Nitrate Utilization Rates Research Articles

Effects of polyethylene terephthalate microplastics on cell growth, intracellular products and oxidative stress of Scenedesmus sp.

Polyethylene terephthalate (PET) has been widely utilized in the synthesis of textile materials and packaging of foods and beverages. In recent years, it has been commonly detected in the form of microplastics (MPs) in wastewater. However, the effects of PET MPs on microalgal intracellular products and their interrelationships have been poorly investigated. In this study, the microalgae Scenedesmus sp. Strain H-1 was exposed to PET MPs to explore their effects on the growth, intracellular products (such as lipids, carbohydrates, and proteins), and antioxidative defense systems of Scenedesmus sp. The results demonstrated that PET MPs significantly reduced Scenedesmus sp. cell growth, with a maximum inhibition rate of 38.25% in the 500 mg L−1 treatment group. PET MPs had negative effects on glucose and nitrate utilization rates and reduced intracellular carbohydrates, intracellular proteins, and photosynthetic pigments. Surprisingly, PET MPs reduced acetyl-CoA carboxylase activity but induced lipid accumulation in microalgae. In addition, PET MPs significantly decreased the essential linoleic acid concentration and increased the palmitic acid content, resulting in reduced biodiesel quality. PET MPs induced the production of reactive oxygen species and malondialdehyde as well as the activities of superoxide dismutase and catalase. The results of the PCA indicated that the response mechanism of Scenedesmus sp. to PET MPs exposure was synergistic. This study provides fundamental data on the impact of MPs on the intracellular products of microalgae.

Denitrification Process Enhancement and Diversity of the Denitrifying Community in the Full Scale Activated Sludge System after Adaptation to Fusel Oil

Implementation of anaerobic digestion of primary sludge in modern wastewater treatment plants (WWTPs) limits the availability of organic carbon for denitrification in conventional nitrification-denitrification (N/DN) systems. In order to ensure efficient denitrification, dosage of the external carbon source is commonly undertaken. However, application of commercial products, such us ethanol or acetate, greatly increases operational costs. As such, inexpensive and efficient alternative carbon sources are strongly desirable. In this study, the use of the fusel oil, a by-product from the distillery industry, was validated in terms of the denitrification process enhancement and impact on the activated sludge bacterial community structure. The experiment was conducted at a full scale biological nutrient removal facility (210,000 PE), in the set of the two technological lines: the experimental line (where fusel oil was introduced at 45 cm3/m3 dose) and the reference line (without an external carbon source addition). During the experimental period of 98 days, conventional nitrate utilization rate (NUR) measurements were carried out on a regular basis in order to assess the biomass adaptation to the fusel oil addition and denitrification process enhancement. While the NURs remained at a stable level in the reference line (1.4 ± 0.1 mg NO3-N/g VSS·h) throughout the entire duration of the experiment, the addition of fusel oil gradually enhanced the denitrification process rate up to 2.7 mg NO3-N/g VSS·h. Moreover, fusel oil contributed to the mitigation of the variability of NO3-N concentrations in the effluent from the anoxic zone. The bacterial community structure, characterized by 16S rRNA PCR—DGGE and the clone libraries of the genes involved in the denitrification process (nirS and nirK), was comparable between the reference and the experimental line during the entire experimental period. In both analyzed lines, the most frequent occurrence of denitrifiers belonging to the genera Acidovorax, Alcaligenes, Azoarcus, Paracoccus and Thauera was noticed. Our results proved that fusel oil would a valuable substrate for denitrification. The addition of fusel oil enhances the process rate and does not reflect a severe selection pressure on the bacterial community at applicable doses. Practical application of fusel oil generates opportunities for the WWTPs to meet effluent standards and reduce operational costs, as well as optimizing waste management for the distillery industry.

