A huge problem is reported at water filtration plant as sand filters are clogging/choking every 4-6 hours. Backwashing the filters multiple times per day is harming water treatment efficiency. Can anyone suggest a solution?
Where is the feed coming from? I'd assume suspended solids content is very high, if so why?
Dear Rajamohan,
Is this a conventional treatment plant preceded by coagulation and clarification or direct filtration?
If it is a conventional plant, check NTU of settled water. If it is greater than 1.5 or 2 NTU, coagulation is the problem causing solids carry-over or loss of blanket in a solids contact clarifier. Conduct jar tests and check chemical dosing pumps for over or under dosing.
If plant is direct filtration, check that raw water turbidity and colour are in normal range.
Check coagulant pumps particularly the polyelectrolyte dosing rate.
Check that the backwash protocol is correct, particularly the air scour.
If above fails to provide an answer, reduce raw water pumping rate and impose water restrictions.
Good Luck
Michael Lever
Hi,
More information is required. Anyway consider a dual media with anthracite.
May be that you have superficial clogging, that is the suspended solids accumulate in the surface of the sand not in overall deep of the sand. This can be corrected with bigger size of sand or again with dual media: coarse anthracite at the top and sand in down layer.
Regards from Spain.
Dear Rajamohan Natarajan
Before giving suggestions I need more details.
1. Filter dimension and flow rate. 2. What is supposed to be purified by the filter. Please give an example of water composition before and after filtration. 3.What is your estimated capacity in cubic meters.
Shlomo Nir.
Dear Natarajan,
We need to know the source of the incoming water. Do you have sedimentation tanks before filter? First of all, if there are particles that can settle in a certain time in the inlet water you mentioned, you should settle them with a sedimentation test (May be they can settle in 30-40 mins). If this is not the case, I think, you can use a plankton net before the sand filter and the pore size of net should be smaller than the diameter of particles in the inlet water. I think this way will be cheaper and more environmentally friendly than a coagulation process. Because you can clean the plankton net easily. Maybe this method might work. You can find a lot of plankton net type and marketing firm in internet. Please test and use a little part of plankton net for a small amount of inlet water before full scale study and inform me about results if possible.
Kind Regards.
- Its waste water recycling or surface water treatment ,Bore well water treatment,In upstream of filter what is the process please clarify and what is the flow of water and tell me the filter size which you use .
I think you need to check suspended solids and turbidity in your raw water. If turbidity is more than 5 NTU and you are using direct filtration than coagulant dose must be revisited otherwise you may need to add tubesettler or any form of settling before filtration. Good luck!
It sounds like you may only be utilizing the top portion of your filter media. If the particulate close packs at or near the filter surface, then it will quickly blind the top portion of the media and trigger a washing. Assuming: 1) influent loading is appropriate with single digit NTU, 2) water flow and filter are sized properly and 3) the media is not tightly packed, you may need adjust your influent's particle size distribution with a filter aid coagulant. Try ca. 0.5 ppm of a polyDADMAC or 0.25 ppm of an Epi-DMA; never add a polyacrylamide flocculant a media filter. Also check if you can crudely replicate the problem with a tabletop size filter using the same media configuration. Hopefully this will get you back to >97% efficiency.
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