During Summer 2010, I worked on the ongoing Plate Settler Spacing project. We spent the first portion of the summer working on the bench-scale treatment train apparatus to achieve consistent and replicable performance. We then collected some interesting data on the performance of tube settlers of various diameters. Floc roll-up failure modes were observed for small tubes, where higher velocity gradient led to poorer performance even at the same predicted capture velocity. It appears that plate settlers could be more tightly spaced and will still perform well, but the velocity gradient must be considered.
I also joined the Stacked Rapid Sand Filtration team, which during the summer of 2010 made the transition from theory to the bench-scale. We constructed a 4" diameter four-layer stacked filter, and a system to dose it with clay and alum to resemble sedimentation tank effluent. This research provided an important proof-of-concept for the stacked filtration technology. The filter showed good turbidity removal performance meeting EPA water quality standards, and backwashing effectively cleaned the filter bed even when 5 NTU water was used in backwash.
During Fall 2010 I led the Stacked Filtration team as we continued to develop the technology. We built a six-layer filter that can be run at the same flow rate for filtration and backwash, inside a clear 4" column so that bed expansion and settling can be observed. We rounded out a proof-of-concept for the SRSF by observing backwash cycles and collecting additional performance data. We have shown that a stacked filter can do everything a conventional filter can do, in a way that makes it practical for use around the world. We also began exploring flow distribution among layers of the filter using dye tracer tests.
I continued to contribute some experimental assistance to the Plate Settler Spacing team, based on my experience from Summer 2010.
At the end of the Fall 2010 semester, the SRSF team built a transportable demo unit in a 3" clear pipe. During winter break, I traveled to Honduras with the AguaClara group, and worked with Jeff Will and Anderson Cordero to demonstrate the filter at Tamara, Agalteca, and Marcala. Our results suggest that the system is viable in the field, and we learned a number of important lessons about the practical challenges this technology will face.
This semester, I am once again leading the SRSF team along with Anderson Cordero. Now that we have proven the basic concept of stacked filtration, there are a number of practical questions that must be addressed as the system moves towards full-scale design and implementation. Our experiments this semester focus on design and operational issues for the SRSF in advance of its first full-scale trial.
I am also continuing to work with the plate settler spacing group, setting up and running experiments and helping with data analysis and organization.