Examination of peat samples collected from hummocks and hollows within a confined bog reveals that peat collected from different locations, designated by surface topography, vary in ash content, ash alkalinity, initial Kjeldahl nitrogen content, and fixed and total nitrogen after ammoniation with an ammonia-air mixture. The values of these properties have shown hummocks and hollows to be true entities having characteristic ranges of certain properties. The results have shown that, although peat is heterogenous with respect to certain properties, use can still be made of determined values if ranges of these values are recognized and utilized. Misinterpretations and meaninglessness of results are possible if this is not done. / Thesis / Master of Science (MSc)

This study addressed the geochemical drivers of Mn removal, including pH, alkalinity and the presence of mineral particles. We conducted laboratory experiments and field monitoring at two drinking water reservoirs in southwestern Virginia – Falling Creek Reservoir (FCR) and Carvins Cove Reservoir (CCR). In laboratory experiments in pH and alkalinity-adjusted nanopure water solutions, we observed substantial Mn removal within 14 days only under high pH conditions (pH≥10). In experiments with high pH and moderate to high alkalinity (> 80 mg/L CaCO3), near-total Mn removal occurred within 2 hours, at a rate of 0.25 mg/L-1 hr-1. Mn removal occurred alongside precipitation of microscopic (<5 μm diameter) and macroscopic (>100 μm diameter) particles. Elemental analysis of particles with energy-dispersive X-ray spectroscopy (EDS) supports their identification as Mn(IV) oxides (MnOx), which suggests Mn removal driven by oxidation. Elevated alkalinity in high pH solutions promotes Mn oxidation by maintaining high pH through buffering, which sustains conditions favorable for Mn oxidation. Our results also suggest sorption of Mn and mineral-catalyzed Mn oxidation by Mn oxides formed through oxidation by dissolved oxygen. In experiments using filtered and unfiltered water from the two reservoirs, we observed significant Mn removal in experiments with unfiltered water, suggesting that particles may remove Mn by catalyzing oxidation or nucleating Mn oxide precipitation. Mn removal occurred at 0.05 d-1 in unfiltered FCR water and 0.002 d-1 in unfiltered CCR water. We observed no Mn removal in filtered water from either reservoir. Scanning electron microscope (SEM) and EDS of visible particles from reservoir water experiments suggests that quartz and clay minerals present in the water column may nucleate or catalyze Mn oxide formation. Overall, this research shows that Mn removal under HOx operation is influenced by a variety of factors, including pH, alkalinity and suspended particles. / Master of Science / Elevated concentrations of manganese (Mn), a naturally occurring contaminant, can impair drinking water quality in several ways – by introducing poor taste and smell, staining pipes and appliances, and potentially harming the health of young children. Hypolimnetic oxygenation (HOx) is a novel water treatment method deployed in lakes and reservoirs to control water column contamination of metals and nutrients, including Mn. By pumping oxygen into lakes and reservoirs, HOx systems create conditions favorable for Mn removal from the water column. Previous work in two southwestern Virginia drinking water reservoirs documented differences between sites in how effectively HOx systems are able to remove Mn. These reservoirs have significant differences in their chemical profiles – most notably in pH and alkalinity, which suggests a role for background water chemistry in influencing removal rates in lakes and reservoirs with HOx systems. We used laboratory experiments to simulate the effects of pH and alkalinity on Mn removal rates in oxygenated lakes and reservoirs. We observed substantial Mn removal within 14 days under high pH conditions (pH 10-11) and negligible removal in solutions at or under pH 8. In experiments with pH 10-11 and alkalinity over 80 mg/L, near-total Mn removal occurred within 24 hours. During the 24 hour removal window, we observed yellow-brown discoloration of our experimental solutions within 12 hours, followed by formation of loosely aggregated brown to black particles. Microscopy and elemental analyses indicate that initial discoloration occurs due to formation of 1-2 μm wide manganese oxides with needle-like crystals. The visible aggregates are also manganese oxides. Based on mineral characterization and the time series of Mn removal observed in our experiments, we believe that initial formation of Mn oxides creates a positive feedback loop in solutions of pH 10-11 and alkalinity over 80 mg/L. Mn oxides promote further Mn oxide formation by facilitating conversion of Mn in solution into forms that easily settle from water. Observations of particulate formation and solution chemistry in filtered vs. filtered reservoir water from FCR and CCR supports a pivotal role for particles in facilitating Mn removal. Our research addresses the impacts of water chemistry Mn removal in drinking water, and improves understanding of Mn cycling in natural freshwaters.

