Maximum Total Nitrogen Removal Research Articles

Nitrogen removal in a single-chamber microbial fuel cell with nitrifying biofilm enriched at the air cathode

Nitrogen removal is needed in microbial fuel cells (MFCs) for the treatment of most waste streams. Current designs couple biological denitrification with side-stream or combined nitrification sustained by upstream or direct aeration, which negates some of the energy-saving benefits of MFC technology. To achieve simultaneous nitrification and denitrification, without extra energy input for aeration, the air cathode of a single-chamber MFC was pre-enriched with a nitrifying biofilm. Diethylamine-functionalized polymer (DEA) was used as the Pt catalyst binder on the cathode to improve the differential nitrifying biofilm establishment. With pre-enriched nitrifying biofilm, MFCs with the DEA binder had an ammonia removal efficiency of up to 96.8% and a maximum power density of 900 ± 25 mW/m2, compared to 90.7% and 945 ± 42 mW/m2 with a Nafion binder. A control with Nafion that lacked nitrifier pre-enrichment removed less ammonia and had lower power production (54.5% initially, 750 mW/m2). The nitrifying biofilm MFCs had lower Coulombic efficiencies (up to 27%) than the control reactor (up to 36%). The maximum total nitrogen removal efficiency reached 93.9% for MFCs with the DEA binder. The DEA binder accelerated nitrifier biofilm enrichment on the cathode, and enhanced system stability. These results demonstrated that with proper cathode pre-enrichment it is possible to simultaneously remove organics and ammonia in a single-chamber MFC without supplemental aeration.

Anammox enrichment from reject water on blank biofilm carriers and carriers containing nitrifying biomass: operation of two moving bed biofilm reactors (MBBR)

The anammox bacteria were enriched from reject water of anaerobic digestion of municipal wastewater sludge onto moving bed biofilm reactor (MBBR) system carriers-the ones initially containing no biomass (MBBR1) as well as the ones containing nitrifying biomass (MBBR2). Duration of start-up periods of the both reactors was similar (about 100days), but stable total nitrogen (TN) removal efficiency occurred earlier in the system containing nitrifying biomass. Anammox TN removal efficiency of 70% was achieved by 180days in both 20l volume reactors at moderate temperature of 26.0°C. During the steady state phase of operation of MBBRs the average TN removal efficiencies and maximum TN removal rates in MBBR1 were 80% (1,000g-N/m(3)/day, achieved by 308days) and in MBBR2 85% (1,100g-N/m(3)/day, achieved by 266days). In both reactors mixed bacterial cultures were detected. Uncultured Planctomycetales bacterium clone P4, Candidatus Nitrospira defluvii and uncultured Nitrospira sp. clone 53 were identified by PCR-DGGE from the system initially containing blank biofilm carriers as well as from the nitrifying biofilm system; from the latter in addition to these also uncultured ammonium oxidizing bacterium clone W1 and Nitrospira sp. clone S1-62 were detected. FISH analysis revealed that anammox microorganisms were located in clusters in the biofilm. Using previously grown nitrifying biofilm matrix for anammox enrichment has some benefits over starting up the process from zero, such as less time for enrichment and protection against severe inhibitions in case of high substrate loading rates.

The use of a submerged membrane batch reactor (S.M.B.R) for co-treatment of landfill leachates and domestic wastewater

Abstract The aims of this work were the examination of the treatment potential of landfill leachates domestic wastewater mixtures by a pilot scale membrane bioreactor system using a submerged plate and frame microfiltration (MF) membrane module and the investigation of the optimum operation conditions for the achievement of maximum COD and total nitrogen removal rates. The bioreactor was inoculated by 60 l of activated sludge and operated at an MLSS content reaching up to 25,000 mg/l; increased COD removal efficiencies were observed reaching up to 98%. High ammonium nitrogen removal efficiencies were achieved reaching up to 99% at extended operation times associated to long SRTs, resulting in effluent concentrations of about 1 mg/l; however, total nitrogen content of effluents was high, about 160 ± 50 mg/l, due to reduced denitrification capacity of the system.

A direct comparison of the performance of the seaweed biofilters, Asparagopsis armata and Ulva rigida

