Total Kjeldahl Nitrogen Removal Research Articles

Intermittent feeding of wastewater in combination with alternating aeration for complete denitrification and control of filaments

In the present study, a laboratory scale system, consisting of a primary settling tank, a continuous stirred tank reactor and a clarifier were constructed and operated, using wastewater from the municipal wastewater treatment plant in Xanthi, Greece. The system operated under intermittent aeration in aerobic/anoxic conditions and feeding of the wastewater once in every cycle. The unit was inoculated with sludge, which originated from the recirculation stream of the local wastewater treatment plant. The wastewater was processed with hydraulic retention time (HRT) of 12 h, in which various experimental states were studied regarding the combination of aerobic and anoxic intervals. The wastewater was fed in limited time once in every cycle of aerobic/anoxic conditions at the beginning of the anoxic period. The two states that exhibited highest performance in nitrification and total nitrogen removal were, then, repeated with HRT of 10 h. The results show that, regarding the nitrification stage and the organic load removal, the intermittent system achieved optimum efficiency, with an overall removal of biological oxygen demand (BOD(5)) and ammonium nitrogen in the range of 93-96% and 91-95% respectively. As far as the total nitrogen removal is concerned, and if the stage of the denitrification is taken into account, the performance of the intermittent system surpassed other methods, as it is shown by the total Kjeldahl nitrogen (TKN) removal efficiency of 85-87%. These operating conditions suppressed the growth of filamentous organisms, a fact reflected at the SVI values, which were lower than 150 ml/g.

Performance of membrane bioreactor to different hydraulic shock loadings

A Membrane Bioreactor (MBR) treating simulated sewage was operated and stabilised for a period of 60 days at an organic loading rate of 3.6 g/COD/day and Hydraulic Retention Time (HRT) of 8 h, during which the MBR showed 95% removal of Chemical Oxygen Demand (COD), 98% removal of Total Organic Carbon (TOC) and TSS, 91% removal of Total Kjeldahl Nitrogen (TKN) and 30% removal of phosphate. The responses of the MBR to different hydraulic shock loadings were studied. The HRT was reduced to 4 h, 2 h, 1 h and 0.8 h to simulate two, four, eight and tenfold increase in flow rate, respectively, for a period of 12 h. During the shock load the influent COD concentration was maintained constant. Under the hydraulic shocks, the COD removal efficiency temporarily reduced to between 92% and 81% and the TOC removal efficiency reduced to between 80% and 48%. TOC removal efficiency was very poor at tenfold hydraulic shock. The TKN and phosphate removal efficiency were slightly affected at twofold hydraulic shock, showing a removal efficiency of 76% and 24%, respectively. The nitrogen and phosphate removal was highly affected at higher shock loads with very high TKN and phosphate concentration in the effluent. The system took much longer time (around 7 to 14 days) to recover in terms of nutrient removal for higher shock loads. The biomass was not at all affected at two, four and eightfold increase in flow rate. The high biomass and sludge retention of the MBR is advantageous to withstand such high and sudden hydraulic shocks, with its ability to recover faster than any other biological reactor.

Treating landfill leachate by electrocoagulation

The determination of the optimal conditions for using electrocoagulation as a treatment for landfill leachate was carried out using surface response methodology. A central composite design was applied to investigate the effect of four control factors, namely current density, pH, time and fluid conductivity, as well as the interaction among (between) them to get an optimal turbidity removal. The independent variables were each coded at three levels and their values were selected on the basis of preliminary experimental results. The central composite design consisted of 29 experimental points with five replications at the centre point. A second order polynomial model was used for predicting the response. Regression analysis showed that more than 95% of the variation was explained by the model wherein current density with a 60.1% contribution turned out to be the factor with the most significant influence. Analysis of variance showed that time, pH, current density and the interaction time/current density had a significant influence on the turbidity removal, The optimal conditions obtained for the removal of turbidity were time 38.8 min, pH 7.6, current density 109.9 A m(-2) and NaCl 2.9 g L(- 1). Experimental results showed that for a 96.9% turbidity removal, similar reduction in Al (97.0%) and Fe (99.5%) concentrations; as well as 66% total Kjeldahl nitrogen removal were obtained. Furthermore, the sludge formed exhibited a good floc size, which separated in less than 10 min by classical sedimentation. The results analysis provided evidence of reduction of chemical pollutants, although the electrocoagulated leachate could not satisfy regulations for the maximum Total Kjeldahl nitrogen leachate discharge level to public wastewater collection systems in the town of Freire, Chile.

