Nitrogen removal from opto-electronic wastewater using the simultaneous partial nitrification, anaerobic ammonium oxidation and denitrification (SNAD) process in sequencing batch reactor

Anammox-based technologies: A review of recent advances, mechanism, and bottlenecks

The removal of nitrogen via the ANAMMOX process is a promising green wastewater treatment technology, with numerous benefits. The incessant studies on the ANAMMOX process over the years due to its long start-up and high operational cost has positively influenced its technological advancement, even though at a rather slow pace. At the moment, relatively new ANAMMOX technologies are being developed with the goal of treating low carbon wastewater at low temperatures, tackling nitrite and nitrate accumulation and methane utilization from digestates while also recovering resources (phosphorus) in a sustainable manner. This review compares and contrasts the handful of ANAMMOX -based processes developed thus far with plausible solutions for addressing their respective bottlenecks hindering full-scale implementation. Ultimately, future prospects for advancing understanding of mechanisms and engineering application of ANAMMOX process are posited. As a whole, technological advances in process design and patents have greatly contributed to better understanding of the ANAMMOX process, which has greatly aided in the optimization and industrialization of the ANAMMOX process. This review is intended to provide researchers with an overview of the present state of research and technological development of the ANAMMOX process, thus serving as a guide for realizing energy autarkic future practical applications.

Partitioned granular sludge coupling with membrane-aerated biofilm reactor for efficient autotrophic nitrogen removal

The partial nitritation-anammox process based on a membrane-aerated biofilm reactor (MABR) faces several challenges, such as difficulty in suppressing nitrite-oxidizing bacteria (NOB), excessive effluent nitrate, and ineffective synergy between denitrification and anammox bacteria. Therefore, a novel partitioned granular sludge coupling with MABR (G-MABR) was constructed. The chemical oxygen demand (COD) and nitrogen removal efficiency were 88.8 ± 1.8 %-92.6 ± 1.2 % and 88.8 ± 1.5 %-93.6 ± 0.7 %, respectively. The COD was mainly lowered in the lower granular sludge-zone, while nitrogen was removed in the upper MABR-zone. NOB was significantly suppressed in the MABR-zone due to competition for substrate with denitrifying bacteria and anammox bacteria. This partitioned configuration reduced the C/N ratio in the MABR-zone, thus facilitating autotrophic nitrogen removal. Both partial nitrification and denitrification provided nitrite for anammox bacteria in granular sludge, whereas partial nitrification mainly supplied nitrite to the anammox bacteria in membrane biofilms.

Simultaneous partial nitrification, anammox, and denitrification in an upflow microaerobic membrane bioreactor treating middle concentration of ammonia nitrogen wastewater with low COD/TN ratio

The rapid start-up and operating characteristics of simultaneous partial nitrification, anammox, and denitrification (SNAD) process was investigated using synthetic wastewater with a low C/N ratio (COD: NH₄⁺-N = 200 mg/L: 200 mg/L) in a novel upflow microaerobic membrane bioreactor (UMMBR). The average removal efficiencies of COD, NH₄⁺-N, and TN in the stable phase were 89%, 96%, and 86%, respectively. Carmine granule, which coexisted with sludge floc, appeared on day 83. The high sludge concentration (12.9-17.2 g/L) and the upflow mode of the UMMBR could establish some anaerobicregions for anammox process. The anammox bacteria and short-cut denitrification (NO₂^-→N₂) bacteria with activities of 4.46 mg NH₄⁺-N/gVSS·h and 2.57 mg NO₂^--N/gVSS·h contributed TN removal of 39% and 61% on day 129, respectively. High-throughput sequencing analysis revealed that the ammonia-oxidizing archaea (AOA, 49.45% in granule and 17.05% in sludge floc) and ammonia-oxidizing bacterial (AOB, 1.30% in sludge floc) dominated the nitrifying microbial community. Candidatus Jettenia (47.14%) and Denitratisoma (10.92%) mainly existed in granule with positive correlations. Some heterotrophic bacteria (OLB13, SJA-15, 1-20, SBR1031, and SJA-28) in sludge floc benefited system stability and sludge activity and protected Candidatus Jettenia from adverse environments.