No description available.

<p>This study investigates the feasibility of using waste glass as a supplementary cementitious material (SCM). By further defining some of the parameters by which waste glass may be incorporated into concrete as a cement replacement, the environmental, economical, and engineering benefits of this material may be realized. Past observations, including the production of alkali silica reaction (ASR) gel, and the lack of pozzolanic reactivity, have limited the acceptance of waste glass as a SCM,</p> <p>Mechanical treatment was used to improve reactivity and provide a particle size at which waste glass performs comparably to ground granulated blast furnace slag and nearly as well as silica fume. At 6.6 µm, the pozzolanic reactivity of waste glass was demonstrated through consumption of Ca(OH)₂ and heat of hydration. Waste glass at a larger particle size (16.5 µm) was as reactive as slag. Use of waste glass at 10% replacement of Portland cement by mass and at a particle size below 100 µm proved useful as a SCM.</p> <p>A relationship between pozzolanic and alkali silica reaction (ASR) was identified with intermediate phases of the reaction present. Calcium silicate hydrates (C-S-H) from the pozzolanic reaction have a Ca/Si ratio of 1.5-2. ASR products generally have a Ca/Si ratio of 0.01-1. The products observed with agglomeration of glass particles had a Ca/Si ratio from 0.5-2. The affects of silica concentration and alkalinity of the solution on the reaction products were explored.</p> <p>A reaction rim was identified around glass agglomerates where fluorescence was observed. The results indicate that ASR can be induced even in low alkalinity cement, and the rate of reaction influences both the characteristics and composition of the reaction product.</p> / Doctor of Philosophy (PhD)

<p> In this study the influence of several water chemistry parameters on the toxicity of Ni to Daphnia pulex in soft water were tested. A reconstituted soft water (pH 7.8, hardness 31.5 mg/L CaCO3) was used as the basis for culture and testing. Daphnia pulex was chosen as a typical cladoceran, one which can be acclimated to very soft water. An understanding of the influence of water chemistry on Ni toxicity in soft water is relevant because metals have higher bioavailability in soft water. The 48h EC50 in the reconstituted soft water (RSW) was 974 μg/L (16 μM) dissolved Ni (95%CI 830- 1081 μg/L). The following factors were examined for their potential for modifying Ni toxicity: Ca, Mg, Na, K, Cl, pH (3 different approaches used) and natural organic matter (NOM, 2 sources tested). Both Ca and Mg protected against Ni toxicity and the relative effect was greater for Ca. Varying the concentrations of Na, Cl or K did not alter the toxicity of Ni. Tests at different pH showed that as pH increased, Ni toxicity decreased. When the test solution pH was adjusted with the organic buffer 3-morpholinepropanesulfonic acid, there was a clear correlation between increasing pH and increasing EC50. The pH tests using bicarbonate to adjust pH did not show this relationship as clearly. Both types of NOM showed a protective effect on Ni toxicity with Nordic Reservoir NOM having a 4 fold greater effect than that of Suwannee River NOM. This research illustrated that the effect of alterations in water chemistry were generally as predicted within the context of the biotic ligand model (BLM) approach. The data provide the information required to develop a BLM for the acute effects of Ni in soft water.</p> / Thesis / Master of Science (MSc)

The Clinch and Powell Rivers located in Southwestern Virginia contain some of the most diverse freshwater mussel assemblages found throughout North America. However, in recent decades mussel species decline has been documented by researchers. The presence of coal mining activity in the watersheds has been hypothesized to be linked to the decline of numerous species and the extirpation of others. The effects of various discharges from an active coal preparation plant facility located in Honaker, Virginia were evaluated for acute and chronic toxicity using field and laboratory tests. The results of the study suggested that the primary effluent from the coal preparation facility had acute and chronic toxicity; however, the settling pond system utilized at this plant mitigated the impacts of the plant from reaching the Clinch River. Along with active mine discharges, acid mine drainage (AMD) has been documented as another potential stressor. Ecotoxicological recovery was evaluated in two acid mine drainage impacted subwatersheds (Black Creek and Ely Creek) in the Powell River watershed following remediation. The results in Ely Creek suggested that successive alkalinity producing systems were effective in mitigating the harmful impacts of AMD as previously impacted sites had decreased water column aluminum and iron levels in conjunction with increased survival in laboratory toxicity tests conducted with Ceriodaphnia dubia and Daphnia magna. Corbicula fluminea (Asian clam) in-situ tests confirmed the results in the laboratory tests as all sites located below the remediated areas had improved survival. However, active AMD influences and loss of quality habitat seemed to be hindering the recovery of the benthic macroinvertebrate community located in Ely Creek. In Black Creek, re-mining and outlet control pond construction have not resulted in a successful remediation in the lower subwatershed. A decrease in Ecotoxicological Ratings at some of the lowest mainstem sites compared to pre-remediation data was observed. Furthermore, decreased survival in sediment associated toxicity tests with D. magna in 2007-08 was supported by 100% Asian clam mortality at the LBC-5 and LBC-6 sites in 2007, while growth impairment in 2008 was observed at the LBC-6 site. / Master of Science

