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Showing papers on "Hydraulic retention time published in 2011"


Journal ArticleDOI
TL;DR: Results from batch experiments suggested that Ag-NP transformation to Ag(2)S occured in the nonaerated tank within less than 2 h, which must be considered in future risk assessments.
Abstract: We investigated the behavior of metallic silver nanoparticles (Ag-NP) in a pilot wastewater treatment plant (WWTP) fed with municipal wastewater. The treatment plant consisted of a nonaerated and an aerated tank and a secondary clarifier. The average hydraulic retention time including the secondary clarifier was 1 day and the sludge age was 14 days. Ag-NP were spiked into the nonaerated tank and samples were collected from the aerated tank and from the effluent. Ag concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS) were in good agreement with predictions based on mass balance considerations. Transmission electron microscopy (TEM) analyses confirmed that nanoscale Ag particles were sorbed to wastewater biosolids, both in the sludge and in the effluent. Freely dispersed nanoscale Ag particles were only observed in the effluent during the initial pulse spike. X-ray absorption spectroscopy (XAS) measurements indicated that most Ag in the sludge and in the effluent was present a...

705 citations


Journal ArticleDOI
TL;DR: It was found that fouling can be controlled if membranes are placed directly in contact with the granular activated carbon (GAC) in an anaerobic fluidized bed bioreactor (AFMBR) used here for post-treatment of effluent from another an aerobic reactor treating dilute wastewater.
Abstract: Anaerobic membrane bioreactors have potential for energy-efficient treatment of domestic and other wastewaters, membrane fouling being a major hurdle to application. It was found that fouling can be controlled if membranes are placed directly in contact with the granular activated carbon (GAC) in an anaerobic fluidized bed bioreactor (AFMBR) used here for post-treatment of effluent from another anaerobic reactor treating dilute wastewater. A 120-d continuous-feed evaluation was conducted using this two-stage anaerobic treatment system operated at 35 °C and fed a synthetic wastewater with chemical oxygen demand (COD) averaging 513 mg/L. The first-stage was a similar fluidized-bed bioreactor without membranes (AFBR), operated at 2.0−2.8 h hydraulic retention time (HRT), and was followed by the above AFMBR, operating at 2.2 h HRT. Successful membrane cleaning was practiced twice. After the second cleaning and membrane flux set at 10 L/m2/h, transmembrane pressure increased linearly from 0.075 to only 0.1 bar...

441 citations


Journal ArticleDOI
TL;DR: Results show that inoculation and enrichment procedures are critical to the initial success of larger-scale systems and better methods will be needed to isolate hydrogen gas produced at the cathode.
Abstract: A pilot-scale (1,000 L) continuous flow microbial electrolysis cell was constructed and tested for current generation and COD removal with winery wastewater. The reactor contained 144 electrode pairs in 24 modules. Enrichment of an exoelectrogenic biofilm required ~60 days, which is longer than typically needed for laboratory reactors. Current generation was enhanced by ensuring adequate organic volatile fatty acid content (VFA/SCOD ≥ 0.5) and by raising the wastewater temperature (31 ± 1°C). Once enriched, SCOD removal (62 ± 20%) was consistent at a hydraulic retention time of 1 day (applied voltage of 0.9 V). Current generation reached a maximum of 7.4 A/m3 by the planned end of the test (after 100 days). Gas production reached a maximum of 0.19 ± 0.04 L/L/day, although most of the product gas was converted to methane (86 ± 6%). In order to increase hydrogen recovery in future tests, better methods will be needed to isolate hydrogen gas produced at the cathode. These results show that inoculation and enrichment procedures are critical to the initial success of larger-scale systems. Acetate amendments, warmer temperatures, and pH control during startup were found to be critical for proper enrichment of exoelectrogenic biofilms and improved reactor performance.

389 citations


Journal ArticleDOI
TL;DR: In this paper, a dual chambered air-cathode MFC was fabricated for the purpose of bioelectricity in batch and continuous systems, where graphite plates were used as electrodes and glucose as a substrate with initial concentration of 30g l −1 was used.

236 citations


Journal ArticleDOI
TL;DR: The development of a continuously operated MDC--upflow microbial desalination cell (UMDC) for the purpose of salt removal demonstrated the potential of the UMDC as either a sole desalinated process or a pre-desalination reactor for downstream desalinating processes.