Simultaneous partial nitritation, anammox, and denitrification process for the treatment of simulated municipal sewage in a single-stage biofilter reactor

This study provides a feasible scheme for the treatment of municipal sewage through simultaneous partial nitritation, anammox, and denitrification (SNAD) process, which was realized in a single-stage biofilter reactor (BFR). First, the BFR was started up to enrich the anaerobic ammonium-oxidizing bacteria (AnAOB) in the upper part of the reactor through the operation mode of the top influent and bottom effluent. Then, the BFR was inoculated with activated sludge and aerated continuously at the bottom to realize the coupling of SNAD, which was accompanied by a two-point influent from the bottom and top effluent. Results indicated that the high removal efficiency of NH₄⁺-N (93.40%), total nitrogen (TN, 89.95%), and soluble chemical oxygen demand (SCOD, 92.68%) were achieved with an air-water ratio of 4.29 and hydraulic retention time (HRT) of 6 h. During the SNAD steady phase for the treatment of simulated municipal sewage with a soluble chemical organic demand to nitrogen (C/N) ratio of 2.31, low concentrations of NH₄⁺-N (4.13 mg/L), TN (6.44 mg/L), and SCOD (11.29 mg/L) were attained in the effluent. High-throughput sequencing analysis indicated that the relative abundance of Nitrosomonas, Candidatus Brocadia, and Denitratisoma were 0.77%, 0.43%, and 4.07% in the biofilm at the 0-12.5 cm zone, respectively, suggesting successful implementation of the SNAD process.

Biodegradable organic matter-containing ammonium wastewater treatment through simultaneous partial nitritation, anammox, denitrification and COD oxidization process

For both nitrogen and COD removal from biodegradable organic matter (BOM)-containing ammonium wastewater, the simultaneous partial nitritation, anammox, denitrification and COD oxidization (SNADCO) process is a promising solution. In this study, with the stable influent ammonium concentration of 250.0 mg/L (nitrogen loading rate of 0.5 kg/m³/d) and the variation of influent COD/NH₄⁺-N (C/N) ratio from 0.0 to 1.6, the performance of the SNADCO process in a one-stage carrier-packing airlift reactor with continuous mode was investigated for the first time. The results showed that until the C/N ratio of 0.8, both the well nitrogen and COD removal targets could be reached. Mass balance calculations indicated that the average nitrogen removal efficiency (NRE) of 80.9% achieved at the C/N ratio of 0.8 were due to both the anammox and denitrification pathways. Correspondingly, the achieved average COD removal efficiency of 94.6% was attributed to both the denitrification and COD oxidization pathways. Based on the specific sludge activity tests and Fluorescence in Situ Hybridization observation, anammox and denitrification bacteria were mainly distributed in the biofilm sludge, while ammonium oxidizing bacteria and ordinary heterotrophic organisms were mainly in the suspended sludge. At the C/N ratio of 1.6, the washout of suspended sludge became serious while the biofilm sludge was well retained, resulting in inefficient nitritation and a subsequent decrease in NRE. The microbial interaction analysis provided a clear explanation of the performance change of the SNADCO process under different C/N ratios. This research enriches the knowledge of the SNADCO process in BOM-containing ammonium wastewater treatment.

Insight into the impacts of organics on anammox and their potential linking to system performance of sewage partial nitrification-anammox (PN/A): A critical review

Partial nitrification-anammox (PN/A) is an energy-efficient process for nitrogen removal from sewage. The influent organics of sewage is usually pre-removed, reducing the risk for enriching anammox bacteria (AnAOB). However, recent studies demonstrate that optimum influent organics could improve nitrogen removal and operational stability of PN/A. Thus, the impact of organics on PN/A-based process should not be overlooked. In this review, the complicated impacts of organics-containing influent on anammox and their linking to apply PN/A are discussed. Firstly, the effect of organics on AnAOB metabolism and the competition relationship between AnAOB and heterotrophic bacteria are summarized. Secondly, the combined effects of influent organics and operational strategies on PN/A-based process were reviewed. Thirdly, how to control influent organics in the real application of PN/A were discussed. Lastly, recent development of the PN/A-based process combined with denitrification were reviewed. Overall, influent organics could be an essential factor for successful application of sewage PN/A.

