Revolutionizing High Ammonia Waste Stream Treatment: Advanced Efficacy of the Novel Granular Sludge Reactor
Creators: Zou, Xin
Publisher: name: University of Alberta Library
Year: 2024

<p>High ammonia waste streams, containing both inorganic and organic nitrogen (N), can lead to algae outgrowth and the formation of disinfection byproducts if not properly treated. These waste streams are traditionally combined with municipal wastewaters for treatment. However, their high ammonia content can compromise the effectiveness of the wastewater treatment plants (WWTPs), leading to more stringent discharge limits for these sidestreams and industrial wastewaters. This thesis aims to develop a highly efficient technology for treating ammonia rich waste streams and to optimize the operation strategies for treating wastewaters with varied carbon to nitrogen (C/N) and alkalinity to nitrogen (Alk/N) ratios.</p>

<p>Aerobic granular sludge (AGS) is featured by its superior biomass retention, high biomass density, excellent settling capacity, and resilience to toxic environments and shock loadings. These attributes make it a promising alternative for high ammonia wastewater treatment, especially those from industrial sources or those contaminated with recalcitrant compounds. Although AGS is a well-established technology for treating municipal wastewaters with low ammonia content and a C/N ratio around 10, its application to high ammonia wastewater has been rarely explored. High ammonia waste streams, often characterized by low C/N and Alk/N ratios, pose significant challenges for AGS application, including slow granulation, granule instability, and limited N removal capacity.</p>

<p>This thesis first examined the impact of C/N ratios and influent solid content on N removal performance and granule structural and functional stability (Chapters 4 and 5). The results demonstrated that high ammonia conditions with low C/N ratios are conducive to the enrichment of highly efficient autotrophic ammonia oxidizing bacteria (AAOB), achieving higher ammonia removal compared to high C/N conditions, where heterotrophic ammonia oxidizing bacteria (HAOB) was dominated. Subsequent tests on high ammonia wastewater with varied C/N and low Alk/N ratios in the AGS system indicated that a C/N ratio over 6 is required for high N removal. Low N removal was observed under conditions of low C/N and Alk/N ratios, likely due to an insufficient denitrification process and low alkalinity availability (Chapter 6). Additionally, a thorough microbial analysis showed that granules contributed more than flocs to N reduction under high C/N conditions, whereas flocs contributed more under low C/N conditions (Chapter 7). </p>

<p>Based on these findings, a new granular sludge reactor (GSR) was developed and tested for its effectiveness in treating high ammonia, low C/N waste streams. The GSR demonstrated an outstanding N removal capacity of up to 4.2 kg N/(m3·d) and a rapid startup for treating wastewaters rich in recalcitrant compounds, as well as efficacy in organic N removal (Chapter 8, 9 and 10). In the GSR, the retention of highly active flocs and small granule, alongside strategies to facilitate the denitrification process for alkalinity recovery, contributed to such high N removal capacity. Furthermore, the GSR proved its capability in N removal and granule stability when using high COD wastewater as carbon source for the denitrification process, highlighting its promising upscaling potential (Chapter 11). </p>

<p>In summary, this thesis has elucidated the impact of waste streams characteristics on AGS treatment performance and identified the critical parameters controlling the enhancement of high ammonia waste stream treatment. Through a deep understanding of the influence of C/N ratios and detailed microbial analysis of the roles of granules and flocs, significant insights were gained. The newly developed GSR has opened up new opportunities for the enhanced removal of both inorganic and organic N from high ammonia waste streams. </p>