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Article

Effect of Anammox Granular Sludge Type on the CANON Process with Immobilized Fillers Treating Domestic Wastewater

by
Jiawei Wang
1,
Shiliang Liu
1,
Yan Zhang
1,
Si Zhang
1 and
Jiaju Liu
2,3,*
1
Hebei Key Laboratory of Water Quality Engineering and Comprehensive Utilization of Water Resources, Hebei University of Architecture, Zhangjiakou 075000, China
2
Research Center for Integrated Control of Watershed Water Pollution, Chinese Academy of Environmental Sciences, Beijing 100012, China
3
College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
*
Author to whom correspondence should be addressed.
Water 2023, 15(7), 1354; https://doi.org/10.3390/w15071354
Submission received: 12 February 2023 / Revised: 24 March 2023 / Accepted: 29 March 2023 / Published: 1 April 2023
(This article belongs to the Special Issue Functional Microorganisms in Wastewater Treatment)
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Abstract

:
Immobilized fillers were prepared using intact and crushed ammonia oxidation granular sludge (AnGS) to compare their effects on the completely autotrophic N-removal over nitrite (CANON) process in domestic sewage. Using pre-aerated domestic sewage as an influent, the effect of granular type on nitrogen removal was investigated under intermittent aeration. The results show that the total nitrogen removal (TNR) of the crushed AnGS immobilized filler was 75.8–80.0% at a dissolved oxygen (DO) concentration of 3 mg/L, while the intact AnGS immobilized filler required a DO of 4 mg/L to achieve the same TNR level. The DO concentration is the key factor affecting the nitrogen removal efficiency, because partial nitrification was affected by the DO concentration. Candidatus Kuenenia was the dominant genus of anaerobic ammonium oxidation (anammox) bacteria, and its relative abundance was higher in the crushed AnGS immobilized filler (21.11%) than in the intact AnGS immobilized filler (9.60%). Furthermore, the immobilized filler could inhibit the growth of nitrite-oxidizing bacteria (NOB), and the relative abundance of Nitrospira, the major NOB genus, decreased after operation. The results of this study indicate that the use of AnGS immobilized filler is a promising strategy to strengthen the CANON process in municipal wastewater treatment.

1. Introduction

In the completely autotrophic N-removal over nitrite (CANON) process, partial nitrification (PN) and anaerobic ammonium oxidation (anammox) both occur in a one-stage reactor, thus achieving autotrophic nitrogen removal [1,2]. Compared with traditional nitrification and denitrification processes, this process has the advantages of requiring no additional organic carbon source, while attaining a high nitrogen removal load and requiring low energy consumption [3,4]. Moreover, compared to the two-stage partial-nitrification/anammox process, the one-stage CANON process has the advantages of a lower infrastructure cost, smaller footprint and less free nitrite acid inhibition [5]. Therefore, it is a more popular approach in engineering applications. At present, the CANON process has been successfully used for nitrogen removal from high-ammonia wastewater [6,7]. However, application of this process to mainstream municipal wastewater still faces great challenges [8].
It is well known that granular sludge can effectively retain functional microorganisms [9] and greatly improve the pollutant removal capacity of a system [10]. Thus, granular sludge is ideal for promoting application of CANON in municipal wastewater treatment; however, the process still faces a long start-up period and susceptibility to adverse environments. Immobilization techniques can effectively shorten the start-up time of a reactor [11] and increase the resistance of bacteria to adverse environments [12], which have been well established to enhance bioremediation performance [13]. More importantly, compared with granular sludge systems, the dissolved oxygen (DO) gradient in immobilized fillers can effectively promote PN [14]. At present, the application of immobilized fillers in the CANON process focuses on nitrogen removal from high-ammonia wastewater [15], but their application in municipal wastewater treatment still needs further study.
Previous studies have focused on promoting nitrogen removal using anammox immobilized fillers prepared from anammox granular sludge (AnGS) [16,17,18]. Wang et al. [19] suggested that large-size AnGS is more conducive to maintaining the activity of anammox bacteria. However, smaller granular sludge particles have a better DO mass transfer performance, which promotes the activity of ammonia-oxidizing bacteria (AOB). Since the activities of AOB and anammox bacteria can affect the nitrogen removal of the CANON process, the choice of the granular type for the inoculating AnGS is important for the application of the CANON process with immobilized fillers to treat municipal wastewater. Moreover, since the microenvironments of different AnGS types will change after immobilization, the structural changes to functional bacteria caused by AnGS types in the CANON process need to be further studied.
In this study, immobilized fillers were prepared using intact and crushed AnGS to investigate their effects on the CANON process in domestic sewage. The objectives were as follows: (1) evaluate the effect of AnGS type on the nitrogen removal performance of the immobilized fillers during the CANON process in domestic wastewater; (2) analyze changes in the microbial composition of the immobilized fillers with the different AnGS types in the CANON process; and (3) discuss the implications of the CANON process with immobilized fillers for mainstream municipal wastewater treatment. This study provides valuable information for practical application of the CANON process for treating municipal wastewater.

