scholarly journals Grain displacement during backwash of drinking water filters

2020 ◽  
Author(s):  
Loren Ramsay ◽  
Feng Du ◽  
Majbritt Lund ◽  
Haiyan He ◽  
Ditte A. Søborg
Keyword(s):  
Grain Size ◽  
Drinking Water ◽  
Pilot Scale ◽  
Sand Filters ◽  
Active Biomass ◽  
Four Dimensions ◽  
Study Country ◽  
Water Filters ◽  
Practical Implications

Abstract Backwashing rapid sand filters causes inadvertent displacement of filter media grains from their previous depths. This displacement can affect the hydraulic function of filters by mixing or segregating media grains, and the function of biofilters through displacement of active biomass and coatings from proper depths. This study quantifies grain displacement in a pilot-scale filter using tracer grains of colored sand, glass beads, anthracite and garnet to determine the effect of grain size, density and shape on grain displacement. Statistical moments are used to describe the depth distributions resulting from displacement during backwashing. Results show that significant grain displacement occurs during backwash consisting of air scour, air-and-water wash and sub-fluidization water-only wash. Here, displacement is largely independent of grain size, density and shape. When fluidization backwash is used, greater displacement and more dependence on grain characteristics is seen. A variety of grain movement phenomena can be observed during the backwashing steps, indicating that grain movement and therefore the resulting displacement is highly inhomogeneous in four dimensions. These results have direct practical implications for the design of rapid sand filters and the optimization of backwashing procedures, while suggesting that the current widespread backwashing practice used in the case study country (Denmark) should be abandoned.

Prospective environmental and economic assessment for biotreatment of micropollutants in drinking water resources in Denmark

2015 ◽  
Vol 15 (6) ◽  
pp. 1405-1413 ◽  
Author(s):  
Ivan Muñoz ◽  
Erik de Vries ◽  
Janneke Wittebol ◽  
Jens Aamand
Keyword(s):  
Drinking Water ◽  
Water Resources ◽  
Economic Assessment ◽  
Pilot Scale ◽  
Impact Categories ◽  
Financial Cost ◽  
Sand Filters ◽  
Immobilized Bacteria ◽  
Drinking Water Resources ◽  
Scale Data

A prospective environmental life cycle assessment (LCA) and financial cost assessment is performed to the application of bioaugmentation to sand filters in Danish waterworks, to remove 2,6-dichlorobenzamide (BAM) from drinking water resources. Based on pilot-scale and laboratory-scale data, we compare bioaugmentation to current alternative strategies, namely granular activated carbon (GAC) adsorption, and well re-location. Both assessments identified well re-location as the least preferred option, however, this result is very sensitive to the distance from the waterworks to the new well. When bioaugmentation is compared to GAC, the former has a lower impact in 13 impact categories, but if immobilized bacteria are used, the impacts are higher than for GAC in all impact categories. On the other hand, from a cost perspective bioaugmentation appears to be preferable to GAC only if immobilized bacteria are used.

Using Pilot-Scale Investigations to Estimate the Remaining Geosmin and MIB Removal Capacity of Full-Scale GAC-Capped Drinking Water Filters

2006 ◽  
Vol 41 (3) ◽  
pp. 296-306 ◽  
Author(s):  
Souleymane Ndiongue ◽  
William B. Anderson ◽  
Abhay Tadwalkar ◽  
John Rudnickas ◽  
Margaret Lin ◽  
...  
Keyword(s):  
Drinking Water ◽  
Contact Time ◽  
Drinking Water Treatment ◽  
Pilot Scale ◽  
Full Scale ◽  
Removal Capacity ◽  
Treatment Facilities ◽  
The City ◽  
Water Filters ◽  
Pilot Tests

