Structural Design of AguaClara Plants, Summer 2011

Lily Siu

Abstract:

Our main objective we wish to accomplish this summer is to analyze the reinforcement configuration and structural strength of the sedimentation and flocculation tank walls. In the previous semester, the structural design team analyzed the structural capabilities of the columns and walls for the Alauca plant using various assumptions and load cases. The previous team analyzed the walls as closely spaced concrete columns. By modeling the walls as columns the flexural support provided by the horizontal reinforcement is unaccounted for, but it allowed for the use of the same tools and procedures that is used for beam analysis. We seek to attempt to validate the previous team’s calculations as well as suggesting methods to analyze the horizontal reinforcement in order to reduce over-designing. This report is meant to augment the Spring 2011 report.

Sedimentation Tank Hydraulics, Summer 2011

Elana Liskovich, Mahina Wang, Jill Freeman, Yiwen Ng

Abstract:

A floc blanket is a dense fluidized blanket of flocs that helps to reduce effluent turbidity in the sedimentation tank by trapping other flocs. The geometry of the sedimentation tank is crucial in determining the extent of floc resuspension by the jet and hence floc blanket formation. To improve tank bottom geometry, nine experiments were conducted, each testing a different tank bottom geometry. The experiments were run in a 1/2 inch wide tank to model a thin slice of the full scale sedimentation tank. The geometry that resulted in the least sludge accumulation and therefore best floc resuspension was two 60 degree inserts leading to a semicircular trench 10 cm in diameter. We also provided initial designs and calculations for a floc weir to maintain the height of the floc blanket. A preliminary experiment was also conducted to evaluate the feasibility of our initial floc weir design.

Sedimentation Tank Hydraulics, Fall 2011

Jill Freeman, Mahina Wang, Saied Khan, Matthew Hurst

Abstract:

A floc blanket is a dense, fluidized bed of particles that forms in the sedimentation tank and helps to reduce effluent turbidity by trapping small flocs and reduces clean water waste through less frequent draining of the sedimentation tank. Floc resuspension is necessary for floc blanket formation so that flocs are recirculated through the tank instead of settling on the tank bottom as sludge. Research was conducted to examine mechanisms for floc resuspension. Parameters important for floc resuspension include energy of the jet stream on its upward flow path, position of the jet as it interacts with solids, and hydrodynamic pressure of the jet compared to hydrostatic pressure of the returning solids. Several geometries were tested with red dye and fully built floc blankets to observe the jet path and velocity profile around the bottom geometry. Best results are achieved through geometries that preserve jet momentum, especially through splitting the jet flow, and geometries that maintain a high jet velocity when contacting solids. Later, quantitative measurements were taken to determine floc blanket performance for various bottom geometries.

Residuals Management, Fall 2011

Patrick Farnham

Abstract:

The Residuals Management sub-team is solving the problem of solids disposal in AguaClara treatment plants. Currently, settled solids from the sedimentation and entrance tanks are drained and routed directly onto the nearby landscape. The newly created stacked rapid sand filtration system will produce backwash water in need of disposal, and spikes of highly turbid influent water bypass the plant by being discharged down the surrounding slope. The research goal is to determine inexpensive and responsible disposal methods for these outflows as well as for precipitate matter removed from the chemical stock tanks. Flow rates and concentrations of all residual flows have been estimated with the help of AguaClara engineers in Honduras, and designs have been created for pipe outlet protection structures which should reduce the erosive power of AguaClara residual flows. The team goal is to identify promising methods and eventually code them into the AguaClara design tool for use in the future and also for possible use in retrofitting current plants.

