Enter the email address you signed up with and we'll email you a reset link. Provide an answer or move on to the next question. Monthly Employment Most current monthly and annual average employment estimates by industry for Alaska, the Municipality of Anchorage, Fairbanks North Star Borough, and the six economic regions. Water Research, 34 14 , Ninety-six answers were received that provided useful insights into the use of activated sludge models and highlighted the main limitations of modelling and the expectations of users for improvements Hauduc et al.
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All though, for local tax rates, the total sales tax rate ranges from 0. Alaska is not like other states. Alaska does not have a state sales tax. How ever, the boroughs, and cities may or may not utilize their own sales tax rates.
The property tax in Alaska depends on the county that the property is owned in. Alaska collects what they call property assessed fair market value of 1. Alaska will collect this each year and considerate as their property tax.
Out of the entire country, Alaska is one of the highest states with average property tax rates. Even though, the exact amount of property tax rates levied will go by which county the property is owned in.
As for individual tax rates, Alaska does not participate, and is the only state the does not require collection of state sales tax, or levy individual income tax, weather it was earned or unearned. The Alaskan state depends solely on petroleum revenues.
How ever, some of the Alaskan cities and local jurisdictions do still collect sales tax revenue. Every Alaskan, including adults, weather single or married, and children, are subject to receiving a payment each year from the Alaska Permanent Fund Corporation. Nine parameters were changed in more than half of the modelling studies: Only a few parameter sets contain measured parameters Makinia and Wells, ; Nuhoglu et al.
Most of the measured values are close to the values used in other modelling projects, except for Stamou et al. All median values are the same as in the original parameter set. Synthesis of database results for ASM1, only modified parameters are mentioned. Marquot ; g: Please refer to the appendix for the parameter definitions. A new default value of 0. This confirms the need to differentiate aerobic and anoxic growth yields. However, in the analysed modelling projects a high maximum growth rate was not always compensated by a high decay rate.
In addition, the temperature correction factor values are sometimes re-evaluated in the course of a project. They are deduced from the parameter determination at a different temperature and therefore include measurement uncertainties. The ranges provided by the 25th and 75th percentiles of the database are generally in agreement with other overview studies, which ranges were not included in the database Weijers and Vanrolleghem, ; Bornemann et al.
However, the ranges from the database differ from these studies for the following parameters: Regarding ASM1, six parameters have been pointed out as subject to changes: These results are supported by the literature data although the chosen 25th and 75th percentiles provide a narrower range for some of the parameters than specified in literature.
The database contains 20 parameter sets for ASM2d, of which 2 are "proposed new default parameter sets" and 18 are "optimised parameter sets" from specific modelling projects. The modelling studies were mainly carried out in Europe 16 , with only two applications in Asia; and mainly on full scale WWTPs Table 2 synthesises the main results for ASM2d.
The sludge ages of the specific modelling projects are between 7 and 22 days. Only the original parameter set is presented. A new default parameter set was proposed by Cinar et al. The majority of the parameters are kept at their original values, from which 33 of the 83 parameters have never been changed: Two types of modelling studies could be distinguished: This protocol is based on batch tests that allow the measurement of many stoichiometric and kinetic coefficients for autotrophs, ordinary heterotrophs and phosphorus accumulating organisms.
Among the 18 modelling studies, 8 parameters - all of which are kinetic parameters - were changed in more than half of the cases: Synthesis of database results for ASM2d model, only modified parameters are mentioned. Discussion Parameters changed in modelling projects compared to original values: Among the eight parameters that were changed most, two have a particularly wide range of values: Furthermore, the users of the Penya-Roja et al.
This could indicate a problem in the ASM2d model structure, such as the simplification of not taking into account glycogen storage and glycogen accumulating organisms in ASM2d Penya-Roja et al.
Another explanation could be that the ASM2d model describes polyphosphate uptake and the growth of PAOs as two independent kinetic processes. However, experimental results show that oxidation of organic stored compounds provides energy for both PAO growth and polyphosphate storage Wentzel et al.
Consequently, PAO growth and polyphosphate storage yield are linked and depend on the oxidation of organic stored compounds.
Therefore some models link both yields to energy production in metabolic models, e. Fixing the ratio between growth and phosphate storage would then assist ASM2d calibration.
Based on expert knowledge, Brun et al. In Brun et al. These two parameters are used in organic compound storage and consumption processes, and their high variability could indicate a problem in the model structure leading to difficulties in the calibration process. This shows that either model users are in most cases relying on the original values, or that the model outputs are not sensitive to these parameters.
The half-saturation coefficients are thought to be dependent on specific environmental conditions. Several modelling protocols suggest measuring some kinetic and stoichiometric parameters: WERF Melcer et al.
However, in current practice few, if any, biokinetic parameters are measured. Limitations of modelling project articles The large literature review on modelling projects revealed that important information is often missing from these articles to enable them to be fully used. This lack of information prevents further analysis of the database, such as an investigation of correlations. It also makes it difficult to evaluate the quality of the modelling projects.
Thus, the modelling projects included in the database had to be considered to be of equal quality. The differences within parameter values therefore are supposed to be linked to the WWTP conditions and not to a wrong calibration or poor data quality.
It should also be noted that there seems to be a lack of published experimental data with respect to parameter values. If parameters were measured it is often difficult to evaluate the results due to missing information on the measurement method. Potential use of the database A number of correlations were searched for in the database including: No significant correlations were found which is probably due to the limited number of datasets. The database has been designed to allow future extensions with new data sets.
A larger database could allow further analysis to: These values should help model users in the calibration step, by showing typical practice in model calibration. However, these parameters should be used with great care since they are the result of averaging practical experience without taking into account parameter correlations or specific environmental conditions.
These results contribute to the knowledge transfer on activated sludge modelling that was requested by respondents of the first survey. This database can be expanded with more modelling projects which would enable further analysis to be carried out.
The authors would like to make this database accessible to the AS modelling community and several solutions are currently under study. The questionnaire provides further information that has not been presented in this study, but will be included in the Scientific and Technical Report of the Good Modelling Practice — Guidelines for use of activated sludge models GMP-TG , such as typical ratios and key numbers currently measured at WWTPs.
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