Carbon Loading Rate Research Articles

Biomethane production and microbial strategies corresponding to high organic loading treatment for molasses wastewater in an upflow anaerobic filter reactor.

Molasses wastewater contains high levels of organic compounds, cations, and anions, causing operational problems for anaerobic biological treatment. In this study, an upflow anaerobic filter (UAF) reactor was employed to establish a high organic loading treatment system for molasses wastewater and further investigated the microbial community dynamics in response to this stressful operation. The biogas production increased with an increase in total organic carbon (TOC) loading rate from 1.0 to 14g/L/day, and then it decreased with further TOC loading rate addition until 16g/L/day. The UAF reactor achieved a maximum biogas production of 6800mL/L/day with a TOC removal efficiency of 66.5% at a TOC loading rate of 14g/L/day. Further microbial analyses revealed that both the bacterial and archaeal communities developed multiple strategies to maintain stable operation of the reactor at high organic loading (e.g., Proteiniphilum and Defluviitoga maintained high abundances throughout the operation; Tissierella temporarily dominated the bacterial community at TOC loading rates of 8.0 to 14g/L/day; and multi-trophic Methanosarcina shifted as the dominant methanogen at the TOC loading rates of 8.0 to 16g/L/day). This study presents insights into a high organic loading molasses wastewater treatment system and the microbial flexibility in methane fermentation in response to process disturbances.

Performance of a novel rotating membrane photobioreactor based on indigenous microalgae-bacteria consortia for wastewater reclamation

Performance of a novel a rotating membrane photobioreactor (R-MPBR) for wastewater reclamation under photosynthetic oxygenation was investigated. The unit was operated in dead-end mode with an alternative physical cleaning strategy based in membrane module rotation. It was found that the carbon loading rate applied (CLR) (9.1–36.6 g DOC·m−3·d-1) determined the dissolved oxygen concentration, affecting nutrient removal, bioflocculation and membrane fouling. Indigenous microalgae-bacteria consortia were effectively developed under each condition. At high CLR values, the dissolved inorganic nitrogen removal was significantly enhanced (81.2 ± 13.9 %), probably due to a simultaneous nitrification–denitrification process as a result of the negligible dissolved oxygen concentration. Decreasing CLR from 36.6 to 9.1 g DOC·m−3·d-1, increased particle size (D(0.5) from 61.9 to 92.8 μm) and decreased biopolymer clusters content (from 50.0 to 2.3 mg DOC·L-1). It also revealed that membrane rotation does not compromise bioflocculation. Cake filtration model showed that fouling was associated to the supernatant fraction, particularly to the biopolymer clusters. Sustainable long-term operation was achieved at a permeate flux of 10 L·h−1·m−2 and CLR ≤ 11.4 g DOC·m−3·d-1. The proposed configuration effectively controlled membrane fouling, allowing to further process optimization.

Flocs enhance nitrous oxide reduction capacity in a denitrifying biofilm-based system: Mechanism of electron competition

Nitrous oxide (N2O) accumulation induced by insufficient electron donors and substrate diffusion restriction is inevitably occurred in denitrifying biofilm-based systems, yet rare mechanism is intensively explored. This study discovered the mechanism of electron competition affecting N2O reduction capacity in two denitrifying biofilm-based systems, and uncovered the role of flocs for mitigating N2O production with varying exogenous organic carbon levels. The results clearly delineated that substrate diffusion restriction of biofilms deteriorated electron donors availability, leading to fiercer electron competition (ratio of 1.95) in the single denitrifying biofilm system. Such competition also occurred with the decreasing carbon loading rates (from 180 to 30 mg-COD/g VSS/h), further resulting in a higher N2O accumulation of 0.95 mg-N/L. By contrast, flocs from the denitrifying biofilm/flocs system can efficiently reduce overall N2O accumulation by 32 %. Also, flocs promoted the higher proportion of the electrons distributed to nitrous oxide reductase (Nos), indicating a strong N2O-reducing capacity. In addition, electrons from Nos inclinedly distributed to nitrate reductase (Nar) with an increase of 21.4 % under co-occurrence of NO3−, NO2− and N2O in the single denitrifying biofilm system, suggesting the mechanism of electron competition was the competition in upstream electron pool. In contrast, electrons from Nos tended to nitrite reductase (Nir) (5.9 %) instead of Nar (2.1 %) in the denitrifying biofilm/flocs system implied the competition in downstream electron pool. This study unraveled that flocs can be applied in denitrifying biofilm-based systems to alleviate N2O emissions and total carbon footprints at wastewater treatment plants (WWTPs).

