Anoxic Sequencing Batch Reactor Research Articles

Pre-anaerobic phase persists benefits for nitrogen removal in high carbon/nitrogen scenarios: Comparative study of aerobic–anoxic and anaerobic–aerobic–anoxic sequencing batch reactors

The pre-anaerobic phase in anaerobic–aerobic–anoxic (AOA) process is critical to intensifying nitrogen removal at low C/N ratios, yet its applicability to high C/N scenarios remains vague. Here, four bench-scale aerobic–anoxic sequencing batch reactors (OA-SBRs) were established at different C/N ratios (3–16.5) and compared with the parallel AOA-SBRs. The results showed that the NH4+–N and TN removal in the OA-SBRs increased by 24.7% and 112.2%, respectively, as the C/N ratio elevated from 3 to 16.5, but they remained lower than those in the AOA-SBRs till carbon leakage. Typical cycle tests indicated that the pre-anaerobic phase probably endowed the endogenous nitrification/denitrification in the AOA-SBRs with kinetic advantages over the canonical ones in the OA-SBRs, supported by the improved enzymatic activities. Further, microbial insights identified more intensive niche competition between heterotrophic nitrifiers/denitrifiers and non-functional heterotrophs in the OA-SBRs, which could explain the poorer nitrogen removal without the pre-anaerobic phase. This study underscores the implications of pre-anaerobic phase in nitrogen removal of AOA process in high C/N scenarios.

Insight into thiosulfate-driven denitrification and anammox process: Bigger aggregates driving better nitrite utilization on ammonium and nitrate contained wastewater

Recent studies have paid attention to thiosulfate-driven denitrification and anammox (TDDA) process on treating ammonium and nitrate contained wastewater. However, technical challenges still existed in coupling denitratation and reducing denitritation to obtain efficient nitrite supply for anammox. By successfully operated two anoxic sequencing batch reactors (ASBR) with two different sizes of TDDA aggregates, the reactor R1 with smaller aggregates (0.195 mm) achieved 83.38% ammonium removal efficiency and 85.39% total nitrogen removal efficiency. In comparison, the reactor R2 with bigger aggregates (0.554 mm) achieved higher ammonium removal efficiency (92.02%) and total nitrogen removal efficiency (90.05%). Different aggregates showed a similar anammox activity and denitratation activity but varied in denitritation activity (3.47 mg/(L·h) in R1 compared to 1.42 mg/(L·h) in R2), indicating bigger aggregates supplied nitrite to anammox process more efficiently. Annwoodia was the pivotal microorganism involved in nitrite acquisition that outcompeted anammox bacteria in smaller aggregates. Bigger aggregates with the less relative abundance of Annwoodia established a more harmonious microbial community to support effective nitrogen removal. This study provides a novel insight into nitrite utilization of TDDA system and sheds light on the operation of ASBR-based TDDA processes for biological nitrogen removal.

The impact of the varying nutrient concentrations on the enhanced biological phosphorus removal performance and functional phosphorus-accumulating and denitrifying genes in an anaerobic–aerobic–anoxic sequencing batch reactor

The denitrifying phosphorus-accumulating organisms (DPAOs) were extensively focused in the past years due to their high efficiencies in simultaneous removal of phosphorus (P) and nitrogen (N) in wastewater treatment. However, it is not clear how this group of bacteria evolve along with the operation process of a specific wastewater treatment system. Here, it is firstly investigated that the effects of simultaneous variations in chemical oxygen demand (COD), P, and N concentrations on enhanced biological phosphorus removal and phosphorus accumulating (PAOs) and DPAOs in an anaerobic–aerobic–anoxicSBR. The results showed that P and N removal ratios were 83.10 ± 6.72% and 64.21 ± 7.10%, 90.38 ± 3.63% and 84.52 ± 4.91%, 78.82 ± 8.78% and 78.71 ± 3.98% corresponding to the SBR operation process of phases I, II and III respectively. The potential PAOs and DPAOs (such as genera Thauera and Dechloromonas ) were clearly enriched at different operation phases, especially at phase II. Q-PCR and correlation analysis indicated that phosphorus accumulating-related ppk1 genes and denitrifying-related genes coexisted in the SBR and their contents varied with influent COD, P, and N concentrations. Moreover, ppk 1 genes clade IIC/IIF and denitrifying-related genes nir K were highly correlated in the SBR. Therefore, simultaneous variations in nutrient concentrations significantly affected the abundance and distribution of functional bacteria and genes related to P and N removal. The results are valuable in N and P removal of practical wastewater treatment engineering

Rapid start-up and performance of denitrifying granular sludge in an upflow sludge blanket (USB) reactor treating high concentration nitrite wastewater.

