Design criteria for nitrification and denitrification of high-strength nitrogenous wastes have be... more Design criteria for nitrification and denitrification of high-strength nitrogenous wastes have been derived by pilot-scale experiments in two submerged filters in series. Molasses proved to be a suitable carbon source in denitrif ication. It has been shown that oxygen is the rate limiting substrate in nitrification and that maximum denitrification rates can only be achieved at an influent COD/NOX−N ratio of approximately 5.
The kinetics of nitrogen removal was studied in upflow submerged nitrification and denitrificatio... more The kinetics of nitrogen removal was studied in upflow submerged nitrification and denitrification filters in series. Nitrification followed first-, half-, and zero-order kinetics. For the half-order range the half-order rate constant was about 0.9gNH4-N1/2m−1/2d−1. The zero-order rate constants for the DO ranges of 2-3 mg/L and 4-5 mg/L were found as 0.47 gNH4-Nm−2d−1 and 1.82 gNH4-Nm−2d−1, respectively. In the zero-order region ammonia removal proceeded as a half-order reaction in oxygen concentration and the half-order rate constants were about 1.4-2.7 gO21/2m−1/2d−1. Nitrite accumulation reached a considerable degree at bulk oxygen to bulk ammonia ratios lower than 5 since the formation of nitrate was inhibited. Similar to nitrification half- and zero-order kinetic regions were also observed in denitrification. The half- and zero-order rate constants for carbon unlimited cases (influent COD/NOx-N>5) were about 0.23 gNOx-N1/2m−1/2d−1 and 1.9 gNOx-Nm−2d−1, respectively. The nit...
Journal of Chemical Technology & Biotechnology, 2009
BACKGROUND: The speciation of metals is often overlooked in understanding their observed inhibito... more BACKGROUND: The speciation of metals is often overlooked in understanding their observed inhibitory effect in biological systems, in particular in nitrification systems. This study examines the effects of Cu, Zn, Ni and Co on a nitrifying sludge, where the aim is to relate inhibition to speciation.RESULTS: Nitrification inhibition was monitored by O2 and CO2 measurements, an approach rarely followed to date. The IC50 value of each metal was expressed in terms of total, free and labile metal. Zn and Cu formed similar species, but had different free and labile fractions. Although free and labile fractions of Cu were much lower than the others, it was the most inhibitory metal. Ni and Co exhibited quite different inhibitory effects on nitrification despite the formation of similar metal species. Co was the least inhibitory metal and exhibited its effect very slowly.CONCLUSION: The study is among the few which examine inhibition and speciation of several metals in a comparative way. In ...
Journal of Chemical Technology & Biotechnology, 2001
Leachate from a municipal landfill was combined with domestic wastewater and was treated in batch... more Leachate from a municipal landfill was combined with domestic wastewater and was treated in batch activated sludge systems. The effectiveness and applicability of the addition of Powdered Activated Carbon (PAC) to activated sludge reactors was investigated. Isotherm tests were carried out with PAC in order to estimate the extent of adsorption of organic matter onto PAC. Then, in activated sludge reactors COD (Chemical Oxygen Demand) removal and nitrification were studied both in the absence and presence of PAC for comparison purposes. In both cases, Oxygen Uptake Rates (OUR) were measured with respect to time in order to investigate substrate removal and change in microbial activity. Addition of PAC to activated sludge increased COD removal by removing mainly the non‐biodegradable fraction in leachate. The COD decreases in batch reactors were best expressed by a first‐order kinetic model that incorporated this non‐biodegradable leachate fraction. With added PAC, nitrification was al...
The biological treatability of a pulp bleaching wastewater from a conventional Kraft pulp mill wa... more The biological treatability of a pulp bleaching wastewater from a conventional Kraft pulp mill was investigated in batch activated sludge reactors. Substrate removal was followed in terms of the parameters COD and BOD5 and by the measurement of spectrophotometric changes. These measurements provided information on the specific pollutant groups that were removed during biodegradation. The nonbiodegradable fraction of these wastes was assessed as 30–40% of the initial wastewater COD. Sludge growth was negligibly small under the present substrate to bio‐mass ratios. Negligible changes in chloride levels during aeration were indicative that no deha‐logenation of chlorinated compounds occurred.
Spent bleaching effluents from the chlorination and extraction steps of a sulfate pulp mill were ... more Spent bleaching effluents from the chlorination and extraction steps of a sulfate pulp mill were subjected to activated carbon treatment to investigate the elimination of nonbiodegradable matter. For this purpose the biotreated waste water containing mainly nonbiodegradable matter was treated with different activated carbon types. The elimination degree of nonbiodegradable matter was determined and adsorption isotherms were generated in terms of the parameters COD, DOC, Color436 and UV254. The removal level was over 90% when the carbon dosage exceeded 10 000 mg/l. AOX compounds could be eliminated over 90%. The isotherms could be expressed by the Freundlich equation. It was shown that the shape of the isotherms was strongly dependent on the carbon dosage employed. According to carbon dosage three different adsorption regions were distinguished and for each region the corresponding Freundlich constants K and n were determined. Carbon addition led to a change in the composition of wastewater as shown by decreasing COD/DOC, UV254/DOC and Color436/DOC ratios. Further it was shown that the relatively fast color and UV analyses were accurate enough to characterize the adsorptivity.