Foam Filtration, Summer 2012

Michelle Gostic, Sarah Levine, Leah Meyerholtz

Abstract

A reticulated polyurethane foam filtration system combined with coagulant dosing has proven capable of providing clean, low-turbidity water; however the necessary addition of coagulant combined with a non-conventional cleaning method makes the foam filtration system inefficient and not ideal to be used on a municipal scale. For this reason, research on foam filtration methods have been geared towards engineering a portable and effective filtration unit to provide clean water to devastated areas in emergency situations. There is a great demand for such technology as proven by the 1994 Rwanda Crisis. In this case, 85-90% of deaths in refugee camps were caused by diarrhea [Toole and Waldman; Doocy and Burnham]. Providing a low-cost, sustainable clean water source in emergency situations is the best way to prevent waterborne diseases and dehydration. The foam filtration team has worked towards designing an apparatus that will provide at least 15 liters of water per day per person, based on the UNHCR’s (United Nations High Commissioner for Refugees) recommendations for refugee situations [UNHCR]. The foam filter is small enough that it can be placed in the back of a pick up truck when needed and hooked up to the car’s engine to harvest electricity needed to power the filtration process. The current AguaClara foam filtration system utilizes a roughing and finishing filter to remove solid particles from influent water. Turbid water enters through the linear flow orifice meter (LFOM), which maintains a linear relationship between the water level and the flow rate of water through the system. Coagulant enters the LFOM in regulated doses to ensure consistent mixing of coagulant with influent water. The water flows through a 30 inch deep roughing filter, consisting of 30 ppi (pores per inch) foam, and then through a 15 inch deep finishing filter, consisting of 90 ppi foam. Before effluent water leaves the system, it is dosed with chlorine and exits the supercritical flow tube. Previous tests showed that head loss from the foam filters was negligible, but recent experimentation with an open system has proven otherwise. Due to the head loss and effluent turbidity standards, the foam filters need to be cleaned. A “plunger” method of cleaning has proven to be an efficient and easy way to clean the foam filters. A long pole with a porous disc attached to one end is used to compress the foam and release solid particles trapped in the 1 filters. This method is similar to squeezing out a dirty kitchen sponge. During the cleaning process, the foam must remain submerged in water to prevent the entrainment of air bubbles that would hinder filter performance. After plunging, the dirty water and released sediment flow out of exit valves located downstream of each filter. At the 2012 National Sustainable Design Expo in Washington D.C. the AguaClara team showed that the foam filter system is effective in removing particles from water at relatively high turbidities; however, data from these tests does not give concrete evidence of the filter’s performance in terms of realistic applications. At the expo, the turbidimeter was not properly calibrated, thus the data collected is not 100% accurate. Additionally, the filters were cleaned every 4 hours. Although this proved that the filters could return to their initial performance level after being cleaned via the plunger method, cleaning every 4 hours may be either too frequent or infrequent to maintain a high volume of treated water with acceptable effluent turbidity, in an emergency situation it is essential to maximize the volume of usable water while still maintaining quality standards. Effluent at the expo was dosed with clay and recycled so that the effluent became the influent. There is a possibility that coagulant built up in the filter columns, due to the recycle, improved performance beyond what it would have been in a more realistic experiment. As a new and relatively unexplored technology, there is much research to be done in the realm of foam filtration. Our current and future research will focus on providing extensive data as to the performance of the foam filtration system at different turbidities as well as identifying more efficient cleaning cycles. The World Health Organization included significantly reducing the number of “people without sustainable access to safe drinking-water and sanitation” in its list of 15 Millennium Development Goals [WHO]. Refining the foam filtration system has the potential to contribute to achieving this goal in addition to providing clean water to those who need it the most.

Foam Filtration, Spring 2012

Katie Edwards, Walker Grimshaw, Bradshaw Irish, Kelly McBride, Nadia Shebaro

Abstract

The Foam Filtration team developed a two-stage emergency water lter. The lter was presented at the 2012 National Sustainable Design Expo in Washington, D.C. as part of the P3 competition for sustainability. While at the expo, rough data was collected on the performance of the pilot scale lter as a proof of concept. The competition also involved submitting a grant proposal highlighting all past research on foam ltration and presenting a plan for future research and eventual implementation.

Laminar Tube Flocculator, Fall 2012

Patience Ruijia Li

Abstract

According to the predictive occulation model proposed by Swetland et. al., 2012, large ocs do not signicantly contribute to turbidity removal  only small colloids can collide eectively and aggregate to a size that will be removed by sedimentation. Based on the hypothesis that large ocs are useless, a oc breakup procedure was devised. Results obtained using a coiled tube occulator and occulation residual turbidity analyzer (FReTA) shows that higher turbidity removal was achieved after breaking the ocs, comparing to results using the same method but without oc breakup. Therefore breaking ocs at regular intervals to maintain continuous growth will promote better performance of occulation. This research nding provided a good reference for future hydraulic occulator design.

Low Flow Flocculator, Spring 2012

Ryan Anthony, Elyssa Dixon, Zac Edwards

Abstract

Open ow occulators, like those currently used in AguaClara plants, increase in cost for lower ow rates (less than 5 L s ). AguaClara must be able to meet the need of a wide range of community sizes, so scaling the design for low ow plants is crucial. This report specically analyzes three dierent scenarios that use obstructions within a pipe to remove the geometric constraints that cause the errors found in the current designs. Two scenarios include placing semi-circular baes (similar to those in open ow occulators) within the pipe and maintaining the spacing between and above the baes or maintaining the area between and above the baf- es. The last scenario involves placing balls on a string through the center of a pipe. A table is provided within this report comparing critical values for these occulators for a 3 L/s plant. An initial comparison of the three options shows that the scenario that maintains area above and between baes is the most eective with materials. However, discrepancies with calculations in the approach using balls as obstructions ultimately yields the results inconclusive.