Effective coagulation is critical to the production of safe, potable drinking water, but variations in the chemical composition of source water can present challenges in achieving targeted contaminant removal and predicting coagulation outcomes. A critical literature review describes factors affecting the hydrolysis reactions of metal salt coagulants and the resulting precipitates. Properties of two key contaminants, turbidity and natural organic matter (NOM), are explored in the context of removal during coagulation, and the influence of co-occurring ions is described. While it is apparent that NOM character determines the minimum achievable organic carbon residual, the effects of water quality—including pH, NOM character and concentration, and concentrations of synergistic and competitive ions—on overall coagulation efficacy and NOM removal may be underestimated. An experimental research plan was devised to investigate the influence of water quality in coagulation and provide data to support the development of a predictive coagulation model. NOM is capable of interfering with ferric iron hydrolysis and influencing the size, morphology, and identity of precipitates. Conversely, calcium is known to increase the size and aggregation of Fe3+ precipitates and increase surface potential, leading to more effective coagulation and widening the pH range of treatment. Experiments and modeling were conducted to investigate the significance of the Fe/NOM ratio and the presence of calcium in coagulation. At the high Fe/NOM ratio, sufficient or excess ferric hydroxide was available for NOM removal, and coagulation proceeded according to expectations based upon the literature. At the low Fe/NOM ratio, however, NOM inhibited Fe3+ hydrolysis, reduced zeta potential, and suppressed the formation of filterable Fe flocs, leading to interference with effective NOM removal. In these dose-limited systems, equilibrating NOM with 1 mM Ca2+ prior to dosing with ferric chloride coagulant increased the extent of Fe3+ hydrolysis, increased zeta potential, decreased the fraction of colloidal Fe, and improved NOM removal. In dose-limited systems without calcium, complexation of Fe species by NOM appears to be the mechanism by which coagulation is disrupted. In systems with calcium, data and modeling indicate that calcium complexation by NOM neutralizes some of the negative organic charge and minimizes Fe complexation, making Fe hydrolysis species available for growth and effective coagulation. Experiments were conducted to investigate the influence of aqueous silica and pH on the removal of natural organic matter (NOM) by coagulation with ferric chloride. Samples with preformed ferric hydroxide were also compared to samples coagulated in situ to assess the role of coprecipitation. The moderate (10 mg/L) and high (50 mg/L) SiO2 concentrations both demonstrated interference with NOM removal at pH 6.5-7.5. In turn, NOM at 2 mg/L as DOC interfered with silica sorption at the moderate silica level and in samples with preformed ferric hydroxide at the high silica level. The combination of NOM and high silica led to decreases in DOC sorption and unexpected increases in silica sorption in the coprecipitated samples. The fraction of colloidal Fe passing a 0.45-μm filter also increased in the coprecipitated samples with both NOM and high silica. It is hypothesized that the combination of NOM and high silica synergistically interfered with Fe precipitation and particle growth processes, with NOM having the greater effect at lower pH and shorter reaction times, and silica exerting greater influence at higher pH and longer reaction time. Direct competition for surface sites and electrostatic repulsion were also influential. An overall goal for this research was the development of a quantitative coagulation model. Previous attempts to model coagulation have been limited by the inherent complexities of simultaneously predicting ligand sorption, metal complexation, floc surface charge, and particle removal. A diffuse layer (DLM) surface complexation model was formulated to simultaneously predict sorption of NOM and other key species, including silica, calcium, and carbonate alkalinity. Predictions of surface potential were used to estimate zeta potential and resulting regimes of effective aggregation and turbidity removal. The model provided good predictive ability for data from bench-scale experiments with synthetic water and jar tests of nine U.S. source waters. Under most conditions, the model provides excellent capability for predicting NOM sorption, calcium sorption, and particle destabilization and adequate capability for predicting silica sorption. Model simulations of hypothetical scenarios and experimental results help to explain practical observations from the literature. The DLM can be optimized to site-specific conditions and expanded to include sorption of additional species, such as arsenic. / Ph. D.

