Graduation Year

2016

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Daniel Yeh, Ph.D.

Committee Member

Jan Bartacek, Ph.D.

Committee Member

Jeffrey Cunningham, Ph.D.

Committee Member

Piet Lens, Ph.D.

Committee Member

John Love, Ph.D.

Committee Member

Aydin Sunol, Ph.D.

Keywords

decentralized treatment, anaerobic baffled reactor, membrane bioreactor, algae, nutrient management

Abstract

For decades, mainstream domestic wastewater treatment has relied on activated sludge processes to remove organic matter, and on biological nutrient removal systems like the A2/O process to remove nutrients. Recently, membrane filtration was also added to the realm of possible technologies for domestic wastewater treatment, with aerobic membrane bioreactors (MBRs) becoming increasingly popular, especially for decentralized, and small to medium scale applications. However, the aerobic activated sludge and MBR processes, which are often combined with biological nutrient removal processes, have high energy costs associated with supplying oxygen to the process, and end up converting the organic matter into CO2 and high amounts of microbial biomass, instead of more useful byproducts.

In order to remedy the aforementioned shortcomings of the aerobic processes, anaerobic wastewater treatment has been a focus of research, with anaerobic baffled reactors (ABRs) and anaerobic membrane bioreactors (AnMBRs) having shown promise for achieving acceptable organic matter removal performance, along with potential to be energy neutral or positive through biogas production. In addition, phototrophic technologies, such as algal photobioreactors, have recently been shown to be able to remove nutrients from waste streams, while at the same time having the potential to be used as feedstock to produce biofuels.

In this dissertation, a novel concentrically-baffled reactor (CBR) was designed that has the potential to reduce heat loss by transfering more of the heat between reactor zones than traditional baffled reactor designs, which will increase energy efficiency for heated systems. A prototype CBR was operated abiotically under varying hydraulic retention times (HRTs) from 4 h to 24 h, and achieved over 90% removal of total suspended solids (TSS) for all HRTs tested with feed particle sizes below 1.7 mm.

In parallel with the baffled reactor research, phototrophic membrane bioreactors (PMBRs) were tested with low aeration conditions to decrease their energy demand, which resulted in nitrification-dominated systems. A phototrophic technology was developed for increasing the pH of waste streams to potentially aid pH-sensitive nutrient recovery processes. Phototrophic pH increase from 6.42±0.13 to 8.87±0.06 was achieved using batch reactors, and an increase of pH from 6.73 to 8.61 was recorded during a continuous reactor trial.

Finally, the CBR was combined with a post-CBR membrane filtration process, and two PMBRs treating the effluent and permeate streams from the CBR in order to achieve complete organic matter and nutrient removal. The combined systems were tested both for high strength-high HRT and low strength-low HRT scenarios. Using the combined CBR-PMBR system, over 90% TN and TP removal were possible for 10 d HRT operation at high-strength feed conditions, with post-CBR membrane filtration. COD removal over 90% was possible for both high-strength and low-strength scenarios under all conditions tested.

Download

Share

COinS