Polymer dose / Ratio to flow.

[KWTPOP]

I am looking for information on polymer and if dosing works as a ratio or if more is not better. We don't have a jar tester available but know that 5 gph of polymer @ 600 gpm works great but we raised the flow to 1000 gpm. Would by using a simple ratio be a way of calculating a new dosage or polymer doesn't work that way. Are there any good books or links relating to polymer dosing and characteristics?

 

[ver101]

KWTPOP;

The 5 GPH is meaningless without the concentration of your polymer solution. Do you know the % concentration of your polymer solution? Usually, the dosage is based on ppm as 100% strength and then diluted to whatever concentration that best suit your application. Polymer usually (but not all) are available in powder form (100%) then dissolved in clean water to .5 to 5% concentration (depending on your dosing equipment set up) for better dispersion.

If you can provide the weight of the powdered polymer you are dissolving in each batch and the volume of your polymer tank,I can calculate the solution concentration that you are using and from there we can calculate the dosage required for your specific application.

Regards,

Ver101

 

[mflam]

As ver101 says, there are a number of ways to optimize polymer dose.
My first question would be, when the flow was increased, was the polymer accomplishing what it is supposed to? If so, leave it alone (not broke, don't fix, etc) You may have noticed some degradation in performance. You could ratio up the dose, as you suggested, but some simple testing could save you a lot of money.
Polymer manufacturer reps can be very helpful. Check with your supplier, or competitors.

 

[KWTPOP]

We are using liquid polymer(Magnafloc E40)with a weight of 0.016. The plant I work for is not going to spend the money for a huge amount of testing. The plant has never ran at that flow so I can't look at back notes. We pump about 820,000gpd. We get a good sludge blanket. This also may be an alum problem. When we cut back on the alum to keep under state regulations we get more pinpoint floc. Too many conflicting answers from people running the plant.

 

[semo]

If your polymer dose was close to optimum at the lower rate, you will have to feed more (GPH) at the higher rate just to maintain the same dosage (PPM).

Let me add that the higher flow rate will increase the upflow rate of your clarifier and the sludge blanket you had before will rise with lighter pieces of floc being carried over your weirs.

Your pH can also have a dramatic affect on the treatment. You don't mention your application (iron/manganese, surface water, etc.) or your water analysis.

Jar testing will get you in the ballpark range for dosage, then you will end up tweaking it for optimum performance. I'm sure the polymer reps can help with the jar tests if you call them.

 

[KWTPOP]

Hi semo. Ground water is our source and and our coaggulation, flocculation and sedimentation all take place in one tank. In addition, our filter backwash pumps feed back into the clarifier. pH is about 7.0-7.2. One person said it should be lower, the previous operator said it should be in the high 7's.

 

[semo]

Are you trying to remove iron/manganese from the groundwater?

Assuming you are, the pH will need to be at least in the upper 7's. I've got several plants where 7.6 to 7.8 is working fine. The iron will drop right out of solution when it gets above 8; but, depending on your chemicals, maintaining this high of a pH can get expensive.

Jar testing is typically done with different polymers at different dosages over a range of pH's to see what works best. Your polymer might work well at a lower pH or it might not. When the jar test is performed you will see what works best.

I personally don't like to return filter backwash to the head of the plant; but, it shouldn't be a large problem if you are returning it at a slow rate.

As I stated however, at the higher plant flows, the sludge blanket will expand causing the lighter flocs to overflow the weirs and your filter run times might decrease. You will see a different water in the clarifiers.

 

[KWTPOP]

We remove most of the iron and manganese through aeration. The clarifier settles out the remaining iron. The backwash feeds back into the clarifier at about 200gpm, but that only runs for about four hours a day. Running a higher alum % really helps but causes us to go over our limit.

 

[semo]

What the aeration does is break the iron out of solution. Then the clarifier allows the iron to flocculate and settle with the assistance of chemicals.

Ten States Standards only allows the backwash return to come back to the head of the plant at 10% of the plant flow. 200 gpm return with a 600 gpm flow seems awful high.

I'm lost now, If you're feeding a polymer I don't understand the alum. It's typically used as a flocculant too and if you use the right polymer, you probably don't need the alum.

You really need to look at the raw water quality to see what needs to be performed so you know what chemicals to feed and then perform some jar tests to check the dosages.

 

[KWTPOP]

We have always run both since the plant was built in the late 70's. We just switched to magnafloc e40 from zeta-lyte 1a polymer after having our water jar tested. I never thought about running without alum, but I am definitely thinking about suggesting it. We are running 1000gpm now not 600gpm. Would you need a higher pH running just the polymer? We adjust our pH with hydrated lime.

 

[semo]

Not necessarily. Different polymers will require different water characteristics; but, alum typically lowers the pH of the water. You can have your polymer rep run tests with and without alum to see what works best.

With the results you can estimate the chemical costs and modify your treatment for optimum quality and cost.

My main point is that you will have to do some jar tests to see what works best. The 1000 gpm only means you have have a higher upflow through your clarifiers, and loading on your aerator and filters. If they are sized for this, you should have no problem treating the water, it will just change the water quality in the treatment stages.

 

[ivanhoe374]

Just grab some jars and do some yourself