scholarly journals MS2 coliphage and E. coli UVB inactivation rates in optically clear water: dose, dose rate and temperature dependence

2018 ◽  
Vol 78 (10) ◽  
pp. 2228-2238 ◽  
Author(s):  
Yu Lian ◽  
Lei Mai ◽  
Nancy Cromar ◽  
Neil Buchanan ◽  
Howard Fallowfield ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Dose Rate ◽  
Ultraviolet B ◽  
Water Disinfection ◽  
High Rate ◽  
Clear Water ◽  
E Coli ◽  
Dose Rates ◽  
Log Reduction ◽  
Wastewater Treatment Systems

Abstract Natural ultraviolet irradiance disinfection is known to play a significant role in both natural wastewater treatment systems and drinking water disinfection processes, while the influence of ultraviolet B (UVB) delivering method on sunlight disinfection outcome is still unclear. This study aims to determine the effects of environmentally relevant temperatures, UVB doses (J m−2) and dose rates (W m−2) on the inactivation and log reduction values (LRVs) of the F-RNA coliphage MS2 and Escherichia coli in optically clear water. E. coli and MS2 were separately incubated and irradiated at five different doses of UVB light that delivered using six UVB dose rates. The results of the study demonstrate that the UVB dose delivering method (combination of dose rate and exposure time) influences inactivation and LRVs of E. coli and MS2 at all UVB doses investigated (up to seven-fold difference). Two phases were identified within the UVB dose rate, UVB inactivation or LRV curves for both organisms; a UVB dose rate limited inactivation phase and a dose rate saturation inactivation phase. The results contribute to a better understanding of UVB disinfection in the environment and natural wastewater treatment systems, potentially improving the design and operation of high rate algal ponds.

The influence of currents on circular secondary clarifier performance and design

1996 ◽  
Vol 34 (3-4) ◽  
pp. 405-412 ◽  
Author(s):  
Andrea Deininger ◽  
Frank W. Günthert ◽  
Peter A. Wilderer
Keyword(s):  
Wastewater Treatment ◽  
Density Currents ◽  
Clear Water ◽  
Performance Measurements ◽  
Design Procedures ◽  
Secondary Clarifier ◽  
Current Design ◽  
Hydraulic Load ◽  
Novel Design ◽  
Wastewater Treatment Systems

Density currents in the deeper zones of clarifiers and currents in the clear water zone have a significant influence on clarifier performance. Measurements of flow velocity profiles were conducted in full-scale horizontally flown circular secondary clarifiers. Relations between the hydraulic load and the development of density currents could be detected. Those patterns are not taken into account in current design procedures. Stationary design approaches are mainly based on the overflow rate. Novel design methods based on the dynamic behavior of flow and density distribution in clarifiers are needed in order to improve the efficacy of wastewater treatment systems.

Virus removal in a pilot-scale ‘advanced’ pond system as indicated by somatic and F-RNA bacteriophages

2005 ◽  
Vol 51 (12) ◽  
pp. 107-110 ◽  
Author(s):  
R.J. Davies-Colley ◽  
R.J. Craggs ◽  
J. Park ◽  
J.P.S. Sukias ◽  
J.W. Nagels ◽  
...  
Keyword(s):  
Pilot Scale ◽  
High Rate ◽  
Virus Removal ◽  
E Coli ◽  
Waste Stabilisation Ponds ◽  
Log Reduction ◽  
Effective Removal ◽  
Solar Uv ◽  
Settling Ponds ◽  
Rna Phage

Advanced pond systems (APS), incorporating high-rate ponds, algal settling ponds, and maturation ponds, typically achieve better and more consistent disinfection as indicated by Escherichia coli than conventional waste stabilisation ponds. To see whether this superior disinfection extends also to enteric viruses, we studied the removal of somatic phages (‘model’ viruses) in a pilot-scale APS treating sewage. Measurements through the three aerobic stages of the APS showed fairly good removal of somatic phage in the summer months (2.2 log reduction), but much less effective removal in winter (0.45 log reduction), whereas E. coli was removed efficiently (>4 logs) in both seasons. A very steep depth-gradient of sunlight inactivation of somatic phage in APS pond waters (confined in silica test tubes) is consistent with inactivation mainly by solar UVB wavelengths. Data for F-RNA phage suggests involvement of longer UV wavelengths. These findings imply that efficiency of virus removal in APS will vary seasonally with variation in solar UV radiation.

An antimicrobial polycationic sand filter for water disinfection

2011 ◽  
Vol 63 (9) ◽  
pp. 1997-2003 ◽  
Author(s):  
Annalisa Onnis-Hayden ◽  
Bryan B. Hsu ◽  
Alexander M. Klibanov ◽  
April Z. Gu
Keyword(s):  
Treatment Plant ◽  
Antimicrobial Properties ◽  
Bacterial Count ◽  
Water Disinfection ◽  
Aqueous Sample ◽  
Secondary Effluent ◽  
E Coli ◽  
Log Reduction ◽  
Disinfection Process ◽  
Aqueous Effluent

A new sand filtration water disinfection technology is developed which relies on the antimicrobial properties of hydrophobic polycations (N-hexylated polyethylenimine) covalently attached to the sand's surface. The efficacy of the filter disinfection process was evaluated both with water spiked with E. coli and with real aqueous effluent from a wastewater treatment plant. For the former, over 7-log reduction in bacterial count was achieved. With real environmental wastewater secondary effluent samples, the E. coli concentration reduction declined to under 2 logs. This reduced inactivation efficiency compared to the model aqueous sample is likely due to the particulate or colloidal matter present that diminishes the contact between the immobilized polycation and the suspended bacteria. Preliminary sand washing methods were tested to assess potential ‘regeneration’ approaches. Potential advantages of the proposed approach over conventional disinfection in terms of eliminating harmful by-products and reducing energy consumption are discussed.