2. Materials and Methods

2.1. Seed Sludge and Preparation of Immobilized Fillers

The AnGS, granule size 2.5–3 mm, was procured from an actual monosodium glutamate wastewater treatment project (Ulanqab, Inner Mongolia, China). The influent NH4+-N concentration was greater than 600 mg/L, and the total nitrogen removal rate (TNR) was 0.67 kg·N/(m3·d). The anammox functional microorganisms in the AnGS were mainly Candidatus Kuenenia and Candidatus Brocadia, with relative abundances of 37.02% and 1.88%, respectively.
After washing three times in deionized water, the AnGS was equally divided into two portions according to weight. One portion was crushed into smaller particles of 0.5~0.7 mm by centrifugal pumping (40 PUMA 2.10 s, Tsurumi Pump, Ōsaka shi, Japan), while the other portion was left intact. The intact and crushed AnGS were mixed with polyvinyl alcohol, calcium carbonate powder and activated carbon powder. Thereafter, hollow-cylinder anammox immobilized fillers were prepared according to the methods of Wang et al. [16] Finally, the immobilized fillers were evenly cut with a cutter into hollow cylinders of 15 mm diameter, 5 mm height and 1–2 mm thickness. The A1 and A2 immobilized fillers correspond to intact and crushed AnGS, respectively (Figure 1).

2.2. Wastewater Characteristics

Domestic wastewater was collected from septic tanks in residential areas of the Beijing University of Technology (Beijing, China). The domestic wastewater was then deposited into a 100 L tank with an aeration plate. The DO concentration in the tank was controlled at 2–3 mg/L for 24 h of aeration prior to use as influent. Microorganisms in domestic sewage use DO to remove organic matter and also reduce the carbon/nitrogen (C/N) ratio of the wastewater. The main characteristics of the domestic sewage with a low C/N ratio are shown in Table 1.

2.3. Reactor Setup and Operation Strategy

For each immobilized filler, a sequencing batch reactor (SBR) with a working volume of 0.8 L was set up (Figure 1). The A1 and A2 immobilized fillers were loaded into their respective SBRs at a filling rate of 20% (v/v). The aeration head in the reactor provided oxygen through an external aeration pump. The diameter of the exhaust hole in the reactor top cover was increased to ensure that gas was smoothly discharged from the reactor and that the DO probe (WTW, München, Germany) could reach inside to monitor the DO concentration. The aeration time was controlled by a timer on the pump. The DO concentration in the reactor was controlled with a regulating valve. The two reactors were placed in a constant-temperature shaker (80 rpm) to maintain the temperature at 30 ± 1 °C (ZHWY-2102C, Beijing, China). The SBRs operated in batch mode with an 8.0 h per operation cycle. Each cycle consisted of feeding (10 min), alternating aerobic/anoxic reactions (10/20 min), settling and drainage (20 min).
In the initial start-up stage of the reactor, the feeding schemes of the A1 and A2 immobilized filler reactors were the same, and the DO concentration was maintained at 3.0 ± 0.1 mg/L during the aeration phase of the reactor operation cycle. The feasibility of start-up and the nitrogen removal performance of the CANON process for the A1 and A2 immobilized filler reactors treating domestic sewage were evaluated. Thereafter, the aeration-stage DO concentration of A1 and A2 immobilized filler reactors was increased to 4.0 ± 0.1 mg/L, and the effect of DO concentration on the nitrogen removal performance of the CANON process was investigated. Moreover, the DO concentration of the A2 immobilized filler reactor was returned to 3 ± 0.1 mg/L on day 23 to evaluate the effect of short-term high-DO operation.

