Comparison of imidazolium ionic liquids and traditional organic solvents: effect on activated sludge processes

Data concerning the biodegradability and ecotoxicity of ionic liquids (ILs) obtained so far are insufficient in the context of IL removal from wastewater in activated sludge systems. Thus, in this work the selected imidazolium ionic liquids and two organic solvents (methanol and acetone) were tested with respect to their influence on activated sludge processes, particularly on the morphology of sludge flocs. The presence of ionic liquids with the chemical structure of 1-alkyl-3-methyl imidazolium bromide in wastewater did not deteriorate biological wastewater treatment processes if their concentration was not higher than 5 mg l−1. Regarding the structure of the ILs studied, the longer the alkyl substituent was, the stronger the effect on sludge flocs. The highest decrease in activated sludge floc area and biomass concentration was exerted by the ionic liquid with the longest alkyl chain, i.e. 1-decyl-3-methylimidazolium bromide. The action of both methanol and acetone on floc size, activated sludge concentration and efficiency of organic pollutants removal was weaker compared to all tested 1-alkyl-3-methyl imidazolium bromides.

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Influence of newly synthesized imidazolium ionic liquids on activated sludge process

Archives of Environmental Protection ◽

10.1515/aep-2015-0038 ◽

2015 ◽

Vol 41 (4) ◽

pp. 40-48 ◽

Cited By ~ 1

Author(s):

Dorota Gendaszewska ◽

Ewa Liwarska-Bizukojć ◽

Cedric Maton ◽

Christian V. Stevens

Keyword(s):

Ionic Liquids ◽

Activated Sludge ◽

Chain Length ◽

Alkyl Chain ◽

Freundlich Isotherm ◽

Alkyl Chain Length ◽

Activated Sludge Process ◽

Biomass Growth ◽

Imidazolium Ionic Liquids ◽

Sludge Flocs

Abstract This study investigates the influence of four imidazolium ionic liquids (ILs) present in wastewater on the activated sludge process. In addition, experiments with inactivated sludge to assess the capacity of this sorbent to remove ILs from the wastewater were conducted. It occurred that the presence of ionic liquids in wastewater reduces biomass growth and size of the sludge flocs. The strongest effect has been found for IL 6 (1-hexyl-2H-3-methyl-4,5-dimethylimidazolium iodide) with the longest alkyl chain length. Also, the degree of ILs removal increases with the alkyl chain length and decreases with the increase of initial concentration of ILs in wastewater. IL 6 reaches the highest degree of ILs removal from wastewater but inhibits the biomass growth and growth of sludge flocs in a greater extent than other tested compounds. Moreover, it was confirmed that newly synthesized ionic liquids can be adsorbed onto inactivated sludge. IL 6 could be adsorbed in a higher degree than other ionic liquids. This adsorption was described by Langmuir isotherm, whereas adsorption of other ionic liquids was described by Freundlich isotherm.

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Floc size distribution and bacterial activities in membrane separation activated sludge processes for small-scale wastewater treatment/reclamation

Water Science & Technology ◽

10.2166/wst.1997.0241 ◽

1997 ◽

Vol 35 (6) ◽

pp. 37-44 ◽

Cited By ~ 38

Author(s):

Boran Zhang ◽

Kazuo Yamamoto ◽

Shinichiro Ohgaki ◽

Naoyuki Kamiko

Keyword(s):

Wastewater Treatment ◽

Activated Sludge ◽

Municipal Wastewater ◽

Membrane Separation ◽

Small Scale ◽

Nitrification Rate ◽

Floc Size ◽

Denitrification Activity ◽

Concentration Changes ◽

Activated Sludge Processes

Activated sludges taken from full-scale membrane separation processes, building wastewater reuse system (400m3/d), and two nightsoil treatment plants (50m3/d) as well as laboratory scale membrane separation bioreactor (0.062m3/d) were analyzed to characterize membrane separation activated sludge processes (MSAS). They were also compared with conventional activated sludges(CAS) taken from municipal wastewater treatment plants. Specific nitrification activity in MSAS processes averaged at 2.28gNH4-N/kgMLSS.h were higher than that in CAS processes averaged at 0.96gNH4-N/kgMLSS.h. The denitrification activity in both processes were in the range of 0.62-3.2gNO3-N/kgMLSS.h without organic addition and in the range of 4.25-6.4gNO3-N/kgMLSS.h with organic addition. The organic removal activity in nightsoil treatment process averaged at 123gCOD/kgMLSS.h which was significantly higher than others. Floc size distributions were measured by particle sedimentation technique and image analysis technique. Flocs in MSAS processes changed their sizes with MLSS concentration changes and were concentrated at small sizes at low MLSS concentration, mostly less than 60 μm. On the contrary, floc sizes in CAS processes have not much changed with MLSS concentration changes and they were distributed in large range. In addition, the effects of floc size on specific nitrification rate, denitrification rate with and without organic carbon addition were investigated. Specific nitrification rate was decreased as floc size increased. However, little effect of floc size on denitrification activity was observed.