Denitrifying granular sludge reactor holds better nitrogen removal efficiency than other kinds of denitrifying reactors, while this reactor commonly needs seeding anaerobic granular sludge and longer period for start-up in practice, which restricted the application of denitrifying granular sludge reactor. This study presented a rapid and stable start-up method for denitrifying granular sludge. An upflow sludge blanket (USB) reactor with packings was established with flocculent activated sludge for treatment of high concentration nitrite wastewater. Results showed mature denitrifying granular sludge appeared only after 15days with highest nitrogen removal rate of 5.844kgN/(m3day), which was much higher than that of compared anoxic sequencing batch reactor (ASBR). No significant nitrite inhibition occurred in USB and denitrification performance was mainly influenced by hydraulic retention time, influent C/N ratio and internal reflux ratio. Hydraulic shear force created by upflow fluid, shearing of gaseous products and stable microorganisms adhesion on the packings might be the reasons for rapid achievement of granular sludge. Compared to inoculated sludge and ASBR, remarkable microbial communitiy variations were detected in USB. The dominance of Proteobacteria and Bacteroidetes and enrichment of species Pseudomonas_stutzeri should be responsible for the excellent denitrification performance, which further verified the feasibility of start-up method.

Effects of azo dye on simultaneous biological removal of azo dye and nutrients in wastewater.

The potential disrupting effects of Azo dye on wastewater nutrients removal deserved more analysis. In this study, 15 days exposure experiments were conducted with alizarin yellow R (AYR) as a model dye to determine whether the dye caused adverse effects on biological removal of both the dye and nutrients in acclimated anaerobic–aerobic–anoxic sequencing batch reactors. The results showed that the AYR removal efficiency was, respectively, 85.7% and 66.8% at AYR concentrations of 50 and 200 mg l−1, while higher AYR inlet (400 mg l−1) might inactivate sludge. Lower removal of AYR at 200 mg l−1 of AYR was due to the insufficient support of electron donors in the anaerobic process. However, the decolorized by-products p-phenylenediamine and 5-aminosalicylic were completely decomposed in the following aerobic stage at both 50 and 200 mg l−1 of AYR concentrations. Compared with the absence of AYR, the presence of 200 mg l−1 of AYR decreased the total nitrogen removal efficiency from 82.4 to 41.1%, and chemical oxygen demand (COD) removal efficiency initially decreased to 68.1% and then returned to around 83.4% in the long-term exposure time. It was also found that the inhibition of AYR, nitrogen and COD removal induced by a higher concentration of AYR was due to the increased intracellular reactive oxygen species production, which caused the rise of oxidation–reduction potential value and decreased ammonia monooxygenase and nitrite oxidoreductase activities.

Nitrogen removal via nitritation pathway for low-strength ammonium wastewater by adsorption, biological desorption and denitrification

Stable nitritation for low-strength ammonium wastewater was the key obstacle for cost-effective and low-carbon biological nitrogen removal. A zeolite biological fixed bed (ZBFB) and an anoxic sequencing batch reactor (ASBR) were successfully applied for achieving nitritation-denitrification of low-strength ammonium wastewater by adsorption, biological desorption and denitrification. Based on free ammonia inhibition on biofilm, stable nitrite accumulation could be realized with suitable operational time and aeration in biological desorption. During cycle operation, adsorption effluent NH4+-N kept at 3.0–4.0 mg/L, biological desorption effluent NO2−-N maintained at 226.8–243.2 mg/L with average nitrite accumulation ratio of 97.18%, and nitrite removal rate was about 0.628–0.672 kg NO2−-N·m−3·day−1, revealing obvious feasibility of ZBFB and ASBR for low-strength ammonium wastewater treatment. High-throughput sequencing analysis results further presented significant microbial community variations happened after cycle operation, with ammonia oxidizing bacteria enrichment and nitrite oxidizing bacteria inhibition in ZBFB and dominance of denitrifiers in ASBR.

