The Floc-Blanket apparatus is a small-scale design of the flocculation and sedimentation system of an AguaClara plant. It is made of aluminum framing, PVC pipe, clear plastic tubing, and glass. The sedimentation tank is specifically designed with a glass tank so that researchers can use image analysis to study the process of floc-blanket formation and sedimentation.
When using the apparatus, researchers mix tap water with a solution of kaolin and clay to make it dirty. A coagulant solution of polyaluminum chloride is mixed with the dirty water before being pumped into the small-scale flocculator. The dirty particles in the water collide with the coagulant and bind together, creating flocs. Once through the flocculator, the water flows into the glass sedimentation tank, where the floc blanket forms.
Researchers use this apparatus to experiment with the process of flocculation and sedimentation and to improve the plant design of the floc-blanket. In a previous experiment, Casey Garland, a PhD student in Environmental and Civil Engineering, changed the size and length of the flocculator tubing to see how it affected particle collision and floc size formation. In another experiment, she altered the coagulant dose to view how it affected the size and distribution of flocs.
The Turbulent Tube Flocculator (TTF) enables the AguaClara team to study flocculation under turbulent flow conditions for the first time. The device, built so that water flowing in the flocculator becomes turbulent, closely mimics the flocculators used in AguaClara water treatment plants. The device achieves turbulent flow by creating over 300 flow expansions. Controlled distortions of the flexible plastic tubing through which the water flows creates the flow expansions.
The TTF is being used to develop a flocculation model for turbulent flow flocculators. The research results will test model predictions, and if the model is correct, then the model will be used to guide design improvements.
The ProCoDA (Process Control and Data Acquisition) software is the brainchild of Monroe Weber-Shirk who saw a need to automate experimentation processes in the lab so that students could collect meaningful data while taking a full course load. The ProCoDA software interfaces with the ProCoDA hardware that was designed and built by Paul J. Charles (equipment technician) with design assistance from Cameron Willkens (information technology operations manager). Researchers can control almost every aspect of their research experiments with the ProCoDA system, including water valves, temperature, pH level, pump speeds, and coagulant dosage. The system can measure many parameters.
ProCoDA software logs all data from experiments. Researchers are able to focus their attention on results rather than processes. The system is completely mobile, and can be moved to any computer with Windows OS and a USB port.
The ceiling of the AguaClara lab is covered in green, blue, and red piping. The colors represent the type of water being pumped in and out of the lab. The system pulls water from the building, regulates the pressure, and diverts it into two tanks. The blue tank combines hot and cold water to make incoming water the same temperature as the room. It is treated to remove excess oxygen and nitrogen gas from the water. The green tank has an activated carbon and micron filter that removes dissolved organics from the tap water. Researchers in the lab use both types of water, depending on their experiments. Once water has been used, it is pumped out of the lab using the red piping.
In the AguaClara design, the ram pump moves clean water from the lowest level of the plant to chemical stock tanks located at the beginning and highest level of the plant. It operates using the energy of the water’s flow rate, rather than electricity. The ram pump team conducts experiments in order to invent improved pumps. The lab is equipped with a ram pump that mimics plant conditions. It is made of PVC pipe, collection buckets, aluminum framing, brass check valves, and an air chamber connected to pressure sensors. Experiments include testing various drive flow rates and adjusting the forces and positive stops that control the main valve. The team has also evaluated various ram pump designs to see which features could be applicable to the AguaClara design.
The Counter Current Stacked Floc Blanket Reactor team is conducting research on the removal of arsenic, fluoride, and dyes from groundwater. The research team uses an apparatus of three reactors in series, which are connected to tanks containing stock concentrations of clay, dye, and coagulant. By using these different concentrations, the team experiments to find the optimal amount of coagulant needed to remove dye from the water. The apparatus is designed to perform separations by density, and data is primarily collected by turbidity meter and spectrophotometry that are monitored with the ProCoDa software. If this research is successful, AguaClara will test the new method of fluoride and arsenic removal in India.
The High Rate Sedimentation-Plate Settlers team uses a lab-scale sedimentation tank to mimic the process in an AguaClara plant. The sedimentation tank in the AguaClara design is the largest and slowest system in the design. This research team is working to decrease the size of each treatment plant by exploring the relationship between plate geometry and floc blanket density. The team is experimenting with different plate spacing, angles, and shapes in order to optimize sedimentation efficiency at high upflow velocities in their laboratory model tank.
The design lab is located next to the AguaClara research facilities. Once research has been perfected, the design lab takes the results from the research teams and translates them into code changes for the plant design. The design lab read past reports, look at current designs, and work with engineers in the field to make design changes. The lab uses Mathcad to code the designs, including the creation of scripts that generate 3-D AutoCAD drawings of the AguaClara water treatment plants. The designs are published on the AguaClara website.
The AguaClara lab at Cornell, located in the basement of Hollister Hall, is part of an international collaboration that is creating improved systems for water purification plants. Monroe Weber-Shirk, Civil and Environmental Engineering, directs a team of more than 50 graduate and undergraduate students who research, invent, and design AguaClara plants, including fundamental mechanisms of flocculation, sedimentation, filtration, and gravity powered chemical dosing. Each year, Weber-Shirk and his students travel to Honduras to visit functioning plants as well as those under construction. “Besides inventing technologies that provide safe drinking water to communities in the Global South, AguaClara is providing students with engagement in real engineering work. The students are involved in every process—from inventing systems and technologies to fabrication and design. They travel and see how their research affects communities. It is a once-in-a-lifetime experience,” says Weber-Shirk.
Each AguaClara plant has a three-step process for cleaning dirty water. Water entering an AguaClara plant is mixed with a dosage of polyaluminum chloride, a coagulant that sticks to the particles and pathogens in the water. The water travels into the flocculator, where carefully engineered turbulence causes particle collisions. Particles collide as they travel through the flocculation system, creating large flocs visible to the human eye (0.1 mm to 1 mm). Water flows up through a sedimentation tank, causing heavy flocs to fall toward the bottom, creating a fluidized bed, or a floc blanket. The floc blanket aids in the capture of small particles. The mechanism of particle capture in the floc blanket is an active research topic. After passing through the floc blanket, water runs through slanted parallel plates, which catch more of the smaller flocs. Water then runs through another AguaClara invention, a stacked rapidsand filter. The water that exits is clean and meets government standards, often at a much higher quality than required.
AguaClara’s Honduran partner, Agua Para el Pueblo, built the first plant in Ojojana, Honduras in 2006, a year after the first plant design was completed at Cornell. Today, 12 plants serve communities in Honduras and two in India. Continuing research at Cornell improves the efficacy and effectiveness of new plants. They are gravity-powered, electricity-free, and scalable to the size of the community they serve. Plants are built using local labor and locally available materials. AguaClara improves public health and the sustainability of community water supply systems, because communities are willing to pay more for high quality, safe drinking water.