The effect of different denitrification and partial nitrification-Anammox coupling forms on nitrogen removal from mature landfill leachate at the pilot-scale

The effects on nitrogen removal from landfill leachate were compared between the denitrification (DN) direct coupling in Partial nitrification (PN)-Anammox (DN+(PN-Anammox)) and pre-DN followed by PN-Anammox (DN-PN-Anammox). Both processes can achieve coupling and high nitrogen removal. However, the DN+(PN-Anammox) process was not conducive to the treatment of high-COD wastewater. The total nitrogen removal rate (TNRR) and total nitrogen removal efficiency (TNRE) were stable at 0.31 kg/(m³·d) and 76.3%. When UASB was added to denitrification and transform the process into DN-PN-Anammox, the influent NH₄⁺-N and COD concentrations were increased to 2230 and 2612 mg/L, TNRR and TNRE reached 0.45 kg/(m³·d) and 96.7%, respectively. The DN-PN-Anammox process not only was able to make full use of degradable COD in wastewater to realize the NO₃^--N removal, but also benefited the growth of autotrophic bacteria. The DN-PN-Anammox reduced the oxygen supply and was more conducive to the treatment of highly-concentrated mature landfill leachate.

Achieving mainstream nitrogen and phosphorus removal through Simultaneous partial Nitrification, Anammox, Denitrification, and Denitrifying Phosphorus Removal (SNADPR) process in a single-tank integrative reactor

Simultaneous partial Nitrification, Anammox, and Denitrification (SNAD) is a promising and energy-efficient nitrogen removal process, which is powerless to eliminate phosphorus and confronted the problem of excessive effluent nitrate once applied in municipal sewage treatment characterized with high C/N ratio (≥2). Herein, by coupling SNAD with denitrifying phosphorus removal (DPR) process in a single-tank reactor, a novel integrative process (termed as SNADPR) was designed to treat municipal sewage. The removal efficiencies of TN, PO₄^3--P, and COD under the optimized conditions (T = 30 °C, HRT = 24 h, DO = 0.45 mg/L) were 89.15 ± 2.19%, 92.93 ± 0.60%, and 99.17 ± 1.58%, respectively. Distinctive microbial community distribution was harvested, where anammox bacteria (AnAOB, Candidatus_Kuenenia and Candidatus_Brocadia) were mainly located in biofilm, whereas denitrifying polyphosphate-accumulating organisms (DPAOs, Dechloromonas and Pseudomonas) and ammonium oxidizing bacteria (AOB, Nitrosomonas) basically lived in suspended floc. The SRT separation between biofilm and floc was reached by conserving AnAOB-rich biofilm and termly discharging phosphorus-rich floc.

Nitritation-anammox process - A realizable and satisfactory way to remove nitrogen from high saline wastewater

In this study, acclimation of freshwater nitritation-anammox sludge to remove nitrogen in high saline and hypersaline wastewater was evaluated, during which the microbes activity and microbial community revolution were revealed to understand the fate of a nitritation-anammox process (SNAP) in response to increasing salt stress. By enhanced aeration, the SNAP system can treat saline (3%) ammonium-rich (185 mg/L) wastewater after gradual adaption. Hypersalinity (5%) caused final deterioration of the SNAP system due to a severe inhibition on anammox activity. Genera Kuenenia (anammox), Nitrosomonas (AOB) and Nitrosovibrio (AOB) bacteria were salt adaptable microbes, while genus Nitrospira (NOB) bacteria were sensitive to salinity. Under the enhanced aeration, AOB bacteria could bear 3% salinity with possible enriched ammonia monooxygenase to stimulate the conversion of ammonium to nitrite by producing more intermediate-hydroxylamine, which could alleviate the negative effect of insufficient hydroxylamine oxidase members in AOB bacteria.

Treatment of municipal sewage with low carbon-to-nitrogen ratio via simultaneous partial nitrification, anaerobic ammonia oxidation, and denitrification (SNAD) in a non-woven rotating biological contactor

In this study, a non-woven rotating biological contactor was evaluated for the treatment of municipal sewage via simultaneous partial nitrification, anaerobic ammonia oxidation (anammox), and denitrification (SNAD). Fluorescence in situ hybridization analysis showed that the dominant bacterial group in the aerobic outer layer of the biofilm was ammonia-oxidizing bacteria (65.13%), whereas anammox (47.17%) and denitrifying (38.91%) bacteria were present in the anaerobic inner layer. Response surface methodology was applied to develop mathematical models for the interaction between C/N and dissolved oxygen (DO) for chemical oxygen demand (COD) and total nitrogen (TN) removal. Results showed that the optimum region for SNAD was at C/N = 1.4-2.3 and DO = 0.2-0.8 mg/L. The most optimal operating condition was determined at C/N = 2.3 and DO = 0.2 mg/L, with actual removal rates of COD and TN were 83.12% and 79.13%, respectively, which are in close model consistency with model prediction (84% and 80%).