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Study of factors affecting simultaneous nitrification and denitrification (SND)

Water Science & Technology ◽

10.2166/wst.1999.0262 ◽

1999 ◽

Vol 39 (6) ◽

pp. 61-68 ◽

Cited By ~ 118

Author(s):

Klangduen Pochana ◽

Jürg Keller

Keyword(s):

Carbon Source ◽

Activated Sludge ◽

Physical Phenomenon ◽

Treatment Plant ◽

Batch Reactors ◽

Sequencing Batch Reactors ◽

Factors Affecting ◽

Floc Size ◽

Sludge Flocs ◽

Activated Sludge Systems

Experiments have been performed to gain an understanding of the conditions and processes governing the occurrence of SND in activated sludge systems. Sequencing batch reactors (SBRs) have been operated under controlled conditions using the wastewater from the first anaerobic pond in an abattoir wastewater treatment plant. Under specific circumstances, up to 95% of total nitrogen removal through SND has been found in the system. Carbon source and oxygen concentrations were found to be important process parameters. The addition of acetate as an external carbon source resulted in a significant increase of SND activity in the system. Stepwise change of DO concentration has also been observed in this study. Experiments to determine the effect of the floc size on SND have been performed in order to test the hypothesis that SND is a physical phenomenon, governed by the diffusion of oxygen into the activated sludge flocs. Initial results support this hypothesis but further experimental confirmation is still required.

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Stability and organocatalytic efficiency of N-heterocyclic carbenes electrogenerated in organic solvents from imidazolium ionic liquids

Electrochimica Acta ◽

10.1016/j.electacta.2014.11.135 ◽

2015 ◽

Vol 153 ◽

pp. 122-129 ◽

Cited By ~ 21

Author(s):

Marta Feroci ◽

Isabella Chiarotto ◽

Francesca D’Anna ◽

Gianpiero Forte ◽

Renato Noto ◽

...

Keyword(s):

Ionic Liquids ◽

Organic Solvents ◽

Heterocyclic Carbenes ◽

Imidazolium Ionic Liquids

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Activated sludge flocculation: direct determination of the effect of calcium ions

Water Science & Technology ◽

10.2166/wst.2001.0669 ◽

2001 ◽

Vol 43 (11) ◽

pp. 75-82 ◽

Cited By ~ 25

Author(s):

C. A. Biggs ◽

A. M. Ford ◽

P. A. Lant

Keyword(s):

Activated Sludge ◽

Direct Determination ◽

Rate Of Change ◽

Valuable Insight ◽

Floc Size ◽

Sludge Flocs ◽

On Line ◽

Flocculation Process ◽

Insight Into

The effect of calcium on activated sludge flocculation dynamics is investigated using a unique experimental technique. The technique allows on-line analysis of the size of activated sludge flocs during flocculation and provides valuable insight into the mechanisms of flocculation. Activated sludge samples were firstly sonicated for 3 minutes at 50W and then stirred at 100 rpm. The floc size was subsequently measured on-line using a Malvern Mastersizer/E. For concentrations of calcium less than 4 meq/L no significant increase in final floc size was observed even though an increase in the initial rate of change of floc size could be seen. Addition of calcium greater than 4 meq/L resulted in a dramatic increase in floc size. Results from this investigation support the theory that cations are involved in flocculation through cationic bridging, and will be used in ongoing investigations to model the flocculation process.

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Tailing propensity in the ultraviolet disinfection of trickling filter and activated sludge wastewater treatment processes

Water Science & Technology ◽

10.2166/wst.2017.242 ◽

2017 ◽

Vol 76 (3) ◽

pp. 623-632 ◽

Cited By ~ 4

Author(s):

Thiam C. Tan ◽

Yaldah Azimi ◽

Ramin R. Farnood

Keyword(s):

