Chemically enhanced gravel pre-filtration for slow sand filters: advantages and pitfalls

2006 ◽  
Vol 6 (1) ◽  
pp. 121-128
Author(s):  
C.C. Dorea ◽  
B.A. Clarke
Keyword(s):  
Negative Impact ◽  
Pilot Scale ◽  
Sand Filtration ◽  
Sand Filters ◽  
Slow Sand Filtration ◽  
Chemical Enhancement ◽  
Dissolved Organics ◽  
Efficiency And Effectiveness ◽  
Slow Sand Filter ◽  
Pre Treatment

The chemical enhancement of gravel (or roughing) filtration with coagulants, i.e. direct (gravel) filtration, has been proposed as a pre-treatment alternative for slow sand filters. However, studies have frequently focused on the efficiencies of the pre-filters in terms of reduction percentages. The effectiveness of the pre-treatment on the subsequent slow sand filtration is not usually cited or even evaluated. By incorporating a pilot-scale slow sand filter in our trials, both aspects of the pre-treatment process were assessed: efficiency and effectiveness. In terms of turbidity reductions, our results demonstrated that chemically enhanced pre-filtration was substantially more efficient (93.2 to 99.5%) than conventional pre-filtration (50.6 to 79.3); this was also observed in terms of reductions in the level of other parameters (i.e. thermotolerant faecal coliforms and dissolved organics). Yet, the use of a coagulant can have a negative impact on the slow sand filtration run.

Treatment of Groundwater with Slow Sand Filtration

1988 ◽  
Vol 20 (3) ◽  
pp. 141-147 ◽  
Author(s):  
T. Hatva
Keyword(s):  
Biological Activities ◽  
Treatment Phase ◽  
Purification Process ◽  
Sand Filtration ◽  
Sand Filters ◽  
Slow Sand Filtration ◽  
Filtration Method ◽  
Pre Treatment ◽  
Full Scale Tests ◽  
Iron Manganese

The purification process and techniques of the slow sand filtration method for treatment of groundwater was studied on the basis of pilot plant and full scale tests and studies of waterworks, to obtain guidelines for construction and maintenance. The purification process consists in general of two principal phases which are pre-treatment and slow sand filtration. Both are biological filters. The main purpose of the pre-treatment is to reduce the iron content of raw water, in order to slow down the clogging of the slow sand filters. Different types of biofilters have proved very effective in the pre-treatment phase, with reduction of total iron from 50 % to over 80 %. During the treatment, the oxidation reduction conditions gradually change becoming suitable for chemical and biological precipitation of iron, manganese and for oxidation of ammonium. Suitable environmental conditions are crucial in the oxidation of manganese and ammonium which, according to these studies, mainly occurs in slow sand filters, at the end of the process. Low water temperature in winter does not seem to prevent the biological activities connected with the removal of iron, manganese and ammonium, the chief properties necessitating treatment of groundwater in Finland.

Elimination of terpenoid odorous compounds by slow sand and river bank filtration of the Ruhr River, Germany

1995 ◽  
Vol 31 (11) ◽  
pp. 211-217 ◽  
Author(s):  
F. Jüttner
Keyword(s):  
Bank Filtration ◽  
Sand Filtration ◽  
Sand Filters ◽  
Slow Sand Filtration ◽  
River Bank ◽  
Lipophilic Compounds ◽  
Slow Sand Filter ◽  
Odorous Compounds ◽  
Aliphatic And Aromatic Hydrocarbons ◽  
River Bank Filtration

The elimination of odorous compounds by river bank and slow sand filtration was studied at the Ruhr River in Germany. The aquifer of the river bank filtration was anoxic and exhibited intense dissimilatory nitrate reduction; the aquifer of the slow sand filter was oxic. Polar monoterpenes, such as linalool, menthol, isobornyl acetate, lipoxygenase products (oct-1-en-3-ol) and geosmin exhibited a much higher percentage elimination than monoterpene hydrocarbons and other lipophilic compounds (dimethyldisulphide, aliphatic and aromatic hydrocarbons). The efficiency of river bank filtration was slightly better than that of slow sand filtration. The schmutzdecke and upper layers of the slow sand filters were responsible for most of the removal of VOC. The deeper layers exhibited only small effects.

Slow sand filtration pre-treatment with alum is efficient, but is it effective?