Endogenous influences on anammox and sulfocompound-oxidizing autotrophic denitrification coupling system (A/SAD) and dynamic operating strategy

The anaerobic ammonia oxidation (anammox) and sulfocompound-oxidizing autotrophic denitrification coupling system (A/SAD) was initiated in an expanded granular sludge bed (EGSB) reactor for nitrogen removal from high-strength wastewater. Owing to cooperation between anammox and partial sulfocompound-oxidation autotrophic denitrification coupling system (PSAD), the highest nitrogen removal efficiency (NRE) of 98.1% ± 0.4% achieved at the optimal influent conditions of conversion efficiency of ammonium (CEA) of 55% and S₂O₃^2--S/NO₃^--N (S/N) of 1.4 mol mol^-1. The activity of the short-cut sulfocompound-oxidizing autotrophic denitrification (SSAD) was also regulated to cope with dynamic CEA in the influent by changing the S/N, which was demonstrated to be effective in alleviating nitrite accumulation when the CEA was between 57% and 61%. Both the anammox and SAD bacteria enriched in the reactor after long-term incubation. Candidatus Brocadia and Candidatus Jettenia might be potentially contributing the most to anammox, while the Thiobacillus was the dominant taxa related to SAD.

Influence of biomass acclimation on the performance of a partial nitritation-anammox reactor treating industrial saline effluents

The performance of the partial nitritation/anammox processes was evaluated for the treatment of fish canning effluents. A sequencing batch reactor (SBR) was fed with industrial wastewater, with variable salt and total ammonium nitrogen (TAN) concentrations in the range of 1.75-18.00 g-NaCl L^-1 and 112 - 267 mg-TAN L^-1. The SBR operation was divided into two experiments: (A) progressive increase of salt concentrations from 1.75 to 18.33 g-NaCl L^-1; (B) direct application of high salt concentration (18 g-NaCl L^-1). The progressive increase of NaCl concentration provoked the inhibition of the anammox biomass by up to 94% when 18 g-NaCl L^-1 were added. The stable operation of the processes was achieved after 154 days when the nitrogen removal rate was 0.021 ± 0.007 g N/L·d (corresponding to 30% of removal efficiency). To avoid the development of NOB activity at low salt concentrations and to stabilize the performance of the processes dissolved oxygen was supplied by intermittent aeration. A greater removal rate of 0.029 ± 0.017 g-N L^-1 d^-1 was obtained with direct exposure of the inoculum to 18 g-NaCl L^-1 in less than 40 days. Also, higher specific activities than those from the inoculum were achieved for salt concentrations of 15 and 20 g-NaCl L^-1 after 39 days of operation. This first study of the performance of the partial nitritation/anammox processes, to treat saline wastewaters, indicates that the acclimation period can be avoided to shorten the start-up period for industrial application purposes. Nevertheless, further experiments are needed in order to improve the efficiency of the processes.

Realization of microbial community stratification for single-stage nitrogen removal in a sequencing batch biofilter granular reactor

A permanent microbial stratified nitrogen removal system coupling anammox with partial nitrification (SNAP) in a sequencing batch biofilter granular reactor (SBBGR) was successfully constructed for the treatment of ammonia-rich wastewater. With a nitrogen loading rate of 0.1kgNm^-3·d^-1, the maximal ammonia and total nitrogen removal efficiencies could reach up to 96.08% and 84.86% on day 108, respectively. The pH, DO profiles revealed a switch of functional species (AOB and anammox) at a typical intermittent aeration cycle. qPCR and high throughput analyses certified a stable spatial microbial stratified community structure. Although, anammox preferred strict anaerobic environment while AOB needed oxygen, a special stratified community structure contributed to conquer this obstacle. Moreover, Bacteroidet, Chlorobi, OD1, Planctomycetes, and Proteobacteria were the dominant species in the SBBGR. Although we have predicted the possible pathways of nitrogen transformation, further studies are needed to validate the pathways in enzymology.

