Application Of Anammox Research Articles

Insight into enrichment of anammox bacteria by a polyurethane sponge carrier coupled with iron-carbon micro-electrolysis under no strict anaerobic condition

A novel composite carrier (ICME-PS) was formed by coupling polyurethane sponge carriers (PS) with different pore sizes (15, 25, 40 ppi) and iron-carbon micro-electrolysis (ICME), which was used for enrichment of anammox bacteria and stable operation under no strict anaerobic condition. An increase of 5.67%-38.55% in specific anammox activity (SAA), an significant enhancement of biofilm stability and an improvement of 14.61%-42.38% in Ca.Brocadia were observed in ICME-PS, compared to PS carriers. ICME played a dual role: 1) contributed to the formation of an anaerobic microenvironment; 2) used for nitrogen cycle reactions. Additionally, small-pore carriers with highest biofilm stability can be used in high shear environments, while medium-pore carriers achieved the highest SAA in stable environments. Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis indicated that ICME application reduced the energy barrier and improved aggregation performance. This study designed a novel composite carrier to broaden the application of anammox under no strict anaerobic condition.

Application of Anammox in the High Ammonium Industrial Wastewater Treatment Plant: Environmental Impacts and Carbon Reduction Potential Via Life Cycle Assessment

Application of Anammox in the High Ammonium Industrial Wastewater Treatment Plant: Environmental Impacts and Carbon Reduction Potential Via Life Cycle Assessment

Aggregation enhances the activity and growth rate of anammox bacteria and its mechanisms

The aggregation of anaerobic ammonium oxidation (anammox) bacteria is important for the start-up and biomass retention of anammox processes. However, it is unclear whether it is beneficial to the activity, growth and reproduction of anammox bacteria. In this study, four reactor systems were developed to explore the effects of aggregation on anammox activity, growth and reproduction, after excluding the contribution of aggregation to sludge settling and retention. Results demonstrated that (i) compared with free-living planktonic bacteria, the aggregated bacteria had a higher volumetric nitrogen removal rate (0.75 kg-N/(m³·d)) and specific nitrogen removal activity (1.097 kg-N/VSS/d). And after 67 days cultivation, it had the higher sludge concentration and relative abundance (92.4%); (ii) compared with acidic polysaccharides and α-d-glucopyranose polysaccharides, β-d-glucopyranose polysaccharide play more essential roles of anammox aggregation; (iii) norspermidine triggered the secretion of α-d-glucopyranose polysaccharides to combat the toxicity, and inhibited biomass growth rate; (iv) immobilization in polyvinyl alcohol (10%) or sodium alginate (2%) gel beads was better than sodium alginate-chitosan gel beads and norspermidine (biofilm inhibitor) for the cultivation of free-living planktonic anammox bacteria. This is the first comparative study of three methods for cultivating free-living anammox bacteria. In conclusion, we found that the aggregation of anammox sludge not only facilitates biomass retention but also enhances the bioactivity, relative abundance, growth, and reproduction rate of anammox bacteria. The work is helpful to understand the formation of anammox granular sludge and contribute to the fast start-up and stable operation in anammox application.

Efficient nitrogen removal from mainstream wastewater through coupling Partial Nitritation, Anammox and Methane-dependent nitrite/nitrate reduction (PNAM)

The application of partial nitritation and anammox to remove nitrogen from mainstream wastewater is of great interest because of the potential to reduce energy cost and carbon dosage. However, this process confronts a dilemma of relatively high effluent nitrogen concentration (>10 mg N/L), owning to the unwanted prevalence of nitrite-oxidizing bacteria (NOB) and the intrinsic nitrate production by anammox bacteria. Here, a novel technology, named the one-stage PNAM, that integrates Partial Nitritation, Anammox and Methane-dependent nitrite/nitrate reduction reactions, was developed in a single membrane biofilm reactor (MBfR). With feeding of synthetic mainstream wastewater containing ∼50 mg NH4+-N/L at a hydraulic retention time of 12 h, more than 95% nitrogen was removed in the established one-stage PNAM process at a practically useful rate of 0.1 kg N/m3/d. Microbial community characterization and in-situ batch tests revealed a sophisticated microbial structure consisting of ammonia-oxidizing bacteria (AOB), anammox bacteria, nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) bacteria and archaea, and a small fraction of NOB and aerobic methanotrophs. The role of methane in removing nitrate was confirmed by switching on/off the methane supply, which relaxed the requirement for NOB suppression. In addition, the established system was relatively robust against temperature variations, evidenced by a total nitrogen removal efficiency above 80% at temperature as low as 14 ℃. The results provide a promising alternative for efficient nitrogen removal from domestic wastewater using methane as the sole carbon source.

