Pond Boss Forums GENERAL QUESTIONS Water chemistry Alum vs Bentonite/Lathanum for Phosphorus Removal?

I am trying to get a better understanding of phosphate mitigation treatments. It seems the more I learn, the more I need to learn. Could someone please explain to me the difference in using alum versus bentonite/lanthanum (Sepro's EutroSorb Products)? I had a suggestion for a "flock and lock" program" which would be alum followed by the EutroSorb. I'm hearing the term "sediment reflux" in relationship to phosphates being rereleased back into the water table. I'm struggling to understand if phosphate will unbind from alum. Does anyone have a link to an article that can give me a better understanding of this entire process?

I'd appreciate any clarification or information anyone can pass along. Thanks!

Are you trying to clear a pond (flocculate) or bind Phosphorus? Bentonite is a colloidal clay and would cause turbidity. Lanthanum temporarily binds to Phosphorus from studies I have heard about. Alum (Aluminum Sulfate) both permanently binds Phosphorus, and can flocculate suspended solids...whichever use is wanted determines the best approach and dose needed

Dena, I don't know of anyone here on the forum more knowledgeable about alum than Rainman.

He is also an excellent driver.

Mailboxes may think differently! LOL

I am trying to bind phosphate in drinking water ponds. In my area we have small 1/3acre -1/2 acre ponds. I am seeing extremely high phosphate levels with the labs classifying them as hypereutrophic. This seems to be a leading cause to algae problems that have been hard to get under control (lyngbea and cyanobacteria). With the history of our area, there are more instances of this issue each year. I need an effective game plan.

Here is an example of a pond I struggled with last year. I decided to spring for lab testing and use this as a test pond for future reference.

Given 1/3 acre and 14ft deep drinking water and recreational pond with adequate Aquashade season long.
5/12 Algae Treatment- 2.5gal Cutrine Plus
6/3 Algae Treatment - 2.5gal Cutrine Plus
7/8 Algae Treatment- 150Lbs Phycomycin + 7g Captain XTR + Adjuvant
7/10 Nutrient Binder- 2qts EutroSorb WC
7/21 Algae Treatment- 5g Captain XTR
8/2 Water LabTest - Free Reactive Phosphate 5.1 ug/L, Total Phosphate 51.2 ug/L
8/2 Algae Lab Test- Heavy presence of Leptolyngbya, Coccomyxa (Chlorophyta); Cosmarium (Streptophyta), much bacteria observed
8/18 Prescribed Algae Treatment - 150lbs Phycomycin + 5g Captain XTR
8/19 Prescribed Nutrient Binder- 2qts EutroSorb WC + 100# EutroSorb G
9/1 Algae Treatment- 5g Captain XTR - 150lbs Phycomycin + 30lbs Cutrine Plus G3.7%
9/9 Algae Treatment - 5g Algymycin
9/13 Algae Treatment - 5g EarthTec
9/19 Water Lab Test- Free Reactive Phosphate 5.0 ug/L, Total Phosphate 120.2 ug/L
9/19 Algae Lab Test-Oocystis, : Scenedesmus (Chlorophyta); Aphanocapsa (Cyanophyta), some bacteria observed
10/18 Nutrient Binder- 100# Aluminum Sulphate + 50# EutrSorb G

While I could knock it back, I was never able to get the algae under complete control. The opinion was that until the nutrient levels get under control, I won't have algae control. It was also explained that there is phosphate in the water table, but also phosphate in the sediment that gets re-released (due to algae growth on the rocks).

With the given information above, would you have a recommendation for treatment (s) this season?

Thanks for your time and help!!

Recommendations:

Next Jan 1st. take a sample of water and send it out for testing. I'd also have them test for heavy metal (copper).

This year I'd stock 20 pounds of Tilapia that are between 6"-9" in size and treat the pond within 5 days pre/post stocking the tilapia in the pond. I would treat the pond as follows: Mix 32 fl. oz. of Cutrine plus liquid and 2 25 gallons of water in a pump up sprayer. Walk around the edges of the pond and spray the solution on algae that is in water <24" deep. Then I'd get Cutrine Plus granules and apply it to the water that is >24" deep out to water depth that is 36" greater than your water clarity reading on a secchi disk. I'd apply the granules at the rate of 20 pounds per surface acre. You will have to calculate how many square feet of surface water you have that meets the criteria that I outlined above to calculate how much Cutrine Plus Granules to apply equally and evenly over that area.

That should fix the problem for this year.

Take another water sample for a test in August. Test during the middle of summer and again in the dead center of the middle of winter. P in the water is highest when the plant/algae growth is the least. The P will be reduced by the Tilapia (it takes P to grow fish flesh, and removing the fish in the Fall will remove P from the water).

If you want to treat the pond for P prior to adding the fish, use enough alum to make a slurry that uses 150 pounds of alum per acre foot of water. If there are no fish in the water, then you don't have to worry about a pH change.

Edit to ask how are you applying the aluminum sulphate?

esshup (and others),

Is there any type of emergent shallow water plants that can be used to take up P during the growing season, and then cut back in the fall with the plant material removed from the pond basin so that the nutrients are NOT recycled into a hypereutrophic pond?

(I was just thinking that if you lowered the pond in the fall to remove the tilapia, you could also cut some plants at the same time.)

Chemistry, plus tilapia, plus plants might be an effective three-pronged approach to get up to "drinking" water level?

The plants that are marginal plants (coming up out of the water) typically don't use as much nutrients out of the water as the submerged plants.

Thanks.

Any submerged plants compatible with human drinking water supply?

Or is rotting vegetation in the fall just as bad as when the algal bloom dies off?

Surely there are some state guidelines on best practices from the period before when most people got their water from a system.

Cody would be a good one to chime in about that, he's familiar with the filtering systems that they typically use in Ohio to filter pond water to make it potable water.