Membrane Bioreactor Treatment of a Simulated Metalworking Fluid Wastewater Containing Ethylenediaminetetraacetic Acid and Dicyclohexylamine

Membrane bioreactors (MBRs) have been installed at automotive plants to treat metalworking fluid (MWF) wastewaters, which are known to contain toxic and/or recalcitrant organic compounds. A laboratory study was conducted to evaluate treatment of a simulated wastewater prepared from a semisynthetic MWF, which contains two such compounds, dicyclohexylamine (DCHA) and ethylenediaminetetraacetic acid (EDTA). Primary findings were as follows: During stable operating periods, almost all chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), and EDTA were removed (by > 96%). During somewhat unstable periods, COD removal was still extremely robust, but removal of EDTA and TKN were sensitive to prolonged episodes of low dissolved oxygen. Nitrogen mass balance suggested 30 to 40% TKN removal by assimilation and 60 to 70% by nitrification (including up to 34% TKN removal via subsequent denitrification). Dicyclohexylamine appeared to be readily biodegraded. Maximum DCHA and EDTA degradation rates between pH 7 and 8 were found. An Arthrobacter sp. capable of growth on DCHA as the sole source of carbon and energy was isolated.

Alum Application to Improve Water Quality in a Municipal Wastewater Treatment Wetland

Nutrient removal in treatment wetlands declines during winter months due to temperature. A 3-mo (wintertime) mesocosm study was conducted to determine the effectiveness of alum in immobilizing P as well as other nutrients during this period of reduced treatment efficiency. Eighteen mesocosms, triplicate alum, and three controls or no alum were established with either Typha spp., Schoenoplectus californicus, or SAV (Najas guadalupensis-dominated). Alum was delivered by timer at a rate of 0.81 g Al m(-2) d(-1) and parameters measured included: pH, soluble reactive phosphorus (SRP), total phosphorus (TP), dissolved organic carbon (DOC), dissolved inorganic nitrogen (DIN), total kjeldahl nitrogen (TKN), and soluble aluminum (Al). Alum-treated mesocosms had significantly lower pH values (8.1) than controls (8.8), but well within the elevated pH range for aluminum toxicity. Alum significantly reduced all measured water column nutrients with the exception of ammonium N, which remained unaffected, and particulate P, which increased. This study demonstrated that seasonal low-dosage alum application to different vegetation communities in a treatment wetland can significantly improve treatment efficiencies for SRP (87 vs. 58%) and TP (62 vs. 44%) but also increase DOC (19 vs. 0%) and TKN (12 vs. -3%) removal capacity to a lesser degree. Alum applications within close proximity of the treatment wetland effluent points should be implemented with caution due to the production of alum floc-bound P which could potentially affect discharge permit compliance for total suspended solids or total P.

Can vertical-flow wetland systems treat high concentrated sludge from a food industry? A mesocosm experiment testing three plant species

We performed a mesocosms experiment using a vertical-flow wetland system to treat liquid sludge in the Mediterranean region. Three common helophyte species, common reed ( Phragmites australis Cav.), broadleaf cattail ( Typha latifolia L.), and yellow flag ( Iris pseudacorus L.), were planted as monoculture and irrigated with a liquid sewage sludge from a food industry, characterised by very high organic concentrations (COD > 8000 mg/L). We studied the benefits of plants by comparing unplanted to planted mesocosms. Results showed the high performance of such vertical-flow wetland systems. Removal efficiency was more than 98% for total suspended solids (TSS) and chemical oxygen demand (COD), and more than 87% for total Kjeldahl nitrogen (TKN). The main removal process was physical filtration by the substrate due to the high proportion of particulate elements in the sludge. Planted mesocosms were more efficient than those unplanted, confirming the positive role of the plants. Mesocosms planted with Phragmites or Typha showed better performances in TKN removal than those planted with Iris. Only in mesocosms planted with Phragmites was there no outflow in summer due to high evapotranspiration.