Effects of sludge morphology on the anammox process: Analysis from the perspectives of performance, structure, and microbial community

The nitrogen removal characteristics, physicochemical properties, and microbial community composition of four different anaerobic ammonium oxidation (anammox) sludge morphologies were investigated. The morphologies considered in this study, namely suspended sludge (Rs), biofilm (Rm), granular sludge (Rg), and encapsulated biomass (Re), were prepared from floc sludge. The results show that Re exhibited the maximum anammox activity, followed by Rg, Rm, and Rs. Additionally, the anammox contribution rate was higher in Rg and Re. The higher extracellular polymer content in Rg promoted sludge accumulation, and tryptophan was observed in Rm and Rg, which was replaced by humic acids in Rs. Re showed the largest specific surface area, hydrophobicity and strength, and its good structure ensured enrichment of anammox bacteria (AnAOB). In terms of the microbial community, the functional bacterium Candidatus Kuenenia accounted for the highest proportion in Rm (39.27%), but the presence of both anaerobic and aerobic regions led to increased community complexity with more nitrifying bacteria. In contrast, Rg and Re had a more specific microbial community. In addition, denitrifying bacteria tended to grow in Rs, while nitrifying bacteria were retained in Rm. The AnAOB were more likely to be enriched in sludge aggregates (both Rm and Rg) and carriers (Re). Through correlation analysis, the potential relationship involving bacterial flora evolution of each sample was clarified. Finally, the structural models of different morphologies of sludge were proposed. This study deepens the understanding of various anammox sludge morphologies as well as provides useful information for the cultivation of AnAOB and further application of anammox.

Improving performance and efficiency of partial anammox by coupling partial nitrification and partial denitrification (PN/A-PD/A) to treat municipal sewage in a step-feed reactor

Improving contribution and nitrogen removal efficiency (NRE) of partial anammox in municipal wastewater is a researching hotspot. This study developed an innovative PN/A-PD/A process with fixed biocarriers in anaerobic/anoxic chambers for actual sewage treatment in a typical step-feed reactor over 390 days. Two coupled pathways providing continuous NO2– (partial nitrification in oxic chambers and partial denitrification in anaerobic/anoxic chambers) for anammox were introduced to the process, achieving 47% nitrogen loss by anammox in stable phase. The influent and effluent total inorganic nitrogen (TIN) were 51.3 and 11.0 mg/L, respectively, even with chemical oxygen demand (COD)/TIN ratio of 2.9. Anammox activity improved from 6.52 to 9.68 mg NH4+-N/gMLSS/d and abundance on the biocarriers raised to 3.16 × 1010 gene copies/g dry sludge. Overall, this study confirmed partial anammox, spatially coupled with partial nitrification and partial denitrification via oxic/anoxic distribution with step feed mode, as an alternative for application of mainstream anammox.

Application of electric fields to mitigate inhibition on anammox consortia under long-term tetracycline stress

The feasibility of applying electric fields to mitigate inhibition of tetracycline (TC) on anammox process and improve system stability was evaluated in this study. Three electric field intensities of 1, 3 and a variable intensity of 1–6 V (VEF) were used to optimize electric field intensity under gradually increasing addition of TC (0.5, 2 and 10 mg L−1). Results showed that the application of electric fields (3 V and VEF) could improve TC tolerance and keep relatively high-efficiency nitrogen removal performance, especially at TC ≥ 2 mg L−1. Furthermore, applying electric fields contributed to mitigate irreversible inhibition and improve the stability of community structure. Underlying mechanism analysis indicated that the main mechanism of applying electric fields to mitigate inhibition relies on sludge structure strengthening. This study explored a novel strategy to reduce the inhibition of antibiotics on microbial denitrification and broaden the application of anammox in industrial water treatment.