Effects of organic carbon and sulfide on the anammox reaction in the anoxic column in the SRDAPN process for treating high-strength wastewater

Low energy consumption treatment of high-strength wastewater is crucial in controlling groundwater pollution and eutrophication in closed waterbodies. In this study, the sulfate reduction, denitrification/anammox, and partial nitrification (SRDAPN) process, which is an effective organic carbon and nitrogen removal process with low energy consumption for low strength wastewater, was applied to treat livestock wastewater with high COD and sulfate concentration, and microbial reaction and community were examined using an anaerobic–anoxic biological filter reactor that simulates circulation from an aerobic reactor. At a total organic carbon loading rate of 2.7–5.8 kgC/m3·day, sulfate reduction and methane production occurred simultaneously in the anaerobic column of the reactor. Specifically, sulfate reduction resulted in organic matter removal rates of 38 and 26% at ambient temperature and 25 °C, respectively. Furthermore, both heterotrophic and autotrophic denitrification occurred in the anoxic column, and when the organic loading rate in the anoxic reactor was below 0.2 kgC/m3·day, 33%–37% of ammonium and 33%–34% of nitrite were removed by the anammox reaction. Heterotrophic denitrification bacteria (Thauera, Comamonas, and Denitratisoma) and sulfur denitrification bacteria (Sulfurimonas denitrificans) grew in the lower and middle parts of the anoxic column, whereas anammox bacteria (2.5% of Candidatus Brocadia at ambient temperature and 9.4% of Candidatus Kuenenia at 25 °C) grew in the upper part of the anoxic column. These results indicate that the SRDAPN process based on sulfur cycle and anammox is useful for treatment of high strength wastewater with low energy consumption.

Nitrogen oxidation and carbon removal from high strength nitrogen habitation wastewater with nitrification in membrane aerated biological reactors

Bioreactors for space habitation systems have unique constraints. One type of reactor that could meet these constraints are membrane aerated biological reactors (MABRs). The objective of this work was to establish the performance and optimal loading capacities of multiple MABRs with a variety of habitation waste streams. The MABRs operated over a large range of organic nitrogen (ON) and organic carbon (OC) loading rates (36–220 g/m3-d and 20–200 g/m3-d, respectively) across all wastewaters excluding humidity condensate (HC) where ON and OC loading rates ranged from 1.6 to 11 g/m3-d and 7–55 g/m3-d, respectively. OC and ON transformation rates (29–210 g/m3-d and 23–170 g/m3-d, respectively) were proportional to loading rates and similar to MABRs treating terrestrial high strength wastewaters at similar loadings. MABR maximum loading rates are limited by ON oxidation which controls pH. Above a pH of ~7.8 ON removal is inhibited by free ammonium due to the elevated concentrations of ON in all wastewaters excluding HC. While loading rates are lower than typical terrestrial systems, the MABRs stably operated for up to 5 years with limited maintenance and no solids processing. This work supports the use of MABRs to reliably stabilize habitation wastewaters with minimal consumables. These results also support the use of these MABRs for terrestrial high strength, low volume wastewaters where complex technology may be unsupportable, such as in rural or developing communities with no centralized treatment or for applications where typical two-phase aeration can lead to undesirable off gassing.

Acclimation Improves Methane Production from Molasses Wastewater with High Salinity in an Upflow Anaerobic Filter Reactor: Performance and Microbial Community Dynamics.