Modeling an in-situ hydrogenotrophic denitrification and oxidation process in an experimental scale aquifer

This paper presents a mathematical model for an in-situ hydrogenotrophic denitrification and oxidation process in an experimental scale aquifer. This model was developed to investigate the stable denitrification performance of the aquifer as well as the effects of varying the molar ratio of nitrate load to hydrogen gas injection (N/H ratio) on the effluent quality in terms of nitrate and nitrite concentrations under a long-term operation. The model could fairly predict the effluent quality in terms of nitrate and nitrite concentrations in the aquifer, in response to the sudden decrease in H2 gas injection as well as different N/H ratios. Furthermore, the model clearly demonstrated that denitrification and nitrification proceeded in each zone injected with H2 gas or O2 gas, respectively, and that stable treatment can be achieved. There were some differences between the experimental data and the model results for nitrate, nitrite, dissolved oxygen, and dissolved hydrogen at the H2-injection zone, implying that mass transfer rates in biofilm should be taken into consideration for more precise modeling. A sensitivity analysis showed that effluent quality in terms of nitrate concentration was the most sensitive to changes in maximum nitrate and nitrite utilization rates.

The metabolic activity of denitrifying microorganisms accumulating polyphosphate in response to addition of fusel oil

The effect of distillery waste product (fusel oil) as an alternative external organic carbon source (EOCS) was investigated in terms of the metabolic properties of denitrifying polyphosphate accumulating organisms (DPAOs). Samples of the non-acclimated biomass were collected from a local full-scale wastewater treatment plant employing A2/O type bioreactors. The acclimated biomass was obtained after cultivation (with fusel oil added) in a bench-scale reactor with a process configuration similar to the full-scale bioreactor. Changes in the functional properties of the biomass were investigated by measuring the phosphate release/uptake rates (PRRs and PURs), and nitrate utilization rates (NURs) with fusel oil in anaerobic-anoxic batch tests. Furthermore, a validated extended Activated Sludge Model no 2d (ASM2d) was used as a supporting tool to analyze the experimental results and estimate the contribution of DPAOs to the overall denitrification. In the non-acclimated biomass with fusel oil, the PRRs, PURs and NURs were low and close to the rates obtained in a reference test without adding EOCS. With the acclimated biomass, the PUR and NUR increased significantly, i.e., 3.5 and 2.7 times, respectively. In the non-acclimated biomass, approximately 60.0 ± 3.6% and 20.0 ± 2.2% of the total NUR was attributed to the utilization of endogenous carbon and examined EOCS, respectively. The remaining portion (20% of the total NUR) was attributed to PHA utilization (linked to PO4-P uptake) by DPAOs. With the acclimated biomass, the contribution of the EOCS to the NUR increased to approximately 60%, while the contribution of the endogenous carbon source decreased accordingly. Very accurate predictions of PURs and NURs (R2 = 0.97–1.00) were obtained with the extended ASM2d. Based on model simulations, it was estimated that the activity of DPAOs and denitrifying ordinary heterotrophic organisms corresponded to approximately 20% and 80% of the total NUR, respectively.

Poly-β-hydroxybutyrate (PHB) production by Synechocystis PCC6803 from CO2: Model development

The biosynthesis of poly-β-hydroxybutyrate (PHB) by bioconversion of CO2 is a sustainable alternative to the non-renewable, petroleum-based polymer production. Indeed, the PHB production by conversion of CO2 contributes to the reduction of the greenhouse-gas concentration in the atmosphere. A kinetic dynamic model of PHB production by autotrophic cultures of Synechocystis PCC6803 was proposed and developed by means of the biochemical networks simulator COPASI.Two classes of cells were assumed to be present in the broth: growing cells, PHB producing cells. The model included the two classes of cells and their nitrogen and phosphate internal quota. The dynamics of the cell growth and PHB production were described taking into account: cellular growth rate; lysis rate; nitrate and phosphate utilization rate; PHB production rate. The assessment of the kinetic parameters and of the yields (model calibration) was carried out by the regression of experimental data. Tests were carried out in photobioreactors under dynamic light system (light/dark cycle) using media characterized by initial nitrate concentration ranging between 0 and 1.5g/L. The developed model was validated with respect to independent experimental set.The proposed model successfully reproduced the experimental data (cell concentration, nitrogen and phosphate concentration and PHB content): the square correlation coefficient of the investigated variable concentrations ranged between 0.81 and 0.99. Parameter sensitivity analysis was carried out to assess the role of the selected parameters on cell growth and PHB accumulation. The dynamics of cellular growth were not significantly affected by a ±20% variation of maximum specific growth rate, of velocity of conversion to PHB producing cells, and of maximum uptake rate of nitrate. The PHB accumulation dynamics were particularly sensitive to the variation of the value of the investigated parameters.The proposed model may support the design and the optimization of a PHB production process by means of autotrophic cultures.

