Document Type
Dissertation
Date of Award
5-31-2022
Degree Name
Doctor of Philosophy in Environmental Engineering - (Ph.D.)
Department
Civil and Environmental Engineering
First Advisor
Lucia Rodriguez-Freire
Second Advisor
Taha F. Marhaba
Third Advisor
Wen Zhang
Fourth Advisor
Murat Guvendiren
Fifth Advisor
Emil Herkert
Abstract
Polyhydroxyalkanoate (PHA) is a biopolymer which has similar properties as fossil-fuel based plastic but also has capacity to biodegrade completely in the environment condition. This project aims to optimize the process to produce bioplastic PHA using activated sludge from wastewater. Specifically, five major research objectives are explored: (i) develop a quantification method of PHA by using Fourier-transform infrared spectroscopy (FTIR)F; (ii) improve the PHA production from mixed microbial cultures (MMC) by optimizing MMC; (iii) simulate the PHA production by using wastewater; (iv) evaluate the application of enzyme (alpha-amylase) in PHA production process; (v) market the investigation of wastewater produced PHA.
The first research study focused on developing a reliable PHA quantification method for complex sample by using FTIR. PHA is synthesized by endogenous microorganisms found in wastewater activated sludge, and the content of PHA in cells is a key factor of PHA production. Thirteen different sludge samples were collected from six wastewater treatment plants (WWTP) from the New York City metropolitan area, and the PHA content were measured by this method and gas chromatography mass spectrometry (GC/MS). FTIR is more suitable to quantify the PHA than GC/MS for a complex sample because of the limitation of GC spectrum separation, the standard availability, and the process of sample preparation. Using a liquid cell in the FTIR method shows a stronger absorbance than using a KBr card, making the liquid cell a better option for low concentration samples. Using a liquid cell with FTIR has the potential to be widely used in similar biopolymer measurements.
Current efforts are focused on developing an enrichment process for optimate the microbial community and PHA accumulation process for PHA production through feast-famine cycles. In this process, alternating relatively short periods of external substrate accessibility (feast) and unavailability (famine) is applied as environmental pressure to increase selectively the PHA-accumulating organisms. As the non-multidimensional scaling (NMDS) analysis, the environmental pressure successfully drives the microbial community change over cycles/time. More specifically, the PHA content increased after the process up to 48% in anerobic/aerobic strategy and 30% in ADF strategy. Additionally, the study of efficiency of enzyme ( a-amylase ) was evaluated by monitoring the volatile fatty acids (VFA) concentration and PHA content. An additional fermentation pretreated with enzyme steps increased VFA concentration and enhanced the PHA production to 41% in ADF strategy. As the application of enzyme, the fermentation is enhanced and improves the VFA generations. Regarding the results, a better design system is expected to be done to develop the application of this technology in real WWTP systems.
This study is expected to enhance and optimized the process of PHA production in industry system by using abundant activated sludge from WWTP.
Recommended Citation
Deng, Bo, "Optimization of polyhydroxyalkanoates (PHAs) bioplastic production from wastewater activated sludge" (2022). Dissertations. 1917.
https://digitalcommons.njit.edu/dissertations/1917
Included in
Biology Commons, Environmental Engineering Commons, Polymer and Organic Materials Commons