2.4. Analytical Methods

2.4.1. Wastewater Quality Analysis

The concentrations of chemical oxygen demand (COD), total nitrogen (TN), NH4+-N, NO2−-N and NO3−-N were analyzed according to APHA standard methods [20].

2.4.2. High-Throughput Sequencing

The effects of different AnGS types on the microbial composition of immobilized fillers in CANON process for domestic sewage were studied. High-throughput sequencing was conducted on the Illumina MiSeq platform (Illumina, San Diego, CA, USA) to analyze the microbial composition of the inoculated AnGS (A0), and the A1 and A2 immobilized fillers were collected after the operation. High-throughput sequencing was performed using the methods of Gao et al. [21] with minor modification. The V3-V4 hypervariable region of the bacterial 16S rRNA gene was amplified with primers 341F (CCTACGGGNGGCWGCAG) and 805R (GACTACHVGGGTATCTAATCC). The obtained bacterial 16S rRNA gene sequences were compared to the National Center for Biotechnology Information (NCBI) database. Using MEGAN software, the 16S rRNA gene sequences were analyzed and classified according to a certain threshold to obtain operational taxonomic units (OTUs). Diversity analysis was performed according to the OTUs, and the final results were visualized.

3. Results and Discussion

3.1. Nitrogen Removal Performance of A1 and A2 Immobilized Fillers during the CANON Process

The nitrogen removal performance of the A1 and A2 immobilized fillers during the CANON process is shown in Figure 2. In the start-up phase of the CANON process, the effluent NH4+-N and TN of the A1 and A2 immobilized filler reactors decreased as the TNR increased, and both reactors were stable on day 10, which indicates that the CANON process can be started in a reactor with domestic sewage and immobilized AnGS under an alternating aerobic/anaerobic operation mode. AnGS takes a long time to establish PN in the CANON process for treating domestic sewage [22,23]. Anammox bacteria tend to grow on granular sludge, while AOB and nitrite-oxidizing bacteria (NOB) tend to grow in flocculent sludge [24], making it difficult to establish PN in a granular sludge system. However, immobilized filler can effectively immobilize functional bacteria therein, thus successfully reducing AOB loss. Wang et al. [25] found that immobilized filler can provide a good environment for promoting AOB growth. In addition, the activity of NOB can be effectively inhibited by an alternating aerobic/anaerobic operation mode [26,27], thereby enhancing the PN of the A1 and A2 immobilized fillers. In summary, the start-up time of the CANON process for treating domestic sewage can be effectively shortened by immobilized AnGS.
After stabilization, the TNR of the A1 immobilized filler reactor was 59.1–67.1%, and the effluent NH4+-N and TN concentrations were 8.8–10.8 mg/L and 18.8–22.9 mg/L, respectively (Figure 2a). For the A2 immobilized filler reactor, the TNR was 75.8–80.0%, and the effluent NH4+-N and TN concentrations were lower than 5 mg/L and 15 mg/L, respectively (Figure 2b). Consequently, the effluent quality was classified as “A” based on the national discharge standard criteria of China (GB18918-2002). The nitrogen removal performance of the CANON process treating domestic sewage was better when using A2 immobilized filler compared to the A1 immobilized filler. The low effluent NO2−-N concentration and high effluent NH4+-N concentration of the A1 immobilized filler reactor indicates that the low PN rate in the A1 immobilized filler caused a lack of NO2−-N substrate during the anammox process (Figure 2c,d). The low PN efficiency was the main reason for the low TNR of A1 immobilized filler in the CANON process. Figure 2c,d show the ΔNO3−-N/ΔNH4+-N ratio for the A1 and A2 immobilized filler reactors. According to previous studies, the theoretical ΔNO3−-N/ΔNH4+-N of the CANON process is 0.11 [1]. The value of ΔNO3−-N/ΔNH4+-N reflects the nitrogen removal pathway of the CANON process. The nitrogen removal pathway of the A2 immobilized filler was dominated by the anammox process. The ΔNO3−-N/ΔNH4+-N ratio of the A1 immobilized filler reactor was less than 0.11 after start-up, which was due to the occurrence of denitrification. Wang et al. [19] found that synergistic denitrification and anammox denitrification were more likely to occur in ANGS of larger particle sizes due to the larger anoxic zone.
In conclusion, based on the different microenvironments and matrix gradients in the immobilized fillers, crushed AnGS has more effective DO transfer than intact AnGS, thus achieving more efficient PN. Because the PN of the AnGS immobilized filler is the rate-limiting step of the CANON process, the DO concentration is the key factor affecting the nitrogen removal efficiency of the CANON process in treating domestic sewage.