For decades, cement mortar relining has been used successfully to extend the life of drinking water pipelines, although, few quantitative data exist on the short-term water quality impacts of this process. This study investigated mortar lining impacts on disinfectant by-product formation, alkalinity, metal leaching, pH and disinfectant consumption, and odor generation shortly after in-situ installation. The experimental design used a 30-day, coupon immersion procedure that simulated a relined 4-inch diameter pipe located in a low-flow system. Four water regimes were utilized; no disinfectant, chlorine (2 mg/L at pH 6 .5 and 8), and chloramines. Flavor Profile Analysis panels evaluated odors of samples and controls. Additionally, the affects of three different phosphate-based corrosion prevention additive regimes were evaluated. Cement mortar leachates impacted water quality significantly during the first week of exposure. Alkalinity, hardness and pH increased dramatically after initial exposure, rising to approximately 600 mg/L as CaCO3 alkalinity, 770 mg/L as CaCO3 hardness, and pH 12 in the first two days. Sharp declines in alkalinity and hardness did not occur until after day 9 when the cement mortar was substantially cured and release of calcium hydroxide lessened. Chlorinated water residual disinfectant decay rate was increased substantially during the initial 24 hours and remained elevated until day 9. After day 1, there was not a significant increase in the formation of regulated haloacetic acids or trihalomethanes. Significant levels of aluminum (< 700 ug/L) and chromium (< 75 ug/L) were released at various times during the test period but their concentrations did not exceed USEPA water quality standards. Cement odor intensity levels were significantly higher than controls, persisted for 14 days, and were of an intensity that would be readily noticeable to consumers. The polyphosphate-based corrosion preventative resulted in less severe water quality effects than other phosphate additives or water without added phosphate. / Master of Science

A lower-alkalinity cement based on MgO and SiO2 blends is analysed to develop clinker-free Fibre Reinforced Cementitious Composites (FRCC) with cellulosic fibres in order to solve the durability problems of this type of fibres when used in FRCC with Portland cement. Hydration evolution from 7 to 28 days of different MgO-SiO2 formulations is assessed. The main hydration products are Mg(OH)2 and M-S-H gels for all the formulations studied regardless of age. Hardened pastes are obtained with pH values &lt; 11 and good mechanical properties compared to conventional Portland cement. 60% MgO-40% SiO2 system is chosen as optimal for the development FRCC since is the most mechanical resistant and is less alkaline compared with 70% MgO-30% SiO2. FRCC based on magnesium oxide and silica (MgO-SiO2) cement with cellulose fibres are produced to study the durability of lignocellulosic fibres in a lower pH environment than the ordinary Portland cement (PC). Flexural performance and physical tests (apparent porosity, bulk density and water absorption) of samples at 28 days and after 200 accelerated ageing cycles (aac) are compared. Two types of vegetable fibres are utilised: eucalyptus and pine pulps. MgO-SiO2 cement preserves cellulosic fibres integrity after ageing, so composites made out of MgO-SiO2 exhibit significant higher performance after 200 cycles of accelerated ageing than Portland cement composites. High CO2 concentration environment is evaluated as a curing treatment in order to optimise MgO- SiO2 matrices in FRCC. Samples are cured under two different conditions: 1) steam water curing at 55°C and 2) a complementary high CO2 concentration (20% by volume). In carbonated samples, Mg(OH)2 content is clearly lowered while new crystals of hydromagnesite [Mg5 (CO3)4&sdot;(OH) 2&sdot;4H2O] are produced. After carbonation, M-S-H gel content is also reduced, suggesting that this phase is also carbonated. Carbonation affects positively to the composite mechanical strength and physical properties with no deleterious effects after ageing since it increases matrix rigidity. The addition of sepiolite in