Nitrogen Removal From Municipal Wastewater Using a Two‐Sludge Denitrification/Nitrification Batch Reactor: Performance and Mechanisms

Biosorption is a common phenomenon, in that organics in wastewater are trapped by sludge flocs. To achieve high nitrogen removal efficiency from the treatment of low chemical oxygen demand (COD) content wastewater, a two‐sludge denitrification/nitrification batch reactor (TDNBR) is successfully established based on the sorption of organic matter by anoxic activated sludge. During 123 days of operation, the TDNBR achieved high ammonia (>99%) and total nitrogen (TN) (80%) removal efficiency. A higher C/N ratio and exchange frequency have no obvious effect on nitrification but effectively enhanced denitrification. The sorption assays indicated that anoxic sludge could take up a large amount of organic matter (23.79–55.62 mg COD g−1 TSS) but has a low sorption capacity of NH4+‐N. Nitrate utilization rate tests reveal that both the soluble and colloidal organics pre‐sorbed on the sludge can be utilized in denitrification with few organics stored as PHA in bacterial cells. Through cyclic study analysis, it was found that, by interchanging the supernatant in oxic and anoxic tanks alternately, nitrification and denitrification processes are successfully separated and high ammonia and TN removal efficiencies are achieved.

ADAPTATION OF THE ACTIVATED SLUDGE TO THE DIGESTATE LIQUORS DURING THE NITRIFICATION AND DENITRIFICATION PROCESSES

The activated sludge process of the digestate liquors after chemical separation was conducted using a 10 L lab-scale sequencing batch reactor (SBR) and a 0.50 m3 pilotscale SBR independently (with pH control). Due to the relatively high concentration of free ammonia (FA), clear inhibitory effects of the digestate liquors on the nitrifying bacteria were observed. The adaptation of the activated sludge to the toxicity was evaluated with the trends of ammonia uptake rate (AUR) and nitrate utilization rate (NUR). The lab-scale AUR values decreased from 5.3 to 2.6 g N/(kg VSS·h) over time after the addition of digestate liquors (5–10% of the reactor working volume), indicating an apparent FA inhibition on the nitrification process in the FA concentration range of 0.3–0.5 mg N/L. The pilot-scale AUR values increased from 1.8 to 3.6 g N/ (kg VSS·h) in the first two weeks and then decreased to 2.4 g N/(kg VSS·h), showing a lag of the inhibition on the nitrifying bacteria at the FA concentration ≈ 0.15 mg N/L. The lab-scale NURs increased from 2.6 to 10.4 g N/(kg VSS·h) over time, and the pilot-scale NURs increased from 1.0 to 4.0 g N/(kg VSS·h) in a similar pattern. The clear dependence of both the lab- and pilot-scale NURs on time indicated the adaptation of the heterotrophic biomass to the digestate liquors. Ethanol – used instead of fusel oil – was found to be a more efficient external carbon source for better adaptation of the activated sludge under unfavorable conditions.

Nitrification, denitrification, and dephosphatation capability of activated sludge during co-treatment of intermediate-age landfill leachates with municipal wastewater