3.2. Effect of DO on Nitrogen Removal by A1 and A2 Immobilized Fillers during the CANON Process

The effect of DO levels on the nitrogen removal performance of the A1 and A2 immobilized fillers during the CANON process is shown in Figure 3. In the A1 immobilized filler reactor, the TNR increased rapidly to 76.8–81.9% after the DO concentration increased from 3.0 ± 0.1 mg/L to 4.0 ± 0.1 mg/L during the aeration stage, and the effluent NH4+-N and TN concentrations were stable below 5 mg/L and 15 mg/L, respectively (Figure 3a,c), which are classified as “A” based on the national discharge standard criteria of China (GB18918-2002). This phenomenon shows that increasing the DO concentration can effectively improve the nitrogen removal effect of the A1 immobilized filler. During the CANON process, PN in the AnGS immobilized filler is completed in two ways, specifically by (1) dissociative AOB in the immobilized filler and (2) AOB on the AnGS surface. Therefore, when the DO concentration increased, the dissociative AOB and the surface AOB can obtain more DO, resulting in increased AOB activity. Previous studies have shown that due to the DO concentration gradient in immobilized fillers, even in high-DO solutions, there is still an oxygen-limiting zone inside the immobilized filler, which effectively limits the NOB activity therein [13,28]. Therefore, the A1 immobilized filler was able to maintain PN after the DO concentration increased. Moreover, with the higher DO concentration, the ΔNO3−-N/ΔNH4+-N ratio of the A1 immobilized filler reactor was stable around 0.11, which indicates that the higher DO concentration weakened the denitrification effect of the immobilized fillers in the CANON process.
When the DO concentration of the A2 immobilized filler reactor was increased from 3.0 ± 0.1 mg/L to 4.0 ± 0.1 mg/L, the TNR of the reactor decreased rapidly to 61.9–70.9%, and the effluent TN concentration increased to 17.1–20.0 mg/L, but the effluent NH4+-N concentration remained below 5 mg/L (Figure 3b). It is worth noting that the effluent NO3−-N of the A2 immobilized filler reactor increased to 9.7–11.1 mg/L, indicating that the higher effluent TN was mainly caused by the increased NO3−-N. Meanwhile, the ΔNO3−-N/ΔNH4+-N ratio of the A2 immobilized filler reactor increased to 0.17–0.21, which is much higher than the theoretical value of the CANON process. The above phenomena indicate that NOB activity in the A2 immobilized filler increased due to the higher DO concentration during the aeration stage, which leads to the destruction of PN. After the DO concentration increased, NOB in the crushed AnGS, which has a larger surface area, could contact more DO than those in the intact AnGS in immobilized filler; therefore, the A2 immobilized filler was less favorable for maintaining PN than the A1 immobilized filler in a high-DO environment. In addition, Han et al. [29] found that the DO distribution in granular sludge of different particle sizes is different and that the DO concentration inside the granules decreased with increasing particle size. Therefore, the small AnGS of the A2 immobilized filler is not conducive to inhibiting NOB activity in a high-DO environment. However, when the DO concentration of the A2 immobilized filler reactor recovered to 3.0 ± 0.1 mg/L during the aeration stage, the TNR of the A2 immobilized filler increased and recovered. Moreover, the effluent NO3−-N concentration of the A2 immobilized filler reactor decreased to 5.9–7.9 mg/L and the ΔNO3−-N/ΔNH4+-N ratio also recovered to about 0.11 after the DO concentration decreased, which indicates that short-term operation under high DO will not destroy the PN of the immobilized filler CANON process. However, long-term operation under high DO could lead to an excessive enrichment of NOB in the immobilized filler, thereby resulting in destruction of PN under low-DO conditions.
In conclusion, compared to the immobilized filler made with intact AnGS, the immobilized filler made with crushed AnGS can achieve a better nitrogen removal effect when treating domestic sewage via the CANON process under a low DO concentration, which is due to the fact that the crushed AnGS improves the opportunity for AOB on the surface in the filler particles to obtain DO, thus enhancing AOB activity. In addition, immobilization is an effective technology to enhance the application of AnGS in municipal wastewater [17,30] because it can provide a good microenvironment within the AnGS, which reduces the adverse impacts caused by the municipal wastewater environment. As a result, the anammox bacteria activity of intact and crushed AnGS in the immobilized filler at the DO concentrations of 3–4 mg/L was not affected. During the CANON process treating domestic sewage, the immobilized filler made of crushed AnGS showed a better nitrogen removal effect than that of the intact AnGS at a low DO concentration; thus, immobilized filler made of crushed AnGS is more suitable for actual municipal wastewater treatment, and it will reduce aeration energy consumption.

