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Fikret Kargi - One of the best experts on this subject based on the ideXlab platform.
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Continuous ethanol fermentation of cheese whey powder solution: effects of Hydraulic Residence Time
Bioprocess and Biosystems Engineering, 2007Co-Authors: Serpil Ozmihci, Fikret KargiAbstract:Continuous ethanol fermentation of cheese whey powder solution was realized using pure culture of Kluyveromyces marxianus (DSMZ 7239) at Hydraulic Residence Times (HRT) between 12.5 and 60 h. Sugar utilization, ethanol and biomass formation were investigated as functions of HRT. Effluent sugar concentration decreased, but percent sugar utilization, ethanol and biomass concentrations increased with HRT. Ethanol productivity was maximum (0.745 gE l^−1h^−1) at an HRT of 43.2 h where the biomass productivity was almost minimum (0.18 gX l^−1 h^−1). The ethanol yield coefficient was almost constant at 0.4 gE g^−1S up to HRT of 43.2 h and the growth yield coefficient was minimum at HRT of 43.2 h. Kinetic models were developed and the constants were determined by using the experimental data.
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Copper(II) ion toxicity in activated sludge processes as function of operating parameters
Enzyme and Microbial Technology, 2007Co-Authors: M. Yunus Pamukoglu, Fikret KargiAbstract:Abstract Effects of Hydraulic Residence Time (HRT) and the sludge age (solids retention Time, SRT) on the performance of an activated sludge unit treating synthetic wastewater containing 14 mg l −1 Cu(II) ion were investigated. Percent COD removal increased with increasing sludge age for both Cu-free and Cu(II)-containing wastewater. However, percent COD removal was lower in the presence of Cu(II) due to Cu(II) ion toxicity on the microorganisms at all sludge ages. Cu(II) ion toxicity was eliminated at high sludge ages (30 days) due to high biomass concentrations. Percent toxicity removals and biomass concentrations increased, but the sludge volume index (SVI) decreased with increasing sludge age. Increases in Hydraulic Residence Time also resulted in increases in percent COD and toxicity removals and also in biomass concentrations, but decreases in the sludge volume index (SVI) for both in the absence and presence of Cu(II) ions. Percent COD removals were much higher in the absence of Cu(II) ions for all HRT levels tested. Copper ion toxicity on COD removal performance of the activated sludge unit was partially eliminated by operation at high sludge ages (30 days) and HRTs (25 h).
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Performance of a hybrid-loop bioreactor system in biological treatment of 2,4,6-tri-chlorophenol containing synthetic wastewater: Effects of Hydraulic Residence Time
Journal of Hazardous Materials, 2006Co-Authors: Serkan Eker, Fikret KargiAbstract:Abstract A hybrid-loop bioreactor system consisting of a packed column biofilm and an aerated tank bioreactor with effluent recycle was used for biological treatment of 2,4,6-tri-chlorophenol (TCP) containing synthetic wastewater. Effects of Hydraulic Residence Time (HRT) on COD, TCP and toxicity removal performance of the reactor were investigated for the HRT values between 5 and 30 h, while the feed COD (2700 ± 100 mg l−1), TCP (300 ± 10 mg l−1) and the solids retention Time (sludge age, SRT, 20 d) were constant. Percent TCP, COD and toxicity removals increased with increasing HRT resulting in more than 90% COD, TCP and toxicity removals at HRT values above 25 h. Biomass concentrations in the packed column and in the aeration tank increased with increasing HRT resulting in low reactor TCP concentrations and therefore high TCP, COD and toxicity removals at high HRT values. Volumetric and specific rates of TCP and COD removals decreased with increasing HRT due to increased biomass and decreased flow rates at high HRT levels. Volumetric and specific removal rates of COD and TCP were maximum at an HRT of 5 h.