Abstract Pilot tests were conducted to investigate the removal of geosmin and 2-methylisoborneol (MIB) by new and semi-exhausted granular activated carbon (GAC) extracted from full-scale filters located in the City of Toronto's drinking water treatment facilities. Four pilot filters containing core-sampled GAC and new sand were fed with settled water from a full-scale plant and operated under conditions similar to those employed at full-scale. None of the pilot filters appeared to be capable of reducing geosmin and MIB concentrations to below the commonly cited threshold odour limits of 4 ng/L for geosmin and 9 ng/L for MIB at the influent levels tested. When operated at a 5-min empty bed contact time (EBCT) with geosmin influent concentrations in the range of about 70 to 110 ng/L, removals ranged from 10 to 38% in filters with 25 to 30 cm of used GAC. In the filter with 25 cm of new GAC, removal was 83%. When operated with a 7.5-min EBCT, the filter containing 95 cm of used bituminous GAC removed 78% of the geosmin present in the influent. For both geosmin and MIB, the effluent concentration and the amount removed increased as influent concentration increased, as was expected. In general, geosmin was better removed than MIB.

The effect of increasing grain size in biosand water filters in combination with ultraviolet disinfection

2013 ◽  
Vol 4 (2) ◽  
pp. 206-213 ◽  
Author(s):  
Timothy E. Frank ◽  
Matthew L. Scheie ◽  
Victoria Cachro ◽  
Andrew S. Muñoz
Keyword(s):  
Grain Size ◽  
Drinking Water ◽  
Produced Water ◽  
Uv Light ◽  
World Health ◽  
E Coli ◽  
Data Points ◽  
Clear Plastic ◽  
Health Organization ◽  
Water Filters

With sand less than 0.70 mm often difficult to source in the field, it is of interest to study larger grained sand for use in biosand water filters (BSF). This study examined how sand grain size affects biological sand water filtration and how the combination of biological sand filtration and ultraviolet (UV) disinfection affects drinking water quality. Two BSFs were built: a control with maximum grain size, dmax = 0.70 mm and an experimental with grain sizes ranging from 0.70 mm to dmax = 2.0 mm. Untreated water was passed through each BSF daily. Results show Escherichia coli and turbidity removal characteristics of the control and experimental BSFs were not significantly different from one another. Both BSFs produced water that met World Health Organization (WHO) drinking water guidelines for turbidity, and although E. coli reduction was over 98% for each BSF, a high initial bacteria concentration resulted in effluent levels above WHO guidelines. Subsequently, effluent from each BSF was placed in clear plastic bottles under UV light, after which water from each BSF met E. coli guidelines. The data yielded promising results for using larger sand in BSFs, but longer duration studies with more data points are needed.

Estimation and modeling of direct rapid sand filtration for total fecal coliform removal from secondary clarifier effluents

2012 ◽  
Vol 65 (9) ◽  
pp. 1615-1623 ◽  
Author(s):  
Yi Li ◽  
Jingjing Yu ◽  
Zhigang Liu ◽  
Tian Ma
Keyword(s):  
Grain Size ◽  
Fecal Coliform ◽  
Loading Rate ◽  
Pilot Scale ◽  
Size Distributions ◽  
Sand Filters ◽  
Loading Rates ◽  
First Order Kinetics ◽  
Secondary Clarifier ◽  
Grain Size Distributions

The filtration of fecal coliform from a secondary clarifier effluent was investigated using direct rapid sand filters as tertiary wastewater treatment on a pilot scale. The effect of the flocculation dose, flow loading rate, and grain size on fecal coliform removal was determined. Direct rapid sand filters can remove 0.6–1.5 log-units of fecal coliform, depending on the loading rate and grain size distribution. Meanwhile, the flocculation dose has little effect on coliform removal, and increasing the loading rate and/or grain size decreases the bacteria removal efficiency. A model was then developed for the removal process. Bacteria elimination and inactivation both in the water phase and the sand bed can be described by first-order kinetics. Removal was successfully simulated at different loading rates and grain size distributions and compared with the data obtained using pilot-scale filters.