This study evaluated the performance of an upflow anaerobic filter (UAF) reactor in the thermophilic methane fermentation of hypersaline molasses wastewater. The high salinity (~ 45mS/cm) of the undiluted wastewater completely inhibited the biogas production. An acclimation strategy involving gradient dilution of the molasses wastewater was implemented to gradually increase the salt stress. Consequently, the biogas production was recovered, inhibited only slightly by the high salinity of the undiluted wastewater. The reactor steadily achieved a high total organic carbon (TOC) loading rate of 5g/L/day, with approximately 60% TOC removal efficiency. Acclimation to the gradually increased salt stress leads to a relative abundance of some halotolerant microbes, such as bacteria from Arcobacter, Tissierella, and Ruminococcaceae, which increased as their hydrolytic and acidogenic abilities adjusted to the incremental increase in salinity. Additionally, hydrogenotrophic methanogens, especially Methanoculleus, showed greater resistance to hypersalinity than aceticlastic methanogens. These results suggest that acclimation of the fermentation microbial community to hypersalinity is an effective strategy to improve methane production from hypersaline molasses wastewater in thermophilic UAF reactors.

Evaluation of deammonification reactor performance and microrganisms community during treatment of digestate from swine sludge CSTR biodigester.

Digestate from anaerobic processes still contains relatively high amount of total organic carbon (TOC) that can inhibit deammonification. In this sense, the present study investigated the interference of TOC in a lab-scale expanded granular sludge bed (EGSB) deammonification reactor treating digestate from a continuous stirred tank reactor (CSTR) swine sludge biodigester. Additionally, the microorganisms community was analyzed when the process was submitted to different operational conditions. The study was divided into three phases according to the C/N ratio (0, 0.5 and 1 for phase I, phase II and phase III, respectively). At phase I the average nitrogen removal efficiency (NRE) was 65 ± 1.6%. With the increase of TOC in phase II (156 ± 8.15 mg L-1) the average NRE was 61 ± 9.8% which is statically equivalent to phase I (p < 0.05). On the other hand, at phase III (TOC was increased to 255 ± 3.50 mg L-1) the NRE decreased to 50 ± 3.9% which was 22% lower than in phase II. Stoichiometric coefficients of N2 was close to theoretical values during all experimental phases, while stoichiometric coefficient of N-NO3- was lower than theoretical values specially during phase III. Ca. Jettenia was favored when the reactor was fed with digestate although its proportion decreased in phase III. Thus, at the conditions employed in the present study it is recommended to use a C/N ratio of 0.5 (TOC concentration around 156 mg L-1) to treat digestate by deammonification process, in order to not diminish anammox microorganisms abundance. Thereby, the microorganisms community can be modulated based on carbon and nitrogen loading rates of a deammonification reactor for swine manure treatment purpose.

Improved membrane sequencing batch reactor: effect of carbon and nitrogen volumetric loading rate on dephosphatation

ABSTRACTA lab-scale anaerobic–anoxic–aerobic membrane bioreactor (A2NO-MBR) fed with synthetic wastewater was operated to investigate the impact of influent carbon and nitrogen volumetric loading rate (VLR) on dephosphatation, and the corresponding influent concentration was 100–300 mg L−1 (COD), 24–50 mg L−1 (NH4+–N) and 4.8–6.0 mg L−1 (TP), respectively. The results demonstrated that carbon VLR had a negligible effect on the COD removal with effluent below 50 mg L−1, and high and stable removal capacity for phosphorus were also obtained, regardless of carbon VLR change. Whereas TN removal efficiency was positively correlated with carbon VLR reduction, and lower carbon VLR produced a negative effect on TN removal. In addition, since nitrate served as an electron acceptor for denitrifying phosphorus removal (DPR), a significant effect on nitrogen and phosphorus removal was observed with different nitrogen VLR. The TN and TP removal efficiency was 68.30 ± 1.36%, 70.70 ± 1.23%, 45.19 ± 1.72% and 41.63 ± 3.09%, 98.14 ± 0.53%, 53.34 ± 2.68% with influent nitrogen VLR of 0.024 ± 0.001, 0.034 ± 0.001 and 0.045 ± 0.001 kg-N/(m3 d), respectively. Moreover, bacterial community structure of sludge samples in Run I and V from anaerobic–anoxic–aerobic-SBR (named A2OSBR_1 and A2OSBR_2) and membrane bioreactor (named N-MBR_1 and N-MBR_2) revealed that Candidatus_Accumulibacter was the most dominant genus in A2OSBR_1 (21.50%) and A2OSBR_2 (18.98%). The relative lower carbon VLR favoured the enrichment of Saprospiraceae, which was related with DPR, with the proportion of 9.31% and 14.61% in A2OSBR_1 and A2OSBR_2. Besides, Nitrospira and Nitrosomonas with proportions of 11.14%, 5.38% in N-MBR_1 and 10.72%, 6.77% in N-MBR_2 were observed, which were likely responsible for the nearly complete nitrification.

