To get 500 TDS

[BinGhanem]

Hi guys,

I'm new here and basically new to RO businesses, we just started an RO plant to distribute water by trucks (5000g and 1000g) to industrial uses and I do have a question in mixing water to get a certain TDS.


My R/O produce water around 150 TDS so an engineer proposed since we need something around 500 TDS to mix the water we produce with the raw water to save on energy and costs. Our raw water is around 6000 TDS which is high.

the picture bellow shows the current setup that been proposed, to mix the produced water with raw water to have something around 500 TDS.

Any idea how to know if we reached to that 500 TDS without keep checking the TDS every second? any other suggestion for this ?

any help going to be very useful.

 

[IRstuff]

No picture found, but that could be my firewall.

Since this is not a static condition, you will need to be measuring TDS continuously, BUT you should check to see what conditions are imposed on the specification itself, i.e., over what time frame is the TDS spec valid? Can you have spikes that are higher, provided they are _____ duration?

TTFN
faq731-376

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[itsmoked]

Agree you do need to continuously check the result or you're going to regret ever mixing.

As for mixing the raw water I suggest you NOT do that but instead mix water that has been prefiltered. Usually you have to prefilter before admitting the water to the RO membranes. That's a sediment filter followed by a carbon-block filter. That water is often about half the TDS of the raw water. It also has been 'filtered' so nothing 'big' is going to accidentally show up in a customer system, like a rock or chunk of iron or sediment. It also means you can probably mix twice the filtered water water into the RO water to stretch your savings.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[bimr]

A mass balance shows that raw water can make up 6% of the finished water.

The simple method is to work on a batch basis. Once the storage tank (or tanker truck) is 94% full of RO water, add raw water to the storage tank using a totalizing meter to monitor the raw volume.

Another method is to install a flow meter on the RO water tank discharge and use the flow meter output (4-20ma) to control injection of the raw water. You can use a metering pump with 4-20ma input to inject the water.

 

[77JQX]

If your source water chemistry is stable, monitor conductivity as a proxy for TDS.