Nano zero-valent iron improves anammox activity by promoting the activity of quorum sensing system

The addition of nano zero-valent iron (nZVI) has been proven to improve the efficiency of the anammox process, however, the mechnism is not clear. Here, the effect of nZVI on anammox microbial community was studied by metagenomic sequencing methods. It was found that 50 mg/L nZVI indeed promoted the removal of NH4+ and NO2− of the anammox reactor and significantly improved the relative abundance of AnAOB (Ca. Brocadia) from 42.1% to 52.5%. What's more, 50 mg/L nZVI increased the abundance of c-di-GMP synthesized protein from 148 rpmr to 252 rpmr in the microbial community and decreased the abundance of c-di-GMP degradation protein from 238 rpmr to 204 rpmr, which indirectly led to the enrichment of c-di-GMP in the microbial community. The enrichment of c-di-GMP reduced the motility of microorganisms in the reactor and promoted the secretion of extracellular polymers by bacteria, which is beneficial to the formation of sludge particles in the anammox reactor. In conclusion, this research clarified the mechanism of nZVI promoting the anammox process and provided theoretical guidance for the engineering application of anammox.

Nutrients removal from low C/N actual municipal wastewater by partial nitritation/anammox (PN/A) coupling with a step-feed anaerobic-anoxic-oxic (A/A/O) system

In this study, a novel combined strategy was successfully established by partial nitritation/anammox (PN/A) within a step-feed A/A/O process integrated with fixed-biocarriers to treat municipal sewage for 200 days. The excellent nutrients removal performance of this system compared with national level of discharging standard were achieved: low total inorganic nitrogen (7.1 mg/L) and phosphorus (0.3 mg/L) in the effluent with the influent (51.1 and 4.2 mg/L) at C/N ratios of 3.4 ± 0.5, mainly attributed to the stable PN (oxic zone) and subsequently anammox effect (anoxic zone). Nitrogen mass balance indicated that anammox contribution in anoxic zones to nitrogen loss could be up to 42% at stable phase. Therefore, aeration and carbon cost could be greatly reduced under low DO, low C/N and aerobic hydraulic retention time (HRT) of 7.4 h condition. The low DO and anammox bacteria retention in anoxic chambers promoted the washout of NOB and combination of anammox and partial nitritation process. During long-term operation, the activity of AOB effectively maintained while that of NOB drastically reduced to 0.1 mg N / g MLSS / h resulting in high and stable nitrite accumulation ratios (about 90%). The achievement of partial nitritation was mainly due to low DO (0.4–0.5 mg/L) and effective retention of anammox bacteria even with a low temperature (14.5 °C). Notedly, anammox activity gradually increased both on the biocarriers and in the flocs while a higher anammox abundance was observed on the biocarriers (2.48%) than that in suspend flocs (0.03%). As above, this study indicated that the novel combined strategies could be applicable to mainstream anammox, and a pilot-scale reactor will be established to verify and promote the industrial application of mainstream anammox.

An effective strategy for in situ start-up of mainstream anammox process treating domestic sewage

The feasibility of in situ start-up of mainstream anammox process was investigated in three parallel sequencing batch biofilm reactors (SBBRs) inoculated with nitrification sludge, partial nitrification sludge, and denitrifying phosphorus removal sludge, respectively. The SBBRs were operated under alternate anaerobic/aerobic/anoxic pattern at ambient temperature (16.5–26.8 °C). The influent organic and nitrogen loading rates were increased stepwise. Anammox bacteria grew exponentially with relative abundance and overall bacterial activity increasing from 0 to 0.004% to 0.29–0.40% and ‘not detected’ to 6–7 mg N/L/h, respectively. Desirable nitrogen removal efficiency of about 86% was obtained in 3–4 months for the influent nitrogen of 40.5–73.6 mg N/L. Anammox was the primary nitrogen transformation pathway. For the anammox bacterial enrichment, biofilm, alternate anaerobic/aerobic/anoxic pattern, and limited aeration played important roles. Seed sludge with high ammonium oxidizing bacterial activity further promoted the start-up of anammox process. The in situ start-up strategy could promote the full-scale application of mainstream anammox.

