Use of bauxite for enhanced removal of bacteria in slow sand filters

2016 ◽  
Vol 17 (4) ◽  
pp. 1007-1015 ◽  
Author(s):  
Daniel Urfer
Keyword(s):  
Drinking Water ◽  
Drinking Water Treatment ◽  
Particle Removal ◽  
Sand Filters ◽  
Filter Surface ◽  
Second Stage ◽  
Slow Sand Filter ◽  
Different Depths ◽  
Filter Bed ◽  
Pilot Tests

Slow sand filtration (SSF) is a well-known process for drinking water treatment and is widely used for the production of biologically stable drinking water and particle removal. The removal process of particles and microorganisms is highly dependent on the buildup of the schmutzdecke at the filter surface. During the ripening period and especially for cold waters, the buildup of the schmutzdecke may take several months until such filters are biologically mature and at steady-state regarding their removal performance for particles and microorganisms. In order to improve the performance of SSF in terms of the removal of bacteria, e.g. Escherichia coli and Enterococcus, pilot tests using natural bauxite as a filter media have been performed. The results showed a significant improvement in bacteria retention within the filter bed of a second-stage slow sand filter containing different depths of bauxite.

A novel acoustic imaging tool for monitoring the state of rapid sand filters

2013 ◽  
Vol 14 (1) ◽  
pp. 107-118
Author(s):  
Nihed Allouche ◽  
Dick G. Simons ◽  
Paul Keijzer ◽  
Luuk C. Rietveld ◽  
Joost Kappelhof
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Acoustic Waves ◽  
Vertical Direction ◽  
Drinking Water Treatment ◽  
The State ◽  
Acoustic Response ◽  
Sand Filters ◽  
Cleaning Procedure ◽  
Filter Bed

A new technology based on acoustic waves is developed to monitor the state of sand filters used in drinking water treatment. Changes in the sand filter, due to the removal of suspended particles from the water and their accumulation in the pores, result in an increase of the bulk density and acoustic speed of the granular material. Consequently, the reflected acoustic response changes as the filter is in use. To monitor these changes, an instrument composed of an omnidirectional transmitter and an array of hydrophones was built. With frequencies ranging between 10 and 110 kHz, high resolution is achieved in the vertical direction enabling the detectability of clogged layers with a minimum thickness of 1 cm. The novel instrument is tested by conducting a monitoring experiment in a filter used in practice. A 2D scan over a part of the filter was performed and repeated every 2 hours over a period of 10 days. An analysis of the data revealed a local increase of the reflected acoustic response with increasing filter run time. The changes in acoustic signal are mainly observed at the upper 5 cm of the sand bed. It is also clear that the filter bed is slowly compacting as a function of time. The total compaction after a period of 10 days reached 3.5 cm. The filter bed is expanded again during the cleaning procedure. Once the procedure is completed, the upper 30 cm of the filter becomes more transparent, showing small accumulations of material at greater depth. The observed changes in the filter bed demonstrate the potential of this acoustic-based tool to monitor the state of rapid sand filters and optimise their performance. The new tool can be used to evaluate the cleaning procedure and is valuable in detecting lateral variations in the filter bed. These variations may indicate local clogging that needs to be removed effectively to avoid deterioration of the overall performance in the long term. This type of information is difficult to obtain from the monitoring techniques currently used in drinking water treatment.

Removal of particulates, natural organic matters, and microorganisms in a surface amended slow sand filter

2002 ◽  
Vol 2 (5-6) ◽  
pp. 387-394
Author(s):  
H.-B. Jun ◽  
Y.-J. Lee ◽  
S.-S. Shin
Keyword(s):  
Surface Treatment ◽  
Raw Water ◽  
Sand Filters ◽  
Water Turbidity ◽  
Turbidity Removal ◽  
Sand Filter ◽  
Organic Matters ◽  
Slow Sand Filter ◽  
Natural Organic Matters ◽  
Filter Bed

Removal characteristics of particulates, natural organic matters, and microorganisms with six slow sand filter units were measured with a diameter of 50 mm and packed with sand to a depth of 50, 150, 300, 600, and two 700 mm, respectively. One of the 700 mm depth filters was amended by covering the surface of the filter bed with a prefilter. The raw water turbidity and pH was in the range of 1.5-2.0 NTU, and 7.0-7.7, respectively. Turbidity in each filter effluent was decreased as the depth of filter medium increased. However, a greater part of influent turbidity was removed within the top layer of the slow sand filters. Turbidity removal in the 700 mm depth filter with prefilter was similar to that without the prefilter, however, the removal of particles smaller than 2 mm was improved with the prefilter. The particles greater than 10 mm could be removed within the upper 50 mm depth in the slow sand filter. A greater fraction of the particles smaller than 2 mm was removed within the upper 50 mm, however, they were also removed in the deeper sand bed. The removal efficiency of DBP precursors represented by DOC and UV-254 absorbance was 9.2-31% and 2-31%, respectively. pH drop in the 50 mm depth filter was 0.12, while that in the 700 mm depth filter was 0.19. The effects of surface treatment with prefilter on UVA and DOC were not apparent.