Assessment of molecular detection of anaerobic ammonium-oxidizing (anammox) bacteria in different environmental samples using PCR primers based on 16S rRNA and functional genes

Eleven published PCR primer sets for detecting genes encoding 16S ribosomal RNA (rRNA), hydrazine oxidoreductase (HZO), cytochrome cd ₁-containing nitrite reductase (NirS), and hydrazine synthase subunit A (HzsA) of anaerobic ammonium-oxidizing (anammox) bacteria were assessed for the diversity and abundance of anammox bacteria in samples of three environments: wastewater treatment plant (WWTP), wetland of Mai Po Nature Reserve (MP), and the South China Sea (SCS). Consistent phylogenetic results of three biomarkers (16S rRNA, hzo, and hzsA) of anammox bacteria were obtained from all samples. WWTP had the lowest diversity with Candidatus Kuenenia dominating while the SCS was dominated by Candidatus Scalindua. MP showed the highest diversity of anammox bacteria including C. Scalindua, C. Kuenenia, and Candidatus Brocadia. Comparing different primer sets, no significant differences in specificity for 16S rRNA gene could be distinguished. Primer set CL1 showed relatively high efficiency in detecting the anammox bacterium hzo gene from all samples, while CL2 showed greater selectivity for WWTP samples. The recently reported primer sets of the hzsA gene resulted in high efficiencies in detecting anammox bacteria while nirS primer sets were more selective for specific samples. Results collectively indicate that the distribution of anammox bacteria is niche-specific within different ecosystems and primer specificity may cause biases on the diversity detected.

Anammox Process

Application of anammox based processes is nowadays an efficient way to remove nitrogen from wastewaters, being good alternative to the conventional nitrification-denitrification process. This chapter reviews the possible configurations to apply the anammox process, being special attention to the previous partial nitritation, necessary to obtain the adequate substrates for anammox bacteria. Furthermore a description of the main technologies developed and patented by different companies was performed, with focus on the advantages and bottlenecks of them. These technologies are classified in the chapter based on the type of biomass: suspended, granular and biofilm. Also a review is presented for the industrial applications (food industry, agricultural wastes, landfill leachates, electronic industry, etc.), taking into account full scale experiences and laboratory results, as well as microbiology aspects respect to the anammox bacteria genera involved. Finally the possibility to couple nitrogen removal, by anammox, with phosphorus recovery, by struvite precipitation, is also evaluated.

Stoichiometric evaluation of partial nitritation, anammox and denitrification processes in a sequencing batch reactor and interpretation of online monitoring parameters

A laboratory-scale sequencing batch reactor (SBR) performing partial nitritation - anammox and denitrification was used to treat anaerobic digester effluents. The SBR cycle consisted of a short mixing filling phase followed by oxic and anoxic reaction phases. Working at 25 °C, an ammonium conversion efficiency of 96.5%, a total nitrogen removal efficiency of 88.6%, and an organic carbon removal efficiency of 63.5% were obtained at a nitrogen loading rate of 0.15 kg N m^-3 d^-1, and a biodegradable organic carbon to nitrogen ratio of 0.37. The potential contribution of each biological process was evaluated by using a stoichiometric model. The nitritation contribution decreased as the temperature decreased, while the contribution from anammox depended on the wastewater type and soluble carbon to nitrogen ratio. Denitrification improved the total nitrogen removal efficiency, and it was influenced by the biodegradable organic carbon to nitrogen ratio. The characteristic patterns of conductivity, oxidation-reduction potential (ORP) and pH in the SBR cycle were well related to biological processes. Conductivity profiles were found to be directly related to the decreasing profiles of ammonium. Positive ORP values at the end of the anoxic phases were detected for total nitrogen removal efficiency of lower than 85%, and the occurrence of bending points on the ORP curves during the anoxic phases was associated with nitrite depletion by the anammox process.

Adsorption and transformation of ammonium ion in a loose-pore geothermal reservoir: Batch and column experiments

Adsorption kinetics and transformation process of ammonium ion (NH4(+)) were investigated to advance the understanding of N cycle in a low-temperature loose-pore geothermal reservoir. Firstly, batch experiments were performed in order to determine the sorption capacity and the kinetic mechanism of NH4(+) onto a loose-pore geothermal reservoir matrix. Then column experiments were carried out at temperatures from 20°C to 60°C in order to determine the transport parameters and transformation mechanism of NH4(+) in the studied matrix. The results showed that the adsorption process of NH4(+) onto the porous media well followed the pseudo-second-order model. No obvious variation of hydrodynamic dispersion coefficient (D) and retardation factor (R) was observed at different transport distances at a Darcy's flux of 2.27cm/h, at which nitrification could be neglected. The simulated D obtained by the CDE model in CXTFIT2.1 increased with temperature while R decreased with temperature, indicating that the adsorption capacity of NH4(+) onto the matrix decreased with the increasing of temperature. When the Darcy's flux was decreased to 0.014cm/h, only a little part of NH4(+) could be transformed to nitrate, suggesting that low density of nitrifiers existed in the simulated loose-pore geothermal reservoir. Although nitrification rate increased with temperature in the range of 20°C to 60°C, it was extremely low and no accumulation of nitrite was observed under the simulated low-temperature geothermal conditions without addition of biomass and oxygen.