Removal of Congo red from textile wastewater by ozonation

Congo red, which has a complex molecular structure with various diazo aromatic groups, is widely used in textile industry as an anionic dye. The purpose of this study was to investigate the degradation of Congo red in laboratory solution which had the chemical properties of the rinse waters of textile manufacturing dye-houses and the samples with Congo red alone wastewater by ozonation and to optimize the reaction parameters such as pH and time which influence the efficiencies of total organic carbon, total kjeldahl nitrogen and chemical oxygen demand removal. Ozonation of Congo red dye were carried out in a semi-batch reactor with constant ozone flow rate and concentration of 23 mL/sec and 13.6 mg/L, respectively. Decolorization was complete within a few minutes of ozonation possibly due to the cleavage of chromophore groups. It was observed that its structural destruction occurs predominantly at higher pHs. The reduction of chemical oxygen demand and destruction of the dye was more than 60 % and 42 %, respectively. Total kjeldahl nitrogen removal was accompanied by slight changes in nitrogen oxides. It can be deduced from the experimental results that: (a) the mineralization is very weak; (b) the reaction follows the indirect mechanism; i.e., the interaction of hydroxyl radicals with the dye and (c) the nitrification is rather predominant. Biological oxygen demand is declined in simulated alkalic and neutral samples respectively. At 13.6 mg O 3 /L, the biological oxygen demand levels were significantly enhanced. This might be attributable to the enhancement of its biodegradation at alkaline pHs.

A modified UCT method for biological nutrient removal: Configuration and performance

A pilot-scale prototype activated sludge system is presented, which combines both, the idea of University of Cape Town (UCT) concept and the step denitrification cascade for removal of carbon, nitrogen and phosphorus. The experimental set-up consists of an anaerobic selector and stepwise feeding in subsequent three identical pairs of anoxic and oxic tanks. Raw wastewater with influent flow rates ranging between 48 and 168 l d −1 was fed to the unit at hydraulic residence times (HRTs) of 5–18 h and was distributed at percentages of 60/25/15%, 40/30/30% and 25/40/35% to the anaerobic selector, 2nd and 3rd anoxic tanks, respectively (influent flow distribution before the anaerobic selector). The results for the entire experimental period showed high removal efficiencies of organic matter of 89% as total chemical oxygen demand removal and 95% removal for biochemical oxygen demand, 90% removal of total Kjeldahl nitrogen and total nitrogen removal through denitrification of 73%, mean phosphorus removal of 67%, as well as excellent settleability. The highest removal efficiency and the optimum performance were recorded at an HRT of about 9 h and influent flow rate of 96 l d −1, in which 60% is distributed to the anaerobic selector, 25% to the second anoxic tank and 15% to the last anoxic tank. Consequently, the plant configuration enhanced removal efficiency, optimized performance, saved energy, formed good settling sludge and provided operational assurance.

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.

&lt;i&gt;Technical note&lt;/i&gt; Biological treatment of industrial wastewater containing formaldehyde and formic acid

The biological treatment of wastewater from an aminoplastic resin-producing industry was studied in a pre-denitrification system. This study reports results on the removal of organic matter and nitrogen compounds from wastewater which contained high levels of formaldehyde and formic acid. The formaldehyde concentration in the feed varied between 2 087.0 and 2 200.0 mg/&#8467;, the mean removal being 99.9%. The mean efficiency of formic acid removal was 99.7%, and its concentration in the feed ranged between 1 384.6 and 1 513.9 mg/&#8467;. The total organic carbon (TOC) values in the feed varied from 1 423.0 to 1 599.5 mg/&#8467;, corresponding to an organic loading rate of about 0.20 kg TOC/m3·d. High TOC removal was achieved, around 92.0%. With regard to nitrogen compounds, the total Kjeldahl nitrogen (TKN) concentration in the feed ranged between 467.8 and 492.3 mg/&#8467;. The applied nitrogen loading rate was around 0.06 kg TKN/m3·d, and the mean percentage of TKN removal was 76.7%. Water SA Vol 32(1)pp:115-118

