Anaerobic Wastwater Treatment, Fall 2013

Ge Gao, Maithili Gokarn, Walker Grimshaw, Caitlin Rose McKinley, Liankun Zhu

Abstract:

Wastewater treatment is an important issue worldwide. Over one billion people across the world have connections to disposal methods for wastewater that remains untreated and instead is directly deposited into the environment, posing great human and environmental health risks. This research represents a union of the AguaClara program at Cornell and the Richardson Lab, with the long term goal of developing a gravity driven system for wastewater treatment and to characterize the general mechanism for anaerobic waste treatment. This team has and will operate under the principles of reducing human impact on the environment by effectively treating domestic wastewater before reintroduction to natural bodies of water and treating waste as a source of energy rather than a sink. Anaerobic treatment methods have been identified as the most appropriate for use in the global south due to their small footprint, low energy requirements, and slow rate of biomass growth. This semester six lab-scale reactors were constructed and operation begun to determine methods for controlling waste treatment efficiency and methane capture. Full scale reactors will use the methane produced within as an energy source to make the waste treatment an energy neutral or energy positive process. Of the six reactors, three were Anaerobic Fluidized Bed Reactors (AFBR) and three were Upflow Anaerobic Sludge Blanket (UASB) reactors. Though the reactors were only operated for a short period of time, they will continue to be operated in the future while data is collected for Chemical Oxygen Demand (COD) removal in addition to biogas production and specifically the methane levels within this biogas. One mathematical model was developed this semester to understand the fluidization characteristics of bio-granules as they develop on support media in the AFBR reactors. This model influenced the decision to use 0.1 mm quartz powder as a support media, and tests will be performed in the future to ensure this model corresponds with the fluid dynamics within the reactors. Microscopic techniques were investigated to determine their efficacy for elucidating the orientation and activity of microbial populations within the anaerobic granules. It is likely these techniques will be used in the future along with quantitative PCR techniques to understand the granules better. Other short term objectives for the study of wastewater treatment in the global south are to reach steady state operation of the reactors in terms of methane production and COD removal and exploration of new influent geometries to best fluidize the sand bed with such small support media.

Expanded Granular Sludge Bed (EGSB) - Spring 2016

Qiu Shen, Stephen Galdi, Zoe Maisel

Abstract:

The Expanded Granular Sludge Bed (EGSB) team was created to work within the wastewater subteam to design and run new, bench-scale, high rate anaerobic reactors. New reactors were designed to create a system with increased upflow velocity of influent, a fluidized bed, and decreased hydraulic retention time without decreased granular retention. Reactors were designed with simple operation in mind, with narrow modules in series rather than a single large reactor with recycle. The reactors were inoculated following abiotic testing of pumping rates, connection seals, and methane sensors. Immediately after inoculation, the granules began to form blockages and back up the reactor. Various forms of agitation seem to alleviate the problem, and automated solutions to the blockage problems has been proposed. In addition to blockages, the first module of the reactor was acidifying due to the low hydraulic residence time and relatively high specific organic loading rate. However, the following three modules were observed producing significant amounts of methane via the sensors, and at the end of an uninterrupted week of operation a COD test indicated about 40 percent total COD removal. With improved methane sensor calibration and a blockage prevention system, the bench-scale setup for high rate anaerobic treatment could potentially become a very versatile tool for testing the limits of anaerobic wastewater treatment and methane bioenergy reclamation.

UASB - Summer 2017

Zac Chen

Abstract:

No abstract included in report.

Conclusion:

The granule settling experiment from Spring 2017 has reached a conclusive result. Due to the high capture velocity relative to the upflow velocity, a full system of plate settlers will not be required of a full scale UASB reactor. There is no substantial impact from drastically decreasing capture velocity. Rather, a smaller settling apparatus such as a sloped exit weir can achieve the similar solid retention rates. More specifically, it was established that a 0.023 mm/s capture velocity can be utilized to increase effluent turbidity. It is with these conclusions, that the Summer 2017 UASB team recommend that future UASB teams move forward with the fabrication of the full-scale design.

UASB - Spring 2017

Zac Chen, Subhani Katugampala, Serena Takada, Linping Xu

Abstract:

Upflow Anaerobic Sludge Blanket (UASB) Reactors are a conventional primary wastewater treatment technology. Improvements to UASB reactors are required for the development of affordable small-scale wastewater treatment systems. This semester, the feasibility of two design modifications to conventional UASB reactors were explored: (1) a submerged gas capture lid (SGCL) to increase gas capture capacity, and (2) plate settlers to improve solids (granules) retention. The results of the SGCL prototype testing showed that the SGCL was gas-tight, which is not achieved in traditional UASB reactors. Additionally, granule settling tests demonstrated that plate settles do not improve settling capacity for small-scale UASB reactors. In the immediate future, AguaClara should fabricate a full-scale UASB reactor that incorporates the SGCL design and other design modifications detailed in the January 2017 EPA P3 Proposal. Eventually, AguaClara should explore post-treatment options to couple with the UASB reactor to develop a complete small-scale wastewater treatment system.