Flow Controller Linearization and Calibration, Fall 2007

Abstract:

Experiments run in fall 2007 indicated that the float valve can hold back head of at least 8m with less than 0.5 cm of change occurring in the flow controller water level in the first 2 m of pressure. Data gathered in the laboratory on outflow rate has followed a linear model in the laminar flow range, but attempts to model the turbulent transition range have produced varying results. It is considered a high priority to develop a reliable model for dosing at higher flow rates, which will be used in the near future at the larger plants.

Float Valve Attenuation Factor, Summer 2008

Introduction:

Until recently, the float valves used in the AguaClara's flow controllers were slightly flawed. The float valve connector included a compression nut, which was easily misplaced or misused, leading to leaks. A new float valve would preferably have pipe threads and be able to connect to a quick connect tube fitting. Furthermore, the float on the float valve was replaced in favor of another float, complicating post manufacturing assembly. A new float valve was found with pipe threads, quick connect tube fitting and had a more appropriate valve attached. However, before the new float valve was to be implemented, a study on the attenuation factor (change in pressure from stock tank over the change in pressure in the constant head tank) was to be conducted.

Flow Controller Calibration, Summer 2008

Introduction:

The flow controller design tool on the Flow Controller page is used to calculate the tube length necessary to achieve a desired flow rate with a certain head loss. It has been observed that the actual flow rates that occur when using the lengths of tube provided by the design tool were consistently much slower than they theoretically should have been. This indicated that there was some problem with the assumptions made by the design tool. The error was most likely due to one of two things. It was possible that the actual diameter of the tubing being used was slightly smaller than the diameter published by the manufacturer, or that there were significant minor losses in the flow controller not being taken into account by the assumption of a linear relationship between flow rate and head loss/tube length. It was decided that rather than having to manually calibrate every new flow controller, it would be better to come up with a new method for finding the tube length needed. The new method would need to take into account the smaller diameter of the tubing and/or the minor losses, and would predict a more accurate flow rate without having to do further manual calculations or having to cut the tube after construction of the flow controller

Chemical Dose Controller Retrofit Designs, Fall 2009

Abstract:

In some AguaClara plants, a surface foam develops at the end of rapid mix. The initial focus of the research was on the chemical conditions required for this surface foam to develop then the focus shifted to the fluid mechanics that make this occurrence possible and the simple retrofit designs that can ameliorate these conditions. In the initial experiments, different chemical conditions were tested for using a series of jar mixers and one-gallon tanks that modeled rapid mix. The first few trials tests ran a constant supply of clay with varying amounts of alum but these did not exhibit any form of surface foam formation. Subsequent trials included organic matter: humic acid, but these only produced large non persistent bubbles. It was not until a stronger surfactant, liquid soap, was added to the baffle spacing that a surface foam with strong persistent bubbles developed. From these experiments it was concluded that air entrainment along with a surfactant in the raw water are the main chemical factors behind surface foam formation.

Upon observing that waterfalls, like the one found in the LFOM, created the ideal fluid dynamic conditions for air entrainment; the second half of the research focused on retrofitting the LFOM at current AguaClara plants. The four designs that were suggested either used a submerged orifice, a vertical surface area or an inclined plane to decrease the velocity of the incoming water through the LFOM. In testing the viability of each design option the three limiting parameters of foam formation from water jets were recognized and documented.

Chemical Dose Controller Surface Foam, Summer 2009

Abstract:

In some AguaClara plants, a surface foam develops at the end of rapid mix. The initial focus of the research was on the chemical conditions required for this surface foam to develop then the focus shifted to the fluid mechanics that make this occurrence possible and the simple retrofit designs that can ameliorate these conditions. In the initial experiments, different chemical conditions were tested for using a series of jar mixers and one-gallon tanks that modeled rapid mix. The first few trials tests ran a constant supply of clay with varying amounts of alum but these did not exhibit any form of surface foam formation. Subsequent trials included organic matter: humic acid, but these only produced large non persistent bubbles. It was not until a stronger surfactant, liquid soap, was added to the baffle spacing that a surface foam with strong persistent bubbles developed. From these experiments it was concluded that air entrainment along with a surfactant in the raw water are the main chemical factors behind surface foam formation.

Upon observing that waterfalls, like the one found in the LFOM, created the ideal fluid dynamic conditions for air entrainment; the second half of the research focused on retrofitting the LFOM at current AguaClara plants. The four designs that were suggested either used a submerged orifice, a vertical surface area or an inclined plane to decrease the velocity of the incoming water through the LFOM. In testing the viability of each design option the three limiting parameters of foam formation from water jets were recognized and documented.