ABSTRACTThis study focuses on the possible use and efficacy of the co-treatment of landfill leachate (intermediate-age) with municipal wastewater. The nitrification, denitrification, and dephosphatation capability of activated sludge acclimated with a mixture of raw municipal wastewater (RWW) with gradually increasing amounts of raw landfill leachate (RLL) (from 0.5 to 5% v/v) were tested. Biochemical tests were conducted simultaneously in batch reactors (BRs). According to the obtained data, the ammonia utilization rate (AUR) was 3.68 g N/(kg volatile suspended solids (VSS)·h) for RWW, and it increased to 5.78 g N/(kg VSS·h) with the addition of 5% RLL. The nitrate utilization rate under anoxic conditions (NURAX) remained at a comparable level of 1.55–1.98 g N/(kg VSS·h). During the anoxic phase, both nitrate utilization and phosphorus uptake occurred, suggesting that denitrifying phosphorus-accumulating organisms (DPAOs) utilized N–NO3. With the addition of RLL, the rates of anoxic and aerobic phosphate uptake (PURAX and PURAE) and phosphate release rate (PRR) decreased. The PRR was likely negatively influenced by high N–NO3 concentrations but not completely inhibited due to the availability of a biodegradable fraction of chemical oxygen demand (COD). Thus, monitoring the NH4–N load in wastewater treatment plant influent before co-treatment is more informative than that using hydraulic-based criteria.Abbreviations: σ – standard deviation; AUR – ammonia utilization rate; DPAO – denitrifying phosphorus-accumulating organisms; MLVSS – mixed liquor volatile suspended solids content; MSW – municipal solid waste; NURAE – nitrate production rate under aerobic conditions; NURAX – nitrate utilization rate under anoxic conditions; PAO – phosphorus-accumulating organisms; PRR – phosphate release rate under anaerobic conditions; PURAX – phosphate uptake rate under anoxic conditions; PURAE – phosphate uptake rate under aerobic conditions; RLL – raw landfill leachates; RM0.5 – raw mixture of RWW with 0.5% (vol.) of RLL; RM3 – raw mixture of RWW with 3% (vol.) of RLL; RM5 – raw mixture of RWW with 5% (vol.) of RLL; RWW – wastewater; VFA – volatile fatty acids; WWTP – wastewater treatment plant

플라이스토세 전기(2.4-1.25 Ma) 동안 베링해 중부 대륙사면 지역의 규조 골격내 유기물 질소동위원소 값에 의한 질산염 이용률의 변화 복원

Because the high latitude region in the North Pacific is characterized by high primary production in the surface water enriched with nutrients, it is important to understand the variation of surface water productivity and associated nutrient variability in terms of global carbon cycle. Surface water productivity change or its related nutrient utilization rate during the Northern Hemisphere Glaciation (NHG; ca. 2.73 Ma) has been reported, but little is known about such circumstances under gradual climate cooling since the NHG. Bulk nitrogen isotope (<TEX>${\delta}^{15}N_{bulk}$</TEX>) of sedimentary organic matter has been used for the reconstruction of nutrient utilization rate in the surface water. However, sedimentary organic matter experiences diagenesis incessantly during sinking through the water column and after burial within the sediments. Thus, in this study we examine the degree of nitrate utilization rate during the early Pleistocene (2.4-1.25 Ma) since the NHG, using the diatom-bound nitrogen isotope (<TEX>${\delta}^{15}N_{db}$</TEX>), which is known to be little influenced by diagenesis, from Site U1343 in the Bering slope area. <TEX>${\delta}^{15}N_{db}$</TEX> values range from ~0.5 to 5.5‰, which is lower than <TEX>${\delta}^{15}N_{bulk}$</TEX> values, but they vary with larger amplitude. Variation patterns between <TEX>${\delta}^{15}N_{db}$</TEX> values and biogenic opal concentration are generally consistent, which indicates that the nitrate utilization rate is closely related to opal productivity change in the surface water. A positive correlation between opal productivity and nitrate utilization rate was observed, which is different from the other high latitude regions in the North Pacific. The main reason for this contrasting relationship is that the primary production in the surface water at Site U1343 is influenced mostly by the degree of sea ice formation. Still, although concerns about diagenetic alteration have been avoided by using <TEX>${\delta}^{15}N_{db}$</TEX>, the effects of the preservation state of biogenic opal and the species-dependent isotopic fractionation on <TEX>${\delta}^{15}N_{db}$</TEX> should be assessed in the future studies.

Cassava stillage and its anaerobic fermentation liquid as external carbon sources in biological nutrient removal

The aim of this study was to investigate the effects of one kind of food industry effluent, cassava stillage and its anaerobic fermentation liquid, on biological nutrient removal (BNR) from municipal wastewater in anaerobic-anoxic-aerobic sequencing batch reactors (SBRs). Experiments were carried out with cassava stillage supernatant and its anaerobic fermentation liquid, and one pure compound (sodium acetate) served as an external carbon source. Cyclic studies indicated that the cassava by-products not only affected the transformation of nitrogen, phosphorus, poly-β-hydroxyalkanoates (PHAs), and glycogen in the BNR process, but also resulted in higher removal efficiencies for phosphorus and nitrogen compared with sodium acetate. Furthermore, assays for phosphorus accumulating organisms (PAOs) and denitrifying phosphorus accumulating organisms (DPAOs) demonstrated that the proportion of DPAOs to PAOs reached 62.6% (Day 86) and 61.8% (Day 65) when using cassava stillage and its anaerobic fermentation liquid, respectively, as the external carbon source. In addition, the nitrate utilization rates (NURs) of the cassava by-products were in the range of 5.49-5.99 g N/(kg MLVSS⋅h) (MLVSS is mixed liquor volatile suspended solids) and 6.63-6.81 g N/(kg MLVSS⋅h), respectively. The improvement in BNR performance and the reduction in the amount of cassava stillage to be treated in-situ make cassava stillage and its anaerobic fermentation liquid attractive alternatives to sodium acetate as external carbon sources for BNR processes.