Strengthened attachment of anammox bacteria on iron-based modified carrier and its effects on anammox performance in integrated floating-film activated sludge (IFFAS) process

Moving-bed biofilm reactor (MBBR) or integrated floating-film activated sludge (IFFAS) process has been proved to be one of the ideal candidates for anammox application. However, the slow development of anammox bacteria (AnAOB) biofilm and unstable bioactivity always limit their wide application. This study developed a type of novel zero-valent iron (ZVI)-based modified carrier for strengthening AnAOB attachment and enhancing anammox performance. Surface properties analysis indicated the iron-based modified carrier revealed electropositive, less hydrophobic, and higher surface free energy compared with conventional high density polyethylene (HDPE) carrier. These surface parameters were positively correlated with total biomass attachment, anammox biofilm development, EPS secretion and heme-c production. IFFAS process filled with iron-based modified carriers could keep relatively stable and high anammox activity at different influent TN loadings (varied from 0.6 to 1.4 kg/(m3∙d)) and showed potential to keep and recover AnAOB bioactivity after six-months-freeze. Microbial analysis confirmed that anammox genus, Candidatus Kuenenia, had a significant niche preference on iron-based modified carrier than conventional HDPE carrier. As a result, the population of Candidatus Kuenenia in IFFAS process filled with modified carriers that contained 2 wt% or 3 wt% ZVI was 1.34 × 106–1.55 × 106 copies/ mg DNA, increased by 20.7–39.6% comparing with that in the control reactor (1.11 × 106 copies/ mg DNA). This study demonstrated AnAOB could be enriched and maintained in situ with high abundance and bioactivity on the iron-based modified carriers, which would be significant for anammox process wide application in full-scale.

Comparison of nitrogen and VFA removal pathways in autotrophic and organotrophic anammox reactors

Organotrophic anammox is a promising process for treating both nitrogen and organic containing wastewater than that of the traditional autotrophic anammox for sole nitrogen removal. However pathways of nitrogen removal particularly at metagenomic level in both processes are still unknown. Here we report, metabolic pathways of nitrogen removal in two lab-scale sequencing batch reactors (SBR), one autotrophic and another organotrophic (TOC/TN = 0.1) anammox bacteria incubated over 220 days. Both reactors showed satisfactory nitrogen removal with 840.31 mg N/L.d and 786.81 mg N/L.d for autotrophic and organotrophic anammox reactors respectively. Four anammox species namely Candidatus B. fulgida, B. sinica, J. caeni and Candidatus K. stuttgartiensis were identified in both reactors. The Candidatus K. stuttgartiensis (4%) was dominant in autotrophic reactor whereas Candidatus J. caeni (10%) in the organotrophic reactor. The supply of organic promoted the growth of anammox bacteria more than three times higher than that of the autotrophic anammox reactor. The functional genes related to the DNRA pathway was obtained in all anammox species except for Candidatus K. stuttgartiensis. The co-existence of other DNRA (Armatimonadetes and Thauera) and partial denitrifying bacteria (Chloroflexi) was also found in both reactors. Moreover, functional genes related to acetate metabolism by acetyl-CoA way were obtained in all anammox bacteria except Candidatus B. fulgida which showed alternative ackA/Pac-t pathways in organic anammox reactor. Overall current results suggest that the anammox, DNRA and partial denitrification were the key nitrogen transformation pathways, particularly in organotrophic anammox reactor. Our findings will improve understanding of the practical application of organotrophic anammox for wider wastewater treatment.

