Search results for "Sludge"
showing 10 items of 320 documents
Effect of chemical and biological surfactants on activated sludge of MBR system: Microscopic analysis and foam test
2015
Abstract A bench-scale MBR unit was operated, under stressing condition, with the aim of stimulating the onset of foaming in the activated sludge. Possible synergies between synthetic surfactants in the wastewater and biological surfactants (Extra-Cellular Polymeric Substances, EPSs) were investigated by changing C/N ratio. The growth of filamentous bacteria was also discussed. The MBR unit provided satisfactory overall carbon removal overall efficiencies: in particular, synthetic surfactants were removed with efficiency higher than 90% and 95% for non-ionic and ionic surfactants, respectively. Lab investigation suggested also the importance to reduce synthetic surfactants presence entering…
Biological Nutrient Removal and Fouling Phenomena in a University of Cape Town Membrane Bioreactor Treating High Nitrogen Loads
2013
The behavior of a University of Cape Town (UCT) membrane bioreactor (MBR) system was investigated for use in biological nutrient removal from real wastewater. The pilot plant was in operation for a period of 165 days, during which an extensive data gathering campaign was conducted. The pilot plant was started up by inoculating it with activated sludge from a nearby wastewater treatment plant, and it was fed by real municipal wastewater characterized by high organic nitrogen concentrations attributable to discharges from industrial wastewater and sporadic landfill leachate. Carbon and biological nutrient removal processes, a sludge production process, and a membrane fouling mechanism were an…
Respirometry for the Characterization of Heterotrophic Biomass Activity: Application to a MBR Pilot Plant Operated with Two Different Start-Up Strate…
2016
A membrane bioreactor (MBR) pilot plant was operated in two subsequent experimental periods (namely, Periods I and II) with different start-up and sludge withdrawal strategies to study its peculiar biokinetic behavior by using respirometric techniques. Two extreme operational conditions were chosen to investigate the different biomass activity under dynamic or pseudostationary conditions during and after the start-up phases. Particularly, the MBR pilot plant was operated with the same volumetric loading rate (VLR) and permeate flux but differently managed during the start-up phase. In Period I, the MBR pilot plant was started up without sludge inoculum and operated without sludge withdrawal…
Insights on mechanisms of excess sludge minimization in an oxic-settling-anaerobic process under different operating conditions and plant configurati…
2022
In the present research, insights about the mechanisms of excess sludge minimization occurring in an oxic-settling-anaerobic (OSA) were provided. The investigation involved two systems operating in parallel. In particular, a conventional activated sludge (CAS) system as control and a system implementing the OSA process both having a pre-denitrification scheme were considered. Five periods (P1-P5) were studied, during which several operating conditions and configurations were tested. Specifically, the hydraulic retention time (HRT) in the anaerobic reactor of the OSA system (P1 8 h, P2-P3 12 h, P4 8 h, P5 12 h) and the return sludge from the anaerobic to the anoxic (scheme A) (P1-P2) or aero…
Comparison between ozonation and the OSA process: analysis of excess sludge reduction and biomass activity in two different pilot plants
2012
The excess biomass produced during biological treatment of municipal wastewater represents a major issue worldwide, as its disposal implies environmental, economic and social impacts. Therefore, there has been a growing interest in developing technologies to reduce sludge production. The main proposed strategies can be categorized according to the place inside the wastewater treatment plant (WWTP) where the reduction takes place. In particular, sludge minimization can be achieved in the wastewater line as well as in the sludge line. This paper presents the results of two pilot scale systems, to evaluate their feasibility for sludge reduction and to understand their effect on biomass activit…
The role of EPS in fouling and foaming phenomena for a membrane bioreactor
2013
In contraposition to conventional activated sludge processes, the foaming phenomenon in membrane bioreactor (MBR) is still in its infancy. On the other hand, although several studies have been carried out for better understanding the fouling phenomenon in MBR there are still some gaps in the up-to-date knowledge. The extracellular polymeric substances (EPSs) may have a primary role in fouling and foaming phenomena which in turn can be crucial for MBRs. The aim of this study is to detect a possible relationship that EPSs may have with fouling and foaming in an MBR for wastewater treatment. Foaming phenomenon is monitored by performing specific foam-tests: Foam Power, Scum Index, Foam Rating …
Precipitation assessment in wastewater treatment plants operated for biological nutrient removal: a case study in Murcia, Spain.
2009
The Murcia Este Wastewater Treatment Plant is the largest wastewater treatment plant in Murcia (Spain). The plant operators have continuously found pipe blockage and accumulation of solids on equipment surfaces during the anaerobic digestion and post-digestion processes. This work studies the precipitation problems in the Murcia Este Wastewater Treatment Plant in order to locate the sources of precipitation and its causes from an exhaustive mass balance analysis. The DAF thickener and anaerobic digester mass balances suggest that most of the polyphosphate is released during excess sludge thickening. Despite the high concentrations achieved in the thickened sludge, precipitation does not occ…
Design and performance of BNR activated sludge systems with flat sheet membranes for solid-liquid separation
2007
The use of immersed membranes for solid-liquid separation in biological nutrient removal activated sludge (BNRAS) systems was investigated at lab scale. Two laboratory-scale BNR activated sludge systems were run in parallel, one a MBR system and the other a conventional system with secondary settling tanks. Both systems were in 3 reactor anaerobic, anoxic, aerobic UCT configurations. The systems were set up to have, as far as possible, identical design parameters such as reactor mass fractions, recycles and sludge age. Differences were the influent flow and total reactor volumes, and the higher reactor concentrations in the MBR system. The performances of the two systems were extensively mo…
Sewage sludge acidogenic fermentation for organic resource recovery towards carbon neutrality: an experimental survey testing the headspace influence
2022
Volatile fatty acids (VFAs) produced by acidogenic digestion of sewage sludge are very interesting bio-products which can contribute to carbon neutrality of wastewater treatment plants. Studies on the production of VFAs from sewage sludge from fermenters with membrane are limited. In view of above, VFAs from a fermenter pilot plant equipped with a membrane bioreactor and fed with real sewage sludge has been monitored. The effect of headspace volume (HdV) on VFA production was studied for the first time to elucidate the optimal operation conditions. Specifically, three fermenter HdV values (namely, 20, 40 and 60% of the total volume) have been investigated. Results revealed that the HdV of 2…
An integral approach to sludge handling in a WWTP operated for EBPR aiming phosphorus recovery: simulation of alternatives, LCA and LCC analyses
2020
[EN] As phosphorus is a non-renewable resource mainly used to produce fertilizers and helps to provide food all over the world, the proper management of its reserves is a global concern since it is expected to become scarcer in the near future. In this work we assessed two different sludge line configurations aiming for P extraction and recovery before anaerobic digestion and compared them with the classical configuration. This study has been performed by simulation with the model BNRM2 integrated in the software package DESASS 7.1. Configuration 1 was based on the production of a PO4-enriched stream from sludge via elutriation in the primary thickeners, while Configuration 2 was based on t…