Pond Boss Forums INTRO Questions & Observations Does water temp affect Alum??

I have a new 6 acre pond. After building I used 1 ton alum and 1/2 ton quick lime for a clarity of almost 28 inches. Then we got 5 inch rain that broke through the silt fences and undid all our good work and the clarity dropped to 8". Today we put in another 1ton alum and 1/2 T lime but the water clarity didn't change from the 8". The air temp was 40-50 degrees, I do not know the water temp. The alum has been stored under a tent for 5 months. There were a few chunks but mostly power. We mixed it like before in a 100gal tank before spraying. It was harder to get it in suspension. Does the water temp render it inactive or does it get old??
Thanks for any and all advice
Wayne
Charlotte NC

No Wayne, it is unaffected by water temperatures...Witout knowing the acre feet of water in a 6 acre pond, 2000 pounds of alum is likely a quarter or less than the amount needed...If you don't clear ALL solids and colloidal clay, you are wasting both time and money by treating it at all.

We put another 42 bags in today and 1,000 lb quick lime
The clarity increased from 8 inches to 10 inches.
They won't have more in stock until next week. Does it hurt to not put it in at one time??
Also is it important to use a outboard motor to stir the water.
We only have an electic motor on the pontoon boat
Again thanks
Wayne

I respectfully disagree with Rex although I agree you may not have used enough. Water is denser as you get closer to 4 C. (39 F) and it's more difficult for particles to settle. I've also noticed this when using alum in cold water.

Alum does not have to be added all at one time although later delayed applications, depending on how much later, may require slightly more product. Alum at least in water warmer than 60F will remain reactive for at least 7days in my experience. IMO chemically trying to clear the water in a new pond before you have a good grassed or vegetation covered watershed is wasteful of time and money. The time, money and efforts are better spent in establishing good vegetation cover. When vegetation is growing well, then be concerned with claring the water. By that time in many instances a big percentage of the suspended solids will naturally settle due to the effects of the developing biocommunity and alum will possibly not be needed.

In the case of colloidal clay, water density is irrelevant. The clay is in ionic suspension.

Alum does not dissolve or disperse in water as most think, rather it becomes a suspension and must be constantly mixed to prevent seperation. AlSO4 is heavier than water and sinks. The concentration of alum is not really cummulative when applied at different times, but the ionic (positive electrical charge) affect is, to a lessened degree. (Like a magnet too far away from metal fines to cause an attraction)

As Bill cody noted, if there is fresh colloidal (negatively charged) clay entering the pond, adding Alum, even at high doses, would be a waste of time and money...providing only temporary clearing of the water between applications and significant rain events causing additional erosion.

I prefer adding Alum in cool water, because the increased water density allows a more complete floculation, thus a more complete removal of ionically suspended solids. With Alum, it is the sheer weight of the tiny particles clumping together (floculating) that allows the floc to sink and cause clearing.

But not all the clay is colloidal nor is it in ionic suspension; some is recent from erosion and will settle in time even without treatment. Alum will more quickly settle that clay.

Not trying to be contrary just don't agree with you 100 percent. I have some experience with settling clay in both warm and cold waters and there is a difference. A chemist even told me there is a difference.

Why wouldn't you just solve the problem of the most clay coming into the pond? It makes sense to me to do it this way. If you don't get to the root of the problem, you will just be running in circles.

It is like cleaning a pond out. The purpose is to have a better pond not one that will instant return to the state before clean out. If this is the case, then it is just wasted dollars.

I know you can not eliminate all silt/clay from coming into the pond but you can stop the majority of it.

That's absolutely correct and what Bill Cody said. I was simply disagreeing with Rex that water temps makes no difference in the settling ability of alum. I believe it does.

There may be a slight time difference in the settling of clay with a proper treatment concentration of alum...denser water makes the floccing more effective because as the floc becomes larger, the sinking speed is somewhat slowed by the water density and the larger sizes of floc created in a denser water, allowing a much larger folc to be created due to the added attachment time as the alum/floc sinks...the magnetic field of the alum that attracts the negatively charged ions in colloidal clay is unaffected by the water density, and the clay fines minute size still move easily toward the positively charged alum ions regardless of the water density as there is so little friction resistance to movement.

Alum is only suggested for clearing colloidal clay, as colloidal clay will NEVER settle without an electrical charge change in the water chemistry....non colloidal clay however will always settle out unassisted and unless time to settle is an issue, alum is not needed for clearing non-colloidal clay.

That should make a disagreement on the treatment effectiveness moot.