Microbial nitrate removal by waste iron shavings from the biological and catalytic ozonation treated dyeing and finishing wastewater

The concentration of total nitrogen (TN) (between 40 and 60 mg/L, mainly nitrate) in the biological and catalytic ozonation treated dyeing and finishing wastewater needs to be reduced before discharge. The present study investigated the feasibility of using waste iron shavings as electron donor for nitrogen removal by biological denitrification. Two anoxic sequencing batch reactors (AnSBR) were continuously operated for more than 100 days. The results showed that the TN removal efficiency increased from 12% in the control reactor (AnSBR-C) to 20% in the reactor with waste iron shavings (AnSBR-Fe). The TN removal was mainly achieved by the reduction of nitrate by heterotrophic denitrification and autotrophic denitrification for AnSBR-Fe. The residual COD (38.4 mg/L) in the effluent of AnSBR-Fe was higher than that (22 mg/L) in the effluent of AnSBR-C, which could be due to that the bacteria preferred to use iron instead of the recalcitrant organics that present in the wastewater. Furthermore, 3DEEM, UHPLC-QTOF and GC–MS analysis were used to characterize the organics in the wastewater, and the results showed that the addition of waste iron shavings affected the degradation of organics during the biological denitrification process.

MCPA biodegradation in an anoxic sequencing batch reactor (SBR)

This research investigated the potential for industrial-strength 2-methyl-4-chlorophenoxyacetic acid (MCPA) degradation by activated sludge microorganisms in a sequencing batch reactor (SBR) under nitrate-reducing conditions. The research was divided into four phases consisting of Phase I (a “proof-of-concept” phase); Phase II (an initial “tolerance” exploration phase); Phase III (an “effect of hydraulic retention time” phase), and Phase IV (a “limits” phase). The SBR successfully and simultaneously removed the nitrates completely and around 98 % of the MCPA up to an initial concentration of 50 mg/L MCPA in the dimethylamine salt form (DMCPA) (Phases I, II and III); however, it took approximately 28 days to observe a steady, high-level of MCPA removal. When the concentration of DMCPA was increased to 75 mg/L (Phase IV), the MCPA removal efficiency dropped to 85 %, but removal was observed only for a relatively short period of time since the biomass appeared to eventually become saturated with the herbicide, stopping conversion of DMCPA to its acid form and halting biodegradation.

Fate of carbon, nitrogen and phosphorus removal in a post-anoxic system treating low strength wastewater

A lab-scale anaerobic–aerobic–anoxic sequencing batch reactor was operated for 135 days with using acetate as sole carbon source to explore the contribution of denitrifying phosphate accumulating organisms to nitrogen and phosphorus removal in a post-anoxic system. The system was operated at an aerobic sludge age of 2.5 days and DO level greater than 2 mg l−1under variable carbon to nitrogen (C/N) and carbon to phosphorus (C/P) ratios. More than 80% of influent nitrogen and phosphorus were removed simultaneously under aerobic conditions. When aerobic denitrification became limited due to the increase of average dissolved oxygen, overall nitrogen removal continued with the same efficiency, but with a larger contribution from anoxic denitrification. On the other hand, enhanced biological phosphorus removal activity decreased significantly as a result of free nitrous acid (FNA) inhibition. Fluorescence in situ hybridization analysis showed that the relative abundance of Actinobacter spp. was decreased by FNA inhibition while the relative abundance of Accumulibacter spp. remained unchanged. Conversely, the relative abundance of glycogen accumulating organisms (GAOs) increased from 7.1% to 23% as a result.