FRCC is studied as a possible additive constituent of the binding matrix. Small cement replacement (1 and 2% wt.) by sepiolite is introduced and studied in hardened cement pastes and, later, in FRCC systems. When used only in cement pastes, it improves Dynamic Modulus of Elasticity over time. Bending tests prove the outcome of this additive on the mechanical performance of the composite: it improves composite homogeneity. Ageing effects are reported after embedding sisal fibres in MgO-SiO2 and PC systems and submitting them to different ageing conditions. This comparative study of fibre degradation applied in different cementitious matrices reveals the real compatibility of lignocellulosic fibres and Mg-based cements. Sisal fibres, even after accelerated ageing, do neither suffer a significant reduction in cellulose content nor in cellulose crystallinity and crystallite size, when exposed to MgO-SiO2 cement. Fibre integrity is preserved and no deposition of cement phases is produced in MgO-SiO2 environment. / Um cimento de baixa alcalinidade à base de blendas de MgO e SiO2 é analisado para o desenvolvimento de Compósitos Cimentícios Reforçados com Fibras (CCRF) celulósicas sem clínquer para resolver os problemas de durabilidade de este tipo de fibras quando são usadas em CCRF com cimento Portland. A evolução da hidratação, desde 7 aos 28 dias, das diferentes formulações é avaliada. Os principais produtos hidratados são o Mg(OH)2 e o gel M-S-H para todas as formulações independentemente da idade estudada. As pastas endurecidas apresentam valores de pH &lt; 11 e bom desempenho mecânico comparado com o cimento Portland convencional. O sistema 60% MgO-40% SiO2 é escolhido como a formulação ótima para o desenvolvimento de CCRF já que é a mais resistente e menos alcalina comparada com 70% MgO-30% SiO2. CCRF com cimento à base de óxido de magnésio e sílica (MgO-SiO2) e fibras celulósicas são produzidos para a análise da durabilidade das fibras lignocelulósicas em ambientes com valores de pH mais baixos comparados com o cimento Portland (PC). O desempenho mecânico a flexão e os ensaios físicos (porosidade aparente, densidade aparente e absorção de água) são comparados aos 28 dias e após de 200 ciclos de envelhecimento acelerado. O cimento à base de MgO-SiO2 preserva a integridade das fibras após o envelhecimento. Os compósitos produzidos com este cimento exibem melhores propriedades após 200 ciclos de envelhecimento acelerado que os compósitos produzidos com cimento Portland. Ambientes com alta concentração de CO2 são avaliados como tratamento de cura para otimizar as matrizes MgO- SiO2 nos CCRF. As amostras são curadas sob 2 condições diferençadas: 1) cura com vapor de água a 55oC e 2) cura com alta concentração de CO2 (20% do volume). As amostras carbonatadas apresentam teores reduzidos de Mg(OH)2 enquanto é produzida uma nova fase cristalina: hidromagnesita [Mg5 (CO3)4&sdot;(OH) 2&sdot;4H2O]. Após a carbonatação, o conteúdo de gel M-S-H é reduzido também, indicando uma carbonatação desta fase. A carbonatação aumenta a rigidez da matriz o que influi positivamente no desempenho mecânico e as propriedades físicas dos compósitos sem efeitos prejudiciais ao longo prazo. A adição de sepiolita em CCRF é estudada como possível adição na composição da matriz aglomerante. Baixos teores (1 e 2% em massa) de cimento são substituídos por sepiolita para o estudo das pastas de cimento hidratado e, posteriormente, dos compósitos. O Módulo Elástico Dinâmico das pastas é incrementado com o tempo pela adição de sepiolita. Os ensaios a flexão demostram que a adição de sepiolita melhora a homogeneidade dos compósitos. Reportam-se os efeitos das fibras de sisal após da exposição a sistemas MgO-SiO2 e PC e submetidas a diferentes condições de envelhecimento. Este estudo comparativo da degradação das fibras expostas a diferentes matrizes cimentícias mostra a compatibilidade das fibras lignocelulósicas com os cimentos à base de Mg. As fibras de sisal, inclusive após o envelhecimento acelerado, não apresentam nem redução significativa no conteúdo de celulose nem na cristalinidade da celulose assim como do tamanho de cristalito, quando expostas a cimentos MgO-SiO2.

