Arvind

  Your approach would depend on the size of the pond and the amount of silt you need to extract.  If the pond is small you can first suspend the silt by using water or air pump flows to generate sufficient agitation to stir and suspend a fine silt.  If successful the silty water could be pumped from the pond and allowed to sit and settle in an appropriately sized baker type storage tank. After sitting the clarified supernatant can then be carefully pumped and returned to the pond. The settled silt residues can then be scraped from the tank and disposed.  A dual tank or holding reservoir can be effective for these types of operation. The cycle can be repeated until silt is satisfactorily cleared.  

Direct filtration of silt is unlikely to work because of its clay like properties.  If the pond is accessible you can also try to remove the silt by use of heavy machinery such as a backhoe. 

Best of Luck

Steve

Suction dredges are often used for this, there are various sizes of dredges, various ways to float them on boat, barge and ways to raise and lower.  Some have sediment cutters and various size screens to limit particles too large for removal, to avoid clogging of pipe.  Dredged marerial often needs dewatering area or piles as waste disposal or removal sites when dewatered.  Fine silts are difficult to settle, but you can estimate how quick sedimnts will settle by putting sample in glass column, dispersing sediment and then testing the specific gravity of solution with floating gaduated testor (forgot name) that measures loss in specific gravity of solution as particles settle, and gives an idea of how long it takes to settle particles so they might be removed.  A miner of gold or aggregate materials may be able to give you some advice.  If the ponds can be drained and materials reached by backhoe, that might be least cost, but if you have silt materials, dewatering to the extent that removal can occur may take some time.  

If you are trying to remove the silt (or silt and clay size particles) from the liquid portion of the pond area, a hydrometer test (ASTM D 422) would be a good place to start. You would need to determine the best way to obtain a representative sample of the material you are trying to remove.  The ASTM D 422 procedure is intended for soil/mineral based material, but your silt could be from another source. You need to consider the specific gravity of the material you are trying to remove, and perhaps the specific gravity of the liquid. 

If you are trying to remove the "silt" material that has settled to the bottom of a pond, suction dredges or dewatering the pond may be your only option. The wastewater industry commonly constructs nearby sand dewatering/drying beds with effluent drains under the sand layer. Depending on the nature of the material to be dewatered, drying can take a long time. If you can drain the pond, or a portion of the pond, for a few days, the remaining wet material could be moved to a dewatering/drying bed. The thickness of the material placed on the bed will depend on the material properties and cycle time required for removal. If you are in a very wet climate, you may need to control precipitation water on the drying bed with a temporary tent or similar cover. You could a construct small scale test bed to see how effective and efficient a dewatering/drying bed would be. When the removed material is dry, construction equipment can be used to remove the silt, where it can be moved to an appropriate disposal facility.  

It depends not only depth but indeed on overall size/dimension of pond. If it is a small one better to use some indegenious technique. may think of using a mesh made of plastic or other ropes or even wire. Drag a fine mesh dipping net across the bottom and lift the silt out. Check the net for cracks or other weakness/defects. you can get pull the net/mesh with tractor or farm animals too. this is just a crude idea may work or may not..

Dear Arvind, why do you want to remove the silt from pond? There is no treatment before the effluents are discharged in the pond? It is a stabilization pond (maturation pond?) with a great area of implantation? What do you mean with domestic water and effluents? The sewer system is combined and the pond receive storm water? Is the pond permeable or impermeable? What is the area of the pond? What is the quantity and characteristics of the silt that you want to remove? Can you clarify?

With respect to wastewater stabilization ponds, see the links below. An excerpt of the first link:

“Operation & Maintenance

Scum that builds up on the pond surface should be regularly removed. Aquatic plants (macrophytes) that are present in the pond should also be removed as they may provide a breeding habitat for mosquitoes and prevent light from penetrating the water column. The anaerobic pond must be desludged approximately once every 2 to 5 years, when the accumulated solids reach one third of the pond volume. For facultative ponds sludge removal is even rarer and maturation ponds hardly ever need desludging. Sludge can be removed by using a raft-mounted sludge pump, a mechanical scraper at the bottom of the pond or by draining and dewatering the pond and removing the sludge with a front-end loader.”

http://akvopedia.org/wiki/Waste_Stabilization_Pond

http://www.eolss.net/Sample-Chapters/C07/E6-144-12.pdf

Thanks a lot

António Manuel

Just excellent innovative thought provoking words with good sense of physics involved therein.  I got enriched in terms of knowledge on this vital entity of real rainwater harvesting..the ultimate key of success in prevailing climate change and social change schenereo. 

Thanks Dear Gaur for your compliments. However wastewater stabilization ponds are a well-known technique for biological treatment since a long time ago, where the processes of treatment that occur are not only physical as also and mainly biochemical. As far as I know stabilization ponds are not used for harvesting rainwater, at least frequently. So surely that your two answers are much more inventive and innovative than mine.

See the Wikipedia link below for more information. An excerpt: “Stabilization ponds (also called lagoons or waste stabilization ponds) use a natural process for wastewater treatment that employs a combination of macrophytic plants, substrates and microorganisms in a more or less artificial pond to treat wastewater. The technique is frequently used to treat municipal wastewater, industrial effluent, municipal run-off or stormwater. After treatment, the effluent may be returned to surface water or reused as irrigation water (or reclaimed water) if the effluent quality is high enough.

Stabilization ponds are commonly used for wastewater treatment in developing countries. Types of treatment ponds include settling basin, anaerobic lagoons, facultative pond and aerated lagoons.”

https://en.wikipedia.org/wiki/Stabilization_pond

Yes..Antonio.. you are absolutely correct and I fully agree with you that sole purpose of stabilization ponds is wastewater treatment/control.

I have two quotes which may not be so accurate and relevant here, but still like to share..

1. wastewater, wasteland, waste air, waste vegetation , waste food etc etc  are very common words to express the emerging issues in their respective regards....

2, can we call them wasted water, wasted land and so on......we have made them wasted owing to some deficiencies in terms of plan, management, application or other stages at initial input levels.

3. Now if they are wasted , can not we go for recover these wasted entities. Say water is wasted in many forms of parcels. one example is what you have very rightly said the stabilization ponds..another one may be prism storages or seasonal flood storages inside natural streams or even on adjacent overland planes. Can we look it from that perspective, and let us take this loss/waste  as an opportunity to  systematically plant its storage to act as stabilization ponds / series of ponds and then one step ahead lets get recycle the harvested waste water for some productive reutility   atleast for quality ground water recharge to add upon in our thirsty acquifers...

thanks for nice gestures shown on my tiny casual comments

Please share me the best answer might you get...