3.3. Microbial Community Structure of A1 and A2 Immobilized Fillers in the CANON Process

3.3.1. Microbial Diversity and Richness

High-throughput sequencing analysis revealed that OTUs and diversity indices changed in the three samples (Table 2). A total of 139,715 effective sequences (Seq num) were generated from the three DNA samples, and 6867 OTUs were obtained by clustering the clipping sequences using a 97% similarity threshold. In general, the domestic wastewater operation increased the microbial diversity. DO and organic matter in the domestic wastewater served as substrates for the various microorganisms in the A1 and A2 immobilized fillers. However, the diversity of A1 immobilized filler was higher, indicating that the community composition was more affected by the domestic sewage. This could be because the transfer of substrates in the intact AnGS immobilized filler was more complicated due to the larger particle size and, compared with the crushed AnGS, the complex environment was more conducive to the growth of various microorganisms.

3.3.2. Microbial Community Composition

Changes in the microbial community structure, with a focus on the composition of functional bacteria, were investigated by comparing the inoculated AnGS with the A1 and A2 immobilized fillers after the CANON process was carried out with domestic wastewater (Figure 4). At the phylum level (Figure 4a), Planctomycetes (41.36%), which is affiliated with anammox bacteria [31,32], was dominant in the inoculated AnGS. After the CANON process, the relative abundance of Planctomycetes in A1 and A2 decreased to 14.35% and 26.13%, respectively, whereas the relative abundance of Proteobacteria increased to 31.23% and 25.95%, respectively. Changes in the microenvironment and influent contaminant load after AnGS immobilization led to these changes. In particular, the higher relative abundance of Proteobacteria, which contains a variety of heterotrophic and denitrifying bacteria, in A1 relative to A2 indicates that the intact AnGS in the immobilized filler may be more conducive to the growth of heterotrophic and denitrifying bacteria.
The variation in dominant microbial genera is shown in Figure 4b. Nitrosomonas was the dominant AOB genus in the A1 and A2 immobilized fillers. It is worth noting that the relative abundance of Nitrosomonas was higher in A2 than in A1, which shows that crushed AnGS as immobilized filler can provide a better microenvironment for AOB growth. In the inoculated AnGS (A0), Nitrospira was the dominant NOB, with a relative abundance of 1.77%, while it decreased in the A1 and A2 immobilized fillers to 0.64% and 0.53%, respectively, after operation, indicating that immobilization of AnGS could effectively inhibit NOB growth. Nitrospira has better substrate affinity for ammonia than Nitrobacter [33]. Therefore, Nitrospira was the dominant NOB in the A1 and A2 immobilized fillers after the CANON process treating low-strength domestic wastewater. In summary, the AnGS immobilized filler can effectively reduce NOB growth while maintaining AOB activity.
