Sedimentation Tank Hydraulics, Summer 2012

Danielle Feng, Jill Freeman, Cari Gandy

Abstract:

In the sedimentation tank of an AguaClara water treatment plant, water flows through the inlet manifold with vertical diffusers that channel the water into the bottom of the tank as a line source. As water exits the vertical diffusers, a semi circular half pipe jet reverser directs the water upward to resuspend flocs to form a floc blanket, or a dense, fluidized bed of particles, in the sedimentation tank below the plate settlers. A floc blanket increases the particle removal efficiency of the sedimentation tank by capturing smaller flocs that would otherwise escape through lamellar sedimentation. A floc blanket also leads to less clean water waste because without a floc blanket, sludge builds up at the bottom of the tank and will require constant draining. While current plant designs use a 0.5” radius jet reverser and centered jet placement, other jet reverser sizes and jet placements were explored to increase floc resuspension and floc blanket stability. A 1.5” radius reverser with asymmetric jet placement was found to be the optimal design for floc resuspension. Floc blanket stability in relation to coagulent dose was also explored, and optimal alum doses for several influent turbidities were determined.

Sedimentation Tank Hydraulics, Fall 2012

Frances Ciolino, Hongyi Guo, Ethan Yen

Abstract:

The sedimentation tank hydraulics team this semester focused on optimizing the floc hopper. Our main goal was to learn more about the floc hopper geometry and reasons for floc blanket failure. We started the semester by looking at the vertical sedimentation velocity. This velocity is controlled by the flow into the tank and affects how fast the particles settle. If this velocity is too high or too low, the sedimentation tank will not form a proper floc blanket.

We also looked into how the plan view area of the floc hopper would effect the floc blanket formation and performance. Changing the size of the floc hopper effects how much of the area allows for up-flow of the water and how much captures the flocs. In our current experiments we are trying different sizes at different wasting rates. We are looking for a size and rate that keeps the plant running efficiently, meaning the least amount of water wasted while keeping the water leaving the plant clean.

One of the ideas we are working on is continuous wasting of the flocs. The idea behind this is to allow for constant removal of flocs instead of collecting the flocs and then manually opening a valve to let them leave the tank. When the wasting rate is optimal, the flocs will be allowed to compact before they are removed so that the least amount of water is lost in the process. Our last experiment looked at finding the proper wasting rate where the rate of particles flowing into the floc hopper is the same as the rate at which the particles are being removed.

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.

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.

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.

Demo Plant, Spring 2012

Sahana Balaji, Muhammed Abdul-Shakoor, Thalia Aoki, Miree Eun, Diana Kelterborn

Abstract:

The AguaClara water treatment process consists of coagulation, flocculation, sedimentation, and filtration, with flow/chemical dose control using gravity. The Demonstration Plant (Demo Plant) is an important educational tool to explain and publicize AguaClara technologies. Currently, a new Demo Plant has been constructed, tested, and documented. This version of the Demo Plant includes a sedimentation tank and a Stacked Rapid Sand Filter (SRSF) as well as a chemical doser and flocculator. The sedimentation tank design is based on the design from the ENGRI 1131 course and includes the formation of a floc blanket. The SRSF shows the new filtration method recently developed by AguaClara. There has also been emphasis on the systematic documentation of both theoretical calculations behind the design and operation of the Demo Plant.

Demo Plant, Summer 2012

Susan Chen, Owen Guldner, Diana Kelterborn

Abstract:

Abstract
The Demonstration Plant (Demo Plant) is an important educational tool to explain and publicize AguaClara technologies. In the Spring of 2012, a new Demo Plant was constructed, tested, and documented which included the two latest AguaClara technologies, a chemical doser and a stacked rapid sand flter (SRSF), as well as the older flocculator and sedimentation tank. However there were still problems with the overall plant layout, the chemical doser, and the SRSF, all of which were dealt with this summer. We completely revised the demo plant structure and system; the SRSF now can completely backwash all four layers, the chemical doser is labeled to include coagulant concentrations, and the overall plant is streamlined for transport and assembly.

Spectrophotometer, Fall 2015

Bryan Melara Sosa & Michael Stella

Abstract:

The goal of this research was to create a spectrophotometer that would efficiently detect red dye concentration in water. Creating a low cost, inline design that would be implemented at each lab station in the AguaClara lab was a priority. Red dye concentration was measured by fabricating a photo sensitive sensor that measured the voltage of different standards of red dye concentration. Then, various red dye standards were tested to calibrate the sensor of the system. The goal of calibration was to check in real-time the efficacy of the AguaClara system (or part of the system under study) by integrating the spectrophotometer with the team’s Process Controller software.

Small Scale Plant Model, Spring 2015

Ed Cheng and Jenny (Ruoyu) Yin

Abstract:

The Small Scale Plant Model Team of Spring 2015 worked to design a clear and portable model of the AguaClara water treatment plant. The current small scale plant model is cumbersome to travel with and difficult to understand for those unfamiliar with AguaClara technologies. After repairing the previous model, the team identified promoting education and awareness the primary purposes of the new model. Representing the water treatment plant in a clear and critical way will be the main objective of the Small Scale Model Team. After a semester of material testing and prototypes, the new small scale model will be completed over summer and fall 2015.

Chemical Dose Controller, Fall 2013

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 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.