Metabolic insights into the enhanced nitrogen removal of anammox by montmorillonite at reduced temperature

Anammox is a low-cost and high-efficiency nitrogen removal technology. However, anammox bacteria are sensitive to realistic temperature variations of municipal wastewater, limiting their practical application in municipal wastewater treatment. In this study, to protect anammox bacteria against variable reduced temperatures, cheap and abundant clay montmorillonite (MMT) particles were used as anammox biomass carriers. Two 5-L sequencing batch reactors with MMT (RB) and without MMT (RA) were operated for 100 days. When the temperature decreased from 37 °C to 10 °C, under a nitrogen loading rate of 0.36 kg-N m−3 d−1, the total nitrogen removal rate was 0.21 kg-N m−3 d−1 in RB, but only 0.025 kg-N m−3 d−1 in RA, demonstrating the improvement of anammox performance at reduced temperatures by MMT. The 16S rRNA gene sequencing analysis verified that MMT promoted the growth of Candidatus Brocadia, resulting in 11% more abundance in RB than RA at 10 °C. Metabolomics analysis revealed MMT promoted the growth of anammox bacteria at reduced temperatures by stimulating metabolic pathways related to bacterial assimilation. In particular, MMT with excellent NH4+ adsorption capacity elevated L-Glutamine and L-Glutamate contents, subsequently stimulating the downstream metabolic pathways, including amino acid biosynthesis, purine and pyrimidine metabolism, and cryo-protectant synthesis. This study provides metabolic insights into how MMT was able to enhance nitrogen removal by anammox at reduced temperatures, which is meaningful towards overcoming the current limitations of the practical application of anammox in treating municipal wastewater.

Spontaneous mainstream anammox in a full-scale wastewater treatment plant with hybrid sludge retention time in a temperate zone of China.

Spontaneous anammox bacteria enrichment at mainstream conditions was reported in a full-scale Wastewater Treatment Plant (WWTP) in a temperate zone of China. The mainstream anammox was observed after WWTP process retrofit, which constructed a hybrid sludge retention time (SRT) system by providing moving carriers in the anaerobic/anoxic tank and was initially designed to enhance the denitrification process in a conventional anaerobic/anoxic/oxic process. The hybrid SRT system achieved 86.0±4.6% total nitrogen (TN) removal via combined mainstream anammox and conventional denitrification. Autotrophic denitrification via mainstream anammox was confirmed by various shreds of evidence including high-throughput sequencing, specific anammox activity test, and 15 N isotopic tracing. Long-term anammox bacteria existence in the biofilm of the carrier in anoxic zones was detected in a much higher relative abundance compared with other spots. The contribution of anammox activity to TN removal was estimated at around 20%-30%. The reasons leading to spontaneous anammox enrichment were mainly attributed to the carriers for slow-growing bacteria growth and dissolved oxygen gradient in the anoxic tank (caused by intermittent aeration) for nitrite production. The insights of this full-scale case study provide important perspectives for future mainstream anammox application, and also the design of an energy-neutral WWTP process. PRACTITIONER POINTS: Spontaneous mainstream anammox in a full-scale WWTP after its retrofit in a temperate zone of China was reported. Anammox bacteria enrichment and long-term stability on moving carriers at mainstream conditions was achieved by modified hybrid SRT system. The hybrid SRT system achieve stable nitrogen removal even in cold winter and high BOD/N situation by combining mainstream anammox with conventional denitrification. Long term full-scale operation demonstrated excellent nitrogen removal with about 20%-30% contribution of mainstream anammox. This full-scale case study provided perspectives for future optimizing mainstream anammox application, and also energy-neutral WWTP process design.

Nitrogen removal mechanism of marine anammox bacteria treating nitrogen-laden saline wastewater in response to ultraviolet (UV) irradiation: High UV tolerance and microbial community shift

Salt stress can be naturally overcome by marine anammox bacteria (MAB), while their low growth rate and sensitivity to operational conditions are still challenges for the application of anammox. To enhance the enrichment of MAB and decipher the effects of ultraviolet (UV) irradiation on MAB, UV was introduced in the nitrogen removal of MAB treating nitrogen-laden saline wastewater for the first time. The results indicated that MAB were resistant to a fairly high UV-C dose, 12000 mJ/cm2. Their relative abundance was enhanced by 1.2 folds under 12000 mJ/cm2 UV-C. However, the relative abundance of Actinobacteria, Acidobacteria, Chloroflexi and Marinicella were greatly dropped with enhanced UV-C dose. The tolerance mechanism was diversified, e.g. excessive extracellular polymeric substances, special structure of MAB and interspecific competition/cooperation. Although further study was still needed, the findings shed a light on MAB enrichment and exploited great potentials of MAB in nitrogen-laden saline wastewater treatment.

