Air absorption at the sampling valve for reverse osmosis effluent
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Hello everyone. While washing the membrane at the water treatment station, I opened the product water sampling valve only to find that no water flowed out. Our sampling valve is connected to the product water side via an air supply connector; after removing the sampling valve, there was suction at the air supply connector. The operating conditions are: inlet water pressure of 0.85 MPa, concentrated water pressure of 0.75 MPa; both the concentrated water and the produced water are discharged into the drain, and all valves in the inlet tank are closed
The description isn’t very clear; is the produced water also discharged into the drain? It is best to take water production samples at the upward-flowing section of the vertical pipe or in the horizontal pipe section; sampling at the downward-flowing section of the vertical pipe will result in failure to obtain samples, a situation similar to that of a jet pump.
The reverse osmosis membrane module has a bypass for discharging water from the product water pipe in order to prevent pressure buildup; there is an explosion-proof membrane on this bypass, and it’s necessary to check whether that membrane has been damaged, as water is discharged through the bypass into the gutter. This results in negative pressure at the sampling valve of the product water pipe. I have encountered such situations before; I’m not sure what the structure of your reverse osmosis module is like
Are there any pictures? Let’s take a look at the scene first and then analyze it?
Is this a sample of a single membrane, or a sample of the total produced water?
It is likely that the outlet of your water discharge pipe is below the membrane module; once the feed pump stops, the liquid in the system flows out due to the siphon effect, resulting in a negative pressure in the system.