Search results for "waste disposal"
showing 10 items of 246 documents
Interactions between calcium precipitation and the polyphosphate-accumulating bacteria metabolism
2007
A sequencing batch reactor that is operated for biological phosphorus removal has been operated under different influent calcium concentrations to study the precipitation process and the possible effects of phosphorus precipitation in the biological phosphorus removal process. Four experiments were carried out under different influent calcium concentrations ranging from 10 to 90 g Ca m(-3). The experimental results and the equilibrium study, which are based on the saturation index calculation, confirm that the process controlling the calcium behaviour is the calcium phosphate precipitation. This precipitation takes place at two stages: initially, precipitation of the amorphous calcium phosp…
The role of fouling mechanisms in a membrane bioreactor.
2007
The present study has aimed to quantify the role of pore blocking and cake layer in a laboratory scale hollow fibre membrane module in submerged configuration. The membrane reactor (MBR) was fed with raw wastewater, only screened with a 2-mm sieve, collected from the Palermo WWTP. The MBR was characterised by an operating volume of 190 L and equipped with an aeration system located on the bottom of the reactor. The MBR operated for 65 days. The permeate was extracted by imposing a constant flux through the membrane (21 Lh−1m−2). The results confirm the importance of pore blocking control during start-up. In particular, it provides a rapid irreversible fouling that takes place at the beginni…
Nutrient recovery from wastewater treatment by ultrafiltration membrane for water reuse in view of a circular economy perspective
2022
The study aims to recover nitrogen from wastewater by employing ultrafiltration membrane in water reuse for agriculture purpose. To such aim, a new reclaimed water quality index (RWQI) is proposed and applied including an innovative protocol for its assessment. Specifically, the influence of filtration and backwashing times for an ultrafiltration system aimed to nutrient recovery has been analyzed. The final goal was to pin down the trade-off between operation costs and effluent quality. Results show that backwashing time play a crucial role in reducing the operation costs; indeed, low values (i.e., 0.5 min) lead to an increase in the number of required chemical cleanings and consequently o…
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…
Editorial: Sustainable wastewater treatment and resource recovery
2020
Water
A semi-industrial scale AnMBR for municipal wastewater treatment at ambient temperature: performance of the biological process
2022
A semi-industrial scale AnMBR plant was operated for more than 600 days to evaluate the long-term operation of this technology at ambient temperature (ranging from 10 to 27 ºC), variable hydraulic retention times (HRT) (from 25 to 41 h) and influent loads (mostly between 15 and 45 kg COD·d−1). The plant was fed with sulfate-rich high-loaded municipal wastewater from the pre-treatment of a full-scale WWTP. The results showed promising AnMBR performance as the core technology for wastewater treatment, obtaining an average 87.2 ± 6.1 % COD removal during long-term operation, with 40 % of the data over 90%. Five periods were considered to evaluate the effect of HRT, influent characteristics, CO…
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…
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…
Trace metals supplementation in anaerobic membrane bioreactors treating highly saline phenolic wastewater
2017
Biomass requires trace metals (TM) for maintaining its growth and activity. This study aimed to determine the effect of TM supplementation and partitioning on the specific methanogenic activity (SMA), with a focus on cobalt and tungsten, during the start-up of two lab-scale Anaerobic Membrane Bioreactors (AnMBRs) treating saline phenolic wastewater. The TM partitioning revealed a strong accumulation of sodium in the biomass matrix and a wash-out of the majority of TM in the reactors, which led to an SMA decrease and a low COD removal of about 30%. The SMA exhibits a maximum at about 6 g Na+ L−1 and nearly complete inhibition at 34 g Na+ L−1. The dose of 0.5 mg L−1 of tungsten increases the …