The tetrasporophyte of Asparagopsis armata has been previously established as a novel seaweed biofilter for integrated land-based mariculture. The species growth and biofiltration rates were much higher than the values described in the literature for Ulva spp., the most common seaweed biofilter. However, a validation of the advantage of one species over the other requires a study of the performances of these two species in the same system at the same time. In this work, we compared the biofiltration performance and biomass yield of A. armata and Ulva rigida cultivated in the effluents of a fish farm in southern Portugal. Comparisons were performed at different water renewal rates and in two seasons of the year. The maximum total ammonia nitrogen (TAN) removal rates were similar for both species in December (2.7 and 2.8 g TAN m–2 day–1 for U. rigida and A. armata, respectively) and higher for A. armata (6.5 g TAN m–2 day–1) than for U. rigida (5.1 g TAN m–2 day–1) in May. Higher differences were observed when estimating the nitrogen biofiltration through the organic nitrogen yield (N yield) of the biomass produced, particularly in May. This estimate is directly related with the biomass yield and the N content in the tissue which were always higher for A. armata than for U. rigida. In December, the maximum biomass yields were 71 g dry weight (DW) m–2 day–1 for A. armata and 44 g DW m–2 day–1 for U. rigida, while in May, the yield of A. armata was 125 g DW m–2 day–1 and of U. rigida was 73 g DW m–2 day–1. This study confirmed that A. armata is indeed a more efficient biofilter than U. rigida. To the best of our knowledge, the production rates reported here are the highest ever reported for macroalgae cultivated in tanks.

Nutrient Retention in Vegetated and Nonvegetated Bioretention Mesocosms

Thirty well-established 240L bioretention mesocosms were used to investigate retention of dissolved nutrients by bioretention systems. Ten mesocosms were comprised of 80cm sandy loam, ten of 80cm loamy sand, and ten of pea gravel with 20cm of loamy sand. Half were vegetated with shrubs/grasses, while the other half had no vegetation (barren). In the first part of our study, the loam and sand mesocosms were dosed with synthetic storm water comprising 0.8mgL−1 total phosphorus (TP) and 4.8mgL−1 total nitrogen (TN). TP retention in the vegetated loam was 91% compared to 73% in the barren, and TN retention was 81% compared to 41% in the barren loam. TP retention was 86–88% in the sand treatments, while TN retention in the vegetated sand was 64%, compared to 30% in the barren. In the second part of our study, all 30 mesocosms were loaded weekly with 45cm of tertiary effluent with high nutrient loads (22.3myear−1 hydraulic load at a flow-weighted average of 4.5mgL−1 TP and 4.8mgL−1 TN, or 1,012kgha−1year−1 TP and 1,073kgha−1year−1 TN). After 50 weeks of loading, cumulative TP retention was 92% in the vegetated loam, 67% in the sand, and 44% in the vegetated gravel. However, TP retention by barren media was 56% in the loam, 39% in the sand, and 14% in the gravel. Cumulative TN retention was 76% in the vegetated loam, 51% in the sand, and 40% in the vegetated gravel. In contrast, maximum TN removal by barren media was 18% in the loam. The increase in TP retention by vegetated systems substantially exceeds phosphorus uptake rates for plants, suggesting that other processes are involved. The increase in TN retention by vegetated systems also exceeds nitrogen uptake rates for plants, suggesting that denitrification is involved.

Simultaneous Nitrification and Denitrification of Municipal Wastewater in Aerobic Membrane Bioreactors

Simultaneous nitrification-denitrification (SND) of municipal wastewater was investigated in a laboratory-scale membrane bioreactor (MBR) operated at two different hydraulic retention times (HRTs), 0.5 and 1 day, dissolved oxygen 3.0 to 0.5 mg/L, and solids retention time (SRT) between 28 and 120 days. The organic loading rate (OLR) (0.11 to 0.64 kg chemical oxygen demand [COD]/m3/d) and influent soluble COD (SCOD)/ total Kjeldahl nitrogen (TKN) ratio (5 to 19) were varied by the addition of glucose. The ammonia-nitrogen and TKN removals were over 97%, and total nitrogen removal was approximately 89% in the MBR. The maximum specific nitrification rates (98 mg N/d/g VSS) and specific denitrification rates (81 mg N/d/g VSS) occurred at an SCOD/TKN ratio of 9.1. The optimum conditions for maximum total nitrogen removal by SND in a single reactor MBR have been found to be low dissolved oxygen (< 0.6 mg/L) and high OLR (approximately 0.64 kg COD/m3/d) at an HRT of 0.5 day and SRT of approximately 85 days.

Assessment of inocula and n-removal performance of anaerobic ammonium oxidation (annamox) for the treatment of "old" landfill leachates

Three kinds of seeding sludge, i,e, conventional activated sludge, anaerobic granularsludge and the nitrifying activated sludge from the nitritation reactor treating agedleachates were evaluated in batch mode to screen the optimized inoculum for the rapidstart-up of ANAMMOX reactor. The feasibility of the ANAMMOX process for thetreatment of aged leachates was also investigated in a modified upflow anaerobic sludgeblanket (UASB, 0,05 m\ The batch experiments revealed that the nitrifying activatedsludge from the nitritation reactor could respectively achieve the NRR (nitrogenremoval rate) of 0,0365 kg N/(m3,d) and the ARR (ammonium removal rate) of 0,013kg N/(m3.d) on day 12, which were greatly higher than those of the other two testedsludge samples, The mixture of the aforementioned nitrifying activated sludge andanaerobic granular sludge was established as an effective inoculum for the prompt startup of ANAMMOX reactor. The maximum total nitrogen removal rate of 0,826 kgN/(m3,d) could be obtained for the treatment of "old" leachates under NLR (nitrogenloading rate) of 1.028 kg N/(m3.d), It is concluded that the N-removal performance ofANAMMOX process is still to be improved for actual engineering application to agedlandfill leachates,