The anammox functional bacteria in the three samples included Candidatus Kuenenia and Candidatus Brocadia, with Candidatus Kuenenia being the dominant anammox genus in A0 (37.02%). After operation of the CANON process, the relative abundance of Candidatus Kuenenia in A1 was 9.60%, while that in A2 was 21.11%. The low-strength domestic wastewater led to a decreased abundance of anammox genera in the AnGS immobilized filler. However, since the immobilized fillers have a long sludge retention time and can better withstand adverse effects of the external environment, they are conducive to maintaining the abundance and dominance of anammox bacteria. In particular, compared with the intact AnGS, the crushed AnGS was more conducive to maintaining the abundance of anammox bacteria. This may be because the mass transfer effect of the smaller particles was better, which is conducive to maintaining anammox bacteria activity. These data support the present observation that AnGS immobilized filler has a good nitrogen removal effect during the CANON process when treating domestic sewage. In addition, the relative abundance of Aridibacter [34] and Thermomonas [35], which are denitrifying bacteria, increased after the CANON process. This phenomenon shows that, although most of the organic matter in the domestic sewage was removed by the pre-aeration treatment, the remaining small amount of organic matter still promoted the growth of denitrifying bacteria within the immobilized fillers. However, denitrifying bacteria growth may not destroy the nitrogen removal efficiency of the CANON process, but it is possible that denitrification could be coordinated with anammox to improve the nitrogen removal efficiency during this process.

3.4. Implications of This Work for Mainstream Municipal Wastewater Treatment

In actual municipal wastewater treatment, achieving a stable anammox process requires a stable PN process and retention of anammox bacteria [36]. The CANON process using AnGS immobilized filler demonstrated excellent nitrogen removal properties for treating domestic sewage with a low C/N ratio. However, the complex organic compounds in municipal wastewater can adversely affect the PN and anammox processes [37,38]. In this study, most organic matter in the domestic sewage was removed by a pre-aeration treatment; however, the huge organic chemical energy contained in the COD of municipal wastewater has great potential for exploitation and utilization. Therefore, sustainable municipal wastewater treatment can be achieved through carbon source conversion to energy technology and the CANON process with AnGS immobilized filler.
This conceptual route adopts the A/B process (Figure 5). In stage A, an organic carbon-capture process is adopted to concentrate the organic carbon source through biological flocculation or a high-rate activated sludge process, and then the extracted carbon source is transferred for co-generation of heat and power (CHP) via anaerobic digestion to generate energy. In stage B, treated municipal wastewater with a low C/N ratio after stage A enters a CANON reactor with AnGS immobilized filler for nitrogen removal. Considering that high N-loading is conducive to maintaining the activity of anammox bacteria, in order to maintain high anammox activity in municipal wastewater, the actual operation time of the CANON process can be shortened to increase the influent N-loading, and the proportion of anaerobic digestion wastewater with a high ammonia concentration can be increased in the influent to increase the influent nitrogen concentration. At the same time, anaerobic digestion wastewater from stage A also enters stage B. Finally, phosphorus is removed by biological phosphorus removal [39] during phosphorus treatment.