Made available in DSpace on 2017-07-10T19:24:07Z (GMT). No. of bitstreams: 1 Adriana_ Neres de Lima Model.pdf: 1114285 bytes, checksum: 5ac5451e63a53706eccc865aabd911c5 (MD5) Previous issue date: 2016-02-16 / Nitrification associated to autotrophic denitrification, up from an elemental sulfur as an electron donor, can be an adequate option during the post-treatment of anaerobic effluent, which contains ammoniacal nitrogen that should be nitrified, and whose low carbon concentrations (C/N<5) make heterotrophic denitrification difficult. Due to the alkalinity consumption in both processes, lime materials can be applied as alkalizing to ensure the nitrogen removal efficiencies. Therefore, based on this finding, this research has proposed nitrification application followed by autotrophic denitrification in a single reactor containing elemental sulfur and dolomitic limestone to remove nitrogen from an anaerobic effluent from a cold storage from poultry industry. Thus, this study was divided into three steps due to some gaps in literature on the application of autotrophic denitrification up from elemental sulfur in real effluents. In the first step, the performance of autotrophic denitrification was evaluated in four anoxic fixed-bed reactors of elemental sulfur and dolomitic lime at 4:0, 3:1, 1:1 and 1:3 ratios. The reactors were submitted to constant nitrogen feed load (0.114 kg N m³ -1 d-1) under five initial alkalinity conditions (1,000, 800, 600, 400 and 200 mg CaCO3 L-1). The reactors showed similar behavior under those five evaluated experimental conditions. The greatest denitrification efficiencies (from 84.8 to 94.9%) were observed in the first three conditions, whose denitrification rate was 0.102 ± 0.002 kg NOx m³ -1 d-1 and apparent consumption of alkalinity superior to 244.8 mg CaCO3 L-1. Denitrification efficiencies tended to decrease due to the decrease in the initial concentration of alkalinity up from the third experimental condition (600 mg CaCO3 L-1) due to an excessive consumption and inadequate increase of alkalinity (< 180 mg CaCO3 L-1) from dolomitic limestone. During the second step, the anoxic reactor with bed composition (1: 3 ratio), whose initial alkalinity condition was 600 mg CaCO3 L-1, operated at 14, 10 and 6 h HRT. The reactor showed denitrification efficiencies of 94.4 ± 2.0; 94.9 ± 2; 71.1 ± 7.8% as well as denitrification rates of 0.115 ± 0.007; 0.164 ± 0.007 and 0.217 ± 0.025 kg NOx m³ -1 d-1 for HDT of 14, 10 and 6 hours, respectively. At the sixth hour-HRT, the applied overload and limited mass transfer may have contributed to performance decrease into the reactor due to the accumulation of gases in the bed. The third step approached about feeding strategies with mixing ammonified as well as nitrified one in different rates 1:3 (E1), 1:1 (E2) and 3:1 (E3) in anoxic-aerobic reactor of fixed bed with elemental sulfur: dolomitic limestone 1: 3, under 1,000 mg CaCO3 L-1 initial condition of alkalinity. The reactor presented some efficiencies of ammoniacal and total nitrogen removal of 67.3 ± 6.4 and 64.2 ± 6.3% for E1 condition, 63.4 ± 6.4 and 53.1 ± 7.1% for E2 and 14.2 ± 4.4 and 33.8 ± 1.7% for E3. The generation of hydrogen sulfide mainly from sulfur imbalance effect in anoxic compartment may have contributed to a partial inhibition of nitrifying bacteria. The difficulty in keeping the nitrification process was characterized as a limiting factor during nitrogen removal. Low total nitrogen removal efficiencies have implied that nitrification followed by autotrophic denitrification from elemental sulfur in a single reactor was inadequate to remove nitrogenous