Particles Detection in Salt Water

Yupp! Use your eyes! KISS principle!

There is people on the boat right?

Further to the cats view of things:

What routing for the water/particle flow is available? What impact was there when there is silt being thrown overboard? Can you even dump it over board?

Are you running the stream over some screens to capture larger particles and sand separate from the water?

Last but not least could you not have an overflow in your tank to get rid of the excess water? Particles would at some point settle in the tank and water "swims up" simply runs back to where it came from.

Seems to me a simple photometer or spectrometer and steady light source is what you need.

Talk to the people at Ocean Optics. They've specialized in optical spectroscopy of ocean water and have expanded their product line into other types of spectroscopy. Some of their equipment in on the latest Mars rover. I'd bet they can set up a system for you that can run off a laptop and give you the info you need. (And their equipment is reasonably priced.) Here's a link to their website:

Ocean Optics

There's another possible way...not too expensive either.

There are fish finders that not only map the bottom contours, but they record depth measurements and GPS coordinates as well. You could use a smaller boat to create a map of areas that need to be suctioned, (including exact depth data), and plug that data into the navigation and suction systems aboard the dredge.

Or better yet, a software package that does it all:

http://www.sciencegl.com/dredge/dredging.htm

kramarat,

Excellent intelligent idea. Fish finder is an ultrasonic scanner and it can do depth mapping of all types of material and surfaces. As there is water in the interfaces, all gaps are removed and hence one can get good signal from reflections.

There are these very important information one can get

Depth of the sea bottom from boat / ship heel

Thickness of the debris and its actual picture of spread over the surface

Warning if there are rocks that may hit your cleaning equipments or boat like Titanic disaster.

Shyam

Any dredging I've seen their not worried about fines suspended in the water. They just let it over flow letting the solids settle out in the vessel. Which is usually a large barge. How big is this tank?

Turbidity measure can go from suspended particle that can't be seen to suspended particle that can't be seen through. Even with water that has turbidity that can't be send through the amount of solids would be very little once they settle out.

One avenue of approach is to weigh it if possible. Any appreciable solids(sand& mud) would cause a weight increase in the line.

Have you considered a reusable filter in-line with the suction side of your pump ? or a centrifugator that captures solids in the outermost diameter of the rotating chamber ?. Both options would let you discharge the clean water back to the estuary.

Simple principle of a turbidity measurement.

Water to be tested is placed in a transparent container & light is allowed from source to pass through the liquid sample. Higher the clarity of water, lesser the turbidity.more light passed through the sample indicates low turbidity.

What best can be done, is the simulation of the cross sectional vertical disposition of the estuary, in a glass jar by artificial means based on the total depth. One can simulate a proportional vertical configuration of the estuary based on average depth, various levels of clear water, progressive turbidity down wards & bottom soft muddy shallow bottom. If one pass NTU meter light rays through various depth values of the jar, the muddy high turbidity regional values can be plotted. One can fix up this range for instrumental values [ say NTU - Neplometric Turbidity Units ], the muddy regional turbidity values can be pre set for switching on the clearing pump after sensing it.

Accordingly a turbidity sensor connected to the foot valve of the flexible immersion hose, will send signals to the data base & in case of shallow muddy region reached the limit sensor can activate the suction pump switch.

In a similar fashion the sensor will also switch off the pump, when all mud is cleared, resulting in low turbidity clear water, so that one can proceed to the next spot.

It is a matter of application. Take jar test trials with Turbidity meter &,get convinced for your self about the concept & try further.

I like the overflowing barge plan. I expect that is what other channel dredgers use when they can't pipe the spoils away. You already have all the necessary equipment, all you need to do is have enough flotation under the spoils tank so it can overflow without sinking the barge.

Two suggestions

Crude method with no additional equipment needed. The pump will draw more current when pumping a slurry rather than salt water. Mark a line on the glass face of the pump motor ammeter. Needle above the line, pumping silt, below the line pumping water.

More accurate method requiring calibrated equipment. Direct the water through a V type weir fitted with a height detector followed by an impact type weigh scale. The weir detects the exact amount of water/silt being pumped and the weigh head detects it's weight. Feed both readings into a computer and calculate the bulk density. Pre-set a threshold to trigger an alarm if the bulk density drops. With standard commercial equipment you should be able to achieve an accuracy of + 1%