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.

scholarly journals Biodegradation Behavior of Ozonated Natural Organic Matter in Sand Filters

2005 ◽  
Vol 9 (1) ◽  
pp. 3-16 ◽  
Author(s):  
J. Z. Wang ◽  
R. S. Summers
Keyword(s):  
Drinking Water ◽  
Organic Matter ◽  
Organic Carbon ◽  
Natural Organic Matter ◽  
Glyoxylic Acid ◽  
Complex Mixture ◽  
Drinking Water Treatment ◽  
Sand Filters ◽  
Substrate Removal ◽  
Exchange Resins

Natural organic matter (NOM) in drinking water is a complex mixture of organic compounds. Some of the compounds are not biodegradable, while others are quickly biodegradable and a third group is more resistant to biodegradation. To have a better understanding of the biofiltration process in drinking water treatment, it is important to identify the elements of the quickly and slowly biodegradable NOM and to characterize the biodegradation rate of each element. In this study, an ozonated NOM solution was used as the substrate. The NOM was isolated from a groundwater in Germany using ion-exchange resins. The ozone dose was 0.35 mg O3/mg DOC (dissolved organic carbon). Previously bioacclimated sand was used as filter media and biomass source and was homogeneously distributed in the filter prior to each run. The substrate removal was evaluated by DOC, biodegradable DOC (BDOC), assimilable organic carbon (AOC), aldehyde and ketoacid analyses. When expressed in terms of the empty bed contact time (EBCT), the results showed that filter velocity in the range of 1.5 to 15 m/hr had no impact on substrate removal. This implies that substrate utilization, not external mass transfer, is the rate limiting step for substrate removal in drinking water biofilters. In this study, compounds or NOM fractions are termed quickly biodegradable if they are removed in the first three minutes of EBCT. 15% of the DOC was removed by the biofilter within three minutes of EBCT and was termed the quickly biodegradable fraction. The BDOC fraction of the ozonated solution was determined to be 40 to 45% of the DOC. In terms of BDOC, about one third of the total BDOC was quickly biodegradable. The AOC results show that about 90% of the total AOC was utilized by Spirillum sp. NOX (AOC-NOX). Most of the AOC was quickly biodegradable and was removed within one minute of EBCT. For aldehydes, glyoxal and methyl glyoxal were removed to below the detection limit after two minutes of EBCT. However, only 60% of formaldehyde removal was achieved in the first two minutes of EBCT, and no additional removal was achieved with increasing EBCT. Additionally, no significant removal of acetaldehyde was observed. The results of ketoacids show that their utilization rates were very high. More than 90% of glyoxylic acid and pyruvic acid were removed within one minute of EBCT.

scholarly journals Methane emission and methanotrophic activity in groundwater-fed drinking water treatment plants

2020 ◽  
Vol 20 (3) ◽  
pp. 819-827 ◽  
Author(s):  
Edmundas Maksimavičius ◽  
Peter Roslev
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Methane Emission ◽  
Drinking Water Treatment ◽  
Ammonia Removal ◽  
Limited Information ◽  
Gas Stripping ◽  
Sand Filters ◽  
Water Treatment Plants ◽  
Methane Oxidizing Bacteria

Abstract Groundwater for drinking water production may contain dissolved methane (CH4) at variable concentrations. Most of this important greenhouse gas is often vented to the atmosphere during primary aeration and gas stripping processes at drinking water treatment plants (DWTPs). However, limited information exists regarding emission and fate of methane at many groundwater-fed DWTPs. This study estimates emission of methane from 1,004 DWTPs in Denmark and includes data from 3,068 groundwater wells. The fate of methane and occurrence of methane oxidizing bacteria in DWTPs was examined, including the potential role in ammonia removal. Methane emission from Danish DWTPs was estimated to be 1.38–2.95 × 10−4 Tg CH4/y which corresponds to 0.05–0.11% of the national anthropogenic methane emission. Trace levels of methane remained in the drinking water after primary aeration and entered the sand filters as a potential microbial substrate. Methanotrophic bacteria and active methane oxidation was always detected in the sand filters at groundwater-fed DWTPs. Methanotrophic consortia isolated from DWTP sandfilters were inoculated into laboratory-scale sand filters and the activity confirmed that methanotrophic consortia can play a role in the removal of ammonia via assimilation and co-oxidation. This suggests a potential for facilitating the removal of inorganic constituents from drinking water using methane as a co-substrate.

Optimization of particle removal in drinking water treatment of reservoir water in a pressure filter plant

2002 ◽  
Vol 2 (1) ◽  
pp. 241-247
Author(s):  
K. Bornmann ◽  
B. Wricke ◽  
D. Habel
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
High Efficiency ◽  
Technological Development ◽  
Drinking Water Treatment ◽  
Particle Removal ◽  
Reservoir Water ◽  
Surface Water Treatment ◽  
Drinking Water Production ◽  
Treatment Step

Most surface water treatment plants use floc-filtration as the most important treatment step in drinking water production. This paper presents a new technological development which allows floc-filtration to be carried out in pressure filters. Experiments in pilot and full scale show its high efficiency. The technological development allows us to treat algal-rich and high turbid matter containing raw water efficiently at high filtration rates. Floc formation can be realised by means of a special reaction tank in front of the filter inlet. Efficient removal of particles and turbidity is achieved if filtration with filter inlet flow controller is used.

Enhanced particle removal in drinking water treatment plants – case studies

2000 ◽  
Vol 41 (7) ◽  
pp. 135-142
Author(s):  
P. Lipp ◽  
G. Baldauf
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Case Studies ◽  
Surface Waters ◽  
Drinking Water Treatment ◽  
Particle Removal ◽  
Water Production ◽  
Water Treatment Plants ◽  
Drinking Water Production

Measurements of parasites in surface waters in Germany showed that their presence is widely spread. Concentrations may reach values up to a maximum of 50 cysts per 100 l. Normally raw waters used for drinking water production show much lower values. In order to ensure sufficient parasite removal in drinking water treatment plants an enhancement of particle removal is required. For filtration processes parameters influencing particle removal are filter media, filtration velocity, flocculant dosage, preozonationand filter back wash. Moderate filtration conditions show best results. Three case studies show that preozonation, optimized energy input and use of flocculants improve particle removal. One case study shows results of the first ultrafiltration plant in Germany treating reservoir and spring water for drinking water production.

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