2013 ◽  
Vol 3 (2) ◽  
pp. 106-111 ◽  
Author(s):  
C. C. Dorea
Keyword(s):  
Process Control ◽  
High Efficiency ◽  
Sand Filters ◽  
Sand Filter ◽  
Limited Effectiveness ◽  
Scale Field ◽  
Slow Sand Filter ◽  
High Turbidity ◽  
Pre Treatment ◽  
Run Lengths

Enhancing the performance of slow sand filter pre-treatment with alum (i.e. direct or contact filtration) has been proposed as an alternative to overcome limitations of conventional gravel (roughing) pre-filtration. Experimental results revealed high turbidity reduction efficiencies in alum-dosed pre-filtration. However, due to the alum coagulation, the nature of the particulates in the pre-treatment effluent changed and had a potential to shorten the downstream slow sand filter run lengths by approximately 50% under the conditions tested. Hence, depending on the effluent turbidity levels the effectiveness of the alum-dosed pre-treatment could be compromised, despite its high efficiency. Relatively low turbidity levels (<2 NTU) were needed to minimise excessive headloss development in alum-dosed filters. However, the necessary resources to achieve such process control may not be available in developing country contexts. Furthermore, full-scale field experiences indicated the limited effectiveness of alum dosing prior to slow sand filters and the difficulties in maintaining an adequate chemical dosing in under-resourced settings.

Tertiary treatment of sewage effluent via pilot scale slow sand filtration

1994 ◽  
Vol 15 (1) ◽  
pp. 15-28 ◽  
Author(s):  
S. Farooq ◽  
A.K. Al‐Yousef ◽  
R.I. Al‐Layla ◽  
A.M. Ishaq
Keyword(s):  
Pilot Scale ◽  
Sewage Effluent ◽  
Sand Filtration ◽  
Tertiary Treatment ◽  
Slow Sand Filtration

Removal of Humic Substances by Oxidation/Biofiltration Processes - a Review

1999 ◽  
Vol 40 (9) ◽  
pp. 141-148 ◽  
Author(s):  
Nigel J. D. Graham
Keyword(s):  
Humic Substances ◽  
Residual Chlorine ◽  
Sand Filtration ◽  
Activated Alumina ◽  
Sand Filters ◽  
Slow Sand Filtration ◽  
The Usa ◽  
The Stability ◽  
Inorganic Adsorbents ◽  
The Uk

The paper is concerned principally with summarising the experience to-date of treating low alkalinity, low turbidity, humic-rich surface waters by the combination of ozone oxidation and biological filtration processes. In the UK, USA and other countries, upland coloured waters have often been treated by slow sand filtration in which only moderate removals of DOC have been achieved (< 20%). The presence of significant levels of humic matter in filtrate waters has led to difficulties in achieving compliance with the standards for colour and THMs, and concern about the stability of residual chlorine and potential biogrowth in water supply pipework. This has led to several investigations (eg. in the UK, Sweden and the USA) of the benefits of applying ozonation prior to slow sand filtration in view of its known capability to decolorise humic substances and enhance biodegradability of the organic fractions. This paper summarises the experience to-date and highlights the benefits and problems that have been identified. Some studies have attempted to compare the relative performances of slow sand filters and granular activated carbon (GAC) filters for the removal of BDOC and the paper reviews the principal findings of these studies in view of the growing worldwide interest in the application of ozone-GAC. One major limitation with the use of ozone-GAC is the need periodically to remove and regenerate the carbon, since bed lives for the removal of humic substances are typically short. An alternative approach is to use inorganic adsorbents instead of carbon which have the potential to be chemically regenerated in-situ. The paper refers to the results of laboratory tests that have been carried out on the potential use of pre-ozonation followed by inorganic adsorbents (eg. Activated alumina, bauxite) for the removal of humic substances.

Assessment of a roughing filtration as a pre-treatment for slow sand filtration of canal water with highly variable feed water turbidity

2017 ◽  
Vol 79 ◽  
pp. 221-227
Author(s):  
Mohammad Yassin ◽  
Nidal Mahmoud ◽  
Kebreab Ghebremichael ◽  
Branislav Petrusevski
Keyword(s):  
Feed Water ◽  
Sand Filtration ◽  
Canal Water ◽  
Water Turbidity ◽  
Slow Sand Filtration ◽  
Pre Treatment