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Para-chlorophenol containing synthetic wastewater treatment in an activated sludge unit: Effects of Hydraulic Residence Time
Journal of environmental management, 2006Co-Authors: Fikret Kargi, Isil KonyaAbstract:Due to the toxic nature of chlorophenol compounds present in some chemical industry effluents, biological treatment of such wastewaters is usually realized with low treatment efficiencies. Para-chlorophenol (4-chlorophenol, 4-CP) containing synthetic wastewater was treated in an activated sludge unit at different Hydraulic Residence Times (HRT) varying between 5 and 30 h while the feed COD (2500 mg l(-1)), 4-CP (500 mg l(-1)) and sludge age (SRT, 10 days) were constant. Effects of HRT variations on COD, 4-CP, toxicity removals and on settling characteristics of the sludge were investigated. Percent COD removals increased and the effluent COD concentrations decreased when HRT increased from 5 to 15 h and remained almost constant for larger HRT levels. Nearly, 91% COD and 99% 4-CP removals were obtained at HRT levels above 15 h. Because of the highly concentrated microbial population at HRT levels of above 15 h, low effluent (reactor) 4-CP concentrations and almost complete toxicity removals were obtained. High biomass concentrations obtained at HRT levels above 15 h were due to low 4-CP contents in the aeration tank yielding negligible inhibition effects and low maintenance requirements. The sludge volume index (SVI) decreased with increasing HRT up to 15 h due to high biomass concentrations at high HRT levels resulting in well settling sludge with low SVI values. Hydraulic Residence Times above 15 h resulted in more than 90% COD and complete 4-CP and toxicity removals along with well settling sludge.
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Hydraulic Residence Time effects on performance of an activated sludge unit treating wastewater containing dichlorophenol.
Water environment research : a research publication of the Water Environment Federation, 2006Co-Authors: Serkan Eker, Fikret KargiAbstract:Wastewaters containing chlorophenol compounds are difficult to treat by biological means because of the toxic effects of those compounds on microorganisms. To investigate the adverse effects of chlorophenols on microorganisms, synthetic wastewater containing 2,4 dichlorophenol (DCP) was biologically treated in an activated sludge unit at different Hydraulic Residence Times (HRTs) between 5 and 40 hours, whereas the feed chemical oxygen demand (COD), DCP concentrations, and sludge age were kept constant at 2500 +/- 50 mg/L, 150 mg/L, and 20 days, respectively. The resazurin method based on dehydrogenase activity was used for assessment of the feed and effluent wastewater toxicity. Percent COD, DCP, and toxicity removals increased, and the effluent COD, DCP, and toxicity levels decreased with increasing HRT. Biomass concentration in the aeration tank increased with increasing HRT because of low levels of DCP at high HRT levels, resulting in high COD, DCP, and toxicity removals. The sludge volume index decreased with increasing HRT, yielding well-settling organisms as a result of low levels of toxicity and high concentrations of active cells. Percent DCP and COD removals decreased with increasing specific DCP loading rate. The rates of DCP and COD removals showed a maximum at a low DCP concentration of 6 mg/L in the aeration tank, corresponding to a 25-hour HRT.
David Andrew Barry - One of the best experts on this subject based on the ideXlab platform.
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Design methodology accounting for the effects of porous medium heterogeneity on Hydraulic Residence Time and biodegradation in horizontal subsurface flow constructed wetlands
Ecological Engineering, 2011Co-Authors: Alessandro Brovelli, O. Carranza-diaz, Luca Rossi, David Andrew BarryAbstract:Horizontal flow constructed wetlands are engineered systems capable of eliminating a wide range of pollutants from the aquatic environment. Nevertheless, poor hydrodynamic behavior is commonly found resulting in preferential pathways and variations in both (i) the Hydraulic Residence Time distribution (HRTD) and, consequently, (ii) the wetland's treatment efficiency. The aim of this work was to outline a methodology for wetland design that accounts for the effect of heterogeneous Hydraulic properties of the porous substrate on the HRTD and treatment efficiency. Biodegradation of benzene was used to illustrate the influence of Hydraulic conductivity heterogeneity on wetland efficiency. Random, spatially correlated Hydraulic conductivity fields following a log-normal distribution were generated and then introduced in a subsurface flow numerical model. The results showed that the variance of the distribution and the correlation length in the longitudinal direction are key indicators of the extent of heterogeneity. A reduction of the mean Hydraulic Residence Time was observed as the extent of heterogeneity increased, while the HRTD became broader with increased skewness. At the same Time, substrate heterogeneity induced preferential flow paths within the wetland bed resulting in variations of the benzene treatment efficiency. Further to this it was observed that the distribution of biomass within the porous bed became heterogeneous, rising questions on the representativeness of sampling. It was concluded that traditional methods for wetland design based on assumptions such as a homogeneous porous medium and plug flow are not reliable. The alternative design methodology presented here is based on the incorporation of heterogeneity directly during the design phase. The same methodology can also be used to optimize existing systems, where the HRTD has been characterized with tracer experiments.