Start-up of simultaneous partial nitrification, anammox and denitrification (SNAD) process in sequencing batch biofilm reactor using novel biomass carriers

Simultaneous partial nitrification, anammox and denitrification (SNAD) process was started-up in a 2.5L sequencing batch biofilm reactor (SBBR) using novel biomass carriers. The SNAD process took only 51d for start-up at nitrogen loading rate (NLR) and organic loading rate (OLR) of 120 and 60g/m(3)-d, respectively. Long-term stable operation of SNAD process was observed at NLR and OLR of 360 and 180g/m(3)-d with average total nitrogen and COD removal efficiencies of >88% and >90%, respectively. The values of conversion ratio [Formula: see text] remained below 0.11 after the start-up period, which further confirmed the long-term stability of SNAD process. Results of polymerase chain reaction (PCR), qualitative PCR, and scanning electron microscopic (SEM) analysis of sludge samples confirmed the co-existence and enrichment of AOB, anammox bacteria and denitrifying bacteria in the reactor and biofilm formation on to the carriers.

Advanced nitrogen removal from wastewater by combining anammox with partial denitrification

The anammox (anaerobic ammonium oxidation) process has attracted much attention for its cost-saving. However, excess nitrate is usually produced which should be further treated. In this study, an innovative process combined anammox with partial denitrification (nitrate→nitrite) was proposed for advanced nitrogen removal in two sequencing batch reactors (SBRs). The nitrate produced in anammox-SBR (ASBR) was fed into partial denitrification-SBR (DSBR), in which the nitrate was reduced to nitrite, and then removed by backflow of the nitrite to ASBR for secondary anammox process. Results showed that ∼80% nitrate in the effluent of previous anammox was converted to nitrite in DSBR. And the maximum nitrogen removal efficiency (NRE) of 94.06% was obtained with total nitrogen (TN) in the effluent of 10.98 mg/L in average. It indicated that desired effluent quality could be achieved, and the advanced nitrogen removal performance was attributed to the successful achievement of partial denitrification.

Treatment of nitrate-rich water in a baffled membrane bioreactor (BMBR) employing waste derived materials

Nitrate removal in submerged membrane bioreactors (MBRs) is limited as intensive aeration (for maintaining adequate dissolved oxygen levels and for membrane scouring) deters the formation of anoxic zones essential for biological denitrification. The present study employs baffled membrane bioreactor (BMBR) to overcome this constraint. Treatment of nitrate rich water (synthetic and real groundwater) was investigated. Sludge separation was achieved using ceramic membrane filters prepared from waste sugarcane bagasse ash. A complex external carbon source (leachate from anaerobic digestion of food waste) was used to maintain an appropriate C/N ratio. Over 90% COD and 95% NO3-N reduction was obtained. The bagasse ash filters produced a clear permeate, free of suspended solids. Sludge aggregates were observed in the reactor and were linked to the high extracellular polymeric substances (EPS) content. Lower sludge volume index (40 mL/g compared to 150 mL/g for seed sludge), higher settling velocity (47 m/h compared to 10 m/h for seed sludge) and sludge aggregates (0.7 mm aggregates compared to <0.2 mm for seed sludge) was observed. The results demonstrate the potential of waste-derived materials viz. food waste leachate and bagasse ash filters in water treatment.

Effectiveness of dairy wastewater treatment in a bioreactor based on the integrated technology of activated sludge and hydrophyte system

The aim of this study was to determine the effectiveness of dairy wastewater treatment in the integrated technology based on the simultaneous use of the activated sludge method (AS) and a hydrophyte system (HS) (AS-HS), in this case, common reed (Phragmites australis) or common cattail (Typha latifolia). Experiments were conducted in an innovative reactor exploited in the fractional-technical scale at the loads of 0.05 mg BOD5/mg.d.m. d (biochemical oxygen demand) and 0.10 mg BOD5/mg.d.m d. The AS--HS enabled improving the removal effectiveness ofbiogenes characterized by concentrations of Ntot., N-NH4 and Ptot. In contrast, the integrated system had no significant reducing effect either on concentrations of organic compounds characterized by BOD5 and chemical oxygen demand parameters or on the structure of AS in the sequencing batch-type reactors.