234 citations


Journal ArticleDOI
TL;DR: Dewatering investigations suggested that the acid pretreated WAS required 40% less cationic polymer addition to achieve the same cake solid content, and optimisation of acid dosing was performed considering digestibility benefits and level of acid required.

229 citations


Journal ArticleDOI
TL;DR: Investigation of a two-stage anaerobic hydrogen and methane process for increasing bioenergy production from organic wastes revealed that by changing the HRT(hydrogen):HRT(methane) ratio of the two- stage process from 3:12 to 1:14, 6.7%, more energy could be obtained.

204 citations


Journal ArticleDOI
TL;DR: In this article, a salt accumulation model is developed in a novel osmotic membrane bioreactors (OMBRs) using a dense salt-rejecting forward osmosis membrane, which exhibits high retention of organic matter and various other contaminants.

185 citations


Journal ArticleDOI
TL;DR: The results showed that there was no inhibition of SRB growth and that heavy metal removal efficiencies of 94-100% were achieved in R1-R3 throughout the experiment and in R4 during the first 8 weeks, and the toxic effect of heavy metals on the SRB consortium was revealed in R5.

177 citations


Journal ArticleDOI
TL;DR: The optimization of a two-phase thermophilic anaerobic process treating biowaste for hydrogen and methane production was carried out at pilot scale using two stirred reactors (CSTRs) and without any physical/chemical pre-treatment of inoculum.

177 citations


Journal ArticleDOI
TL;DR: Though the power density and current density of the BEMR system were not very high, compared with other high-output MFC systems, electricity recovery could be further enhanced through optimizing the operation conditions and BemR configurations.
Abstract: A novel bioelectrochemical membrane reactor (BEMR), which takes advantage of a membrane bioreactor (MBR) and microbial fuel cells (MFC), is developed for wastewater treatment and energy recovery. In this system, stainless steel mesh with biofilm formed on it serves as both the cathode and the filtration material. Oxygen reduction reactions are effectively catalyzed by the microorganisms attached on the mesh. The effluent turbidity from the BEMR system was low during most of the operation period, and the chemical oxygen demand and NH(4)(+)-N removal efficiencies averaged 92.4% and 95.6%, respectively. With an increase in hydraulic retention time and a decrease in loading rate, the system performance was enhanced. In this BEMR process, a maximum power density of 4.35 W/m(3) and a current density of 18.32 A/m(3) were obtained at a hydraulic retention time of 150 min and external resister of 100 Ω. The Coulombic efficiency was 8.2%. Though the power density and current density of the BEMR system were not very high, compared with other high-output MFC systems, electricity recovery could be further enhanced through optimizing the operation conditions and BEMR configurations. Results clearly indicate that this innovative system holds great promise for efficient treatment of wastewater and energy recovery.

Journal ArticleDOI
TL;DR: The efficiency of dissolved methane collection by degasification from the effluent of a bench-scale upflow anaerobic sludge blanket (UASB) reactor treating synthetic wastewater was investigated and total CH(4) recovery efficiency increased from 71% to 97% at 15 °C as a result of degAsification.

Journal ArticleDOI
TL;DR: The results indicate that a slow increase in the grease waste dose could be a strategy that favours biomass acclimation to fat-rich co-substrate, increases long chain fatty acid degradation and reduces the latter's inhibitory effect.

Journal ArticleDOI
TL;DR: A laboratory-scale moving bed biofilm reactor (MBBR) with a volume of 4 L was used to study the biodegradation of coal gasification wastewater and maximum removal efficiencies of 81%, 89%, 94% and 93% were obtained for COD, phenols, SCN(-) and NH(4)(+)-N, respectively.

Journal ArticleDOI
TL;DR: In this paper, a moving bed biofilm reactor was used to remove nitrogen from wastewater with a low C/N ratio by simultaneous nitrification and denitrification (SND).

Journal ArticleDOI
TL;DR: The response of the SNAD system towards the shock in substrate loading and operating conditions was evaluated by sensitivity index and the extent of total nitrogen (TN) removal by partial nitrification with anammox and denitrification was modeled using stoichiometric relationship.

Journal ArticleDOI
TL;DR: The results from this study suggest the two stage anaerobic process can be effectively used for energy recovery and for stabilization of hydrolysate at an aerobic conditions.