Activated Sludge ◽

Suspended Particle ◽

Uv Disinfection ◽

Distribution Data ◽

Trickling Filter ◽

Floc Size ◽

Sludge Flocs ◽

Filter System ◽

Secondary Effluents ◽

Wastewater Samples

In this paper, the effect of suspended flocs on the tailing of ultraviolet (UV) disinfection kinetics of secondary effluents was examined. To achieve this goal, final effluents produced in two processes for treating wastewater; namely, a trickling filter system and an activated sludge system, were collected and their UV disinfection were compared. Tailing of the UV dose response curve was controlled by the fraction of flocs that are both culturable and UV-resistant, referred to as the ‘tailing propensity’. Using this parameter, the contribution of various floc size fractions in reducing the UV disinfection efficiency of wastewater samples was quantified. Activated sludge flocs larger than 125 μm exhibited as much as 35 times greater tailing propensity than smaller flocs in the range of 20–25 μm. Within a fixed size range, the tailing propensity of flocs generated in the trickling filter system was 3 to 8 times higher than that of activated sludge flocs, and this difference increased with the floc size. A mathematical model was developed to predict the UV disinfection of secondary effluents from suspended particle size distribution data. The model showed good agreement with experimental results.

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Early warning-system for operation-failures in biological stages of WWTPs by on-line image analysis

Water Science & Technology ◽

10.2166/wst.2002.0566 ◽

2002 ◽

Vol 46 (4-5) ◽

pp. 117-124 ◽

Cited By ~ 7

Author(s):

W. Heine ◽

I. Sekoulov ◽

H. Burkhardt ◽

L. Bergen ◽

J. Behrendt

Keyword(s):

Wastewater Treatment ◽

Activated Sludge ◽

Wastewater Treatment Plants ◽

Biological Parameter ◽

Chemical Parameters ◽

Floc Size ◽

Sludge Flocs ◽

Operation Conditions ◽

Physico Chemical ◽

Microscopic Picture

By the observation and evaluation of the microscopic picture of activated sludge samples it is possible to introduce another biological parameter additional to conventional physico-chemical parameters for the control of biological stages of waste water treatment plants. Considering the fact that parameters like floc size and floc size distribution, structure of the flocs (compact/open), shape of the flocs (round/irregular) allow perceptions of the adjusted operation conditions of the biological stages, evidence for changing operation conditions or threatening operation disturbances can be recognised. This recognition takes place at a very early phase, because the morphology of activated sludge flocs reacts very fast to changing conditions. An automatic image analysis of activated sludge floc pictures would enable the introduction of a new sum parameter to enhance operation control of aeration tanks. By a statistical evaluation of the processed sludge images several parameters can be used to describe the alteration of activated sludge flocs characteristics. With these biological parameters it is possible to detect altered operation conditions or threatening or existing operation problems at an early phase. Thus it is possible to plan suitable countermeasures. Furthermore, the microscopic picture is the only parameter, that gives important information about the structure of the activated sludge flocs and the biozenosis. In comparison with the mainly used physico-chemical parameters, that just give information about the inlet and outlet of the wastewater treatment plants, the microscopic picture is the only parameter that gives information about the biology of the wastewater treatment process. By means of this biological parameter an improved control and regulation of the biological stages of wastewater treatment plants can be obtained.

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Modeling and optimizations of mixing and aeration processes in bioreactors with activated sludge

Journal of Physics Conference Series ◽

10.1088/1742-6596/2130/1/012027 ◽

2021 ◽

Vol 2130 (1) ◽

pp. 012027

Author(s):

J Zaburko ◽

G Łagód ◽

M K Widomski ◽

J Szulżyk-Cieplak ◽

B Szeląg ◽

...

Keyword(s):

Activated Sludge ◽

Electric Energy ◽

Active Sludge ◽

Wastewater Treatment Process ◽

Sludge Flocs ◽

Model Studies ◽

Aeration System ◽

Pollutants Removal ◽

Batch Bioreactors ◽

Exact Amount

Abstract Mixing aimed at homogenization of the volume of bioreactors with the activated sludge is of great importance for the proper course of the wastewater treatment process. It affects both the efficiency of pollutants removal and the properties of the activated sludge related to its sedimentation. The mixing process in bioreactors can be carried out in different ways. In batch bioreactors in the aeration phase or flow bioreactors in aerobic chambers, mixing is carried out through aeration systems. These systems should aerate the activated sludge flocs for efficient biological treating of wastewater, as well as effectively homogenize the volume of the bioreactor. Hence, it is important to choose such a design of the aeration system and its operation settings that provide the amount of air ensuring the exact amount of oxygen for the implementation of technological processes, counteract sedimentation of sludge at the bottom of the reactor, are reliable as well as economical in operation (demand of electric energy). The paper presents the model studies aimed at optimization of the design and settings of aeration and mixing systems used in active sludge bioreactors.

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