Modifications of unit processes for finished water quality improvement at the Kueui water treatment plant in Seoul

2002 ◽  
Vol 2 (5-6) ◽  
pp. 193-199
Author(s):  
M.J. Yu ◽  
H.M. Cho ◽  
J.Y. Koo ◽  
I.S. Han ◽  
E.M. Gwon ◽  
...  
Keyword(s):  
Water Quality ◽  
Drinking Water ◽  
Water Treatment ◽  
Treatment Plant ◽  
Drinking Water Treatment ◽  
Water Treatment Plant ◽  
Pilot Scale ◽  
Sand Filters ◽  
Water Treatment Plants ◽  
Sedimentation Basins

Recently, Seoul city has tried to modify and upgrade the existing facilities and utilities and to improve the established water treatment plants, instead of application of a new treatment process. These efforts have finally lowered the turbidity of finished water below 0.1NTU. Small lab-scale and pilot-scale experiments have been conducted and they have provided optimum parameters for the design and operation of drinking water treatment plants. In addition, quantitative and/or trace analysis technologies developed for monitoring water quality of effluent from unit processes and automization of facilities, have contributed to the improvement of turbidity in drinking water. The Kueui water treatment plant, one of the drinking water treatment plants in Seoul, produces finished water with 0.08 NTU. It results from the operators' continuous endeavor to lower the turbidity in a scale of 0.01 NTU. The data for 12 months indicated that turbidity of settled water was less than 1.16 NTU and that of filtered water was less than 0.12 NTU for 95% of the period. Sedimentation basins and sand filters satisfy the recommended turbidity criteria, 2 NTU and 0.3 NTU, respectively. Also Kueui water treatment plant has focused on the control of organic matters to decrease in DBPs and on the removal of microorganisms.

Advanced treatment for taste and odour control in drinking water: case study of a pilot scale plant in Seoul, Korea

2007 ◽  
Vol 55 (5) ◽  
pp. 111-116 ◽  
Author(s):  
W.H. Joe ◽  
I.C. Choi ◽  
Y.A. Baek ◽  
Y.J. Choi ◽  
G.S. Park ◽  
...  
Keyword(s):  
Drinking Water ◽  
Removal Efficiency ◽  
Tap Water ◽  
Pilot Scale ◽  
Chlorine Concentration ◽  
Advanced Treatment ◽  
Raw Water ◽  
Han River ◽  
Odour Control

Taste and odour problems of tap water in Seoul are attributed to 2-methylisoborneol (2-MIB) and trans-1,10-dimethyl-trans-9-decalol (geosmin), which are the result of metabolism of algae and chlorine for disinfection. This study was carried out to measure 2-MIB and geosmin in the raw water from the Han River, to investigate removal efficiency of GAC and BAC integrated with post-ozonation, and to minimise and quantify the required chlorine concentration as a final disinfectant through the candidate process.

scholarly journals Optimization of regenerated bone char for fluoride removal in drinking water: a case study in Tanzania

2006 ◽  
Vol 4 (1) ◽  
pp. 139-147 ◽  
Author(s):  
M. E. Kaseva
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Drinking Water ◽  
Contact Time ◽  
Fluoride Removal ◽  
Bone Char ◽  
Removal Capacity ◽  
Maximum Value ◽  
The World

This paper presents findings of a study on optimization and application of the regenerated bone char media for the defluoridation of drinking water in Tanzania where more than 30% of all water sources have fluoride concentrations above the 1.50 mg/l which is recommended by the World Heath Organization (WHO). In this study, regeneration temperature, regeneration duration, contact time, regenerated bone char dosage and particle size were investigated. Results indicate that the highest fluoride removal and adsorption capacity were 70.64% and 0.75 mg-F/g-bc, respectively, for a sample with bone char material that was regenerated at 500°C. In this study the optimum burning duration was found to be 120 min, which resulted in residual fluoride that varied from a maximum value of 17.43 mg/l for a 2 min contact time to a minimum value of 8.53 mg/l for a contact time of 180 min. This study further indicated that the smallest size of regenerated bone char media (0.5–1.0 mm diameter) had the highest defluoridation capacity, with residual fluoride which varied from 17.82 mg/l at 2 min contact time to 11.26 mg/l at 120 min contact time. In terms of dosage of the regenerated bone char media it was established that the optimum dosage was 25 g of bone char media with a grain size of 0.50–1.0 mm. This had a fluoride removal capacity of 0.55 mg-F/g-BC. Column filter experiments indicated that regenerated bone media is capable of removing fluoride from dinking water to meet both WHO and Tanzania recommended values.

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