Published by Ashish Yadav, Assistant Director at Ministry of Defence, India
Hello Everyone,
Suggestions are invited on replacement of sand media with AFM in Rapid Sand filter. We are facing problems of Rapid Sand filter clogging, mud ball formation, and turbid water after filtration.
Hello
The filter clogging is due to the formation of mud balls in that case, which increases the pressure on the filter that's what cause a salting-out of the particles previously retained on the filter which will rise the turbidity after filtration.
That turbidity after filtration could be also due to a bad backwach of the filter or a saturation of the media if it has been used for a long time.
And also if there is no pretreatment i think that coagulation floculation followed by a decantation could be a solution to reduce the mud ball formation and consequently a less rapid clogging of the filter which lead at the end to a good quality after filtration in terms of turbidity.
Published by Racha Bouchenak khelladi
Pre-chlorination !
I had the problem of mud ball formation filtering water coming from one artificial reservoir preliminary treated in one DAF plant for algae removal.
The filter is double layer anthracite plus sand.
The problem was solved increasing the air+water backwash and decreasing the polymer dosage in the DAF.
The high turbidity in the treated water is symptom of some preferential way in the filter probably related with low backwash efficiency.
Also the quick clogging can be related with low backwash efficiency but also with the filter solid loading, incorrect sand size and suspended solid characteristic.
You can try to follow the suggestions of Mr Derek French and to do some pilot plant test(always the best way to follow) as suggested by Mr Coronado.
Published by Vincenzo Scarlata
Turbidity of feed water plays a very important role in filtration. If Turbidity is more then Head loss increases & needs frequent back washing.
Type of turbidity also plays an important role. Compressible particle reduces filtration rate
Mud ball formation is a typical phenomenon associated with amount and characteristics of turbidity.
Please improve the turbidity removal in sedimentation tank
Rajendrakumar V Saraf
Published by Rajendrakumar Saraf
I suggest you;
Published by Vithana Gamage Upali Ranjith
Ashish, we use AFM with excellent results. So we know the product. If you want to contact me direct send an email to dougJim Solari Doug
Published by Doug Fletcher, Solari Energy Pty Ltd - Owner CEO
Need higher Pre-Chlorination dosage.
Is there any pretreatment process prior to sand filtration? What quantity of solids are being removed e.g. TSS & Turbidity? There is not enough information to provide. Is this water for drinking, RO feed, boiler use etc????
Published by Karen Baker, Managing Director at Waterdoc Limited
I agree with Michael Chipps, Amirtharajah's does conclude that a sub fluidized backwash with air is the best way to backwash a filter. The difficulty is that the media will be highly fluidized and may backwash out of a pressure vessel (not sure if this is gravity filter or pressure vessel). Air scour prior to backwash will help, if you don't have it you may need to install it. Simply changing the media will not solve the problem Media that is backwashed without an air scour cycle does not change size or change shape, be definition "fluidization" in water only means the filter grains don't touch during backwash. You need to make sure you getting full fluidization (use ~30% expansion as a guideline) and make sure your backwash is long enough. Pull grabs from the backwash waste and backwash until the waste effluent is < 50 ntu (closer to 25 would be better) and this will tell you if your backwash is long enough.
Published by Derek French, Wateropolis Inc. - Founder
Hello Ashish Yadav,
we can provide you with a hard coal, which has excellent filtration characteristics and also adsorption characteristics. This coal has a BET-surface of 500 m²/cm. With a sandfilter you have a surface filtration. Due to the granulation of our material, you have a deep bed filtration instead. Allowing you to increase the lifetime of the filtration process as well as the amount of solids and suspended particles. Furthermore we could investigate, whether an ultrafiltration might lead to a better process or might be required. We will need more data to give you an excellent solution for the problems you are facing.
Should you be intrested, just let me know and I am pleased to help you in this matter.