Influence of hydraulic retention time and carbon loading rate on the production of algae

This paper is focused on the assessment of the production of algae in batch bioreactors. Hydraulic retention time, carbon loading rate and light color were the inputs of the study and algae production the main output. Bioreactors were operated in semi-continuous mode and tests lasted two months, more than two times the period required to meet a steady-state response. This steady-state was verified with plateau responses in both, soluble parameters and suspended solids. Results points out the great relevance of temperature. Likewise, they show that green light improves the production of algae, as well as long HRT and high CLR. Maximum production rates attained were in the range 4–14 mg d−1 L−1. The ratio COD /TSS for this biofuel was almost constant (3.13 mg COD mg−1 TSS) but the quality of the product obtained in terms of the Mean Oxidation State of Carbon is completely different. Longer HRT leads to lower MOSC and hence to potentially more valuable fuels.

Feasibility of in situ enriching anammox bacteria in a sequencing batch biofilm reactor (SBBR) for enhancing nitrogen removal of real domestic wastewater

In this study, enhanced removal of nitrogen from real domestic wastewater with low organic carbon to nitrogen ratio of 2.1–3.6 was achieved in a sequencing batch biofilm reactor (SBBR) with enriching anammox bacteria in situ. The SBBR was inoculated with ordinary nitrification sludge and operated under alternative anaerobic, aerobic and anoxic patterns. During the start-up period, influent nitrogen and carbon loading rate gradually increased. According to the quantitative microbial analysis, the growth of ammonium oxidizing bacteria and anammox bacteria were promoted, resulting in an increase from 6.56 × 104 to 1.51 × 107 and from 1.11 × 104 to 1.69 × 106 gene copies·mL−1, respectively. During the steady period (Day 102–205), nitrogen removal efficiency of 88.2% was achieved with an effluent total nitrogen of 6.3 mg N·L−1 for average influent ammonium of 53.9 ± 4.0 mg·L−1. Nitrogen removal was steady when temperature decreased from 27.0 to 12.8 °C. Variations in nitrogen compounds suggested that anammox reaction could be the main pathway for nitrogen removal, according to the results of activity batch and continuous tests. For the high nitrogen removal performance, biofilm and post-anoxic unit could play important roles. Overall, this study provided an alternative method to improve the removal of nitrogen from sewage by directly enriching anammox bacteria.

Performance study on organic carbon, total nitrogen, suspended solids removal and biogas production in hybrid UASB reactor treating real slaughterhouse wastewater

The performance of slaughterhouse wastewater treatment was studied in Hybrid Upflow Anaerobic Sludge Blanket Reactor (HUASBR) consisting of polypropylene media as attached growth surface. During acclimation phase, the amount of real slaughterhouse wastewater was gradually increased, whereas the amount of synthetic wastewater was proportionally decreased in a mixed feed to the reactor. The batch performance was evaluated by feeding 1000 ml of raw slaughterhouse wastewater and observing consistent Chemical Oxygen Demand (COD) removal over a batch period of 72 h. After attaining maximum COD removal efficiency and maximum methane gas production, the reactor was operated under continuous mode with gradually increasing Total Organic Carbon (TOC) loading rate. The reactor showed steady increase in the TOC removal efficiency as well as incremental biogas production. In this study, TOC loading rate was varied in the range of (1.12–14.19)kg TOC/m3/d corresponding to decremental Hydraulic Retention Time (HRT) of (24–6) hours. The HUASBR enhanced the TOC removal efficiency in slaughterhouse wastewater up to maximum of 95.85% under the TOC loading rate of 6.97 kg TOC/m3/d for 10 h HRT. The TSS removal efficiency was observed to be in the range of (72–98) % throughout the study. Similarly, The TN removal was also recorded between (48–78) % out of all the continuous operations. The maximum methane gas production rate was observed as 61.5 L/d at 10 h HRT.

