Alajuela – Treatment wetlands – Ecosystems/Environmental engineering – Katie
Hola blog followers! Today we spent our precious time at the Fabio Baudrit project in Alajuela. It was certainly a busy and fulfilling day. After many strenuous hours of planning we were able to bring our floating mat designs into reality. After many hours of construction, the three groups each took a turn creating an inventory of a section of the anaerobic digester / wetland system. The final activity of the day was the actual floating of the mat in the wetland to see if our designs would float. Read on to see what the results were!
The Fabio Baudrit project is an exploration of Solar-Biopower generation through a cooperation between MSU and UCR funded by a grant from the U.S. Department of State (see link below). The innovative and unique aspect of the digester system is that the solar water heaters are able to create a thermophilic environment (50 degrees C) in the anaerobic digester. Traditional digesters in non-equatorial regions of the globe are only able to achieve mesophilic temperatures efficiently (35 degrees C). The advantage to using thermophilic temperatures is that the breakdown of materials is quicker, more robust and has a shorter retention time. This integrated system is beneficial because it overcomes the unsteady energy flow supplied by solar. A mixed waste stream of manure and other agricultural or food wastes are input and transformed using a consortium of microbiota, anaerobic digestion, and biological post treatment. The outputs are bio-energy, fertilizers, a reduction in greenhouse gas (GHG) emission, and clean water. It is possible that 600 MW per year of electricity could be produced via these wastes. This would be 10% of the electricity required in Costa Rica!
The wetland has several benefits including that it is low cost and low maintenance. However the cost is high: $54.5 K/Ha for a surface wetland and $215 K/Ha for a subsurface flow treatment wetland. A subsurface wetland is more efficient at greywater treatment so may be worth the extra cost.
On day two of our trip, in La Selva, our group was broken into three smaller groups and was presented with the problem of designing a floating mat as a treatment mechanism for the liquid effluent in one of the four wetland cells. This is because it is easier to harvest the plant biomass and, more importantly, the senescent plant matter will be store on the mat and not enter the wetland pool causing an undesirable anaerobic environment. It was a challenge and learning experience in ways I never would have expected. It gave us a true experience of engineering design. A number of times we had to modify our designs due to supply limitations. Sometimes we had to work extra hard to merge our Spanish – English communication. After about a week of refining the designs we were able to manifest our ideas. As you can see in the picture there were moments of chaos and confusion.
But in the end we created 4 amazing floating mats to be proud of. It was necessary to balance the forces acting on the floating mats to assure they would float. The forces included the weight of the mass with plants relative to the bouyant force. It was somewhat complex because it was necessary to estimate the current and potential weight of the biomass. We each planted vetiver (Vetiveria zizanioides) plants into our coconut fiber. It was really cool that the 4 groups (our 3 plus an impromtu UCR group) had the same supplies and created 4 significantly different mats. The supplies available included:
- PVC pipe
- coconut fiber
- plastic mesh
- landscape fabric
- chainlink fence
- epoxy glue
In the midst of all of the building we also created an inventory of the solar biodigestor and wetland systems. It was much more complicated than we anticipated because many of the components were buried or difficult to access.
This was one of the busiest days of the trip! I am so happy to have had the opportunity to work with these fine folks.
*This is the pre departure blog. I could not have ever imagined how amazing this trip would be or how much I would learn. . . . .
This is the Fabio Baudrit project! It is situated at the Fabio Baudrit Experiment Station, University of Costa Rica in Alajuela. The city of Alajuela is located in the Southeast portion of the province of Alajuela. (A mere 4,272 miles from my home in Corvallis, OR) Our group will visit on December 27-28, 2012.
The project involves using solar bio-power to create clean energy. One technology used to achieve this is a wetland for the treatment of organic wastes created by anaerobic digestion. The wetland can not only treat the effluent but also creates an attractive habitat for local plant and animal species. Here is a photo from a presentation by Dr. Dawn Reinhold of the wetland in disrepair. The plant matter floating on the surface is duckweed. It is a very aggressive species though not considered invasive. Notice the algae growing on the surface. This is an indication that the biomass has been allowed to grow too rapidly. The wetland became filled with biomass and began to release H2S and methane. This led to a very foul odor. In the realm of rotten eggs I’m sure. It has been hypothesized that a more frequent removal of the plant mass would increase the functionality of the wetland.
I am very excited to learn more about the floating mat design. Floating mats are fabricated and the wetland plants are grown directly into these mats instead into the substrate in the benthic zone. This allows for much easier harvest of the plant matter and also as the plants sinesce the dead material will remain on the floating matt. This will avoid the undesirable anaerobic conditions created when the plant biomass is decomposing under water.
I am very excited to see the current state of the wetland and to do what we can to improve the situation.
(hello, goodbye, and life is abundant!)
–This site presents research on the potential of Floating Mats to remove nutrients in runoff, done at Clemson University in South Carolina.
–This site is in Spanish, but describes the Fabio Baudrit experimental station and all of the work they are doing including related articles.
–Michigan State Grants:
–Department of State grant details