Intermittent aeration in one-stage partial nitritation/anammox process

This study investigated the influence of different aeration strategies, characterized by the ratio (R) between non-aerated and aerated phase duration and dissolved oxygen concentration (DO), on one stage partial nitritation/anammox process performance and efficiency treating reject water. The activity of anammox bacteria, ammonium oxidizers, nitrite oxidizers and denitrifiers was determined by measuring specific anammox activity (SAA), oxygen uptake rate (OUR) and nitrate utilization rate (NUR). The results showed that with the same DO level during continuous aeration and intermittent aeration R=1/3 (in one hour), nitrogen removal efficiencies were similar. This means that introduction of intermittent aeration with R=1/3 can shorten the duration of aeration without any loss of process efficiency. Around 17–20% of the total decrease in ammonium and nitrate occurred in the non-aerated phase when intermittent aeration with R=1/3 was applied. Moreover, introduction of non-aerated phases enhanced the activity of anammox bacteria and limited that of nitrite oxidizers.

Poplar GATA transcription factor PdGNC is capable of regulating chloroplast ultrastructure, photosynthesis, and vegetative growth in Arabidopsis under varying nitrogen levels

Photosynthesis and nitrogen availability are crucial to the accumulation of biomass. The GATA transcription factor family plays important roles in chloroplast development and nitrogen metabolism. Here, we cloned, for the first time, the GATA transcription factor PdGNC from the fast-growing poplar clone NE-19. The overexpression results from Arabidopsis under high nitrate, sufficient nitrate, and low nitrate (LN) support that PdGNC increased the chloroplast number and size per cell in leaf and stem, improved the chlorophyll level by 26.12 % and exhibited the highest starch content in LN. Overexpression of PdGNC also had pronounced effects on chloroplast ultrastructure by increasing the number of grana and thylakoids. The photosynthetic rate in transgenic LN lines was 42.17 % higher than in the wild type through modification of the chlorophyll fluorescence parameters Fv/F0, Fv/Fm, qP, NPQ, and ΦPSII. Morphologically, PdGNC promoted longer primary roots and larger leaf areas, and exhibited a higher relative growth rate in LN. Altogether, PdGNC improved photosynthetic capacity and plant growth under low nitrate levels; thus, it could potentially be used in transgenic breeding to improve nitrate utilization and plant growth rates under limited nitrogen conditions.

Distillery fusel oil as an alternative carbon source for denitrification - from laboratory experiments to full-scale applications.

Industrial waste products may be a viable alternative to commercial external carbon sources. In this study, the properties of fusel oil (distillery waste product) were investigated in terms of temperature dependency of denitrification and acclimation period. Furthermore, results obtained during three different full-scale trials were used to verify similarities with and differences from the results obtained under laboratory-scale conditions. Batch experiments with non-acclimated biomass revealed a very strong temperature dependency of the denitrification process (θ = 1.15, R(2) = 0.92) in the range of examined process temperatures (13-22 °C). Fusel oil had minor (or no) effects on the behaviour of NO2-N and PO4-P. Significantly lower nitrate utilization rates were observed during acclimation to fusel oil in the full-scale bioreactors compared to a bench-scale reactor. This may primarily be attributed to lower doses of fusel oil, lower process temperatures and more complicated process configurations (resulting in non-optimal use of fusel oil for denitrification). Results obtained from both laboratory-scale experiments and full-scale trials suggested that an acclimation period of a few weeks would be required to reach the maximum denitrification capability of process biomass, even though positive effects of dosing can be observed almost immediately.