Chemical Dose Controller, Spring 2011

Matthew Higgin, Adam Salwen, and Christopher Guerrero

Abstract:

Accurate chemical dosing is important in water treatment plants to ensure optimal conditions for flocculation, sedimentation and disinfection of the treated water. The linear chemical dose controller uses laminar flow through a small diameter tube to create a linear relationship between head loss and chemical flow. The linear flow orifice meter then maintains a linear relationship between plant flow and water elevation. The linear relationships simplify chemical dosing for plant operators who may have a limited education. Our team is researching the upper-flow limit of the linear dose controller and developing innovative designs to increase the capacity of this system to function in plants with flow rates approaching and above 100 L/s. Furthermore, we are redesigning and simplifying the linear flow orifice meter algorithm to improve its precision and performance in the field.

Chemical Dose Controller, Spring 2012

Frank Owusu-Adarkwa, Julia Mertz, Ruju Mehta

Abstract:

Continuous, accurate chemical dosing is an essential part of AguaClara plant function. Proper dosing ensures effective flocculation, sedimentation, filtration and disinfection. The chemicals that must be added at different points during the water treatment process are coagulant (PACl or Alum may be used) and chlorine. The linear chemical dose controller (LCDC) is a device that the plant operator can use to directly set doses of coagulant and disinfectant based on the flow rate into the plant. Previous LCDC designs have only been configured to add coagulant prior to flocculation. The triple-doser design is capable of adding coagulant before the influent water enters the stacked rapid sand filter and of adding chlorine for disinfection before the treated water enters the distribution tank. The Spring 2012 team is introducing a more sophisticated LCDC device that will allow the operator to set and monitor the two doses of coagulant and the dose of disinfectant, for a total of three chemical doses, on a single dosing apparatus. In order to ensure accurate chemical dosing, we are testing and documenting the calibration of the new LCDC. Ultimately, we will determine a method for the triple-armed dosing mechanism to be built and added to plants on site, putting a focus on simplicity and elegance of design so that the AguaClara LCDC can be constructed with local resources.

Chemical Dose Controller, Fall 2012

David Buck, Andrea Castro, Rudra Koul

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 􏰂ow 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. Previous designs for the LCDC functioned at lower flow rates, but design changes were necessary for increased flows and dosing of two chemicals: a coagulant and a disinfectant. The Fall 2012 team created and refined a prototype of the proposed dosing system design. Also, the team concentrated on system aesthetics by: creating a new counter weight, engraving the lever arm scale, adding an engraved AguaClara logo and anodizing the lever arm assembly. Once complete a refined calibration method was devised and documented and the system was tested for linearity of the chemical dosage with respect to the dosing scale and linear flow orifice meter (LFOM) height changes due to varied plant flow. Both tests resulted in a linear fit with an R2 value of 0.9967 for the chemical dose percent data and an R2 value of 0.9955 for the plant 􏰂ow height data. The maximum percent error in the linear relationship between chemical dosing and dosing percentage was 63%. The maximum percent error in the linear relationship between chemical dosing and the LFOM height change was 34%. Errors were below the desired 10% at all data points except the data point corresponding to the lowest chemical dose, which suggests that the LCDC maintains a linear relationship at higher flows and is less accurate at low chemical flows. Error associated with chemical dosages with respect to the percent dosage can be attributed to the scale being offset from the zero (or pivot) point of the lever arm by approximately two centimeters. Error associated with changes in chemical􏰂flow rate with respect to changes in the plant flow rate can be attributed to the weight of the drop tube assembly.

Ram Pump – Spring 2012

Christine Curtis, Harrison Gill, Teresa Wong

Abstract:

AguaClara plants are driven entirely by gravity. This makes it difficult to provide treated, running water in the plants to fill chemical stock tanks and to provide bathroom service. The Ram Pump sub-team was charged with designing and optimizing a pump to elevate a small amount of water in the plant. The pump works by transferring the momentum from a large amount of water falling a short distance into the potential energy to raise a small amount of water. Initial efforts were focused on designing and building a modular test pump to characterize how ram pumps function and how to optimize performance and ease of construction for specific sites. To accomplish this, we developed a MathCAD document to characterize the testing parameters that we anticipated would most affect the modular pump performance. From these parameters, we were able to collect data regarding cycle time, mass pumped per cycle, and aver- age 􏰃ow of the pump under various configurations. Future teams should explore better data acquisition methods to collect instantaneous velocity data within each cycle. Eventually, decisions regarding the design of the full-scale pump will be made based on experimentation with adjusting these parameters.

Filter Flow Control - Spring 2017

Matt Cimini, Alex King, Tanvi Naidu

Abstract:

The objective for the Filter and Treatment Train Flow Control team (FTTFC team) this semester was to design and construct a weir module that would allow the plant operator to easily redirect sucient flow for filter backwash without shutting o↵ other filters’ flow. The goal of the design was to be easily constructible, easy to operate, strong enough to withstand water pressure and require no calculations for plant use. The team designed several removable weir options and ultimately chose a hinged design. The design is similar to a dog door that will be shut during normal flow and open during backwash. The model was fabricated and tested under conditions simulating a 20 L/s plant. The weir module was strong enough to withstand the flow, was easy to construct and was simple to open and close even with the water pressure against it and therefore was a success. There was some significant leakage around the weir flap. Therefore, construction and design should focus on recommendations for watertightness of the flap if this design is to be used in an AguaClara plant in the future.