Anaerobic Wastewater Treatment, Summer 2013

Walker Grimshaw, Fanny Okaikue, Sushil Shanbhag

Abstract:

The summer 2013 wastewater treatment team was the first group in AguaClara to explore wastewater treatment for developing countries. The long term goal of the wastewater treatment research is to apply the governing concepts of AguaClara: Drinking Water to the sustainable treatment of wastewater. This involves small-scale treatment strategies that utilize minimal energy and treat water of greatly varying flow. The technology must be transparent and easily operable by an individual with minimal training. The research in the summer of 2013 attempted to initially design and construct multiple upflow anaerobic sludge blanket (UASB) reactors to better understand the operation of such an anaerobic technology. Additionally, anaerobic granules were studied for their makeup and metabolic processes. Throughout the summer, two reactors were constructed, one of which was modified for use with a support media, in this case sand. During operation, COD removal and gas production were monitored, both of which initially reached a high level before declining greatly until the reactors were abandoned. Each reactor was operational for approximately one month. Future research will work to improve treatment efficiencies and maintain a constant effluent quality through use of support media and further investigation of the metabolism of anaerobic bacteria involved in wastewater treatment.

Anaerobic Wastwater Treatment, Fall 2013

Ge Gao, Maithili Gokarn, Walker Grimshaw, Caitlin Rose McKinley, Liankun Zhu

Abstract:

Wastewater treatment is an important issue worldwide. Over one billion people across the world have connections to disposal methods for wastewater that remains untreated and instead is directly deposited into the environment, posing great human and environmental health risks. This research represents a union of the AguaClara program at Cornell and the Richardson Lab, with the long term goal of developing a gravity driven system for wastewater treatment and to characterize the general mechanism for anaerobic waste treatment. This team has and will operate under the principles of reducing human impact on the environment by effectively treating domestic wastewater before reintroduction to natural bodies of water and treating waste as a source of energy rather than a sink. Anaerobic treatment methods have been identified as the most appropriate for use in the global south due to their small footprint, low energy requirements, and slow rate of biomass growth. This semester six lab-scale reactors were constructed and operation begun to determine methods for controlling waste treatment efficiency and methane capture. Full scale reactors will use the methane produced within as an energy source to make the waste treatment an energy neutral or energy positive process. Of the six reactors, three were Anaerobic Fluidized Bed Reactors (AFBR) and three were Upflow Anaerobic Sludge Blanket (UASB) reactors. Though the reactors were only operated for a short period of time, they will continue to be operated in the future while data is collected for Chemical Oxygen Demand (COD) removal in addition to biogas production and specifically the methane levels within this biogas. One mathematical model was developed this semester to understand the fluidization characteristics of bio-granules as they develop on support media in the AFBR reactors. This model influenced the decision to use 0.1 mm quartz powder as a support media, and tests will be performed in the future to ensure this model corresponds with the fluid dynamics within the reactors. Microscopic techniques were investigated to determine their efficacy for elucidating the orientation and activity of microbial populations within the anaerobic granules. It is likely these techniques will be used in the future along with quantitative PCR techniques to understand the granules better. Other short term objectives for the study of wastewater treatment in the global south are to reach steady state operation of the reactors in terms of methane production and COD removal and exploration of new influent geometries to best fluidize the sand bed with such small support media.

Demo Plant – Fall 2012

Owen Guldner and Diana Kelterborn

Abstract:

The Demonstration Plant (Demo Plant) is an important educational tool to explain and publicize AguaClara technologies. In the Spring of 2012, a new Demo Plant was constructed, tested, and documented which included the two latest AguaClara technologies, a chemical doser and a stacked rapid sand flter (SRSF), as well as the older flocculator and sedimentation tank. In the summer of 2012 the demo plant structure and system was completely revised; the SRSF was fixed so that it can completely backwash all four layers, the chemical doser was labeled to include coagulant concentrations, and the overall plant was streamlined for transport and assembly. This semester we finalized construction materials and methods and built four more demo plants to be used at Cornell and abroad.

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.

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.

Regional Planning - Spring 2016

Lauren Frazier, Yu Jin Hur, Disha Mendhekar

Abstract:

The scope of the semester was to analyze the feasibility and need for an AguaClara plant in India. The team decided to focus on India asa country of potential implementation as India already has AguaClara LLC workers on the ground building connections. The team approached the analysis through large-scale research, gathering data on India’s water sources, demographics, geography, and economy. There are ten ideal characteristics that would suggest a potential site. The team conducted research on India to determine locations with these characteristics. The team also created an optimization model using Matlab to visually display the deliverable in the form of a color-coded map.

Ram Pump, Fall 2015

Priya Aggarwal, Juan Guzman, Joshua Levi Ringquist

Abstract

The ram pump used at AguaClara plants uses gravity and hydraulic principles to operate. The surge in pressure of the water due to the closing of the waste valve is used in the ram pump to lift water to a higher elevation. The ram pump is placed below the water treatment plant and it is used to drive the water to the chemical stock tanks and the restrooms located above the plant. Ram pump design parameters, specifically spring components, check valve type, and air chamber size, were tested to determine their effects on ram pump efficiency. Additionally, the pump needed to be reassembled this semester. The team has changed the design to make it more portable to avoid needing to rebuild the pump if it must be moved again. It is much easier to test different parts of the pump when leaks occur or if a part does not work as it is supposed to with the new setup. The team also tested air chambers and different spring lengths this semester.

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.