grant for the Spring 2016 fluoride removal reactor, the subteam seeks to improve fluoride purification by testing lab-scale systems to compare a single reactor with reactors in series. At the beginning of this semester, the subteam identified potential issues with floc buildup at the bottom of the reactor. Thus, a sloped plane bottom geometry was incorporated into the reactor system to encourage recirculation of the flocs. Additionally, experiments with high concentrations of PACl resulted in clogging of the apparatus due to PACl buildup. Clay was incorporated into the influent stream to abate this PACl buildup. Initial testing of fluoride removal with the updated one and two reactor systems provided results that seem to indicate slightly better fluoride removal efficiency with two reactors, but more data collected by future testing is required to make a concrete conclusion

EStaRS - Spring 2015

Sarah Bolander, Skyler Erickson, Liza Johnson, Subhani Katugampala, Lilly Mendoza

Abstract:

The Spring 2015 EStaRS team built upon the work of previous semesters to optimize the original filter design as well as to develop alternative strategies to sections of the filtering process. Over the course of the semester, the team altered the process for attaching the filter cap in order to prevent future cases of blow­off, adjusted the system for controlling water level height during backwash, and ran tests on filtration efficiency. While at the beginning of the spring semester the team’s goals also included developing a method of testing and recognizing bed fluidization within the filter, looking into a method of running multiple filters in parallel, and setting parameters for backwash duration and frequency, the team changed directions and concerned itself with the implementation of a new filter injection system to combat the problems associated with using slotted pipes.

EStaRS - Fall 2015

Skyler Erikson, Lilly Mendoza, Natalie Mottl, Lishan Zhu

Abstract:

The Fall 2015 EStaRS team reworked the lab scale setup of the EStaRS filter to work without a large pool to preserve lab space. The team then finished the orifice inlet implementation that was begun in Spring 2015, and provided an operating procedure for both filtration and backwash to avoid trapping sand in the inlets during the transition. The biggest takeaway from the operating procedure is that orifices can be operated successfully as long as the backwash transition does not create a drastic pressure change. Slowly closing the gate valve on the backwash siphon provides a gradual change and does not trap sand in the inlets. This procedure was the result of numerous inlet cloggings, and thus the team also devised a method for unclogging inlets without disassembling the filter. The team also implemented a pressure sensor to track headloss accumulation through the filter bed in the entrance tank. This pressure sensor was used to measure a clean bed headloss which is very close to the design clean bed headloss.

Fluoride - Spring 2016

August Longo, Pooja Desai, Katie Dao

Abstract:

In many developing countries, high levels of fluoride in groundwater have been found to have chronic effects on bone health. Though some countries intentionally add fluoride to water in order to strengthen teeth, overexposure to fluoride has grown as a problem worldwide. The Fluoride team has been working to solve this very issue, by testing and developing a fluoride removal system fit for AguaClara plants in India and Honduras. In spring 2016, the Fluoride team built on the previous work of the Fluoride and Countercurrent Stacked Floc Blanket Reactor team to create a more optimal and efficient fluoride removal system. In the fall, the Fluoride team worked to understand the efficiency of fluoride removal using polyaluminum chloride (PACl) while the CSFBR team developed a reactor system to remove undesirable soluble particles. This semester, a new system was built consisting of a single floc blanket formed using PACl and clay. In the future, this system will be optimized by changing flow rates and dosages to better understand fluoride treatment and optimize AguaClara plants for fluoride removal.

High Rate Sedimentation - Summer 2017

Christopher Galantino and Andrew Kang

Abstract:

The High Rate Sedimentation team designed, fabricated, and experimented on various sedimentation designs with an upflow velocity of 3 mm/s while maintaining a efficient effluent turbidity and reducing cost and space. Working off where the Spring 2017 team left off, the HRS team continued to research the effects of floc blanket height, tube settler length, varying geometries, and the size-driven floc blanket formation hypothesis. The HRS team concluded that the height of floc blanket may not provide better performance, as originally thought. Also, it has been concluded that the Trapezoidal geometry is not necessary, but provided insight on the behavior of floc on bends.

Filter Constrictions - Spring 2017

Jillian Whiting, Janak Shah, and Samantha He

Abstract:

The goal of the Filter Constrictions Team was to test the hypothesis that particles are captured preferentially at flow restrictions in sand filters. There was evidence for this from work done by the Milli-Sedimentation Team and the Stacked Rapid Sand (StaRS) Filter Theory Team. The goal of the team was to create a flow constriction in a 0.5 mm channel in a flow cell reactor, and take a video of the particles at the constriction. The video was taken using Point Grey FlyCapture Software, and provided evidence about the hypothesis that flow constrictions serve as particle collection sites.

StaRS Filter Theory - Fall 2017

Lucinda Li, Liz Cantlebary, Lingzi Xia, Dylan Vu

Abstract:

Sand filters have historically been used to lower the turbidity of water, and continue to be used in many conventional water filtration systems. Dynamic modeling, as opposed to static modeling, of rapid stand filtration accounts for the buildup of particles over time in the filter, and this un- derstanding is needed for better filter design and operation. Past sub-teams found that head loss increases linearly with time. This research proposes the hypothesis that flocs are captured in rings created by filter grains, which on a larger scale implies an active filtration zone where empty pores become clogged by the flocs. This active zone moves throughout the bed until there is no remaining space for particles to clog. This research will examine major and minor head loss, along with efflu- ent turbidity, to find optimal filter performance based on varying flow rate, coagulant dosage, and influent turbidity in a 1.967m L/s sand filter. Based on this research, it is hypothesized that the sand bed can filter a certain amount of mass before failing.