Nitrogen removal pathway of anaerobic ammonium oxidation in on-site aged refuse bioreactor

The nitrogen removal pathways and nitrogen-related functional genes in on-site three-stage aged refuse bioreactor (ARB) treating landfill leachate were investigated. It was found that on average 90.0% of CODCr, 97.6% of BOD5, 99.3% of NH4(+)-N, and 81.0% of TN were removed with initial CODCr, BOD5, NH4(+)-N, and TN concentrations ranging from 2323 to 2754, 277 to 362, 1237 to 1506, and 1251 to 1580 mg/L, respectively. Meanwhile, the functional genes amoA, nirS and anammox 16S rRNA gene were found to coexist in every bioreactor, and their relative proportions in each bioreactor were closely related to the pollutant removal performance of the corresponding bioreactor, which indicated the coexistence of multiple nitrogen removal pathways in the ARB. Detection of anammox expression proved the presence of the anammox nitrogen removal pathway during the process of recirculating mature leachate to the on-site ARB, which provides important information for nitrogen management in landfills.

Towards energy neutral wastewater treatment: methodology and state of the art

Conventional biological wastewater treatment processes are energy-intensive endeavors that yield little or no recovered resources and often require significant external chemical inputs. However, with embedded energy in both organic carbon and nutrients (N, P), wastewater has the potential for substantial energy recovery from a low-value (or no-value) feedstock. A paradigm shift is thus now underway that is transforming our understanding of necessary energy inputs, and potential energy or resource outputs, from wastewater treatment, and energy neutral or even energy positive treatment is increasingly emphasized in practice. As two energy sources in domestic wastewater, we argue that the most suitable way to maximize energy recovery from wastewater treatment is to separate carbon and nutrient (particularly N) removal processes. Innovative anaerobic treatment technologies and bioelectrochemical processes are now being developed as high efficiency methods for energy recovery from waste COD. Recently, energy savings or even generation from N removal has become a hotspot of research and development activity, and nitritation-anammox, the newly developed CANDO process, and microalgae cultivation are considered promising techniques. In this paper, we critically review these five emerging low energy or energy positive bioprocesses for sustainable wastewater treatment, with a particular focus on energy optimization in management of nitrogenous oxygen demand. Taken together, these technologies are now charting a path towards to a new paradigm of resource and energy recovery from wastewater.

The development of a reverse anammox sequencing partial nitrification process for simultaneous nitrogen and COD removal from wastewater

In order to achieve simultaneous removal of nitrogenous and organic pollutants, a novel reverse anammox-partial nitrification nitrogen removal process was developed. During steady operation, the maximum nitrogen and COD (chemical oxygen demand) removal efficiencies were over 90%, with influent NH4(+)-N and COD concentrations of 300 and 100mgL(-1). The optimum recycle ratio of Membrane bioreactor (MBR for partial nitrification) and fixed bed reactor (anammox) for this process was recommended as 3 due to increasingly larger recycle ratio caused slight increase in TN (total nitrogen) removal efficiency. Additionally, the steady nitrogen removal rate was obtained at 0.92-1.03kgNm(-3)day(-1). Considering its great potential in nitrogen removal, this reverse process will be revealing for the study of anammox technique.

Coexistence of nitrifying, anammox and denitrifying bacteria in a sequencing batch reactor