The removal of nitrogen using an autotrophic hybrid hollow-fiber membrane biofilm reactor

A hollow-fiber membrane biofilm reactor (HF-MBfR) treating nitrogen in synthetic wastewater was studied in respect to nitrification and denitrification ability using autotrophic microorganism over a period of 260 days. The hybrid HF-MBfR system consists of a nitrification HF-MBfR and denitrification HF-MBfR. Oxygen and hydrogen were supplied through the lumen of fibers as electron acceptor and donor. In Phase I, two HF-MBfR were operated separately during the period of 149 days. And then, the HF-MBfR were operated by hybrid system that is connected continuously. The hybrid HF-MBfR was operated at hydraulic retention time (HRT) of 4 h, 2 h, and the volumetric NH 4 +-N loading rate increased from 0.42 to 1 28 kgNH 4 +-N/m 3d by increasing NH 4 +-N concentration of influent from 150 to 200 mgN/L. The average total nitrogen removal efficiency was above 98% during the experiment steps and the maximum volumetric total nitrogen removal rate was 1.20 kgN/m 3d in the hybrid HF-MBfR system. In this study, the results suggested that this hybrid HF-MBfR system operated effectively for nitrogen removal in an inorganic environment and can be used stably as a high rate nitrogen removal technology.

Effect of C/N values on microbial simultaneous removal of carbonaceous and nitrogenous substances in wastewater by single continuous-flow fluidized-bed bioreactor containing porous carrier particles

A single continuous-flow fluidized-bed bioreactor system consisting of porous carrier particles for retaining microbes was constructed to simultaneously remove carbonaceous and nitrogenous substances in wastewater under different C/N (mass ratio) values. The suspended microbial concentration in the bioreactor was extremely low compared with that of retained microbes. A TOC removal of >91% and a maximum total nitrogen removal of 85% were achieved under a moderate C/N value. By using a set of simplified reaction kinetics, the multiple microbial reactions involved in the simultaneous removal process of carbonaceous and nitrogenous components were analyzed. The related kinetic parameters in terms of carbonaceous and nitrogenous loadings were obtained.

Theoretical analysis on nitrogen removal of the step-feed anoxic-oxic activated sludge process and its application for the optimal operation

The nitrogen removal efficiency of the step-feed anoxic-oxic activated sludge process, which has two anoxic tanks and two oxic tanks, was theoretically discussed on the basis of the stoichiometry of denitrification and nitrification reactions. As the first step, effluent NH4-N and NO3-N concentrations were formulated with four parameters; 1) a, equivalent ratio of alkalinity to ammonia in influent, 2) b, that of substrate to ammonia, 3) r, step ratio of influent to the second anoxic tank and 4) R, return (+ recycle) sludge ratio. This calculus was done for the possible sixteen (=24) cases which show different reaction patterns in four tanks, and 12 cases out of 16 were found to be available. The effects of step ratio, r were examined in its range of 0 - 1 at a fixed R value, and it was found that the increase of r alters the outcome in a different way depending on the ranges of a and b. Consequently, zoning of a-b coordinates was successfully made, and the optimal r value for maximum total nitrogen removal was obtained in each zone. In addition, the optimal volume allocation of the four tanks was discussed and the ratios were formulated for each zone.

Theoretical analysis on nitrogen removal of the step-feed anoxic-oxic activated sludge process and its application for the optimal operation

The nitrogen removal efficiency of the step-feed anoxic-oxic activated sludge process, which has two anoxic tanks and two oxic tanks, was theoretically discussed on the basis of the stoichiometry of denitrification and nitrification reactions. As the first step, effluent NH4-N and NO3-N concentrations were formulated with four parameters; 1) a, equivalent ratio of alkalinity to ammonia in influent, 2) b, that of substrate to ammonia, 3) r, step ratio of influent to the second anoxic tank and 4) R, return (+ recycle) sludge ratio. This calculus was done for the possible sixteen (=24) cases which show different reaction patterns in four tanks, and 12 cases out of 16 were found to be available. The effects of step ratio, r were examined in its range of0 – 1 at a fixed R value, and it was found that the increase of r alters the outcome in a different waydepending on the ranges of a and b. Consequently, zoning of a-b coordinates was successfully made, andthe optimal r value for maximum total nitrogen removal was obtained in each zone. In addition, the optimal volume allocation of the four tanks was discussed and the ratios were formulated for each zone.