Page 19 - Griffin Gazette Issue 2 - 2022

Dissolved oxygen is measured in parts per million or milligrams per liter. Multiple
manufacturers produce dissolved oxygen meters in either handheld or inline
forms. BioTherm’s YSI DO Meter is a handheld meter that uses optical methods
to measure dissolved oxygen by comparing luminescence in the presence of
oxygen. Hannah’s handheld DO meter, on the other hand, uses polarographic
sensing methods, which measure based on electrochemical properties of an
electrolyte solution. Either method produces accurate readings, but maintenance
of sensors will differ based on the equipment.

RELATIONSHIP BETWEEN WATER TEMPERATURE AND
DISSOLVED OXYGEN
An important tip to remember is, as water temperature goes up, dissolved oxygen
goes down. Water is able to hold less oxygen the hotter it gets. The below chart
from Dramm displays this relationship.

DO the Toob
and YSI Meter
Biotherm's
dissolved oxygen
augmentation
and monitoring
options

BIOTHERM’S THE TOOB
Rather than using an airstone and air pump, some growers are choosing even
more active oxygen injection strategies, which often require more specialized
equipment. One such piece of equipment is the TOOB from BioTherm. With
an inline installation and an oxygen tank hookup, the TOOB enables super-
saturation of irrigation water with dissolved oxygen. While typical saturation levels
of oxygen in water sit around 8 to 9 ppm, the TOOB allows water to reach up
to 40 to 45 ppm oxygen. This supersaturation with oxygen keeps root systems
healthy throughout the growing cycle. While the TOOB can be used in any type of
production style, systems such as deep water culture and nutrient film technique
will likely see the highest benefit.

DRAMMWATER AND OZONE
Dissolved oxygen addition can also be achieved through chemical reactions.
DRAMMwater has always favored the use of ozone as a sanitizer for a number
of reasons: not only is it effective, it has a secondary benefit of breaking down
into gaseous oxygen within irrigation water. Ozonation has become a favorite
among growers looking to use sanitizers with little to no residue and additional
benefits to irrigation water. Ozonation to provide sanitizing action can benefit
irrigation systems of all types by helping to cut down on algae and biofilms, as
well as eliminating fungal and bacterial pathogen inoculum in water sources.
Growers should be cautious when adding ozonation to fertigation water, however,
as ozone can oxidize certain subsets of nutrients when concentrations are high.
Implementing a mixing chamber between ozonation and fertilizer injection sites
often alleviates this concern.