Biological Treatment of Meat Processing Wastewater Using Lab-Scale Anaerobic-Aerobic/Anoxic Sequencing Batch Reactors Operated in Series

In the eastern Africa sub-region, many industries discharge untreated effluents to nearby water resources, thereby polluting the environment. This is because the technologies applicable for wastewater treatment are expensive for these small-medium sized companies with low profit margins. Slaughterhouses belong to this category of industrial setup. The objective of this study was to investigate treatment of meat processing wastewater using anaerobic– aerobic/anoxic Sequencing Batch Reactors (SBRs) operated in series. Reactors were operated for one year using meat processing wastewater. Hydraulic retention time was 2 days for the anaerobic SBR, and 1 day for the aerobic/ anoxic SBR while the organic loading was 12.8 kg COD/m3/day. In the anaerobic SBR, removal efficiencies for total and soluble chemical oxygen demand (TCOD and SCOD), total suspended solids (TSS) and turbidity were 79, 76, 79, and 70%, respectively, with effluent mean concentrations of 3554 ± 58 mg/L, 762 ± 3 mg/L, 2307 ± 21, and 2800 ± 9 FAU. Conductivity, ammonia-nitrogen, ortho-phosphates and total phosphorus concentrations increased by 38, 80, 81 and 71%. Pollutant removal efficiencies in the aerobic/anoxic SBR were 98, 96, 97, 89, 74, 97, 91, 90, and 86% for TCOD, SCOD, BOD, TSS, turbidity, ammonium nitrogen (NH4 +–N), total nitrogen (TN), orthophosphorus (o-PO4 3-–P), and total phosphorus (TP), respectively. Except TKN (35 ± 4 mg/L) and o-PO4 3-–P (8 ± 1 mg/L), all other parameters in the aerobically treated effluent met national discharge standards. Thus, abattoir effluent can be treated using anaerobic–aerobic/anoxic SBR system.

POPULATION ANALYSIS IN HIGH-NITRATE WASTEWATER TREATMENT IN SEQUENCING BATCH REACTORS

The pickling liquor used in the stainless steel manufacturing process is a mixture of nitric and hydrofluoric acid which generates wastewater with nitrate concentrations ranging between 500 and 6000 mgNO3--N/L. In the present study, laboratory-scale anoxic Sequencing Batch Reactors (SBRs) were used to treat high nitrate wastewaters. Two different sludge inocula were tested: one from a Municipal Solid Waste Leachate Treatment Plant (LTP), and the other from a Sewage Treatment Plant (STP). Methanol and sugar-rich wastewater were assayed as alternative carbon sources for denitrification. The best results (removal of 700 mg NO3-N/L in 6 hours of operating) were obtained when using methanol as external carbon source and inoculum from the LTP. Phylogenetic analysis of the bacteria present in the bioreactors using 16S rDNA sequences showed the presence of members of three bacterial phyla: Proteobacteria (Alfa, Gamma and Beta classes), Bacteroides and Actinobacteria. Bacteria belonging to the genera Pseudomonas, Aeromonas, Comamonas, Flavobacterium and Tessaracoccus were identified, Paracoccus being the most conspicuous denitrifying genus. Although most of the isolated bacteria harbour the nosZ denitrification gene, three of them, Paracoccus sp R-24665, Paracoccus denitrificans ATCC19367 and Paracoccus sp WB1, stood out in terms of their denitrifying capacity in both the synthetic and original wastewater, employing methanol as the carbon source. The results open the way to implementing and optimizing the full-scale treatment of industrial wastewater contaminated with nitrate.

Kinetics Analysis of Anaerobic/Anoxic SBR Denitrifying Phosphorus Removal System

Kinetic equations of soluble components are analyzed in an anaerobic/ anoxic sequencing batch reactor (A/A SBR) enriched with denitrifying phosphorus removing bacteria (DPB) sludge. Mathematical model is established for denitrifying phosphorus removal process. The model is based on the simplification of the metabolic model for biological phosphorus removal by DPB. A proper set of kinetic parameters was calculated from the data obtained in the batch tests. The model was subsequently applied for the simulation of cycle behavior of soluble components in the A/A SBR. The results of the simulation indicated that the model can predict the concentration of each component for denitrifying phosphorus removal successfully.

APPLICATION OF ANOXIC BATCH PROCESS TO TREAT HIGH NITROGEN CONCENTRATION OF LEAKAGE FROM OLD LANDFILLS

This study aims to treat TNO, (nitrogen oxides include nitrite and nitrate) in leakage of old landfills by anoxic biological methods with TNO, concentration is about 1,000 mg/L. Anoxic sequencing batch reactor is applied in this study. Denitrification using anoxic reactor hasn't had obvious indication of anammox mechanism, however, nitrogen removal through denitrification is high if it is supplied with sufficient carbon. The optimal ratio between added COD and N-nitrite is 1.5:1 and the ratio between reducing COD and reducing nitrite is 2.2:1 in which 30% of reducing COD is available COD nitrite removal may achieve 95% if nitrogen loading is 0.115 (kg reducing N-NO/moday) or 0.115 (g reducing N-NO/g MLSS. day). Therefore, total N-ammonia removal of biological treatment is about 80-85%.