Chemical Dose Controller - Spring 2013

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.

Chemical Dose Controller - Fall 2014

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 influent 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 o􏰂 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 fluoroelastomer seals that are more resistant to chlorine 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 sketch-up file has been created and sent to Hancock Precision for fabrication. This new doser will primarily be used in low 􏰄ow plants in India which only require chlorine delivery.

Fabrication - Spring 2015

Stephen Galdi, Natalie Mottl

Abstract:

The team’s task is to test, troubleshoot, and complete the scale model of the weir system developed by last semester’s team. By the end of the semester, the team will create as et­up and video that accurately portrays the behavior of the water through the full scale weir system. The Fabrication Team aims to create a plant that is easier to operate, troubleshoot, and build.

Ram Pump - Spring 2019

Ching Pang, Cheer Tsang, Alyssa Ju, Iñigo Cabrera

ABSTRACT:

The AguaClara Vertical Ram Pump (ACVRP) is an innovation that will enable water to be pumped from lower elevations to higher elevations using the driving force of falling water. The ACVRP improves on a conventional ram pump design by increasing its space efficiency and decreasing its capital cost. Although a prototype had been built, it did not reach its target pumping efficiency. The goal of this semester was to optimize the ram pump efficiency by finding the necessary forces to open and close the valve at the ideal times.

Ram Pump - Summer 2019

Ching Pang, Alyssa Ju

Abstract:

AguaClara plants contain chemical dosage tanks that require water to make liquid chemical stocks. The AguaClara Vertical Ram Pump (ACVRP) is an innovation that elimantes the need for plant operators to manually displace water up to the dosage tanks. Water is pumped from a lower to higher elevation by harvesting kinetic energy from the treated water flowing out to the community's water distribution system. The design is a modification of the conventional ram pump that allows the waste water to be contained within the pump system due to the inline feature of ACVRP. Compared to a conventional ram pump, the ACVRP is more operator-friendly and requires lower capital cost. Teams from past semesters have determined that the previous version of the ACVRP was inefficient due to a significant amount of head loss. The goal of this summer was to reduce head loss in the design and to determine the efficiency of the improved ACVRP.

Ram Pump - Fall 2019

Ching Pang, Alycia Storch, Payton Hunter

Abstract:

Previous Ram Pump teams have created mathematical models describing velocities, forces, flow rates, headlosses, etc. in the AguaClara Vertical Ram Pump (ACVRP); performed experiments to learn more about what actually happens in the system; and have made redesigns to the setup and ACVRP itself to further improve its efficiency, likeliness to an AguaClara plant, and to increase the ease of assembly and adjustment. This semester the team plans to fabricate a new lab setup that integrates the setup into the work bench for a redesign of the ACVRP, and to further explore ways to improve its efficiency. The team has decided on a new design that eliminates the bottom check valve of the ACVRP and the threaded rod and compression spring that it housed and instead includes an extension spring that will be at the top of the head tank. The extension spring will be connected to a hook on the top of the plate with metal wire rope. It is expected that the functionality and process of the ACVRP will not change but making fine-tune adjustements to the initial and final forces of the spring will be easier to make because there will be easier access to the spring. The team created a materials list for the new parts needed and is currently updating the CAD model to reflect the changes. The team plans to construct the new lab setup and ACVRP design and then to perform experiments as well as improve theoretical equations to further optimize the ACVRP.

Fabrication: Constant Head Tank - Spring 2016

Anna Doyle, Valerie Shao, Serena Takada

Abstract:

The main problem with the plastic Tupperware Constant Head Tank (CHT) containers currently used in the the AguaClara water treatment plants is that they are not chlorine resistant so they have to be replaced frequently. This issues was addressed by the fabrication team this semester. New CHTs were designed, fabricated ,and evaluated to determine the best to be implemented at AguaClara treatment plants. The first design was fabricated from clear PVC sheets and constructed using PVC welding; the second was constructed out of a PVC pipe and cap. The two designed were then compared in terms of ease of construction, functionality, and costs. Based on this analysis and the recommendations from the AguaClara engineers, the second design was determined to be the best and will be implemented in future AguaClara water treatment plants.

Chemical Dose Controller - Spring 2017

Annie Cashon, Cynthia Chan, Susan McGrattan, Karan Newatia

Abstract:

The Chemical Dose Controller (CDC) system was designed to maintain a constant chemical dose to the treatment train as the plant flow rate and influent turbidity change. This semester, the CDC team worked on expanding the modular design from previous semesters in order to improve ease-of-use during operation, better access to the system for plant operators, and greater system efficiency overall. The team designed and fabricated a new and improved constant head tank and calibration columns systems. This semester the CDC team also collaborated with the 1 L/s plant sub-team to create a CDC system for low flow rates.