Upflow Anaerobic Sludge Blanket (UASB)

Fall 2015

The Fall 2015 Upflow Anaerobic Sludge Blanket (UASB) group has continued the previous work of the AguaClara anaerobic wastewater groups. Challenges addressed during this and next semester include testing reactor leakage and creating an airtight design, combining a UASB unit with a GSBR unit in an attempt to improve overall treatment capacity, and oxygen stress testing to determine the robustness of the reactor. The beginning of the semester was spent cleaning and removing biomass from reactors, testing for leaks using a bubble solution, and performing a single-day pressure test in an attempt to approximately quantify the volumetric leakage rate. Two UASB reactors were inoculated and began producing biogas within the first week of operation. COD analysis and gas chromatography were performed to characterize the efficiency of COD treatment and methane production within the reactors. UASBs are part of AguaClara's wastewater program, which is working to expand wastewater treatment programs in rural areas in Honduras and future AguaClara work sites.

Spring 2016

The Spring 2016 Upflow Anaerobic Sludge Blanket (UASB) group moved from the teaching lab to the AguaClara lab. As a result of the smaller lab space and problems with older reactors, 4 new reactors were built of a height of roughly 2.4 ft, and an inner diameter of 1". The reactors were designed to have a hydraulic retention time of 4 hours, based on vavlues in the literature. The upflow velocity was fixed at 0.05 mm/s. This upflow velocity is 2x lower than the lowest value found in literature. It was decided that it was similar to an operating UASB range and was chosen due to equipment constraints including pump size available, feed concentration, and required inlet flow rate. The team has modified the new reactors to have fewer ports to the reactor to minimize opportunities for gas leakage. The team also added a union in the center of the reactor body to make it easy to disassemble when maintenance is required. It is our hope that the next UASB group will be able to use the newly fabricated reactors to assess the effect of oxygen stress and variable influent strength on culture resilience.