Conductivity 3

[tomb7us]

Hello,

I have a question that ive been pondering. How does sugars and fats influence conductivity in water. Basically we have a process here where we run 30% solids milk through an evaporator and separate the milk and water to 60% solids.

What happens is we have carryover of milk into the water exit stream (cow water). Right now we have been measuring conductivity, and pH to get a basis of water quality and the conductivity ranges was 15-20 (micro Siemens i think is the units) down to 2-8 with a separator pressure change. But how does sugar and milk influence your readings on conductivity (we run sweetened milk through the evaporator).

Second is conductivity a good measure to use for water quality given what we are separating (we are trying to clean up the water to use it elsewhere since the milk causes build up and slime later on).

We just sent samples to be measured for turbidity and im trying to swing corporate to buy a hand held.

 

[Unotec]

If I am not mistaken, based on temperature, fats and sugars will only affect conductivity by solubility. Fats will decrease conductivity if they get dissolved; same thing with sugars although these will dissolve much easier. I might be wrong, but I recall doing something like this in school.

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[Compositepro]

Sugars are non-ionic and therefore non-conductive. Milk fats are emulsions - meaning that they are actually microscopic particles in the water. The fats are not dissolved. That is why milk is white. The particles scatter light. Conductivity would not be a good measurement unless there is a correlation between these ingredients and electrolytes (which are conductive) in the milk. But raw water probably has about the same conuctivity.

 

[hacksaw]

Food science is complex field, but milk definitely contains electrolytes and hardley non-conductive. The non-conductive proteins and fats play a role too. Ultimately you need your own lab testing to characterize the correlations valid for your stream.

mineral content of fresh milk is given below:

MineralContent per litre
----------------------------------
Sodium (mg)350-900
Potassium (mg)1100-1700
Chloride (mg)900-1100
Calcium (mg)1100-1300
Magnesium (mg)90-140
Phosphorus (mg)900-1000
Iron (ug)300-600
Zinc (ug)2000-6000
Copper (ug)100-600
Manganese (ug)20-50
Iodine (ug)260
Fluoride (ug)30-220
Selenium (ug)5-67
Cobalt (ug)0.5-1.3
Chromium (ug)8-13
Molybdenum (ug)18-120
Nickel (ug)0-50
Silicon (ug)750-7000
Vanadium (ug)tr-310
Tin (ug)40-500
Arsenic (ug)20-60

 

[tomb7us]

Maybe i need to clarify. The conductivity measurement we are taking is of the waste stream (cowwater) which i think is basically DI water with tiny amounts of milk/sugars still in it. The water is basically clear, yet you can still smell milk.

What would be the best way to test our water for general cleanliness? Turbidity?

 

[tomb7us]

Also, what is the differnce between an NTU and FTU for turbidity, are they not the same thing? I see references to NTU/FTU being the same and some that arenot. Our turbidity measurments are below 10 NTU's

 

[cheute79]

Wastewater is a rather complex thing, since it varies from process to process and even day to day. It should be possible to use conductivity, but is probably not practical. Why? Consider: Is the milk really uniform in fat content, the assay of micro-nutrients and trace minerals (my guess is that it varies by what field the grain and grass were grown on, the age of the feed, how recent and intense the rains have been, etc.)

Turbidity might be a reasonable method, and should be more feasible than conductivity, but again, turbidity will be impacted by the fat content and minerals that could change the surface tension (which in turn will impact droplet size of the suspension). I suggest turbidity might be the way to go, but it may very well take some months of data to get control information. With a typical of <10 NTU, and "hand held" might not get you the repeatability you need, either.

RE NTU and FTU, this is probably more a function of the calibration standard you use. The actual methods and standards are somewhat different, but almost all that I have seen in the last 20 years has been in NTUs. Some of the FTUs reported are hold-overs from the old days.