The Removal of Selenium from Water by Slow Sand Filtration

1992 ◽  
Vol 26 (9-11) ◽  
pp. 2137-2140 ◽  
Author(s):  
P. L. Carlo ◽  
L. P. Owens ◽  
G. P. Hanna ◽  
K. E. Longley
Keyword(s):  
Loading Rate ◽  
Feed Solution ◽  
Drainage Water ◽  
Elemental Selenium ◽  
Sand Filtration ◽  
Sand Filters ◽  
Slow Sand Filtration ◽  
Hydraulic Loading Rate ◽  
Selenium Removal ◽  
Removal Efficiencies

The feasibility of selenium removal from drainage water by slow sand filtration (SSF) was investigated. Two anaerobic laboratory-scale slow sand filters, operated in parallel, received synthetic feed solution. Selenate reduction and subsequent selenium removal were monitored during five experimental filtrations. The results suggest that selenium removal occurred by the dissimilatory reduction of selenate to elemental selenium. This reduction was independent of sulfate. Selenium removal efficiencies were governed by the hydraulic loading rate (HLR).

Performance comparison of a pilot-scale membrane bioreactor and a full-scale sequencing batch reactor with sand filtration: treatment of low strength wastewater from a northern Canadian Aboriginal Community

2005 ◽  
Vol 51 (6-7) ◽  
pp. 483-490
Author(s):  
K. Frederickson ◽  
N. Cicek
Keyword(s):  
Wastewater Treatment ◽  
Membrane Bioreactor ◽  
Cold Water ◽  
Batch Reactor ◽  
Pilot Scale ◽  
Performance Comparison ◽  
Batch Reactors ◽  
Sand Filtration ◽  
Sand Filters ◽  
Aboriginal Communities

Northern Aboriginal communities in Canada suffer from poor wastewater treatment. Treatment systems on 75% of Manitoban Aboriginal communities produce substandard effluent despite the presence of sophisticated treatment systems. A 200-litre, pilot-scale membrane bioreactor (MBR) was established on the Opaskwayak Cree Nation to investigate the feasibility of MBRs in mitigating Aboriginal wastewater treatment issues. The pilot system was remote controlled and monitored via the Internet using the program pcAnywhere. The community utilized two existing sequencing batch reactors (SBR) and three sand filters for wastewater treatment. The community wastewater was relatively weak and highly fluctuating which led to poorly settling sludge that readily fouled the sand filters. A comparison study between the MBR and SBR was undertaken from September to December 2003. Operated at a 10-hour hydraulic retention time and 20-day solids residence time, the MBR outperformed the SBR and sand filtration on BOD and suspended solids removal. Furthermore, the MBR showed high levels of nitrification despite relatively cold water temperatures.

Removal of microbes from municipal wastewater effluent by rapid sand filtration and subsequent UV irradiation

2003 ◽  
Vol 47 (3) ◽  
pp. 157-162 ◽  
Author(s):  
R.L. Rajala ◽  
M. Pulkkanen ◽  
M. Pessi ◽  
H. Heinonen-Tanski
Keyword(s):  
Uv Irradiation ◽  
Suspended Solids ◽  
Municipal Wastewater ◽  
Water Source ◽  
Pilot Scale ◽  
Wastewater Effluent ◽  
Sand Filtration ◽  
Pre Treatment ◽  
Uv Transmittance ◽  
Rapid Sand Filtration

The elimination of wastewater microbes is often necessary when effluent receiving waters are reused for different purposes e.g. for irrigation or as a raw water source of drinking water. In the present study, rapid sand filtration (SF) combined with the use of polyaluminium chloride coagulation was used as a pre-treatment to improve the quality of wastewater effluent before further treatment with UV irradiation. Pilot-scale experiments were run in four treatment plants in Finland. Treatment performance was followed by measuring physical and microbial parameters. Rapid sand filtration reduced suspended solids, turbidity and colour of effluents by about 90%, 70-80% and 20-50% respectively. It also improved the UV transmittance of water by up to 20%. Microbes and phosphorus were reduced by 90-99% and to 0.05 mg/L respectively. UV irradiation further reduced the number of microbes up to 99.9%. The efficiency of UV doses in pilot UV reactors was confirmed with collimated-beam device determinations and with added FRNA phages. More than 99.9% reduction of MS2 was achieved with the dose of 140mWs/cm2 in pilot UV reactors. Rapid sand filtration and the subsequent UV irradiation reduced the number of all the tested microbes to a low level, often below the detection limit. Suspended solids and the water turbidity were reduced to 1-2 mg/L and ~1 NTU respectively.

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