An activated sludge treatment plant for integrated removal of carbon, nitrogen and phosphorus

During the last decade more stringent effluent requirements concerning the nutrients effluent values have been imposed by legislation and social concern. This paper presents a pilot-scale activated sludge prototype system which combines the UCT concept and the step denitrification cascade for integrated removal of carbon, nitrogen and phosphorus. The experimental unit includes an anaerobic selector and stepwise feeding in subsequent anoxic and oxic vessels for removal of BOD 5/COD, suspended solids, nitrogen, and phosphorus. Raw municipal wastewater with influent flow rates ranging between 48–120 L/d was fed to the unit at residence times of 7–18 h and specific BOD 5 loading rates of 0.23–1.08 kg BOD 5/(kg MLVSS —d). The results of a full year operation show high removal efficiencies of organic matter of about 88% as total COD and 92% removal for BOD 5, complete nitrification (93– 99% removal of ammonia-nitrogen), high removal of Total Kjeldahl Nitrogen ranging between 87 and 97% and total nitrogen removal through denitrification of 70%. Phosphorus removal is fair because of the intense fluctuations in the incoming phosphate concentration. Moreover, plant configuration provides operational conditions that suppress filamentous bacteria and favour growth of floc-formers, leads to high sludge settleability characteristics (SVI < 130 ml/g).

Aerobic Granular Sludge Systems: The New Generation of Wastewater Treatment Technologies

The paper reports the results of a laboratory investigation aimed at evaluating the effectiveness of an innovative technology, SBBGR (sequencing batch biofilter granular reactor), based on aerobic granular biomass, for treating diluted (i.e., municipal wastewater) or concentrated (i.e., municipal landfill leachates) wastewater. When this technology was applied to the treatment of municipal wastewater, the results showed that, even at maximum organic load (i.e., 7 (kg of COD)/m3·d), the chemical oxygen demand (COD) in the treated effluent was lower than 50 mg/L. In addition, total Kjeldahl nitrogen (TKN) removal efficiency was higher than 87% up to an organic load of 5.7 (kg of COD)/m3·d, corresponding to a nitrogen load of 0.8 (kg of TKN)/m3·d. During the treatment of a mature municipal landfill leachate, the SBBGR proved suitable for removing the entire biodegradable compound content (i.e., about 80% of the COD content of the leachate) up to an applied organic loading value of 1.1 (kg of COD)/m3·d. During the whole investigation, the process was characterized by a low sludge production, about 1 order of magnitude lower than that of conventional systems.

Stabilization Pond Systems: Cost Estimation for the Treatment of Piggery Waste

This work presents the results from monitoring the three pond systems for the treatment of piggery waste, carried out over 12 months, with the objective of determining operational design parameters to minimize the treatment system costs. The first system consisted of two anaerobic and one facultative pond, the second and third systems were constituted by two anaerobic, two facultative, and one maturation pond, on a pilot scale, arranged in series. The three-pond systems achieved an efficiency of 91% for the removal of total chemical oxygen demand (TCOD) and 87% for total Kjeldahl nitrogen (TKN). A mathematical model to minimize treatment costs for these wastes was developed, within economic concepts. A simulation of costs was made for a treatment system with a flow rate of 20 m3/day and an efficiency level of about 90% for TCOD and TKN removal. The costs were US$812.40 for earth, US$6,360.60 for construction, US$4,530.90 for lining, and US$6,760.70 for pond maintenance, resulting in a total cost of US$18,464.60 for this flow rate and a unitary cost of the order of US$1.30 per swine/year.

