July 2018

Typically, unseasonable warm days and

cool nights can cause them. These air

temperatures can also affect lagoon

water temperatures, especially if the

temperature of the water surface

becomes lower than the temperature of

water on the bottom of the lagoon. If

that happens, the lagoon cell may

actually flip, bringing with it solids

resting on the bottom of the cell. Those

anaerobic solids contain offensive

gases such as hydrogen sulfide and

methane and can cause odor

complaints. Should that occur, then

treatment may be needed.

The recommended treatment for a

turnover is to add sodium nitrate to the

affected cell. Sodium nitrate is readily

available and comes in granular form,

usually in 50-pound bags. When added

to a lagoon experiencing a turnover,

sodium nitrate provides additional

oxygen that hastens the recovery. EPA

recommends adding 100 pounds of

sodium nitrate per surface acre and

then subsequent applications, if

needed, of 50 pounds per surface acre.

The best way to add sodium nitrate is

in the wake of a low-horsepower boat

motor. Operators should take care

when using a boat, not to stir up more

solids on the bottom of the pond.

Otherwise, the recovery and

elimination of offensive odors may

take even longer.

I would like to make one last

comment about adding enzymes or bio-

catalysts to sewage lagoons. They are

not needed! Raw sewage naturally

contains the enzymes needed to

promote and sustain good treatment

and adding more is simply a waste of

money. I have seen several small

communities over the years spend

thousands of dollars for such products

with no improvement. If your system is

Filamentous algae come in various forms, but this variety forms dense, free-floating

mats that block sunlight and adversely affect treatment. It is more common in

ponds and lakes than free-flowing water and can produce prolific growth in waters

rich in nutrients, like sewage lagoons. In the case of the lagoon in this photo, the

cell looked perfect four to five days before the filamentous algae appeared. Then it

rapidly overtook the lagoon.

The recommended

treatment for a

turnover is to add

sodium nitrate to the

affected cell.