compounds of anaerobic effluent from a cold storage from poultry industry / A nitrificação acoplada à desnitrificação autotrófica, a partir do enxofre elementar como doador de elétrons, pode ser uma opção adequada no pós-tratamento de efluentes anaeróbios, os quais contêm nitrogênio amoniacal que deve ser nitrificado, cujas baixas concentrações de carbono (C/N<5) dificultam a desnitrificação heterotrófica. Devido ao consumo de alcalinidade nos dois processos, materiais calcários podem ser utilizados como alcalinizantes para garantir as eficiências de remoção do nitrogênio. Com base nessa constatação, esta pesquisa propôs a aplicação da nitrificação seguida da desnitrificação autotrófica em único reator contendo enxofre elementar e calcário dolomítico na remoção de nitrogênio de efluente anaeróbio proveniente de frigorífico avícola. Devido às lacunas presentes na literatura sobre a aplicação da desnitrificação autotrófica a partir do enxofre elementar em efluentes reais, esse estudo foi dividido em três etapas. Na primeira etapa, avaliou-se o desempenho da desnitrificação autotrófica em quatro reatores anóxicos de leito fixo de enxofre elementar e calcário dolomítico nas proporções de 4:0, 3:1, 1:1 e 1:3. Os reatores foram submetidos à alimentação de carga nitrogenada constante de 0,114 kg N m³ -1 d-1 em cinco condições de alcalinidade inicial (1000, 800, 600, 400 e 200 mg CaCO3 L-1). Os reatores apresentaram comportamento semelhante nas cinco condições experimentais avaliadas. As maiores eficiências de desnitrificação (entre 84,8 e 94,9%) foram observadas nas três primeiras condições, com taxa de desnitrificação de 0,102±0,002 kg NOx m³ -1 d-1 e consumo aparente de alcalinidade superior a 244,8 mg CaCO3 L-1. As eficiências de desnitrificação tenderam a diminuir em função do decréscimo da alcalinidade inicial a partir da terceira condição experimental (600 mg CaCO3 L-1) devido ao consumo excessivo e ao incremento insuficiente de alcalinidade (<180 mg CaCO3 L-1) a partir do calcário dolomítico. Na segunda etapa, o reator anóxico com composição de leito na relação de 1:3, em condição inicial de alcalinidade de 600 mg CaCO3 L-1, foi operado em TDH de 14, 10 e 6 horas. O reator apresentou eficiências de desnitrificação de 94,4±2,0 e 94,9±2 e 71,1±7,8% e taxas de desnitrificação de 0,115±0,007, 0,164±0,007 e 0,217±0,025 kg NOx m³ -1 d-1 para os TDH de 14, 10 e 6 horas, respectivamente. No TDH de 6 horas, a sobrecarga aplicada e a limitada transferência de massa, devido ao acúmulo de gases no leito, podem ter contribuído para diminuição do desempenho do reator. A terceira etapa abordou estratégias de alimentação com mistura de efluentes amonificado e nitrificado em diferentes proporções de 1:3 (E1), 1:1 (E2) e 3:1 (E3) em reator anóxico-aeróbio de leito fixo de enxofre elementar: calcário dolomítico de 1:3 em condição inicial de alcalinidade de 1000mg CaCO3L-1. O reator apresentou eficiências de remoção de nitrogênio amoniacal e total de 67,3±6,4 e 64,2±6,3% para a condição E1, 63,4±6,4 e 53,1±7,1% para E2 e 14,2±4 e 33,8±1,7% para E3. A geração de sulfeto de hidrogênio a partir, principalmente, do efeito de desproporção do enxofre no compartimento anóxico, pode ter contribuído para a inibição parcial das bactérias nitrificantes. A dificuldade em manter o processo de nitrificação foi caraterizada como fator limitante na remoção de nitrogênio. As baixas eficiências de remoção de nitrogênio total indicaram que a nitrificação seguida da desnitrificação autotrófica, a partir do enxofre elementar em único reator, não foi adequada para remover compostos nitrogenados de efluente anaeróbio de frigorífico avícola