Zeolites are a group of volcanic minerals that are hydrated calcium potassium sodium aluminosilicates in which water is
held in channel ways by absorption. The lattices are negatively charged, and they loosely hold positively charged cations such as calcium, sodium, potassium, and ammonium. Their ability to exchange one cation for another is known as their “cation exchange capacity” or CEC. Once the ammonium ion is in the lattice, it is not water-soluble. They chemically filter
out the ammonium.
BRZ zeolite is especially adapted as a direct replacement for sand, sand and anthracite, and multi-media water filtration media. It has a much finer nominal rating (3 to 5 microns) than sand (20 microns), and consequently it filters out more fine particulates. See Usage documents on water filtration.
INTRODUCTION TO AQUACULTURE
Oxygen and ammonia are the two most important parameters in aquaculture. The oxygen is relatively easily controlled,
but the ammonia is much more difficult. Ammonia, the un-ionized form of ammonia (ammonia gas) is produced from the
gills and urine from the fish as well as from the bacterial decomposition of the unused food and fecal material. Fish utilize
the nitrogen component of digested proteins, the amino group (NH2) to build new proteins. However, when they utilize the proteins for energy, they cannot metabolize the nitrogen, and the amino group is split off as ammonia gas. Ammonia gas solubilizes readily in water to form ammonium ion. Ammonia is toxic, and it reduces the ability of the hemoglobin in the
blood to hold oxygen. Additionally, ammonia damages the gill structure further impairing the fish in getting oxygen.
There are three ways to reduce ammonia in the water. First would include mechanical filtering of unused food and fecal material. Although sand and charcoal have been used extensively, zeolite is much more effective. It has a nominal rating of 3 to 5 microns (sand is typically 20 microns), it loads 2 to 3 more times the particulate load of sand, and it reduces the number
of backwashes (see usage document on water filtration). Second would be the use of a biological filter in which bacteria mineralize the organic nitrogen compounds. The process can be aerobic or “nitrification,” or anaerobic or “denitrification.” Nitrification is the most popular, and it involves the oxidation of ammonia to nitrite and then to nitrates by autotrophic bacteria (Nitrosomonas and Nitrobacter). The huge surface area of BRZ makes it an excellent host for bacteria. Third, the ammonia can be chemically filtered by clinoptilolite. A zeolite filter system can be used to mechanically remove food wastes and fecal material. It also removes the ammonia and becomes a host for aerobic bacteria that eat the ammonia. As such, it becomes all three filter systems in one if properly applied.
NOTES ON THE USE OF CLINOPTILOLITE IN AQUACULTURE
- The ammonium promotes the growth of algae in the pond or tank and the algae will grow on the BRZ where they
- utilize some of the ammonium. However, the algae on the BRZ will inhibit the absorption of the ammonium into the BRZ. The algae must be washed off to accelerate the adsorption of the ammonium.
- Excretion of ammonia by fish increases with the activity of the fish, an increase in the temperature, and an increase
- in the feed ration. A rise of 13 degrees F can cause a 10-fold increase in the rate of excretion.
- The percentage of ammonia gas in solution increases with an increase in temperature.
- A reduction of dissolved oxygen (DO) increases the acute and chronic toxicity of ammonia.
- The toxicity of ammonia decreases with an increase of salinity up to 30% sea water (9 % salt).
- Adsorption efficiency of BRZ is unaffected by water temperature.
- Adsorption efficiency of BRZ decreases in water of low pH.
- Adsorption efficiency of BRZ decreases as water hardness increases. Other cations such as Ca, Na, Mg, and K compete more effectively than ammonium for the exchange position. Optimum efficiency occurs when the hardness is less than 44 mg/l.
- The effective depth of penetration for ammonium into BRZ is about ½ inch. As a result, smaller granules are more effective than larger granules. Too many fines increase the turbidity, however.
- BRZ will reduce ammonia in proportion to the amount of BRZ used.
- BRZ is typically not used in seawater due to the high hardness and the amount of sodium. In seawater, BRZ has approximately only 5% of the capacity that it has in fresh water. Much more massive amounts of BRZ must be used in seawater that is typically not economic.
- Ammonium loaded BRZ can be regenerated by using a saline back wash solution followed by a rinse cycle.
- Alternatively, aerobic bacteria, algae, or plants can be used to regenerate the BRZ.