A Laboratory Scale Sequencing Batch Reactor with the Addition of Acetate to remove Nutrient and Organic Matter in Pig Slurry

The influence of carbon addition on performance of a laboratory-scale, anaerobic–anoxic–anaerobic–anoxic sequencing batch reactor [(An/Ax)2 SBR] in biologically removing nitrogen and organic matter from swine slurry was investigated in this study. The SBR was operated on three cycles per day (8 h per cycle) at constant 20 °C using raw slurry feeding until it reached a steady functional condition. After that, the SBR was subjected to a feeding treatment with addition of acetate. The sludge retention time and hydraulic retention time were maintained at 21 and 3·3 days for the experiment. The results indicate that with acetate addition, the removals of ammonium nitrogen, total Kjeldahl nitrogen, chemical oxygen demand, biochemical oxygen demand, and total phosphorus are 100·0%, 98·7%, 97·4%, 100·0%, and 98·7%, respectively. While without acetate addition, the corresponding reductions are 100·0%, 100·0%, 97·7%, 100·0%, and 97·8%. None of the feeding treatments (slurry alone or with acetate) appear to be effective in removing nitrate and nitrite due possibly to insufficient time allocated for denitrification, even when carbon is readily available. The removal of dissolved phosphorus by phosphorus-accumulating organisms reaches 87·2% with acetate addition but only 67·9% without. A good reduction in total solids (77·5% and 78·8%), total volatile solids (97·0% and 95·6%), total suspended solids (99·9% and 99·3%), and total volatile suspended solids (99·1% and 98·4%) for both treatments is also observed.

Effect of prefermentation on denitrifying phosphorus removal in slaughterhouse wastewater

An anaerobic–anoxic sequencing batch reactor (A 2 SBR) coupled with a fixed-bed nitrification reactor for simultaneous carbon, nitrogen and phosphorus removal was evaluated using slaughterhouse wastewater. Whereas the treatment could not be successfully carried out on the raw wastewater, the process showed very good nutrient removal performances after prefermentation. The removals of COD, N-NH 4 and P-PO 4 achieved were 99%, 85% and 99%, respectively. The increase in volatile fatty acid (VFA) and phosphate concentrations in the effluent after prefermentation may explain the high levels of biological carbon, nitrogen and phosphorus removal observed. A simple prefermentation is, therefore, necessary but sufficient to ensure good performances of the denitrifying enhanced biological phosphorus removal (EBPR) process.

Treatment of a synthetic Nylon production wastewater under denitrifying conditions in an anoxic sequencing batch reactor

AbstractA synthetic Nylon production wastewater high in nitrate (400–800 mg/L NO3‐N), total organic carbon (TOC=2000 mg/L), and chemical oxygen demand (COD=5450 mg/L) was treated in a laboratory‐scale, anoxic Sequencing Batch Reactor (AxSBR). The purpose was to determine the extent of organic carbon removal with different nitrate doses and the feasibility of achieving complete removal of oxidized forms of nitrogen (NOx) and organic carbon. The organic carbon consisted of 27 different alcohols, acids, aldehydes, and ketones. A concentration of 400 mg/L NO3‐N (NOx‐N/C=0.2) in the AxSBR resulted in removal of 33% TOC and 35% COD. Doubling the concentration to 800 mg/L NO3‐N (NOx‐N/C=0.4) increased removal of TOC and COD to 46% and 44%, respectively. An equivalent of 5000 mg/L NO3‐N (NOx‐N/C=2.5) was required to achieve 92% removal of TOC and COD. Under nitrate‐limiting conditions the readily degraded organics included: n‐butanol, methanol, ethanol, n‐propanol, l‐pentanol, cyclopentanol, picric acid, formic acid, acetone, n‐butyraldehyde, and propionaldehyde; and less readily degraded were s‐and t‐butanol, isopropanol, cyclohexanol, MEK, and cyclohexanone.