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Influence of substrate heterogeneity on the Hydraulic Residence Time and removal efficiency of horizontal subsurface flow constructed wetlands
2009Co-Authors: O. Carranza-diaz, Alessandro Brovelli, Luca Rossi, David Andrew BarryAbstract:Horizontal, subsurface flow constructed wetlands are wastewater treatment devices. The influent polluted water flows through a porous substrate where the contaminants are removed, for example by microbial oxidation, surface adsorption and mineral precipitation. These systems are widely used with varying degrees of success to treat municipal and agricultural contaminated waters and remove the organic carbon and nutrient load. Constructed wetlands are an appealing and promising technology, because they (i) are potentially very efficient in removing the pollutants, (ii) require only a small external energy input and (iii) require low maintenance. However, practical experience has shown that the observed purification rate is highly variable and is often much smaller than expected. One of the numerous reasons proposed to explain the variable efficiency of constructed wetlands is the existence of highly conductive zones within the porous substrate, which produce a dramatic reduction of the Hydraulic Residence Time and therefore directly decreases the overall water purification rate. This work aims to understand quantitatively the relationship between the spatial variability in the Hydraulic properties of the substrate and the effective Residence Time in constructed wetlands. We conducted two suites of stochastic numerical simulations, modelling the transport of a conservative tracer in a three-dimensional simulated constructed wetland in one case, and the microbial oxidation of a carbon source in the other. Within each group of simulations, different Hydraulic conductivity fields were tested. These were based on a log-normal, spatially correlated random field (with exponential spatial correlation). The amount of heterogeneity was varied by changing the variance correlation length in the three directions. For each set of parameters, different realizations are considered to deduce both the expected Residence Time for a certain amount of heterogeneity, and its range of variation. We found a clear relationship between the extent of heterogeneity and both the Residence Time decrease and its variability. These results provide a design aid for the optimal design of new constructed wetlands or for retrofitting old systems.
Adam P. Jarvis - One of the best experts on this subject based on the ideXlab platform.
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Metal removal mechanisms in a short Hydraulic Residence Time subsurface flow compost wetland for mine drainage treatment
Ecological Engineering, 2016Co-Authors: Cj Gandy, Je Davis, Patrick Orme, Hugh Potter, Adam P. JarvisAbstract:Abstract The performance of an innovative pilot-scale subsurface flow compost wetland for the attenuation of zinc in mine drainage was investigated. The particular novelty of the system, which operated under ambient environmental conditions, was the short Hydraulic Residence Time (HRT) of 7.5–14.5 h. Short HRT is crucial because it reduces absolute wetland size and construction cost, which can be major impediments to use of wetlands. Over a 2 year period mean treatment efficiency was 67.5% (total Zn) and 84.4% (0.45 μm filtered Zn). Mean volume-adjusted removal rates for total and filtered Zn were 0.92 g/m3/day and 1.05 g/m3/day respectively. Both water and compost analyses showed bacterial sulfate reduction to be the most important Zn removal process within the subsurface flow wetland: water analyses showed consistent decreases in sulfate concentration through the system, whilst Acid Volatile Sulfide − Simultaneously Extracted Metals (AVS-SEM) analysis of the compost revealed concentrations of Zn up to 12,227 mg/kg and AVS up to 9066 mg/kg. Geochemical modelling using PHREEQC also showed that biogeochemical conditions within the wetland favored Zn attenuation as its sulfide: ZnS was the only solid Zn phase that was super-saturated in the wetland effluent water (mean Saturation Index of +9.52). Preliminary investigation of the use of liquid waste carbon sources to further enhance performance were ambiguous, but the results of the research nevertheless show the potential of short Hydraulic Residence Time subsurface flow compost wetlands as a low cost treatment option for metal-polluted abandoned mine drainage.