Kind regards,
Jan-Peter Kiel
Published by Jan-Peter Kiel, Owner and managing director at FLUIDTEC Flüssigkeitstechnologie
the candles we do does the job of sand filter and much more, compact, nanoclay candles see www.watsan.in. Zero maintenance, zero water wastage and zero electricity
Published by Chandrasekaran J., Founder Director at Watsan Envirotech private Limited
Hi Ashish,
I suggest you;
(1). Test/analyze your turbid treated water to ascertain the contaminant responsible for the turbidity and then target that in your filter packing/recharge.
(2). Check if your sand is very smooth, then use fine grade on coarse grade after your under-drain gravel, at the bottom.
(3). The analysis of the "turbid treated water" will indicate if you need to include activated carbon, ion exchange resins, etc in your recharge.
(4). Control your backwash flow rate, it is not too good to be very high or very low.
(5). A good filter packing/recharge and on-time/proper backwashing will solve the clogging problems.
Regards.
Justin (MACJAMES - www.macjamesglobal.com)
Pl. try filter cartridges with PVC spools wound by cotton if the flow is low for higher flows ' Sandex Filters" are best" In case of turbidity Pl. get them inspected and maintained as per schedule.
Published by MUHAMMAD ILYAS KHAN, DGM, Manager (Purification), Director New Ventures at (BST). at SSGC, PPL & BST
I think it's a backwash problem. Did your backwash steps include air+water? Or only air and then water?
Published by Eneko Suaga Baeza, Técnico de tratamiento de aguas y Puesta en Marcha
Air followed by water
Published by Ashish Yadav, Assistant Director at Ministry of Defence, India
Please let me know difference in effects of both .
Published by ABHAYANKER BANERJEE
Apparently you used silicate sand.
General advices:
1. Replace silicate sand on activated glass.
2. Use two fractions of activated glass (large and small)
3. Provide back-washing washing of the glass with water. At the same time, the glass is recharged
4. Observe the recommended work criteria.
Published by Vitalijus Gediminas
is it possible to carry out a primary filtration prior to the sand filters? C
Published by Craig Rothleitner, Director at Urban Stormwater Technologies Pty Ltd
As per the available facility, primary filtration is not an option
Published by Ashish Yadav, Assistant Director at Ministry of Defence, India
is it possible to carry out a primary filtration prior to the sand filters? C
Published by Craig Rothleitner, Director at Urban Stormwater Technologies Pty Ltd
I hate to be the one to tell you. But you actually have 2 problems. First you are using sand and mechanical filters. You may be partially cleaning the water but the residue will be in concentrate and be dumped somewhere. Searching for a process that augments a failed way of doing things makes no sense. Most of which you speak was 1950,s technology. Since the late 70's microbial cleaning of waste and waste water is the preferred method and at 1% of the old technology's cost. The major benefits are: all waste is reduced into its elemental/nutritional form, there is zero residue to flush into rivers to the ocean, 40 years of monthly testing's had no pathogens, chlorine is no longer needed, all heavy metals are chelated into their elemental form. Lastly and most important the cleaned water is potable. Not the answer you were looking for. But best solutions need to be at the top of your options list. G'day mate.
Published by Guy McGowen, President/CEO/Chief Science Officer
From experience of a project where this was tried it won't do any good for improving the problems that you describe. You would be far better advised to address the issues causing this which are likely to be inadequate air scour or backwashing, possibly poor distribution of air and backwash. I wouldn't go much on their claims of removing specific substances either. Converting to a combined air scour and backwash would be more likely to work.
Published by Steve Oxtoby, Process Engineer
As granular media is backwashed repeatedly it 'tumbles' and loses its sharp edges, essentially going off-spec. Then media starts getting washed out and there is less in place, accelerating the problems. Inspect the grains using microscope or magnifying glass. If they are rounded off you could have a sieve-size test conducted to verify but if it has been in service for several years just replace it. I suggest replacing it all at once not adding-to. Assuming the ongoing operations include monitor and adjust backwash rate and duration, carefully control coagulant dose and regularly look for underdrain problems.
Published by Bob Foerster, Executive Director at Nevada Rural Water Association
Media is certainly old. It was commissioned in 1992. Thereafter, many a times media has been added but just to compensate the loss during backwash. Replacing all at once looks like a solution here. Thanks!
Published by Ashish Yadav, Assistant Director at Ministry of Defence, India