The role of plants in the removal of nutrients at a constructed wetland treating agricultural (dairy) wastewater, Ontario, Canada

The South Nation River Watershed, in eastern Ontario, Canada, is an agricultural watershed impacted by excess nutrient loading primarily from agricultural activities. A constructed wetland for the treatment of agricultural wastewater from a 150-cow dairy operation in this watershed was monitored in its eighth operating season to evaluate the proportion of total nitrogen (TN) (approximated by total Kjeldahl nitrogen (TKN) due to low NO 3 −) and total phosphorus (TP) removal that could be attributed to storage in Typha latifolia L. and Typha angustifolia L ., which dominate this system. Nutrient loading rates were high, with 16.2 kg ha −1 d −1 N and 3.4 kg ha −1 d −1 P entering the wetland and loading the first wetland cell. Plant uptake accounted for 0.7% of TKN removal when the vegetated free water surface cells were considered together. However, separately, in the second wetland cell with lower N and P loading rates, plants accounted for 9% of TKN, 21% of NH 4 + and 5% of TP removal. Plant uptake was significant to overall removal given wetland age and nutrient loading. Nutrient storage during the growing season at this constructed wetland helped reduce the nutrient load entering the watershed, already stressed by intensive local agriculture.

Integrated faecal sludge treatment and recycling through constructed wetlands and sunflower plant irrigation

Faecal sludge (FS) from the on-site sanitation systems is a nutrient-rich source but can contain high concentrations of toxic metals and chemicals and infectious micro-organisms. The study employed 3 vertical-flow CW units, each with a dimension of 5 x 5 x 0.65 m (width x length x media depth) and planted with cattails (Typha augustifolia). At the solid loading rate of 250 kg total solids (TS)/m(2).yr and a 6-day percolate impoundment, the CW system could achieve chemical oxygen demand (COD), TS and total Kjeldahl nitrogen (TKN) removal efficiencies in the range of 80-96%. A solid layer of about 80 cm was found accumulated on the CW bed surface after operating the CW units for 7 years, but no clogging problem has been observed. The CW percolate was applied to 16 irrigation sunflower plant (Helianthus annuus) plots, each with a dimension of 4.5 x 4.5 m (width x length). In the study, tap water was mixed with 20%, 80% and 100% of the CW percolate at the application rate of 7.5 mm/day. Based on a 1-year data in which 3 crops of plantation were experimented, the contents of Zn, Mn and Cu in soil of the experimental plots were found to increase with increase in CW percolate ratios. In a plot with 100% of CW percolate irrigation, the maximum Zn, Mn and Cu concentrations of 5.0, 12.3 and 2.5 mg/kg, respectively, were detected in the percolate-fed soil, whereas no accumulation of heavy metals in the plant tissues (i.e. leaves, stems and flowers) of the sunflower were detected. The highest plant biomass yield and oil content of 1000 kg/ha and 35%, respectively, were obtained from the plots fed with 20% or 50% of the CW percolate.

Post-Treatment of Anaerobic Bioreactor Effluent Using Jet Loop Reactor (JLR)

Abstract A novel post-treatment system, jet loop reactor (JLR), was proposed for anaerobic bioreactor effluent polishing purposes. The performance of the JLR, with respect to residual organics, total Kjeldahl nitrogen (TKN) and ammonia-nitrogen removal at different hydraulic retention times (HRTs), was the main focus of this study. The JLR, on average, was capable of removing approximately 99% of ammonia-nitrogen and 95% of TKN at HRTs of 8 and 5 h, respectively. The integrated system had an average removal of more than 85% of total BOD and COD and more than 95% of filtered BOD and COD. However, the JLR did not have a consistent performance due to dynamic MLSS concentration (and SRT). Overall the results indicate that the JLR can be considered as a feasible alternative for post-treatment of anaerobic bioreactor effluent.

Water Quality Improvement through Bioretention Media: Nitrogen and Phosphorus Removal

High nutrient inputs and eutrophication continue to be one of the highest priority water quality problems. Bioretention is a low-impact development technology that has been advocated for use in urban and other developed areas. This work provides an in-depth analysis on removal of nutrients from a synthetic stormwater runoff by bioretention. Results have indicated good removal of phosphorus (70 to 85%) and total Kjeldahl nitrogen (55 to 65%). Nitrate reduction was poor (< 20%) and, in several cases, nitrate production was noted. Variations in flowrate (intensity) and duration had a moderate affect on nutrient removal. Mass balances demonstrate the importance of water attenuation in the facility in reducing mass nutrient loads. Captured nitrogen can be converted to nitrate between storm events and subsequently washed from the system. Analysis on the fate of nutrients in bioretention suggests that accumulation of phosphorus and nitrogen may be controlled by carefully managing growing and harvesting of vegetation.