Journal ArticleDOI
TL;DR: In this paper, co-digestion of swine manure (SM) and energy crop residues (ECRs) was studied and the results obtained from batch tests, a mixture with a 50% ECR content was selected for the second stage of the study.
Abstract: Anaerobic co-digestion involves the treatment of different substrates with the aim of improving the production of biogas and the stability of the process. In this research, co-digestion of swine manure (SM) and energy crop residues (ECRs) was studied. The mixtures evaluated contained SM combined with maize (Mz), rapeseed (Rs) or sunflower (Sf) residues. Batch and semi-continuous experiments were performed to determine methane (CH4) yields and the behavior of reactors while co-digesting agricultural wastes. Three different proportions of ECRs were tested in batch experiments for co-digestion with SM: 25, 50, and 75% volatile solids (VS). On the basis of the results obtained from batch tests, a mixture with a 50% ECR content was selected for the second stage of the study. Mesophilic reactors with a 3 L working volume were used for semi-continuous experiments. The hydraulic retention time (HRT) was set at 30 days and the reactors were kept under these operational conditions over four HRTs. The addition of ECR to the co-digestion system resulted in a major increase in the amount of biogas produced daily. The highest biogas yield was obtained when co-digesting Rs (3.5 L/day), although no improvement was observed in specific gas production from the addition of the co-substrate.

Journal ArticleDOI
TL;DR: Molecular analysis implied that nitrate and nitrite were denitrified into nitrogen by the same microorganisms as well as influent concentration, HRT and temperature are important factors affecting the denitrification efficiency.
Abstract: Sulfur-limestone was used in the autotrophic denitrification process to remove the nitrate and nitrite in a lab scale upflow biofilter. Synthetic water with four levels of nitrate and nitrite concentrations of 10, 40, 70 and 100 mg N/L was tested. When treating the low concentration of nitrate- or nitrite-contaminated water (10, 40 mg N/L), a high removal rate of about 90% was achieved at the hydraulic retention time (HRT) of 3 hr and temperature of 20–25°C. At the same HRT, 50% of the nitrate or nitrite could be removed even at the low temperature of 5–10°C. For the higher concentration nitrate and nitrite (70, 100 mg N/L), longer HRT was required. The batch test indicated that influent concentration, HRT and temperature are important factors affecting the denitrification efficiency. Molecular analysis implied that nitrate and nitrite were denitrified into nitrogen by the same microorganisms. The sequential two-step-reactions from nitrate to nitrite and from nitrite to the next-step product might have taken place in the same cell during the autotrophic denitrification process.

Journal ArticleDOI
TL;DR: The results indicate that the suspended ceramic carrier is an excellent MBBR carrier that has high strength, optimum density (close to water), and high porosity.

Journal ArticleDOI
TL;DR: The methane yield was shown to be highly influenced by the A.D. plant Organic Loading Rate and by feedstock quality; hydraulic retention time had only limited effects.

Journal ArticleDOI
TL;DR: The performances in these two dry anaerobic co-digestion systems fed with different mixtures of OSW were continuously operated under mesophilic conditions and were comparable to the ones achieved in the conventional wet digestion and thermophilic dry digestion processes.

01 Jan 2011
TL;DR: In this paper, the potential of microalgal bacterial flocs (MaB-flocs) was investigated for the secondary treatment of sewage supplemented with different flue gas flow rates (FGFRs) from a coal power plant.
Abstract: Although microalgae are promising for a cradle-to-cradle design approach of sewage treatment, their application is hampered by high harvesting costs and low C:N ratios of sewage. Therefore, the potential of microalgal bacterial flocs (MaB-flocs) was investigated for the secondary treatment of sewage supplemented with different flue gas flow rates (FGFRs) from a coal power plant. Effluent (N, P, turbidity and pH) and off gas discharge levels (NOx, SOx) met the European discharge limits with a hydraulic retention time of only 0.67 days and an FGFR of 0.6 L h−1 (0.0025 vvm). This FGFR provided sufficient carbon and resulted in removal efficiencies of 48 ± 7% CO2, 87 ± 5% NOx and 99 ± 1% SO2. MaB-flocs settled fast reaching up to a density of 19 g VSS L−1. High biomass productivities (0.18 g L−1 day−1) were obtained under a low light intensity. This successful reactor performance indicates the large potential for the industrial application of MaB-flocs for flue gas sparged sewage treatment.