Effects of the ammonium loading rate on nitrite-oxidizing activity during nitrification at a high dose of inorganic carbon

ABSTRACTIn this study, the effects of the ammonium loading rate (ALR) and inorganic carbon loading rate (ILR) on the nitrification performance and composition of a nitrifying bacterial community were investigated in a moving bed biofilm reactor, using poly(vinyl alcohol) (PVA) sponge cubes as a supporting carrier. Between the two ALRs of 0.36 and 2.16 kg-N m−1 d−1, stable partial nitritation was achieved at the higher ALR. Inorganic carbon was dosed at high levels: 33.1, 22.0, 16.4, 11.0, and 5.4 times the theoretical amount. Nonetheless, nitrification efficiency was not affected by the ILR at the two ALRs. Quantitative PCR analysis of ammonia- and nitrite-oxidizing bacteria revealed that ALR is an important determinant of partial nitritation by accumulating ammonia-oxidizing bacteria in the nitrification system. In comparison, two nitrite-oxidizing bacterial genera (Nitrobacter and Nitrospira) showed almost the same relative abundance at various ALRs and ILRs. Terminal restriction fragment length polymorphism targeting the gene of ammonia monooxygenase subunit A revealed that Nitrosomonas europaea dominated under all conditions.

Patterns, drivers and implications of dissolved oxygen dynamics in tropical mangrove forests

Estuarine mangrove forests regulate and facilitate many ecological processes, and provide nursery ground for many commercially important species. However, mangroves grow in sediments with high carbon loading and high respiration rates which can potentially influencing the dissolved oxygen (DO) dynamics of tidal water flowing into mangrove forests, as bacteria strip DO from the incoming water to carry out metabolic functions. In turn this is likely to influence the way nekton and other aquatic organisms utilize mangrove forests. Despite these possibilities, previous work has focused on looking at DO dynamics within mangrove creeks, with little research focusing on understanding DO dynamics within the mangrove forests themselves during tidal inundation or of DO levels of pools within the forest remaining once the tide has ebbed. The present study investigates the pattern in DO at various distances within an estuarine Rhizophora stylosa forest in tropical north Queensland. DO levels were recorded at 5 min interval over 2 days and multiple tidal cycles, data were collected between 2013 and 2014 for a total of 32 tidal cycles encompassing multiples seasons and tidal amplitudes. There were substantial fluctuations in DO, often varying from normoxic to hypoxic within the same tidal cycle. A range of factors influenced DO dynamics, in particular: tidal height, amount of sunlight, tidal phase, and distance from the outer edge of the mangrove forest. In fact, spring tides tend to have high DO saturation, particularly during the flooding phase, however as the tide starts ebbing, DO depletes rapidly especially in areas further inside the forest. Moreover during tidal disconnection the remnant pools within the forest quickly became anoxic. These variations in DO suggest that the use of mangrove forests by animals is likely to be constrained by their ability to withstand low DO levels, and provides a plausible explanation for the apparent paucity of benthic organism observed inside similar mangrove forest in previous studies of South Pacific mangroves. Low DO levels coupled with low densities of benthic prey also provides a likely explanation for the limited utilisation of landwards areas of these forests by fish and other nekton.