Production of Biomass (Algae-Bacteria) by Using a Mixture of Settled Swine and Sewage as Substrate

This paper presents the use of a mixture of settled swine and sewage as substrate for biomass production, mainly constituted by microalgae Chlorella vulgaris and aerobic bacteria, growing outdoor at different dilution rates in a continuous mode. The experiments were carried out in 16-litre volume laboratory ponds operating at hydraulic retention times (HRT) in a range of 4–14 days equivalent to dilution rates (D) in a range of 0.250–0.071 d−1. Total chemical oxygen demand (TCOD), soluble chemical oxygen demand (SCOD), total biochemical oxygen demand (TBOD5), total suspended solids (TSS), volatile suspended solids (VSS), total Chlorophyll (Σ C), total Kjeldahl nitrogen (TKN), ammonia nitrogen, total phosphorous, orthophosphate and pH were monitored. An empirical relationship between the dilution rate (D) and the removal efficiencies of TCOD, SCOD, TBOD5, TKN and total phosphorous was found. The occurrence of an inhibition process for TCOD, TBOD5, TKN and total phosphorous removals was observed. The Andrews kinetic model was successfully applied to these experimental data, while the Monod model was more suitable for studying the variation of the SCOD removal rate with the effluent SCOD concentration. The maximum microalgal biomass productivity was found to be in the range of 93–98 mg VSSA/L d (37.2–39.2 g/m2d) at dilution rates in the range of 0.167–0.250 d−1, where VSSA is the concentration of microalgae expressed in VSS. In the case of the bacteria, the productivity increased linearly with the dilution rate being maximum at a D value of 0.25 d−1. It was concluded that the mixture of pre-treated swine and sewage used as substrate, contributed to the obtention of a high biomass (microalgae-bacteria) production, providing a simple technology feasible to be applied in developing countries.

Development and evaluation of a radial anaerobic/aerobic reactor treating organic matter and nitrogen in sewage

The design and performance of a radial anaerobic/aerobic immobilized biomass (RAAIB) reactor operating to remove organic matter, solids and nitrogen from sewage are discussed. The bench-scale RAAIB was divided into five concentric chambers. The second and fourth chambers were packed with polyurethane foam matrices. The performance of the reactor in removing organic matter and producing nitrified effluent was good, and its configuration favored the transfer of oxygen to the liquid mass due to its characteristics and the fixed polyurethane foam bed arrangement in concentric chambers. Partial denitrification of the liquid also took place in the RAAIB. The reactor achieved an organic matter removal efficiency of 84%, expressed as chemical oxygen demand (COD), and a total Kjeldahl nitrogen (TKN) removal efficiency of 96%. Average COD, nitrite and nitrate values for the final effluent were 54 mg.L-1, 0.3 mg.L-1 and 22.1 mg.L-1, respectively.

Pós-tratamento de efluente nitrificado da parboilização de arroz utilizando desnitrificação em reator UASB

Um sistema combinado reator UASB-reator aeróbio foi utilizado para a remoção de nitrogênio total e DQO de efluente de parboilização de arroz. O experimento foi realizado em reatores de bancada, com volumes de 4 L (UASB) e 3,6 L (reator aeróbio). Os parâmetros de operação pH, temperatura, alcalinidade e concentração de ácidos voláteis foram monitorados durante o período experimental. Para o reator aeróbio de mistura completa, foi determinada, também, a concentração de oxigênio dissolvido. O sistema combinado reator UASB-reator aeróbio apresentou uma eficiência de remoção de carbono de 84% e uma eficiência de remoção de nitrogênio total Kjeldahl de 83%. O sistema proposto, nas condições experimentais, demonstrou ser adequado para remoção, simultânea, de DQO e de compostos oxidados de nitrogênio, em reator UASB.