Microbial diversity reveals the partial denitrification-anammox process serves as a new pathway in the first mainstream anammox plant

A full-scale sewage treatment plant in Xi'an city is discovered as the first mainstream anaerobic ammonia oxidation (anammox) treatment process in China. Whether its biological mechanism is the nitritation-anammox or partial denitrification (PD)-anammox brought violent controversy between two groups. As a third party, here we uncovered the mystery of the moving-bed biofilm reactor (MBBR) as a PD-anammox process by analyzing the diversity and phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) of microbes in anoxic pond. Anammox bacteria was found in the MBBR anoxic tank, which abundance is 8.9 times of that in the common anaerobic-anoxic-oxic process, confirming the existence of anammox process. The denitrifying bacteria (DNB) content in the anoxic tank is 5.9 times of the content of ammonia oxidizing bacteria (AOB), thus the DNB-anammox system is proved at the microbial composition level. The PICRUSt analysis found that ammonium nitrogen is mainly derived from the deamination of urea. The functional genes NAR and AMO of DNB and AOB are 910.84 and 5.80 rpms, respectively. The NAR gene content is 157.0 times of the AMO gene content and it is proved at the genetic level that the nitrite in the anoxic pool is mainly derived from denitrification. This study demonstrated the feasibility and advantages of the PD-anammox in the anammox process, which is different from the traditional nitritation-anammox demonstrated in Strass Wastewater Treatment Plant, Austria and Changi Water Reclamation Plant, Singapore and provided an alternative option for the mainstream application of anammox.

Deep insights into the green nitrogen removal by anammox in four full-scale WWTPs treating landfill leachate based on 16S rRNA gene and transcripts by 16S rRNA high-throughput sequencing

Inoculation of anaerobic ammonium oxidation (anammox) bacteria-enriched pellets into the full-scale conventional wastewater treatment plants (WWTPs) treating landfill leachate is an effective and economical way to achieve the engineering application of anammox, a green nitrogen removal process. Current knowledge of the active members in the microbial communities of these WWTPs with active anammox granulation remains limited. In this study, the overall microbial communities in these four WWTPs treating landfill-leachate were analyzed using 16S rRNA gene high-throughput sequencing. At the same time, transcriptionally active groups in these aeration tanks, which were inoculated with exogenous anammox pellets were delineated by the reverse-transcribed 16S rRNA sequencing. Anammox bacteria and nitrifiers were enriched in the aeration tanks benefited from the high ammonium inputs, and the significant accumulation of the slow-growing anammox bacteria was positively related to the biomass immobilization on surfaces of carrier materials. In total, 8610 operational taxonomic units (OTUs) were observed in the four aeration tanks and only 29.0% of all OTUs were transcriptionally active, but the percentage of transcriptionally active members in the 1004 core OTUs (OTUs observed in all aeration tanks) were up to 62.2%. Only 11.6% of all OTUs were the core, but they accounted for up to 67.4% of the total DNA reads. The core microorganisms in the aeration tanks tended to be more abundant and active than the others in the community. Some inactive heterotrophic microbes were also detected with dominance in the microbial communities of the aeration tanks, likely from the dead cells and microbial migrations from influent, suggesting the metabolically functional importance of an organism in the WWTPs cannot be accurately assessed by the relative abundance of taxa based on DNA sequencing. Our findings broaden the current understanding on the active microbial communities of WWTPs for implementing the active anammox process and re-affirm the necessity of differentiating between active and inactive microbial groups in any open ecosystems.

