In Honduras, a Calcium Hypochlorite solution is used in the Agua Clara flow controllers to chlorinate the drinking water. Unfortunately, due to the precipitation of calcium carbonate, the system clogs, which leads to large decrease in the flow rate (and thus dosing) of the chlorinating solution. The goal of these experiments were to find the contributing factors to failure (significantly decreased flow rate) by modeling a hypochlorinator in use in Honduras.
Monica Hill, Aditi Naik, Ritu Raman
The Summer 2010 Chemical Dose Controller (CDC) Team has spent the summer exploring the challenges associated with manufacturing precise orifices. The team has run a series of tests measuring flow rate on orifices created from Legris polyamide, flare cap fittings, refrigerator caps, and carburetor jets to determine their precision and accuracy. The orifices manufactured from polyamide were deemed inadequate, which caused the team to consider in- house and off-the-shelf manufactured orifices created from brass, which showed much lower deviations from the expected flow rate. This report describes the results of the team's experiments on four different types of orifices and endeavors to set future goals for next semester's CDC Team.
Abstract
Accurate alum dosing is vital for plant operation as it has a great impact on the effectiveness of flocculation and sedimentation. The nonlinear chemical dose controller (CDC) is designed to handle turbulent flow chemical dosing used in conjunction with the newly designed Rapid Mix Tube. In contrast, the linear CDC requires that the chemical flow in the dosing tube is laminar.
The linear CDC uses the linear relationship between laminar flow and major losses in the doser tube to maintain a constant chemical dose with varying plant flow rates. However, when the flow in the dosing tube is turbulent, the linear relationship no longer exists. In this case, a nonlinear CDC, one that uses minor losses to control flow rates, can be used to maintain a constant chemical dose with the varying plant flow rates. By using an orifice to control chemical flow, the CDC will have the same nonlinear response to increasing flow as the plant flow rate, which is controlled by an orifice. A dual scale system on the lever arm will increase accuracy in dosing at smaller doses.
Figure 1 shows a conceptual design of the dosing system. A float in the entrance tank is connected to one end of the lever arm and allows for the arm to move up or down based on varying plant flow rates. As plant flow rates increase, the float rises, and the lever arm connecting the dosing orifice falls increases the elevation difference between the constant head tank and dosing orifice to power chemical flow. As the flow rate decreases the elevation difference decreases and the chemical flow rate slows down.
Figure 1: Nonlinear chemical dose controller schematic
There are two dosing tubes coming out of the constant head tank each with a different size orifice fitting attached to the end. The two different sized orifices allow for the plant operator to dose alum at two different scales, a high and low scale. The operator will choose which orifice will be used based upon the desired alum dose the operator wishes to apply to the water, a parameter that depends on raw water characteristics. The two scales on the lever arm, as seen in Figure 1, correspond to one of the dosing tubes; for instance, the higher scale (20-100 mg/L) will be used when the larger orifice size is needed. The dosing tube which is not in use is merely lifted to a higher elevation than the constant head tank level and is clipped onto a hook to prevent the flow of alum through this unused orifice.
After the alum exits the dosing orifice it flows down through a rigid tube which then injects the alum over a rapid mix conduit which connects the entrance tank and the flocculator. The rapid mix tube has two orifices which create macro and micro eddies to ensure the uniform distribution of coagulant into the raw water.
Eva Luna, Drew Hart, Larry Lin, Roy Guarecuco
The Fall 2010 Chemical Dose Controller team has focused on designing the dose controller to be visually accessible, more aesthetically attractive, and robust. The apparatus will be mounted on a plywood board secured to the plant wall. The team has begun construction on a prototype for the design. In this report we have documented the design process and all of the component parts used in the prototype.
Matthew Higgins, Adam Salwen, Christopher Guerrero
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.
Matthew Higgins
Accurate chemical dosing in water treatment plants is imperative to ensure optimal efficiency during flocculation, sedimentation, filtration and disinfection. AguaClara designed the linear chemical dose controller (LCDC) and linear flow controller (LFC) systems to allow plant operators to reliably set and maintain a desired dose of coagulant and disinfectant. A linear relationship between head loss and chemical ow is created by using the major head loss through a small diameter tube to control the flow. To maintain this linear relationship, the systems have been designed to eliminate sources of minor head loss. Our team is actively working to minimize minor head losses through the systems, reduce the systems' maximum percent error and standardize the components and calibration techniques to be used to fabricate the systems in the field.
