Search results for "Activated Sludge"
showing 10 items of 143 documents
Greenhouse gas emissions and the links to plant performance in a fixed-film activated sludge membrane bioreactor - Pilot plant experimental evidence
2017
The present study explores the interlinkages among the operational variables of a University of Cape Town (UCT) Integrated Fixed Film Activated Sludge (IFAS) membrane bioreactor (MBR) pilot plant. Specifically, dedicated experimental tests were carried out with the final aim to find-out a constitutive relationship among operational costs (OCs), effluent quality index (EQI), effluent fines (EF). Greenhouse gas (GHG) emissions were also included in the study. Results showed that the EQI increases at low flow rate likely due to the dissolved oxygen (DO) limitation in the biological processes. Direct GHGs increase with the increasing of the air flow due to the anoxic N2O contribution. Irreversi…
Fate of endocrine disruptor compounds in an anaerobic membrane bioreactor (AnMBR) coupled to an activated sludge reactor
2018
[EN] The occurrence and fate of three groups of micropollutants - alkylphenols, pentachlorophenol and hormones - were studied in a pilot plant consisting of an anaerobic membrane bioreactor (AnMBR) coupled to an activated sludge reactor (University of Cape Town configuration - UCT). Under anaerobic conditions, the octylphenol and technical-nonylphenol soluble concentrations increased producing negative degradation ratios (i.e., -175 and -118%, respectively). However, high 4-n-nonylphenol and bisphenol-A degradation ratios (92 and 59% for 4-n-nonylphenol and bisphenol-A, respectively) as well as complete pentachlorophenol, estrone, 17 beta-estradiol and 17 alpha-ethinylestradiol removal were…
Study of the factors affecting activated sludge settling in domestic wastewater treatment plants
1992
A study has been made of the influence of the process parameters on the settling characteristics of sludge in domestic wastewater treatment plants. The experiments were conducted at a pilot plant situated at the Wastewater Treatment Plant of Valencia, Spain (1,000,000 inhabitants). The influent to the pilot plant was the same as that of the plant. It was found that F/M ratios in the range of 0.25-0.60 g DBO5/g MLVSS day produce values of SVI representative of good settleability of the sludge. Values of sulphide concentration in the influent above 1.0 mg/l negatively affect the process, causing bulking and floating sludge. High values of fats were found to have no influence on the SVI, but d…
Quantification of kinetic parameters for heterotrophic bacteria via respirometry in a hybrid reactor
2010
Over the last decade new technologies are emerging even more for wastewater treatment. Among the new technologies, a recent possible solution regards Moving Bed Biofilm Reactors (MBBRs) that represent an effective alternative to conventional processes. More specifically such systems consist in the introduction of plastic elements inside the aerobic reactor as carrier material for the growth of attached biomass. Recently, one of the mostly used alternatives is to couple the Moving Bed Biofilm Reactor (MBBR) process with the conventional activated sludge process, and the resulting process is usually called HMBBR (Hybrid MBBR). In the MBBR process the biofilm grows attached on small plastic el…
Foaming in membrane bioreactors: Identification of the causes
2012
Membrane bioreactors (MBRs) represent by now a well established alternative for wastewater treatment. Their increasing development is undoubtedly related to the several advantages that such technology is able to guarantee. Nevertheless, this technology is not exempt from operational problems; among them the foaming still represents an "open challenge" of the MBR field, due to the high complexity of phenomenon. Unfortunately, very little work has been done on the foaming in MBRs and further studies are required. Actually, there is not a distinct difference between conventional activated system and MBR: the main difference is that the MBR plants can retain most Extracellular Polymeric Substan…
The role of EPS concentration in MBR foaming: analysis of a submerged pilot plant.
2010
Foaming in Membrane BioReactor (MBR) is a frequently discussed topic. Some authors reported that the phenomenon is due to filamentous organisms, like at Conventional Activated Sludge (CAS) plants. However, in recent years, other authors reported that the Extra-cellular Polymer Substances (EPSs) concentration is an important factor for controlling foam as well. Nevertheless, even if a number of MBR plants are affected by foaming, presently there are no suitable methods to evaluate the phenomenon. To facilitate the study of this controversial phenomenon in an MBR system, certain foam tests proposed in the past for CASPs were investigated. The results of the tests were able to adequately measu…
Aerobic moving bed biofilm reactor treating thermomechanical pulping whitewater under thermophilic conditions.
2002
The continuously operated laboratory scale Kaldnes moving bed biofilm reactor (MBBR) was used for thermophilic (55 degrees C) aerobic treatment of TMP whitewater. In the MBBR, the biomass is grown on carrier elements that move along with the water in the reactor. Inoculation with mesophilic activated sludge gave 60-65% SCOD removal from the first day onwards. During the 107 days of experiment, the 60-65% SCOD removals were achieved at organic loading rates of 2.5-3.5 kg SCODm(-3) d(-1), the highest loading rates applied during the run and HRT of 13-22h. Carbohydrates, which contributed to 50-60% of the influent SCOD. were removed by 90-95%, while less than 15% of the lignin-like material (3…
Experimental sulphide inhibition calibration method in nitrification processes: A case-study.
2020
[EN] Sulphide is one of the inhibitors in the nitrification process in WWTP in regions with sulphate rich soils. As little information is currently available on sulphide nitrification inhibition, the aim of this study was to develop a method based on a modification of the Successive Additions Method to calibrate the effect of sulphide on the activity of ammonia-oxidising bacteria (AOB) and nitrite-oxidising bacteria (NOB). The developed method was then applied to activated sludge samples from two WWTPs with different influent sulphide concentrations. In both cases, sulphide had a greater inhibitory effect on NOB than AOB activity. The sulphide inhibition was found to be lower in the activat…
An extension of ASM2d including pH calculation
2003
This paper presents an extension of the Activated Sludge Model No. 2d (ASM2d) including a chemical model able to calculate the pH value in biological processes. The developed chemical model incorporates the complete set of chemical species affecting the pH value to ASM2d describing non-equilibrium biochemical processes. It considers the system formed by one aqueous phase, in which biochemical processes take place, and one gaseous phase, and is based on the assumptions of instantaneous chemical equilibrium under liquid phase and kinetically governed mass transport between the liquid and gas phase. The ASM2d enlargement comprises the addition of every component affecting the pH value and an i…
Influence of volatile solids and pH for the production of volatile fatty acids: batch fermentation tests using sewage sludge
2021
The aim of this work was to study the effect of volatile suspended solid (VSS) and pH on volatile fatty acids (VFA) production from waste activated sludge (WAS) fermentation by means of batch tests. The final goal was to gain insights to enhance VFA stream quality, with the novelty of using WAS with high sludge retention time. Results revealed that the optimum conditions to maximize VFAs and minimize nutrients and non-VFA sCOD are a VSS concentration of 5.9 g/L and initial pH adjustment to pH 10. The WAS bacterial community structures were analysed according to Next Generation Sequencing (NGS) of 16S rDNA amplicons. The results revealed changes of bacterial phyla abundance in comparison wit…