Foam Filtration, Fall 2011

Bradshaw Irish, Anna Lee, Rachel Philipson

December 12, 2011

Abstract

The Foam Filtration team is attempting to determine an application that utilizes polyurethane foam as a water filtration medium. Our work consists of running experimental trials which characterize the filtration properties of polyurethane foam. Polyurethane foam is not a conventional filtration medium, and through extensive work, we have proven that it can successfully produce effluent turbidities below US EPA standards. In addition to the characterization of foam as a filter medium, we have previously investigated the possibility of utilizing polyurethane foam at the point-of-use scale. A feasibility study determined that a polyurethane foam point-of-use unit would require the addition of coagulant and expensive moving parts. Therefore, the new focus of the Foam Filtration research team is on the design of an emergency water treatment system using polyurethane foam. This unit will consist of a roughing and finishing filter. Previous research characterized the performance of the finishing filter and current laboratory tests are focused on evaluating performance of the roughing filter.

Fabrication, 2011 Spring

Primary Author: Daniel Cohen

Secondary Author: Travis Hartway

Abstract:

The fabrication team developed fabrication methods and designs to be used at AguaClara construction sites that are feasible and economical. We worked to improve hole cutting/drilling methods, designed entrance tank components such as trash racks and an adjustable overflow weir, investigated methods to attach pipes to the inlet manifold, and sought a longer lasting on-site power source. We developed a much better understanding of the AguaClara project and made several valuable contributions to implement in future construction sites.

Fabrication, 2011 Summer

Abstract

The Fabrication team focused on three main goals for the Summer 2011 semester. Firstly, we worked on developing a system to recharge a cordless power drill without using an electrical wall socket. Our solution was to connect the battery charger directly to a car battery, which may be easily brought to the site. Secondly, we researched more effective ways to remove plugs from hole saws. We determined that the commercially available Lenox speed-slot hole saws would best resolve this problem. Thirdly, we developed, tested, and improved a jig to help facilitate the assembly of plate settler modules.

Demo Plant, 2011 Fall

Breann Liebermann, Sahana Balaji, Muhammed Abdul-Shakoor

Abstract

The technology behind the AguaClara water filtration process features filtration through coagulation, flocculation, and sedimentation and flow/chemical dose control using gravity. Currently, an LFOM has been fabricated and tests have been done to see if a linear relationship exists between flow rate and height of water. Final touches will be put on the chemical doser. Currently, we are in the middle of fabrication of the sedimentation tank and tests will be done shortly to see if a floc blanket can in fact form.

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.

Stock Tank Mixing, Spring 2012

Julie Silva

Abstract:

The Stock Tank Mixing team is required to improve the mixing process for the coagulant and disinfectant in the stock tank. Previous teams have developed the centrifugal pump design, which can mix the following chemicals: aluminum sulfate (alum), polyaluminum chloride (PACl) and calcium hypochlorite (Ca(ClO)3). This team decided to focus on the use of polyaluminum chloride. Due to its chemical properties, it is most likely the future coagulant of most AguaClara plants. The stock tank mixing team plans to design a mixing system that will improve operator ease in use of the mixer, achieve a truly homogeneous mixer, and be scalable to larger plants. The team will also create operator guidelines, and provide the operator with a verification of homogeneity.

Stacked Rapid Sand Filer Pilot Scale, 2012 Spring

Eva Johnson, Jordanna Kendrot, Bill Kuzara

Abstract:

The stacked rapid sand filter has been proven to be an alternative to traditional rapid sand filtration systems, and their efficiency makes them an appropriate component in gravity powered municipal-scale water treatment facilities. In this study, a pilot-scale apparatus has been create as a model of the hydraulic controls throughout a full-scale stacked rapid sand filter system. After installation and field testing at Tamara, it is vital for the backwash segment of filter operation to be controlled for a more efficient use of the system. The purpose of the current experimentation and lab procedures are to determine the optimal backwash cycle time necessary for the filter to remove as much particulate matter as physically possible with a short filter-to-waste cycle, thus reducing the overall rinse cycle time. Further research will be needed in determining how to lessen bubble formation, be it in the inlet box or filter itself, and in measuring the change in flow distribution throughout filtration and backwash. A four-layer rapid sand filter was created to test filter efficiency versus monetary compensation from using less sand in the filter box, but was shown to have less than optimum particulate matter removal when compared to the tested six-layer.