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Hydraulic Performance and Iron Removal in Wetlands and Lagoons Treating Ferruginous Coal Mine Waters
Wetlands, 2014Co-Authors: Faradiella Mohd Kusin, Adam P. Jarvis, Cj GandyAbstract:A study of Hydraulic Residence Time has been conducted for several UK Coal Authority mine water treatment systems to evaluate the impact of Residence Time on the overall Hydraulic performance and iron removal within the systems. A series of tracer tests were conducted within the Coal Authority mine water treatment wetlands and lagoons to measure actual Hydraulic Residence Time. The tracer Residence Time distributions (RTDs) were analysed based on a tanks-in-series (TIS) model to yield the mean Residence Time and corresponding Hydraulic characteristics of the systems. The relationship between iron retention and Residence Time was tested against a first-order removal model. The mean Hydraulic efficiency is 69 % for the wetlands compared to 24 % for the lagoons, mainly attributable to comparatively greater volumetric efficiency within the wetland systems. The mean number of TIS, n, is 3.9 for the wetlands and 2.1 for the lagoons, illustrating considerably different flow patterns between wetlands and lagoons. There is also a notable difference of treatment efficiency for iron; mean of 81 % and 47 % for wetlands and lagoons, respectively. Generally, it appears that system Hydraulic efficiency (derived from the principle of TIS model) corresponds with iron retention in the treatment systems.
Cj Gandy - One of the best experts on this subject based on the ideXlab platform.
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Metal removal mechanisms in a short Hydraulic Residence Time subsurface flow compost wetland for mine drainage treatment
Ecological Engineering, 2016Co-Authors: Cj Gandy, Je Davis, Patrick Orme, Hugh Potter, Adam P. JarvisAbstract:Abstract The performance of an innovative pilot-scale subsurface flow compost wetland for the attenuation of zinc in mine drainage was investigated. The particular novelty of the system, which operated under ambient environmental conditions, was the short Hydraulic Residence Time (HRT) of 7.5–14.5 h. Short HRT is crucial because it reduces absolute wetland size and construction cost, which can be major impediments to use of wetlands. Over a 2 year period mean treatment efficiency was 67.5% (total Zn) and 84.4% (0.45 μm filtered Zn). Mean volume-adjusted removal rates for total and filtered Zn were 0.92 g/m3/day and 1.05 g/m3/day respectively. Both water and compost analyses showed bacterial sulfate reduction to be the most important Zn removal process within the subsurface flow wetland: water analyses showed consistent decreases in sulfate concentration through the system, whilst Acid Volatile Sulfide − Simultaneously Extracted Metals (AVS-SEM) analysis of the compost revealed concentrations of Zn up to 12,227 mg/kg and AVS up to 9066 mg/kg. Geochemical modelling using PHREEQC also showed that biogeochemical conditions within the wetland favored Zn attenuation as its sulfide: ZnS was the only solid Zn phase that was super-saturated in the wetland effluent water (mean Saturation Index of +9.52). Preliminary investigation of the use of liquid waste carbon sources to further enhance performance were ambiguous, but the results of the research nevertheless show the potential of short Hydraulic Residence Time subsurface flow compost wetlands as a low cost treatment option for metal-polluted abandoned mine drainage.
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Hydraulic Performance and Iron Removal in Wetlands and Lagoons Treating Ferruginous Coal Mine Waters
Wetlands, 2014Co-Authors: Faradiella Mohd Kusin, Adam P. Jarvis, Cj GandyAbstract:A study of Hydraulic Residence Time has been conducted for several UK Coal Authority mine water treatment systems to evaluate the impact of Residence Time on the overall Hydraulic performance and iron removal within the systems. A series of tracer tests were conducted within the Coal Authority mine water treatment wetlands and lagoons to measure actual Hydraulic Residence Time. The tracer Residence Time distributions (RTDs) were analysed based on a tanks-in-series (TIS) model to yield the mean Residence Time and corresponding Hydraulic characteristics of the systems. The relationship between iron retention and Residence Time was tested against a first-order removal model. The mean Hydraulic efficiency is 69 % for the wetlands compared to 24 % for the lagoons, mainly attributable to comparatively greater volumetric efficiency within the wetland systems. The mean number of TIS, n, is 3.9 for the wetlands and 2.1 for the lagoons, illustrating considerably different flow patterns between wetlands and lagoons. There is also a notable difference of treatment efficiency for iron; mean of 81 % and 47 % for wetlands and lagoons, respectively. Generally, it appears that system Hydraulic efficiency (derived from the principle of TIS model) corresponds with iron retention in the treatment systems.