The role of biodegradable particulate and colloidal organic compounds in biological nutrient removal activated sludge systems

The efficiency of denitrification and enhanced biological phosphorus removal in biological nutrient removal activated sludge systems is strongly dependent on the availability of appropriate carbon sources. Due to high costs of commercial compounds (such as methanol, ethanol, acetic acid, etc.) and acclimation periods (usually) required, the effective use of internal substrates is preferred. The aim of this study was to determine the effects of slowly biodegradable compounds (particulate and colloidal), as internal carbon sources, on denitrification, phosphate release/uptake and oxygen utilization for a full-scale process mixed liquor from two large wastewater treatment plants located in northern Poland. Since it is difficult to distinguish the effect of slowly biodegradable substrate in a direct way, a novel procedure was developed and implemented. Four types of one- and two-phase laboratory batch experiments were carried out in two parallel reactors with the settled wastewater without pre-treatment (reactor 1) and pre-treated with coagulation–flocculation (reactor 2). The removal of colloidal and particulate fractions resulted in the reduced process rates (except for phosphate release). The average reductions ranged from 13 % for the oxygen utilization rate during the second phase of a two-phase experiment (anaerobic/aerobic), up to 35 % for the nitrate utilization rate (NUR) during the second phase of a conventional NUR measurement.

Evaluation of industrial organic waste as an alternative external carbon source for denitrification in the biological nutrient removal process

The mixed liquor of organic wastes (MLOW) produced from a 1,4-butanediol production process was tested as an external carbon source for denitrification in the biological nutrient removal (BNR) process. The fraction of non-biodegradable chemical oxygen demand (NBDCOD) in the MLOW was estimated to be approximately 0.2% by measuring the oxygen uptake rate (OUR). The specific denitrification rate (SDNR) of MLOW and methanol from a nitrate utilization rate (NUR) test was confirmed to be approximately 13.02 and 12.68 mgN/gVSS/hr, respectively. The results indicated that the denitrification capability of microorganisms applying the MLOW was similar to that of using methanol as an external carbon source for the BNR process. The feasibility of MLOW for a stainless steel wastewater treatment plant (WWTP) was investigated. The low concentration of effluent nitrogen indicated a denitrification capability for MLOW similar to that for methanol. These results support the potential of MLOW as a substitute for methanol in the BNR process.

Modeling hydrolysis of slowly biodegradable organic compounds in biological nutrient removal activated sludge systems

Hydrolysis is an important process in biological wastewater treatment and is known to be the rate-limiting step in organic carbon removal from municipal or industrial wastewater. The influence of the readily biodegradable chemical oxygen demand fraction in biological wastewater treatment systems has been extensively investigated, but little is known about the effects of slowly biodegradable substrate (XS) on denitrification and enhanced biological phosphorus removal. The biodegradation of XS is initiated by hydrolysis, which is an integral part of activated sludge models, such as the Activated Sludge Model no. 2d (ASM2d). This process is slower than heterotrophic growth and thus becomes the rate-limiting step for the biodegradation of organic compounds. The aim of this study was to evaluate different concepts of modeling the hydrolysis process using the original and modified version of ASM2d. Batch test results obtained at a large biological nutrient removal (BNR) plant in Gdansk (Poland) provided an experimental database for comparison of the two model predictions. Both models were compared in terms of their predictions for the most important process rates in BNR activated sludge systems. In comparison with the orginal ASM2d, the modified model had no or only minor effect on the predicted nitrate utilization rate, phosphate release rate and anoxic/aerobic phosphate uptake rate, but better predicted the oxygen uptake rate. The average ARDs (average relative deviations) were 19.0 and 29.3% (original ASM2d) vs. 13.4 and 20.4% (modified ASM2d), respectively, for the settled wastewater without pretreatment and after coagulation-flocculation.

