Search results for "Sludge"
showing 10 items of 320 documents
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…
Optimizing the H3PO4 leaching conditions of post-precipitated sewage sludge using response surface methodology
2018
The leaching procedure of post-precipitated aluminium phosphate sludge with dilute phosphoric acid was developed. The leaching offers a route to recover both critical phosphorous from sewage sludge and the metal used in precipitation. Using phosphoric acid as leaching solution makes it possible to continue the recovery process without the need to remove chloride or sulfate anions. The optimization of the leaching was based on experimental three-level-four-variable central composite face-centered design. The four variables included were acid concentration, volume of acid, temperature and time of leaching. The leaching was conducted for dewatered and water-containing sludge (total solid conte…
A method for measuring low-weight carboxylic acids from biosolid compost
2006
Concentration of low-weight carboxylic acids (LWCA) is one of the important parameters that should be taken into consideration when compost is applied as soil improver for plant cultivation, because high amounts of LWCA can be toxic to plants. The present work describes a method for analysis of LWCA in compost as a useful tool for monitoring compost quality and safety. The method was tested on compost samples of two different ages: 3 (immature) and 6 (mature) months old. Acids from compost samples were extracted at high pH, filtered, and freeze-dried. The dried sodium salts were derivatized with a sulfuric acid–methanol mixture and concentrations of 11 low-weight fatty acids (C1–C10) were a…
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…
A supervisory control system for optimising nitrogen removal and aeration energy consumption in wastewater treatment plants
2002
A fuzzy logic supervisory control system for optimising nitrogen removal and aeration energy consumption has been developed. This control system allows optimising and controlling the dissolved oxygen (DO) concentration in the aerobic reactors, the blowers discharge pressure and the effluent ammonia and nitrate concentrations. DO is controlled by adjusting control valve opening and blower discharge pressure is controlled by modifying rotational speed of the blowers. Optimum nitrification/denitrification is achieved by modifying the DO set point in the last aerobic reactor and the internal recirculation. This system has been tested by simulation in a Bardenpho process using the Activated Slud…
A modification to the Activated Sludge Model No. 2 based on the competition between phosphorus-accumulating organisms and glycogen-accumulating organ…
2001
A modification to the ASM2 is proposed which permits representation of the competition between phosphorus accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) in a nutrient removal activated sludge system. Some important aspects, which are not considered in ASM2, are discussed. The proposed modification includes denitrification by PAOs, PAO glycogen storage capability and GAO metabolism model. It is shown that the proposed modification is capable of describing pilot plant data using a single set of stoichiometric and kinetic parameters over three different sludge ages (16, 14 and 12 days). The modified ASM2 may be applicable to a wide range of situations where PAOs and G…