Design criteria for nitrification and denitrification of high-strength nitrogenous wastes have be... more Design criteria for nitrification and denitrification of high-strength nitrogenous wastes have been derived by pilot-scale experiments in two submerged filters in series. Molasses proved to be a suitable carbon source in denitrif ication. It has been shown that oxygen is the rate limiting substrate in nitrification and that maximum denitrification rates can only be achieved at an influent COD/NOX−N ratio of approximately 5.
The kinetics of nitrogen removal was studied in upflow submerged nitrification and denitrificatio... more The kinetics of nitrogen removal was studied in upflow submerged nitrification and denitrification filters in series. Nitrification followed first-, half-, and zero-order kinetics. For the half-order range the half-order rate constant was about 0.9gNH4-N1/2m−1/2d−1. The zero-order rate constants for the DO ranges of 2-3 mg/L and 4-5 mg/L were found as 0.47 gNH4-Nm−2d−1 and 1.82 gNH4-Nm−2d−1, respectively. In the zero-order region ammonia removal proceeded as a half-order reaction in oxygen concentration and the half-order rate constants were about 1.4-2.7 gO21/2m−1/2d−1. Nitrite accumulation reached a considerable degree at bulk oxygen to bulk ammonia ratios lower than 5 since the formation of nitrate was inhibited. Similar to nitrification half- and zero-order kinetic regions were also observed in denitrification. The half- and zero-order rate constants for carbon unlimited cases (influent COD/NOx-N>5) were about 0.23 gNOx-N1/2m−1/2d−1 and 1.9 gNOx-Nm−2d−1, respectively. The nit...
Journal of Chemical Technology & Biotechnology, 2009
BACKGROUND: The speciation of metals is often overlooked in understanding their observed inhibito... more BACKGROUND: The speciation of metals is often overlooked in understanding their observed inhibitory effect in biological systems, in particular in nitrification systems. This study examines the effects of Cu, Zn, Ni and Co on a nitrifying sludge, where the aim is to relate inhibition to speciation.RESULTS: Nitrification inhibition was monitored by O2 and CO2 measurements, an approach rarely followed to date. The IC50 value of each metal was expressed in terms of total, free and labile metal. Zn and Cu formed similar species, but had different free and labile fractions. Although free and labile fractions of Cu were much lower than the others, it was the most inhibitory metal. Ni and Co exhibited quite different inhibitory effects on nitrification despite the formation of similar metal species. Co was the least inhibitory metal and exhibited its effect very slowly.CONCLUSION: The study is among the few which examine inhibition and speciation of several metals in a comparative way. In ...
Journal of Chemical Technology & Biotechnology, 2001
Leachate from a municipal landfill was combined with domestic wastewater and was treated in batch... more Leachate from a municipal landfill was combined with domestic wastewater and was treated in batch activated sludge systems. The effectiveness and applicability of the addition of Powdered Activated Carbon (PAC) to activated sludge reactors was investigated. Isotherm tests were carried out with PAC in order to estimate the extent of adsorption of organic matter onto PAC. Then, in activated sludge reactors COD (Chemical Oxygen Demand) removal and nitrification were studied both in the absence and presence of PAC for comparison purposes. In both cases, Oxygen Uptake Rates (OUR) were measured with respect to time in order to investigate substrate removal and change in microbial activity. Addition of PAC to activated sludge increased COD removal by removing mainly the non‐biodegradable fraction in leachate. The COD decreases in batch reactors were best expressed by a first‐order kinetic model that incorporated this non‐biodegradable leachate fraction. With added PAC, nitrification was al...
The biological treatability of a pulp bleaching wastewater from a conventional Kraft pulp mill wa... more The biological treatability of a pulp bleaching wastewater from a conventional Kraft pulp mill was investigated in batch activated sludge reactors. Substrate removal was followed in terms of the parameters COD and BOD5 and by the measurement of spectrophotometric changes. These measurements provided information on the specific pollutant groups that were removed during biodegradation. The nonbiodegradable fraction of these wastes was assessed as 30–40% of the initial wastewater COD. Sludge growth was negligibly small under the present substrate to bio‐mass ratios. Negligible changes in chloride levels during aeration were indicative that no deha‐logenation of chlorinated compounds occurred.
Spent bleaching effluents from the chlorination and extraction steps of a sulfate pulp mill were ... more Spent bleaching effluents from the chlorination and extraction steps of a sulfate pulp mill were subjected to activated carbon treatment to investigate the elimination of nonbiodegradable matter. For this purpose the biotreated waste water containing mainly nonbiodegradable matter was treated with different activated carbon types. The elimination degree of nonbiodegradable matter was determined and adsorption isotherms were generated in terms of the parameters COD, DOC, Color436 and UV254. The removal level was over 90% when the carbon dosage exceeded 10 000 mg/l. AOX compounds could be eliminated over 90%. The isotherms could be expressed by the Freundlich equation. It was shown that the shape of the isotherms was strongly dependent on the carbon dosage employed. According to carbon dosage three different adsorption regions were distinguished and for each region the corresponding Freundlich constants K and n were determined. Carbon addition led to a change in the composition of wastewater as shown by decreasing COD/DOC, UV254/DOC and Color436/DOC ratios. Further it was shown that the relatively fast color and UV analyses were accurate enough to characterize the adsorptivity.
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