Dynamics of organic matter, nitrogen and phosphorus removal and their interactions in a tidal operated constructed wetland

This paper demonstrates the potential of tidal flow operated constructed wetland application for the removal dynamics of organic matter, nitrogen and phosphorus. Near-complete removal of organic matter was achieved with a constant removal efficiency of 95%, irrespective of TOC influent loadings ranged from 10 g/m2·d to 700 g/m2·d. High NH4+−N removal at 95% efficiency under influent loading of 17 g/m2·d, was stably obtained and was not negatively influenced by increasing influent organic carbon loading rate. Increased influent TOC loading (350 g/m2·d to 700 g/m2·d) significantly enhanced denitrification capacity and increased TN removal from 30% to 95%. Under tidal flow operation, a higher carbon supply (C/N = 20) for complete TN removal was demonstrated as comparing to that observed in traditional CWs approaches. In addition, the removal of phosphorus was strongly influenced by organic loadings. However, further investigations are needed to elucidate the detailed mechanism that would explain the role of organic loading in phosphorus removal.

Monitoring the Location of Cathode-Reactions in Li-O2 Batteries

The performance of Li-O2 batteries is typically evaluated by specific capacity and cyclability in order to facilitate quantitative comparison in literature. The accuracy of such comparison is limited, however, due to the wide range of factors which control the reported specific capacities. These comparisons are not always fair as some factors, which can highly influence the obtained specific capacities, are often neglected. A rigorous and systematic study has been conducted in order to identify the isolated effect of diverse parameters on the performance of these promising batteries. The analysis of cells with different carbon contents reveals that the discharge reactions do not necessarily take place throughout the electrode mass, but instead occur preferentially in closest proximity to the oxygen gas-electrolyte interface. The effective activity of the cathode material is therefore reduced as distance from this interface increases. This work demonstrates that the lack of standardized measurement protocols hinders the rapid development of this technology due to the difficulties inherent in the direct comparison of cells with wide-ranging measurement conditions. In addition, it has been demonstrated that both the employed carbon loading and current rate critically affect cycling lifetime.

A case study of a pilot high rate algal pond for the treatment of fish farm and domestic wastewaters

ABSTRACTBACKGROUNDMicroalgae‐based technologies have emerged as a promising approach for simultaneous wastewater treatment and fish food production able to overcome the main limitations in the aquaculture sector. The current study focused on the mechanisms of carbon and nutrient removal from fish farm and domestic wastewaters in a 180 L outdoors pilot high rate algal pond (HRAP) at different hydraulic retention times (HRTs) considering water evaporation losses.RESULTSMaximum chemical oxygen demand, total Kjeldahl nitrogen and total phosphorus removal efficiencies of 77 ± 9%, 83 ± 10% and 94 ± 6%, respectively, were recorded during the treatment of fish farm wastewater at 10 d of HRT. Carbon and nitrogen were removed by assimilation into biomass (52 ± 12% and 74 ± 22%, respectively) and stripping, while phosphorus was mainly assimilated into biomass (69 ± 23%). Carbon stripping, along with the low carbon and nutrient loading rates supplied, resulted in low biomass productivities (maximum of 5 g m−2 d−1). A successful solids removal was achieved in the settler (82 ± 18%), which entailed effluent solid concentrations below the maximum permissible discharge limit.CONCLUSIONDespite the successful wastewater treatment supported by the HRAP, the high water evaporation losses (up of 15 L m−2 d−1) could compromise the technical and environmental viability of this green wastewater treatment technology. © 2014 Society of Chemical Industry

Impact of hydraulic and carbon loading rates of constructed wetlands on contaminants of emerging concern (CECs) removal

Constructed wetlands remove trace organic contaminants via synergistic processes involving plant biomass that include hydrolysis, volatilization, sorption, biodegradation, and photolysis. Wetland design conditions, such as hydraulic loading rates (HLRs) and carbon loading rates (CLRs), influence these processes. Contaminant of emerging concern (CEC) removal by wetland plants was investigated at varying HLRs and CLRs. Rate constants and parameters obtained from batch-scale studies were used in a mechanistic model to evaluate the effect of these two loading rates on CEC removal. CLR significantly influenced CEC removal when wetlands were operated at HLR >5 cm/d. High values of CLR increased removal of estradiol and carbamazepine but lowered that of testosterone and atrazine. Without increasing the cumulative HLR, operating two wetlands in series with varying CLRs could be a way to improve CEC removal.