A review on anammox process for the treatment of antibiotic-containing wastewater: Linking effects with corresponding mechanisms

Antibiotic is widely present in the effluent from livestock husbandry and the pharmaceutical industry. Antibiotics in wastewater usually have high biological toxicity and even promote the occurrence and transmission of antibiotic resistant bacteria and antibiotic resistance genes. Moreover, most antibiotic-containing wastewatercontains highconcentration of ammonia nitrogen. Improper treatment will lead to high risk to the surrounding environment and even human health. The anaerobic ammonium oxidation (anammox) with great economic benefit and good treatment effect is a promising process to remove nitrogen from antibiotic-containing wastewater. However, antibiotic inhibition has been observed in anammox applications. Therefore, a comprehensive overview of the single and combined effects of various antibiotics on the anammox system is conducted in this review with a focus on nitrogen removal performance, sludge properties, microbial community, antibiotic resistance genes and anammox-involved functional genes. Additionally, the influencing mechanism of antibiotics on anammox consortia is summarized. Remaining problems and future research needs are also proposed based on the presented summary. This review provides a better understanding of the influences of antibiotics on anammox and offers a direction to remove nitrogen from antibiotic-containing wastewater by the anammox process.

Application of anammox within an integrated approach to sustainable food waste management and valorization

In this study, the anammox process was applied for the first time to the treatment of ammonium-rich liquid residues produced by the two-stage anaerobic digestion of food waste (2sAD-FW); such residues may represent a significant environmental issue if not properly managed. A granular anammox reactor was fed with a progressively increasing share of partially nitritated 2sAD-FW wastewater. An alternative operating strategy based on partial by-pass of the partial nitritation unit was tested, in order to regulate the influent NO2/NH4 molar ratio without chemical addition. High nitrogen removal efficiency (89 ± 1%) and negligible nitrite discharge rates were achieved, together with high nitrogen removal rate/nitrogen loading rate (NRR/NLR, 97 ± 1%) and stable specific anammox activity (0.42 ± 0.03 gN2-N/gVSS d). The observed NH4-removed/NO2-removed/NO3-produced molar ratio was in agreement with anammox stoichiometry, as confirmed by the low contribution (<5%) of denitrification to nitrogen removal. Moreover, the possibility of using digital color characterization of granular biomass as a novel, simple tool for the monitoring of anammox biomass enrichment and process performance was investigated under dynamic conditions, using real wastewater: changes in granule color correlated well with the increasing share of 2sAD-FW wastewater in the influent (R2 = 83%), as well as with the decrease of anammox biomass abundance in the reactor (R2 = 68%). The results suggest that anammox may be successfully integrated into a 2sAD-FW system, thus enhancing its environmental sustainability.

The effect of carrier addition on Anammox start-up and microbial community: a review

The Anaerobic Ammonia Oxidation (Anammox) wastewater treatment process has attracted significant attention ever since its discovery in the Netherlands in the 1990′s. This has mostly been due to the potential cost-effectiveness associated with the process in large scale application. However, the application of the Anammox process on an industrial-scale has been curtailed mainly due to the long start-up time of the Anammox bacteria. In order to ensure the feasibility of industrial-scale Anammox application, researchers have employed various means; experimenting with different reactor types, membrane types, as well as the usage of chemicals such as hydrazine, acyl-homoserinelactones (AHL), etc. Most recently however, more attention has been directed towards the addition of biomass carriers such as biochar, zeolites, sponges, non-woven membrane etc. for the optimization of the Anammox process. This article provides an up-to-date overview of the various carriers (Non-woven fabric, Biochar, Down-flow hanging sponge, Zeolite, Zero-violent iron, Polyethylene glycol gel, Activated-carbon, Polyethylene sponge, etc.) that have so far been used to better the performance of the Anammox process. It also focuses on the effect of these biomass carrier additions on the microbial growth and community structure. Understanding the metabolomics of microorganisms in carrier-amended media promises to enhance our knowledge of carriers’ influence on the microbial community structure. Generally, the metabolic effects of carrier-amendment on microbial growth and community are largely uninvestigated. Future researches focusing on this area could tremendously improve our comprehension of the inner-workings of the carrier amended Anammox set-up.