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Hydraulic Residence Time and iron removal in a wetland receiving ferruginous mine water over a 4 year period from commissioning
Water Science and Technology, 2010Co-Authors: Faradiella Mohd Kusin, A P Jarvis, Cj GandyAbstract:Analysis of Residence Time distribution (RTD) has been conducted for the UK Coal Authority's mine water treatment wetland at Lambley, Northumberland, to determine the Hydraulic performance of the wetland over a period of approximately 4 years since site commissioning. The wetland RTD was evaluated in accordance with moment analysis and modelled based on a tanks-in-series (TIS) model to yield the Hydraulic characteristics of system performance. Greater Hydraulic performance was seen during the second site monitoring after 21 months of site operation i.e. longer Hydraulic Residence Time to reflect overall system Hydraulic efficiency, compared to wetland performance during its early operation. Further monitoring of Residence Time during the third year of wetland operation indicated a slight reduction in Hydraulic Residence Time, thus a lower system Hydraulic efficiency. In contrast, performance during the fourth year of wetland operation exhibited an improved overall system Hydraulic efficiency, suggesting the influence of reed growth over the lifeTime of such systems on Hydraulic performance. Interestingly, the same pattern was found for iron (which is the primary pollutant of concern in ferruginous mine waters) removal efficiency of the wetland system from the second to fourth year of wetland operation. This may therefore, reflect the maturity of reeds for maintaining efficient flow distribution across the wetland to retain a longer Residence Time and significant fractions of water involved to enhance the extent of treatment received for iron attenuation. Further monitoring will be conducted to establish whether such performance is maintained, or whether efficiency decreases over Time due to accumulation of dead plant material within the wetland cells.
Michael B. Timmons - One of the best experts on this subject based on the ideXlab platform.
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effect of temperature Hydraulic Residence Time and elevated pco2 on acid neutralization within a pulsed limestone bed reactor
Water Research, 2007Co-Authors: Barnaby J. Watten, Po Ching Lee, Philip L. Sibrell, Michael B. TimmonsAbstract:Limestone has potential for reducing reagent costs and sludge volume associated with treatment of acid mine drainage, but its use is restricted by slow dissolution rates and the deposition of Fe, Al and Mn-based hydrolysis products on reactive surfaces. We evaluated a pulsed limestone bed (PLB) reactor (15 L/min capacity) that uses a CO2 pretreatment step to accelerate dissolution and Hydraulic shearing forces provided by intermittent fluidization to abrade and carry away surface scales. We established the effects of Hydraulic Residence Time (HRT, 5.1-15.9 min), temperature (T, 12-22 degrees C) and CO2 tension (PCO2, 34.5-206.8 kPa) on effluent quality when inlet acidity (Acy) was fixed at 440 mg/L (pH = 2.48) with H2SO4. The PLB reactor neutralized all H+ acidity (N = 80) while concurrently providing unusually high levels of effluent alkalinity (247-1028 mg/L as CaCO3) that allow for side-stream treatment with blending. Alkalinity (Alk) yields rose with increases in PCO2, HRT and settled bed height (BH, cm) and decreased with T following the relationship (R2 = 0.926; p<0.001): (Alk)non-filtered = -548.726+33.571.(PCO2)(0.5)+33.671.(HRT)+7.734.(BH)-5.197.(T). Numerical modeling showed CO2 feed requirements for a target Alk yield decrease with increases in HRT, T and the efficiency of off-gas (CO2) recycling.
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Effect of temperature, Hydraulic Residence Time and elevated PCO2 on acid neutralization within a pulsed limestone bed reactor
Water research, 2007Co-Authors: Barnaby J. Watten, Po Ching Lee, Philip L. Sibrell, Michael B. TimmonsAbstract:Limestone has potential for reducing reagent costs and sludge volume associated with treatment of acid mine drainage, but its use is restricted by slow dissolution rates and the deposition of Fe, Al and Mn-based hydrolysis products on reactive surfaces. We evaluated a pulsed limestone bed (PLB) reactor (15 L/min capacity) that uses a CO2 pretreatment step to accelerate dissolution and Hydraulic shearing forces provided by intermittent fluidization to abrade and carry away surface scales. We established the effects of Hydraulic Residence Time (HRT, 5.1-15.9 min), temperature (T, 12-22 degrees C) and CO2 tension (PCO2, 34.5-206.8 kPa) on effluent quality when inlet acidity (Acy) was fixed at 440 mg/L (pH = 2.48) with H2SO4. The PLB reactor neutralized all H+ acidity (N = 80) while concurrently providing unusually high levels of effluent alkalinity (247-1028 mg/L as CaCO3) that allow for side-stream treatment with blending. Alkalinity (Alk) yields rose with increases in PCO2, HRT and settled bed height (BH, cm) and decreased with T following the relationship (R2 = 0.926; p