scholarly journals Bactericidal activity of Ag nanoparticle-impregnated fibreglass for water disinfection

2009 ◽  
Vol 7 (4) ◽  
pp. 657-663 ◽  
Author(s):  
Gordon Nangmenyi ◽  
Wei Xao ◽  
Sharifeh Mehrabi ◽  
Eric Mintz ◽  
James Economy
Keyword(s):  
Silver Nanoparticles ◽  
Silver Content ◽  
Immersion Test ◽  
Water Disinfection ◽  
X Ray Diffraction ◽  
Thermal Regeneration ◽  
X Ray ◽  
E Coli ◽  
Log Reduction ◽  
Activated Carbon Fibres

A new bactericidal system composed of fibreglass impregnated with silver (Ag) nanoparticles was developed and tested. Silver content, particle size and distribution were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The antibacterial effectiveness was evaluated against Escherichia coli (E. coli, ATCC 29055). The minimum inhibitory loading was determined to be less than 1.8 wt% of silver nanoparticles per gram of fibreglass. In a 1 h immersion test, using a 0.1 mg fibreglass mat ml−1, with 2.9 wt% loading of silver nanoparticles completely disinfected 100 ml of 106 CFU ml−1 of E. coli, dramatically outperforming activated carbon fibres impregnated with silver. Inactivation rate studies of 0.05 mg fibreglass mat ml−1 (Ag 1.8 wt%) with 1012 CFU E. coli displayed a 7 log reduction in 5 minutes. The activation and reuse of fibreglass (Ag 4.3 wt%) maintained its full effectiveness after two cycles of use and thermal regeneration at 350°C.

The Role of Protozoa in High Rate Wastewater Treatment Systems

1980 ◽  
Vol 15 (2) ◽  
pp. 187-201
Author(s):  
R. Booth ◽  
J.G. Henry ◽  
D. Prasad
Keyword(s):  
Wastewater Treatment ◽  
Hydraulic Retention Time ◽  
Mixed Population ◽  
High Rate ◽  
Ciliated Protozoa ◽  
Effluent Quality ◽  
The Poor ◽  
In Series ◽  
Wastewater Treatment Systems ◽  
Sludge Settleability

Abstract Three continuous, laboratory scale, high rate biological wastewater treatment systems operating in a similar mode were evaluated. The feed was a synthetic sewage with a COD and BOD of approximately 300 mg/l and 200 mg/l, respectively. The total hydraulic retention time in each system was 2-1/4 hours - 40 minutes aeration, 95 minutes sedimentation. The applied food to microorganism ratios (F/M) were equal to or greater than one. Systems I and II employed a single aerobic reactor whereas System III employed two aerobic reactors in series each with a hydraulic retention time of 20 minutes. Sludge was returned to the second reactor only, thus establishing dispersed growth in the first reactor and a mixed microbial population in the second. System I was strictly a bacterial system isolated from atmospheric contamination. System II employed a mixed population of ciliated protozoa and bacteria. Tests performed included soluble COD reduction, effluent, mixed liquor and return sludge suspended solids, SVI, pH, polysacharides, bacteria count, and protozoan count. Comparison of System I (bacterial) and System II (mixed population) revealed an improvement in effluent quality (SS, Total COD) as a result of the presence of ciliated protozoa. The higher effluent SS in System I was a result of the poor settleability of dispersed growth. Based on the knowledge of the effects of protozoa on dispersed growth, System III (bacterial reactor and mixed population reactor in series) was established to determine if such a series arrangement would further improve treatment efficiency. Several different two stage reactor system configurations were investigated including sedimentation after the first reactor with the effluent passing to the second reactor. Such an arrangement proved impractical due to the poor settleability of the dispersed growth associated with a predominantly bacterial system. System III resulted in a vast improvement in sludge settleability while maintaining an effluent quality equal to that of System II. This improvement in sludge settleability indicates improved system stability and reduced handling costs.

Bacterial removal in three pilot-scale wastewater treatment systems for rural areas

1997 ◽  
Vol 35 (11-12) ◽  
pp. 197-200 ◽  
Author(s):  
M. Garcia ◽  
E. Bécares
Keyword(s):  
Wastewater Treatment ◽  
Rural Areas ◽  
Pathogenic Bacteria ◽  
Removal Rate ◽  
Treatment Plant ◽  
Free Water ◽  
Pilot Scale ◽  
High Rate ◽  
Total Coliforms ◽  
Wastewater Treatment Systems

A comparative study on the removal of several pathogenic bacteria and their indicators was carried out at three natural wastewater treatment systems: stabilisation pond, high-rate algal pond and a free-water macrophyte system, retention times being 24, 5 and 3 days respectively. The macrophyte system showed higher removal efficiency for most of the groups, followed by stabilisation pond and high rate algal pond. All systems showed their highest efficiencies in the reduction of total coliforms, ranging from 98.68% for the stabilisation pond to 99.48% for the macrophyte process. Highly significant differences were found between the systems for bifidobacteria, C. perfringens and total coliforms removal. Pathogens and their indicators showed a different behaviour in their daily removal rate depending on the treatment plant.

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