Stacked Rapid Sand Filter Full Scale, Spring 2012

Michelle Wang, Steph Lohberg, Chris Holmes

Introduction:

The purpose of this report is to effectively summarize the progress that has been made to fabrication methods for the stacked rapid sand filtration system over the course of the semester. The stacked rapid sand filtration system is a new technology developed by AguaClara. It has many advantages over traditional sand filtration systems. First, it uses less water to backwash, because the filter layers are stacked. The filtration system also uses the same water for to backwash all the filter layers, producing a concentrated waste stream and reducing backwash time. Furthermore, this technology is much easier to operate than conventional rapid sand filters. It fits all the criteria of AguaClara technology, as the normal filtration and backwash cycles are driven by gravity. Materials are relatively cheap and widely available in Honduras. Finally, this filtration system has been proven to lower the effluent turbidity sufficiently, producing treated water below the EPA standard of 0.3 NTU and often even less than 0.01 NTU. The first field scale design of this filtration system was recently implemented at the AguaClara plant in Tamara. There have been several previously unforeseen issues that have arisen. In Tamara, in order to fit the slotted pipes into the trunk line and end lines, compression slots were cut into the slotted pipes. However, this allowed sand to leak into the inlet and outlet plumbing. Sand leakage is a serious issue because it increases head loss in the filter, reduces the length of the filter cycles, lowers the efficiency of the filter, and makes it harder to backwash. One of our main goals for this semester was to find a way to make a sand-tight connection between the slotted pipes and the trunk line and end lines. Another challenge we are facing is to find a new construction method so that the manifold can be built outside of the filter box. After the manifold is completely assembled, it will be lowered into the filter box as a unit. A key part to our progress this semester is the steady feedback from the team in Honduras at the Tamara site. Changes that we make this semester will aid in the maintenance of the Tamara filter and the design and implementation of the next stacked rapid sand filtration system in San Nicolas.

Stacked Rapid Sand Filter Bench Scale, Spring 2012

Danhong Luo, Weiling Xu, Huifei Wu, Main Editor: Michael Adelman

Abstract:

Stacked rapid sand filltration (SRSF) is a novel technology for AguaClara water treatment plants. Our team goal is to improve the performance of the SRSF by studying fundamental questions such as the self-healing nature of ow distribution among layers and the effect of upstream energy dissipation rate on performance. In the self-healing test, we found that it is hard to let the sand bed itself control what the flow distribution will be, and that surface removal dominated in the filtration process. The depth filter test reveals that surface removal dominated in the self-healing test, and flow distribution improved when surface removal effects were eliminated. For the energy dissipation rate test, we assume the filter performance would be improved with the increasing energy dissipation rate, while current experiments have not show the result. Therefore, further testing should be addressed in the energy dissipation rate study.

Low Flow Stacked Rapid Sand Filter , Summer 2012

Christian Compton, Alli Hill, Amanda Rodriguez, Samuel Taube

Abstract:

No abstract available for this research.

Smart Phone Turbidimeter, Fall 2012

Abstract:

An open-source, low-cost turbidity meter.

The high cost of equipment to monitor water quality often puts valuable health tools out of reach for many communities in developing countries. Our low-cost device measures the turbidity, or "cloudiness", of water due to suspended particles, and can detect potentially dangerous concentrations of dirt in water -- even when they are invisible to the human eye! Our device integrates with a remote data-acquisition system to enable record keeping and real-time observation of water quality in rivers, wells, and treatment plant

Sedimentation Tank Hydraulics, Spring 2012

Jill Freeman, Mahina Wang, Matthew Hurst, Saied Khan, Yiwen Ng

Abstract:

A floc blanket is a dense, fluidized bed of particles that forms in the sedimentation tank. It helps to reduce effluent turbidity by trapping small flocs and reduces clean water waste through less frequent draining of the sedimentation tank. Floc resuspension is necessary for floc blanket formation so that flocs are recirculated through the tank instead of settling on the tank bottom as sludge. Research was conducted to examine the effectiveness of the retrofitted Marcala sedimentation tank. At high influent turbidities, a steady floc blanket was obtained, but performance was slightly compromised when the influent turbidity was lowered to simulate Marcala conditions during the dry season. A floc blanket visibly formed with an influent turbidity of 5 NTU after about 1 week but “seeding” the tank with coagulated flocs will minimize floc blanket formation time. Images were also acquired for hindered sedimentation velocities of 0.6 mm/s, 1.2 mm/s, and 1.6 mm/s and analyzed with a floc-water interface program using a region of interest to better understand hydraulic processes within a floc blanket. Complete settling curves from this data confirmed wall effects significantly affect settling velocity. A floc hopper proved to be effective at controlling the height of the floc blanket when the accumulated flocs were drained at an adequately high flow rate. A lower alum dose of about 39 mg/L for an influent turbidity of 100NTU resulted in a less sticky sludge that could be more easily drained from the hopper.