4. Conclusions

In this study, the effects of granular sludge type and DO level on the nitrogen removal performance of immobilized fillers were studied during the CANON process for treating domestic wastewater. The AnGS immobilized filler can achieve a good nitrogen removal performance in the CANON process. The DO concentration is the key factor affecting the nitrogen removal efficiency of the immobilized fillers in the CANON process for treating domestic wastewater. Compared with the intact AnGS in immobilized filler, the crushed AnGS in the immobilized filler improves the opportunity for AOB on the surface of the filler particles to obtain DO under a low DO concentration, thereby enhancing PN. The AnGS immobilized filler maintained a competitive advantage for the functional bacteria Candidatus Kuenenia and prevented the growth of the NOB Nitrospira. Meanwhile, the crushed AnGS is more conducive to maintaining the abundance of anammox bacteria. Using AnGS immobilized filler is a feasible strategy to strengthen the CANON process for treating domestic sewage.

Author Contributions

Methodology, J.W. and J.L.; software, S.L.; data curation, S.Z.; writing—original draft preparation, Y.Z.; writing—review and editing, J.W. and J.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Science and Technology Project of Hebei Education Department, grant numbers BJK2023052 and QN2021052, and the Natural Science Foundation of Heilongjiang Province of China, grant number LH2022E110.

Data Availability Statement

All the data have been provided in the manuscript.

Conflicts of Interest

The authors declare no conflict of interest.

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Water 15 01354 g001 550
Figure 1. Schematic of the A1 and A2 immobilized filler reactors.
Figure 1. Schematic of the A1 and A2 immobilized filler reactors.
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Figure 2. The nitrogen removal performance of the A1 (a,c) and A2 (b,d) immobilized filler reactors.
Figure 2. The nitrogen removal performance of the A1 (a,c) and A2 (b,d) immobilized filler reactors.
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Figure 3. The effect of DO on the nitrogen removal performance of the A1 (a,c) and A2 (b,d) immobilized filler reactors.
Figure 3. The effect of DO on the nitrogen removal performance of the A1 (a,c) and A2 (b,d) immobilized filler reactors.
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Figure 4. Relative abundance of microorganisms in the A1 and A2 immobilized fillers at the phylum (a) and genus (b) levels.
Figure 4. Relative abundance of microorganisms in the A1 and A2 immobilized fillers at the phylum (a) and genus (b) levels.
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Figure 5. Conceptual model for municipal wastewater treatment based on the CANON process with AnGS immobilized filler.
Figure 5. Conceptual model for municipal wastewater treatment based on the CANON process with AnGS immobilized filler.
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Table
Table 1. Characteristics of the domestic sewage after aerating.
Table 1. Characteristics of the domestic sewage after aerating.
COD
(mg/L)		TN
(mg/L)		NH4+-N
(mg/L)		NO2−-N
(mg/L)		NO3−-N
(mg/L)		C/N RatiopH
Range43.2~61.552.0~69.246.2~64.70.2~0.70.2~1.10.9~1.57.7~7.9
Average56.859.955.20.40.91.27.8
Table
Table 2. The diversity index of the samples.
Table 2. The diversity index of the samples.
Sample IDSeq NumOTU NumACE IndexChao1 IndexSimpson Index
A055,90113951705.561624.730.12
A142,397285120,145.4712,374.470.02
A241,417262119,118.5710,527.830.06
Notes: ACE and Chao1 indices: a higher number indicates a greater species richness. Simpson index: A higher number indicates a lower community diversity
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Wang, J.; Liu, S.; Zhang, Y.; Zhang, S.; Liu, J. Effect of Anammox Granular Sludge Type on the CANON Process with Immobilized Fillers Treating Domestic Wastewater. Water 2023, 15, 1354. https://doi.org/10.3390/w15071354

AMA Style

Wang J, Liu S, Zhang Y, Zhang S, Liu J. Effect of Anammox Granular Sludge Type on the CANON Process with Immobilized Fillers Treating Domestic Wastewater. Water. 2023; 15(7):1354. https://doi.org/10.3390/w15071354

Chicago/Turabian Style

Wang, Jiawei, Shiliang Liu, Yan Zhang, Si Zhang, and Jiaju Liu. 2023. "Effect of Anammox Granular Sludge Type on the CANON Process with Immobilized Fillers Treating Domestic Wastewater" Water 15, no. 7: 1354. https://doi.org/10.3390/w15071354

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