1,720,963 research outputs found
Mathematical modeling of wastewater treatment plants foroperational costs minimization
No full textIn this work, state of the art mathematical models (ASM,1 ASM3, and ADM from the International Water Association) are applied to simulate the behavior of the biological units (activated sludge with predenitrification and anaerobic digestion) of the wastewater treatment plant of S. Colombano (FI), the main aim of the modeling exercise being the simulation of various operational strategies for cost minimization. Two commercially available simulation platforms were used: AQUASIM (Eawag, CH) and WEST (DHI, Denmark).
Two years operational data were used for model validation. Required modifications are discussed and an integrated model including both water and sludge lines is presented. Satisfactory
predictions were obtained for effluent concentrations, mixed liquor suspended solids in the activated sludge basin and COD removal efficiency of the anaerobic digester.
Finally, the integrated model was used for scenarios analyses, including the prediction of the impact on operational costs of two a alternative operational strategies (1) the regulation of the aeration rate in the nitrification tank based on a set-point value for the effluent ammonium concentration; (2) a decrease in the sludge age from 40 to 10d. Reduction in the operational costs from 11 to 23% were predicted by the implemented models
A simple method to evaluate the short-term biogas yield in anaerobic codigestion of WAS and organic wastes
No full textThe present study was aimed at setting and applying a procedure to measure the anaerobic
degradability of different organic substrates by short-term tests (2–7 days) carried out at labscale
with a low food to biomass (F/M) ratio. All tests were carried out using an acclimated
sludge taken from a pilot-plant anaerobic digester (200 L). Trials were performed with a
manometric system.
The experimental reliability of the device in measuring the anaerobic degradability was
assessed by several preliminary tests carried out using acetate and glucose as reference
substrates. The average conversion to methane was 99% for acetate and of 83% for glucose. The
results of tests in triplicate showed the high repeatability of the method with an average
coefficient of variation lower than 2%.
Then, the lab-scale procedure was applied to study the short-term anaerobic degradability of
complex organic substrates: thickened waste activated sludge, two kinds of organic fraction of
municipal solid waste (a kitchen waste and a fruit and vegetable waste collected at the wholesale
market of Florence), olive mill wastewater and freshly harvested grass. Results indicated that
organic fraction of municipal solid waste, olive mill wastewater and grass were characterized by
a much higher anaerobic degradability if compared to the thickened activated sludge, well in
agreement with literature data
An integrated approach in a municipal WWTP: anaerobic codigestion of sludge with organic waste and nutrient removal from supernatant
No full textCo-digestion appears to be an interesting solution to increase the biogas production of poorly performing under-loaded digesters of waste activated sludge. In the Florence WWTP anaerobic codigestion could increase nitrogen and phosphorus loading rates and thus lower the nutrient removal efficiency. In order to develop an integrated solution to upgrade the Florence WWTP, the different process units were tested in experimental plants. Anaerobic codigestion with source-collected organic solid waste in a pilot-scale bioreactor showed an increase of GPR from 0.15 to 0.45 Nl biogas/l/d with 23% of organic waste loaded. Autotrophic nitrogen removal was carried out in two lab-scale pilot plants which were fed with a real anaerobic supernatant after phosphate removal via struvite formation. The nitritation MBBR has been working for one year at steady-state conditions with a perfect nitrite/ammonium ratio equal to 1:1. Anammox biomass enrichment was performed in a suspended biomass SBR and the specific nitrogen removal rate increased from 1.7 to 58 gN/kgVSS/d in 375 days
Experimental determination of Anammox decay coefficient
No full textThis paper describes an experimental method used to evaluate the anaerobic ammonium oxidation (Anammox) decay coefficient by means of a batch test. The test was carried out using an experimental procedure based on manometric measurements of the dinitrogen gas that is produced by the Anammox process. The accuracy of the procedure had previously been assessed, and the method was used to determine the specific Anammox activity (SAA mg N2-N g VSS−1 d−1,) and the maximum nitrogen production rate (MNPR, NmL N2 L−1 d−1) under several different conditions. A specific batch test, which lasted for 148 days, was performed to assess the decay coefficient. The activity decrease was monitored and the estimated value of the decay coefficient was found to be 0.0048 d−1 at 35 °C, for which the corresponding half-life time of the Anammox biomass was 145 days. This value is higher than other values reported in the literature, but in accordance with the slow growth rate of the Anammox bacteria
Microcalorimetric and manometric tests to assess Anammox activity.
No full textThe present study compares two experimental methods to evaluate Anammox activity based on the assessment of (1) the N2 production rate by a manometric device, as previously proposed, and (2) the heat production rate by a microcalorimeter. Two samples of Anammox suspended biomass were taken from a pilot-plant, and their specific Anammox activity measured by both techniques. Both methods were successfully applied. As for calorimetric tests, they were performed for the first time on Anammox enriched sludge samples. Comparisons between the specific Anammox activities estimated by manometry and calorimetry and between expected (from the reaction enthalpy) and measured heat productions were performed. Promising results
were obtained
Anammox enrichment in conventional sludge samples via a simple fed-batch procedure with activity measures
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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