Jordanna Kendrot and Frank Owusu-Adarkwa
Continuous and accurate chemical dosing in water treatment plants is required for optimal efficiency during flocculation, sedimentation, filtration and disinfection. AguaClara designed the linear chemical dose controller (LCDC) and the Linear Flow Controller (LFC) systems to allow plant operators in Honduras to easily set and maintain the dose of coagulant and disinfectant through one system. A linear relationship between the head lost and chemical flow is created by using only major head loss, where the flow is controller by a small diameter tube. To continue using this linear relationship, the current experimental system has been designed with the goal of eliminating minor head loss. Our team is actively working towards the continuation of this work, decreasing the minor head losses throughout the systems, reducing the systems maximum percent error under 10% and standardizing the components and calibration techniques that will be used to fabricate this system in the field.
Matthew Higgin, Adam Salwen, and Christopher Guerrero
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.
Frank Owusu-Adarkwa, Julia Mertz, Ruju Mehta
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.
David Buck, Andrea Castro, Rudra Koul
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 chemicalflow rate with respect to changes in the plant flow rate can be attributed to the weight of the drop tube assembly.
Zeyu Yao, Saugat Ghimire
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 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 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 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.
Andrea Castro, Kent Chan, Saugat Ghimire
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.
Zeyu Yao, Saugat Ghimire
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 sandfilters 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.
Annie Cashon, Jeanette Liu, Christine Leu
The Chemical Dose Controller is a device that maintains a constant chemical dose as the plant flow rate changes. This semester, the Chemical Dose Controller team has started doing research on chlorine compatibility with the constant head tank. Part of this assignment includes exploring alternative CHT designs in hopes of maximizing durability and efficiency while minimizing costs. The team is also considering scaling the CDC system down by looking into the single lever arm design. The team has begun recording these adjustments in a CDC assembly manual for future CDC teams that includes photos and item lists. Finally, the team has reached out to the team in India, in hopes of working out a cost effective and reliable system for future shipments.
Serena Takada
This semester, the Chemical Dose Controller (CDC) Team improved the AguaClara Automated Design Algorithm by updating the CDC drawing file to reflect recent updates in the CDC system design. Updating the CDC drawing code will allow clients and team members to obtain an accurate design of the current AguaClara plant designs using the AguaClara Design Tool. When 1 the existing CDC drawing code was implemented with the most uptodate drawing at the beginning of the semester, AutoCAD outputted the design illustrated in Figure 2. As shown in Figure 2, with the existing code, the CDC system is located inside of the Flocculator even though it should be mounted on the outside wall of the Flocculator. This was the starting point of the challenge. By the end of the semester, the CDC dosing system and lever arm were mounted against the Entrance Tank and Flocculator wall.
Zeyu Yao, Saugat Ghimire
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
Andrea Cashon, Saugat Ghimire, Jeanette Liu
The Chemical Dose Controller team completed the design and fabrication of the single lever arm assembly. This assembly will be utilized in low flow plants that only require a chlorine doser. The new Chemical Dose Controller maintains the same functionality of the previous model. It will also be chemically resistant and require fewer materials, lowering fabrication and shipping costs. The team also created a float valve for the constant head tank that has fewer corrosive metal components and has the floatin line with the orifice. The team has created a new height adjustment system for the constant head tank and a dosing tube air removal system that utilizes a wye channel. Additionally, the entrance tank float was redesigned to be smaller and lighter, for easier and cheaper shipping. Finally, the team created an items catalog that contains every single component - and it’s corresponding McMaster-Carr identification number - used in a Chemical Dose Controller system. This catalog will help future Chemical Dose Controller teams order components and construct new systems.
Whatever it is, the way you tell your story online can make all the difference.
Annie Cashon, Christine Leu, Auggie Longo
The Chemical Dose Controller is a device that maintains a constant chemical dose as the plant flow rate changes. After working alongside the foam filtration team in El Carpintero, Honduras this past January, the CDC team has changed the lab set-up to be more reflective of the systems in the field. Specifically, the major head loss element was changed to be vertically-oriented instead of horizontal to decrease the footprint of the CDC system. During the Spring 2015 semester, the CDC team will run a variety of experiments with the new system including head loss testing, determining flow breakpoints, and testing units at stock concentrations. In addition to testing the system through a variety of experiments, several design changes will be looked into this semester. This included tasks such as making the constant head tank from locally available items in Honduras, as well as making the constant head tank chlorine resistant. Finally, the team is compiling a system of equations to convert the CDC system into a modular, packaging item for future shipment. With design changes in mine, a major goal of the CDC team this semester will be to create an assembly manual and parts-list.
Cynthia Chan, Anna Doyle, Ashish Sangai
The Linear 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. Past CDC teams worked on improving the the design of the Constant Head Tank (CHT), and making the CDC system modular. This semester the CDC team redesigned the CHTs so that all four tanks were connected to each other, and so that the calibration columns were attached to the CHT module. Additionally, the team recreated and modified the modulat CDC system designed in past semesters to address the goals of being fully chemical resistant, compact, and simple in operation and maintenance. The new CHT will be demonstrated and eventually implemented in Honduras.