Combined anaerobic-aerobic and UV/H2O2 processes for the treatment of synthetic slaughterhouse wastewater

The biological treatment of a synthetic slaughterhouse wastewater (SSWW) is studied using an anaerobic baffled bioreactor (ABR) and an aerobic activated sludge (AS) at a laboratory scale in continuous mode. The total organic carbon (TOC) loading rate, the total nitrogen (TN) loading rate, and the flow rate are 0.03–1.01 g/(L.day), 0.01–0.19 g/(L.day), and 2.93–11.70 mL/min, respectively. The results reveal that combined anaerobic-aerobic processes had higher efficiency to treat SSWW than a single process. Up to 96.36% TOC, 80.53% TN, and 99.38% 5-day carbonaceous biochemical oxygen demand (CBOD5) removal from an influent concentration of 1,009 mgTOC/L, 420 mgTN/L, and 640 mgCBOD5/L at the hydraulic retention time (HRT) of 6.24 days and a flow rate of 3.75 mL/min are achieved. The UV/H2O2 process is studied to treat a secondary effluent of SSWW with TOC loadings of 65–350 mg/L. Up to 75.22% TOC and 84.38% CBOD5 removal are obtained at the HRT of 3 h with H2O2 concentration of 900 mg/L. Optimum molar ratios of 13.87 mgH2O2/mgTOCin and 4.62 mgH2O2/mgTOCin.h are also obtained. Combined anaerobic-aerobic and UV/H2O2 processes enhanced the biodegradability of the TOC, TN, and CBOD5 present in the SSWW. Up to 99.98% TOC, 82.84% TN, and 99.69% CBOD5 overall removals are obtained for an influent concentration of 1,005 mgTOC/L, 200 mgTN/L, and 640 mgCBOD5/L at the HRT of 4 days and a flow-rate of 5.90 mL/min.

Electron competition among nitrogen oxides reduction during methanol-utilizing denitrification in wastewater treatment

Limited availability of carbon sources has been regarded as an important factor leading to N2O accumulation during denitrification in wastewater treatment. By varying the carbon (methanol) loading rate to a methanol utilizing denitrifying culture in the presence of various electron acceptors (nitrate, nitrite, N2O and their combinations), this study quantitatively investigated the electron distribution among different nitrogen oxide reductases during denitrification. The results showed that electron competition occurs under not only carbon limiting but also carbon abundant conditions. The electron distribution among the nitrogen oxide reductases is affected by the carbon loading rate, with a lower fraction of electrons distributed to the N2O reductase with reduced carbon loading rate. N2O accumulation occurs when the electron flux going to nitrite reduction is higher than that going to N2O reduction. The study also showed that, for the culture investigated, the carbon to nitrogen ratio is not a key factor leading to N2O accumulation.

Simultaneous removal of TOC and TSS in swine wastewater using the partial nitritation process

AbstractBACKGROUND: Considering biological nitrogen removal, the partial nitritation connected with the anaerobic ammonium oxidation (anammox) process is a promising alternative for nitrogen elimination at high loading rates. The objective of the present study was to evaluate the establishment and operation of a partial nitritation process in an airlift reactor with simultaneous removal of total organic carbon and suspended solids using swine wastewater.RESULTS: The partial nitritation reactor was inoculated with a nitrifying sludge at 2.1 gTSS L−1 and fed with an UASB reactor effluent. High organic carbon loading rates, above 2 kgTOC m−3 d−1 have been shown to be potential inhibitors of the partial nitritation process due to competition between autotrophic and heterotrophic bacteria. In this study, the partial nitritation process was established using undiluted swine wastewater, with HRT of 24 h, 1.84 mgO2 L−1 (SD = 0.41) DO, loading rate of 1.14 gTOC L−1 d−1 and 0.91 gN‐NH3 L−1 d−1 for more than 100 consecutive days. At the same time, the system proved to be an effective tool in TOC and TSS removal, reaching 84.9% (SD = 9.3) and 83.1% (SD = 0.1), respectively.CONCLUSION: This result enhances partial nitritation application as a technology for high load nitrogen converting, and allows the possibility of connection with anammox reactors. Copyright © 2012 Society of Chemical Industry