Biofilms & Biogranules: Engineered bioprocesses are capable of inducing aerobic or anaerobic microbes to either 1) attach to abiotic surfaces to form biofilms, or 2) attach to each other’s cell surfaces to form spherical biogranules (i.e. aerobic or anaerobic granules). The dense structure of those aggregates allows for exceptionally high microbial concentrations to be captured in bioprocesses for faster bioreaction rates and swift separation of purified supernatant. In additon, multiple species of microbial consortia responsible for various pollutant degradation (e.g., C, N, and P removal) inhabit layered structures inside these aggregates along the mass diffusion gradient based on their symbiotic relationships. That being said, all existing biological functions of modern wastewater plants can potentially be consolidated onto one biogranule or one tiny piece of biofilm.
Anaerobic Digestion: Anaerobic digestion includes a series of biological processes through which microorganisms break down biodegradable material in the absence of oxygen. One of the valuable end products is methane gas, which can be combusted into electricity and heat, or processed into renewable transportation fuels. This technique can be applied for high strength wastewater treatment, excessive sludge minimization, and the stabilization of food waste as well as agricultural residuals such as livestock manure, crop waste, and yard waste.
Anammox: anaerobic ammonium oxidation is an energy and resource efficient approach for removing nitrogen from wastewater. It takes advantage of redox reaction between ammonium and nitrite to produce nitrogen gas. Anammox reduces the demand for oxygen (nitrification) and eliminates the need for organics (denitrification). Despite successful full-scale applications to treat sidestream, there are still unsolved problems such as decay rate of anammox bacteria and disposal of residue nitrate. In addition, applying anammox to mainstream treatment is still at an early stage. We have developed an anammox treatment system based on membrane aeration for precise control of oxygen supply and a hybrid system for mainstream anammox applications.
Forward Osmosis: forward osmosis (FO) is an emerging membrane technology for water/wastewater treatment. Because of different salinity across a semi-permeable membrane (FO membrane), osmotic pressure can drive water flux from a high water potential side to a low water potential side. FO has been studied to desalinate seawater or brackish water, or extract water from treated wastewater. Our research of FO technology focuses on water recovery from wastewater, reducing reverse salt flux, and exploring new draw solutes that can be easily regenerated.
Resource Recovery: recovery of valuable resources such as Nutrient, Energy and Water (NEW) is critically important to achieve sustainable wastewater management. Our research focuses on development of new technologies for NEW recovery. One of the example systems is based on synergistic cooperation among anaerobic digesters, microbial electrolysis cell, forward osmosis, and struvite formation. The new systems aim to maximize NEW recovery and minimize resource input such as consumption of energy and chemicals.
Biofuel and Bioproducts: hydrolysis is usually a rate-limiting step in the biological conversion of abundant cellulosic biomass into biofuel and bioproducts. Our research revealed that biofilms are advantageous to microbial hydrolysis by focusing limited extracellular enzyme resources on the surface of recalcitrant biomasses in close proximity. This close proximity also places biofilms in a superior position for hydrolysate harvesting and fermentation. Therefore, this application of biofilm holds promise to integrate saccharification and fermentation into a single consolidated bioprocess to convert the most abundant organics on earth (e.g. cellulose) into biofuels (e.g. ethanol and H2) and bioproducts (e.g. bioplastics and lactate).
Bioelectrochemical System: bioelectrochemical system (BES) is based on interaction between microorganisms and solid electron acceptors/donors. Bacteria respire with an anode electrode while oxidizing organic compounds. As a result, electrons are generated and transferred to a cathode where a terminal electron acceptor such as oxygen or nitrate is reduced. Representative BES include microbial fuel cells (MFCs) for bioelectricity generation, microbial electrolysis cells for hydrogen production, and microbial desalination cells for simultaneous wastewater treatment and saline water desalination. Our BES research ranges from fundamental studies to system scaling up.
Membrane Bioreactors: our research of MBRs focus on integration of membrane technology with osmotic systems, bioelectrochemical systems or algal bioreactors. Such integration aims to achieve mutual benefits with enhanced treatment performance and optimized operation. Examples of research include recovery of draw solute for reuse in osmotic MBRs, improving nutrient removal in MBERs, and stimulating algal growth or improve algae separation using FO or ultrafiltration membranes.