Aerobic methane oxidation coupled to denitrification in a membrane biofilm reactor: Treatment performance and the effect of oxygen ventilation

Aerobic methane-oxidation coupled to denitrification (AME-D) process was successfully achieved in a membrane biofilm reactor (MBfR). PVDF membrane was employed to supply the methane and oxygen for biofilm, which was coexistence of methanotrophs and denitrifier. With a feeding NO3(-)-N of 30 mg/L, up to 97% nitrate could be removed stably. The oxygen ventilation modes impacted the denitrification performance remarkably, resulting in different nitrate removal efficiencies and biofilm microorganism distribution. The biofilm sludge showed a high resistance to the DO inhibition, mainly due to the co-existing methanotroph being capable of utilizing oxygen perferentially within biofilm, and create an anoxic micro-environment. The denitrification of both nitrate and nitrite by biofilm sludge conformed to the Monod equation, and the maximum specific nitrate utilization rate (k) ranged from 1.55 to 1.78 NO3(-)-N/g VSS-d. The research findings should be significant to understand the considerable potential of MBfR as a bioprocess for denitrification.

Distillery Fusel Oil as an Alternative Carbon Source for Denitrification – from Laboratory Experiments to Full-Scale Applications

Industrial waste products may be a viable alternative to commercial external carbon sources. In this study, the properties of fusel oil (distillery waste product) were investigated in terms of temperature dependency of denitrification and acclimation period. Furthermore, results obtained during three different full-scale trials were used to verify similarities with and differences from the results obtained under laboratory-scale conditions. Batch experiments with non-acclimated biomass revealed a very strong temperature dependency of the denitrification process ( θ = 1.15, R 2 = 0.92) in the range of examined process temperatures (13–22 °C). Fusel oil had minor (or no) effects on the behaviour of NO 2 -N and PO 4 -P. Significantly lower nitrate utilization rates were observed during acclimation to fusel oil in the full-scale bioreactors compared to a bench-scale reactor. This may primarily be attributed to lower doses of fusel oil, lower process temperatures and more complicated process configurations (resulting in non-optimal use of fusel oil for denitrification). Results obtained from both laboratory-scale experiments and full-scale trials suggested that an acclimation period of a few weeks would be required to reach the maximum denitrification capability of process biomass, even though positive effects of dosing can be observed almost immediately.

Distillery wastes as external carbon sources for denitrification in municipal wastewater treatment plants

In this study, by-products from alcohol production were examined in terms of their potential application as external carbon sources for enhancing denitrification in biological nutrient removal systems. Three types of batch tests were used to compare the effects of the distillery by-products, such as fusel oil, syrup and reject water, on the non-acclimated activated sludge. Much higher nitrate utilization rates (NURs) were observed for the latter two carbon sources. In the conventional NUR measurements (one-phase experiments), the observed NURs with syrup and reject water were 3.2-3.3 g N/(kg VSS h) compared with 1.0 g N/(kg VSS h) obtained for fusel oils from two different distilleries. When the carbon sources were added at the beginning of the anoxic phase preceded by an anaerobic phase (two-phase experiments), the NURs were 4.2 g N/(kg VSS h) (syrup and reject water) and 2.4-2.7 g N/(kg VSS h) (fusel oils). The heterotrophic yield coefficient, determined based on the conventional OUR measurements, varied in a relatively narrow range (0.72-0.79 g COD/g COD) for all the examined carbon sources. Due to advantageous composition (much higher COD concentrations and COD/N ratios), fusel is a preferred carbon source for practical handling in full-scale wastewater treatment plants.

Effect of carbon source and COD/NO3−–N ratio on anaerobic simultaneous denitrification and methanogenesis for high-strength wastewater treatment

The effect of carbon source and COD/NO(3)(-)-N ratio on denitrification and methanogenesis in mixed methanogenic matrix was investigated in this study. Industrial wastewater, anaerobic treated cassava stillage (CS) and glucose synthetic wastewater were used as carbon sources respectively for comparison. Experimental results showed that denitrification was the main nitrate reduction pathway for all COD/NO(3)(-)-N ratios tested in two substrates. Simultaneous denitrification and methanogenesis occurred at COD/NO(3)(-)-N higher than 7 regardless of carbon sources. Incomplete denitrification was observed at COD/NO(3)(-)-N ratio below 7 in both the anaerobic effluent of CS and glucose-fed cultures due to the insufficient available organic carbon. The nature of carbon sources was observed to play a key role in the nitrate and organic carbon utilization rates. COD/NO(3)(-)-N ratio had a strong effect on the organic matter utilization pathways. Methanization consumed more organic matter than denitrification with further increase of COD/NO(3)(-)-N ratio above 7 in two substrates. Results of VFA variation suggested that propionate and butyrate were preferably utilized by the denitrifiers than acetate.