Elevated nitrogen removal efficiencies from ammonium-rich wastewaters have been demonstrated by several applications, that combine nitritation and anammox processes. Denitrification will occur simultaneously when organic carbon is also present. In this study, the activity of aerobic ammonia oxidizing, anammox and denitrifying bacteria in a full scale sequencing batch reactor, treating digester supernatants, was studied by means of batch-assays. AOB and anammox activities were maximum at pH of 8.0 and 7.8–8.0, respectively. Short term effect of nitrite on anammox activity was studied, showing nitrite up to 42 mg/L did not result in inhibition. Both denitrification via nitrate and nitrite were measured. To reduce nitrite-oxidizing activity, high NH₃-N (1.9–10 mg NH₃-N/L) and low nitrite (3–8 mg TNN/L) are required conditions during the whole SBR cycle. Molecular analysis showed the nitritation-anammox sludge harbored a high microbial diversity, where each microorganism has a specific role. Using ammonia monooxygenase α–subunit (amoA) gene as a marker, our analyses suggested different macro- and micro-environments in the reactor strongly affect the AOB community, allowing the development of different AOB species, such as N. europaea/eutropha and N. oligotropha groups, which improve the stability of nitritation process. A specific PCR primer set, used to target the 16S rRNA gene of anammox bacteria, confirmed the presence of the “Ca. Brocadia fulgida” type, able to grow in presence of organic matter and to tolerate high nitrite concentrations. The diversity of denitrifiers was assessed by using dissimilatory nitrite reductase (nirS) gene-based analyses, who showed denitifiers were related to different betaproteobacterial genera, such as Thauera, Pseudomonas, Dechloromonas and Aromatoleum, able to assist in forming microbial aggregates. Concerning possible secondary processes, no n-damo bacteria were found while NOB from the genus Nitrobacter was detected.

Ambient temperature SNAD process treating anaerobic digester liquor of swine wastewater

In present study, effluent from anaerobic digestion of swine wastewater was treated by the simultaneous partial nitrification, anaerobic ammonium oxidation and denitrification (SNAD) process using a lab scale 5L sequencing batch reactor (SBR) under ambient temperature. The fluctuation of anaerobic digester liquor quality (COD, 387 ± 145 mg/L; TKN, 662 ± 190 mg/L; NH₄(+)-N, 519 ± 134 mg/L) and temperature created difficulties to develop a stable SNAD process in the SBR (days 1-285). Fed batch feeding strategy was adopted to have a stable condition in the reactor and overcome the negative effects of organic nitrogen. The average total nitrogen, NH₄(+)-N and COD removal efficiencies in the SBR under steady state conditions (days 485-523) were 80%, 96% and 76%, respectively. The results showed that presence of organic nitrogen, mode of feeding and reactor temperature affects the SNAD process.

Partial nitrification and anammox process: a method for high strength optoelectronic industrial wastewater treatment

Completely autotrophic nitrogen removal over nitrite (CANON) process was employed in an 18 L sequencing batch reactor (SBR) for treatment of optoelectronic industrial wastewater containing high strength ammonium nitrogen (3712 ± 120 mg NH4(+) - N L(-1)). About 89% of total nitrogen and 98% of NH4(+) - N removal efficiencies were observed at the loading rate of 909 g N m(-3) d(-1) and the HRT of 4 d. A profound variation in the performance of CANON process was experienced at high DO exposure (above 1 mg L(-1)) and high nitrite concentration (above 100 mg L(-1)). Inhibition due to high DO exposure was found to be reversible phenomenon whereas the synergistic inhibition of nitrite, free ammonia and free nitrous acid was irreversible. The fluctuation of reactor temperature between 17 and 37 °C did not affect the performance of CANON system. The CANON process was stably controlled at high nitrogen loading rate for more than one month. The co-existence of aerobic and anaerobic ammonium oxidizing bacteria in the reactor was detected by The PCR analysis. About 5 fold increase in amount of anammox bacteria over a period of 258 days was confirmed from the results of qPCR on day 487.

Development of a simultaneous partial nitrification, anaerobic ammonia oxidation and denitrification (SNAD) bench scale process for removal of ammonia from effluent of a fertilizer industry

A simultaneous partial nitrification, anammox and denitrification (SNAD) process was developed for the treatment of ammonia laden effluent of a fertilizer industry. Autotrophic aerobic and anaerobic ammonia oxidizing biomass was enriched and their ammonia removal ability was confirmed in synthetic effluent system. Seed consortium developed from these was applied in the treatment of effluent in an oxygen limited bench scale SNAD type (1L) reactor run at ambient temperature (∼30°C). Around 98.9% ammonia removal was achieved with ammonia loading rate 0.35kgNH(4)(+)-N/m(3)day in the presence of 46.6mg/L COD at 2.31days hydraulic retention time. Qualitative and quantitative analysis of the biomass from upper and lower zone of the reactor revealed presence of autotrophic ammonia oxidizing bacteria (AOB), Planctomycetes and denitrifiers as the dominant bacteria carrying out anoxic oxidation of ammonia in the reactor. Physiological and molecular studies strongly indicate presence of anammox bacteria in the anoxic zone of the SNAD reactor.