Journal ArticleDOI
TL;DR: The use of membrane sequencing batch reactors, operated at HRT of 8, 16 and 24h, was considered for the treatment of a synthetic petroleum wastewater, and increase in HRT resulted in statistically significant decrease in MLSS.

Journal ArticleDOI
TL;DR: In this article, the effect of various parameters such as pH, voltage, hydraulic retention time (HRT), and number of aluminum plates between the anode and cathode on efficiency of treatment are investigated.
Abstract: BACKGROUND: The present study describes an electrocoagulation process for treating laundry waste-water using aluminum plates. The effect of various parameters such pH, voltage, hydraulic retention time (HRT), and number of aluminum plates between the anode and cathode on efficiency of treatment are investigated. RESULTS: Experimental results showed that by increasing HRT, treatment efficiency increases but beyond 45 min changes are negligible. Among the results for chemical oxygen demand (COD), phosphorus, detergent, colour and turbidity, the lowest decrease was found for phosphorus. The larger the HRT, the greater the electrical current needed to achieve constant voltage and temperature in the system. The pH of the influent is a very significant variable which affects the treatment of laundry waste-water considerably, the optimal range being 6.0–8.0. In addition, it was found that the pH increases from 8.3 to more than 10 over the first hour of treatment after which the pH remains relatively constant. Finally, kinetic analysis indicates that the adsorption system obeys a second-order kinetic model. CONCLUSION: The aluminum hydroxide generated in the cell decreases the concentration of pollutants in laundry waste-water to a permissible level. It is concluded that, compared with other treatment processes, electrocoagulation is more effective in treating laundry waste-water under appropriate conditions. Copyright © 2011 Society of Chemical Industry

Journal ArticleDOI
TL;DR: In this article, the ability of tropical horizontal subsurface constructed wetlands (HSSF CWs) planted with Typha angustifolia to remove four widely used pharmaceutical compounds (carbamazepine, declofenac, ibuprofen and naproxen) at a relatively short hydraulic residence time of 2-4 days was documented.

Journal ArticleDOI
TL;DR: Combined processes of biological anaerobic baffled reactor (ABR) and UV/H2O2 at a laboratory scale were studied to treat a synthetic slaughterhouse wastewater in this article.
Abstract: Combined processes of biological anaerobic baffled reactor (ABR) and UV/H2O2 at a laboratory scale were studied to treat a synthetic slaughterhouse wastewater. In this study, the total organic carbon (TOC) loadings of 0.2–1.1 g/(L day) were used. The results revealed that combined processes had a higher efficiency to treat the synthetic slaughterhouse wastewater. Up to 95% TOC removal was obtained for an influent concentration of 973.3 mgTOC/L at the hydraulic retention time (HRT) of 3.8 days in the ABR and 3.6 h in the UV photoreactor. Meanwhile, up to 97.7% and 96.6% removal of chemical oxygen demand (COD) and 5-day carbonaceous biochemical oxygen demand (CBOD5) were observed in the ABR for the same influent concentration, respectively. Comparatively, for an influent concentration of 157.6 mgTOC/L, the UV/H2O2 process alone with the TOC loading of 0.06–1.9 g/(L h) was also studied, in which, up to 64.3%, 83.7%, and 84.3% of TOC, COD, and CBOD5 removal were observed, respectively, at the HRT of 2.5 h with hydrogen peroxide (H2O2) concentration of 529 mg/L. It was found that individual ABR and UV/H2O2 processes enhanced the biodegradability of the treated effluent by an increased CBOD5/COD ratio of 0.4 to 0.6. An optimum H2O2 dosage of 3.5 (mgH2O2)/(mgTOCin h) was also found for the UV/H2O2 process.

Journal ArticleDOI
TL;DR: Evidence for homo-acetogens included accumulation of acetate at high concentrations in the anode compartment; detection of formate, a known intermediate during reductive acetogenesis by the acetyl-CoA pathway; and detection offormyl tetrahydrofolate synthetase genes by quantitative real-time PCR.

Journal ArticleDOI
TL;DR: The results suggest that the MFC signal can reflect the dynamic variation of AD and can potentially be a valuable tool for monitoring and control of bioprocess.

Journal ArticleDOI
TL;DR: The feasibility of hydrogen generation from palm oil mill effluent (POME), a high strength wastewater with high solid content, was evaluated in an anaerobic sequencing batch reactor (ASBR) using enriched mixed microflora, under mesophilic digestion process at 37°C as mentioned in this paper.