StaRS Filter Theory - Spring 2018

Alison Valibuena, Liz Cantlebary, Dylan Vu

ABSTRACT:

Sand filters have historically been used to lower the turbidity of water and are still used in conventional filtration systems. The research in this report is based on the hypothesis that flocs are captured in rings created by filter grains, which implies there is an active filtration zone where empty pores become clogged by the flocs. This active zone moves throughout the bed until there is no remaining space for particles to clog. This research examines the factors that influence the time it takes for the filter to clog. Several key factors affect the failure time including size and density of flocs and were explored through experiments with different coagulant doses and with a constriction placed before the filter.

Unit Process Analysis pH - Fall 2019

Floc pH — Justin Lee, Jena Rozanski, Rafaella Bruzual

ABSTRACT:

The Unit Process Operations pH subteam wanted to explore the performance of the AguaClara sedimentation tank as a function of pH. Filtration within the sedimentation tank is complex and the performance is often a factor of floc blanket. When the coagulant dosage exceeds a certain amount, the pH probe will be coated with coagulant, leading to inaccurate pH measurements within the plant. Therefore, the team wanted to determine this coagulant dosage and use that value as the constant coagulant dosage for all experimental trials. The team hopes to use this information to uncover new insights on how filtration performance changes in different pH ranges.

StaRS Filter Theory - Fall 2019

Wenjie Lu, Claire Kenwood, Kelly Ly

ABSTRACT:

StaRS (Stacked Rapid Sand) Filtration is crucial to the water treatment process. As one of the last steps in AguaClara’s water treatment, StaRS filters are responsible for removing the last of the unwanted particles. In order to operate effectively under EPA standards, the filters must reduce the turbidity to 0.3 NTU or less. In efforts to better refine the AguaClara filters, variables such as grain size, the height of the active zone, coagulant dosage will be tested in order to increase the failure time. At the beginning of experimentation, the Fall 2019 StaRS sub-team will focus specifically on the grain size.

StaRS Filter Theory - Spring 2019

Barbara Oramah, Lainey Reed, Pablo Alonso Alguacil and Ronya Strom

ABSTRACT:

Stacked Rapid Sand (StaRS) Filtration is the last stage in an AguaClara treatment plant. The filters are used to further reduce the turbidity of water to meet EPA standards of 0.3 NTU or less. As a whole, the StaRS sub-team is working to develop a mathematical model to describe sand filtration. This semester, the StaRS Filter Theory team worked towards running experiments with the three newly constructed StaRS filters with varying sand grain sizes. This research will show the extent to which sand grain size has an effect on filter performance.

Fluoride Automated System - Spring 2019

Fluoride Auto – Dominic Grasso, Melissa Louie, Desiree Sausele, Emily Spiek

Abstract:

The Spring 2019 Fluoride Auto subteam aimed to determine the optimal dosage of polyaluminum chloride (PACl) needed to precipitate fluoride ions out of influent water to meet the World Health Organization’s drinking water standard for fluoride concentration (1.5 mg/L). The team accomplished several fabrication tasks, including lengthening the flocculator used by the Fall 2018 subteam and constructing a new sedimentation tube. The team tested the new apparatus with PACl and red dye to visually determine that it worked properly and that aggregated particles (flocs) were exiting the tube through the floc weir. The team then aimed to run experiments with fluoride but experienced difficulty calibrating the fluoride probe. Upon acquiring a new probe in the future, the team will analyze fluoride removal efficiency using the Langmuir Adsorption Model.

Fluoride - Fall 2019

Fluoride Auto — Sarah Huang, Cindy Jin, Melissa Louie, Emily Yueh

Abstract:

The World Health Organization estimates that globally over one million people face adverse health consequences due to fluoride contamination of drinking water. The current state of fluoride removal technology is not suitable for water treatment plants, and continuous fluoride removal systems do not exist. The Fluoride team aims to develop a cheap and efficient apparatus to reduce ionic fluoride from contaminated water to a safe level. The Fall 2019 team hopes to redesign the flocculation process to optimize the adsorption of fluoride to polyaluminum chloride (PACl) coagulant and the sedimentation process to minimize PACl-fluoride complexes in the effluent, ultimately producing potable water.

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!

Unit Process Analysis: Coagulant - Fall 2019

Ada Lian, Sarah Paquin

Abstract:

The Fall 2019 Unit Processes Analysis Coagulant (UPAC) team’s objective is to reduce capital and operating costs and improve particle removal efficiency for the AguaClara water treatment process, specifically by analyzing the response of the system to varying coagulant dosage. To analyze the system response, we will run a series of trials on a treatment plant sedimentation model, varying the coagulant dosage and recording observations regarding the effluent turbidity, floc formation, and floc blanket formation. Through this experiment, the team will be able to establish a minimum coagulant dosage, which could lower operating costs, and to learn valuable information about the interactions between coagulant and the primary particles of the influent water at high coagulant dosages.

Humic Acid, Kaolin, Floc/Sed Model - Spring 2019

Matthew Lee, Walter Guardado, Carolyn Wang

Abstract:

This semester, samples of HA at 5 mg/L, 10 mg/L and 15 mg/L and concentrations of clay at 10 NTU, 100 NTU and 100 NTU are tested separately to find the respective absorbances. The individual absorbances recorded are used to compare with the mixture of different concentrations of clay and HA to find the additive aspects of the mixture. The results of these tests will investigate how absorbance and spectrophotometry can be used to quantify the concentrations of humic acid and clay in water mixtures. A mathematical model that relates the concentrations of clay and humic acid to the stream's absorbance and turbidity will be developed. This model will increase the capabilities of AguaClara plants and technology in measuring the dirtiness of nearby water sources. The model will also give insight on how efficient and effective current processes are in removing humic acid from water