Dedicated To The Tribal Aquaculture Program

June 2002-Volume 40

Topics Of Interest:

Custom Built Live Fish Transporting/Hauling Tanks
The Engineering Behind Increased Sedimentation
Barley Straw, An Organic Algaecide
Water Degassing
Segmented Packed Columns
Ozone Generators
UV Sterilization
Heater Sizing Guide
Water Control Structures and Culverts
Aeration Systems
Netting
List of Manufacturers

Custom Built Live Fish Transporting/Hauling Tanks

Jefferson Fiberglass, 1524 Mac Arthur Ave. Harvey, La 70058, Phone: (504) 347-6612, E-Mail

Jefferson Fiberglass has been building fiberglass products since 1966.  Information and pictures of their products are available on their website.  Please contact them if you have any questions.  Specific features from their newest live fish hauling tanks include:  

• Any size one, two, three, or four compartments.
• Turn key units, single drain or multiple.
• Insulated foam, wood core exterior, slide gate for quick discharging.
• Quick coupling kamlock fittings, on board oxygenation systems.
• 12 VDC electrical wiring to pumps with pilot light and breaker switches.
• Stainless steel lifting eyes and hardware.
• Oxygen flow meter and copper manifold.
• Mat-Combo fiberglass laminate, gelcoat finish interior and exterior.
• Five year warranty on structural frames and fiberglass work.
• Overflow with plugs, three way slope drain to valve.
• Any color and any shape, sight gauge connections, ship anywhere.

• Do whatever is possible to allow fish feces to drop intact into the waste collection area with minimal damage. Minimize the use of pumps, aerators and air diffusers wherever feces is present.
  
• Do not pump the waste prior to separation. Design for gravity flow (or siphon) into a sedimentation tank or basin. Splashing and turbulence can attach air bubbles and break apart solids. Feces and food particles smaller than 40 microns may never settle.
  
• Here is a good sedimentation basin design: Wide inlet (to reduce velocity), a surface area of .7 to 1.4 sq. ft. of basin per gpm flow, wide outlet weir (never a stand pipe), no baffles (which increase velocities) and a simple waste drain. A depth of just a few inches is enough for most designs.
  
• Be careful not to convert your solid waste into dissolved waste.
  
• If further filtration is required after sedimentation, pump the water to an affinity bead clarifier or particulate filter.
  
• Clean both the settling area and filters at least once a day.

Research through Aquatic Weeds Research Unit U.K. suggests barley straw to be highly effective in the control of algae. How about that, an organic approach to algae control. It takes six to eight weeks for barley straw to become active after it is placed in moving water. After that, barley straw will remain an active algaecide for approximately 6 months. Microbial growth, oxygen and warm water temperatures activate the decomposition of the straw.  Barley straw decomposes slowly so its oxygen demand does not cause problems unless an excessive amount of straw is used. Stagnant water will go anaerobic inside the straw bundle killing the microbes.

Barley straw is most effective in shallow (1 m) water with sunlight and good circulation. Clear water means less straw is needed. However, with turbid, muddy water, and less sunlight, more straw may be required to do the same job. Low temperatures are less effective.

Water surface area is used to calculate dosage. In still water ponds, the minimum quantity of straw needed to control algae is 2.5 grams of straw per square meter of water surface. In water with a severe algae problem, high first treatments up to 50 g per m² may be required. 

Start with small quantities and monitor effects. Barley straw may be pre-started 
in non-algae problem areas with good oxygenated water flows.

You can tie the straw in small bundles, make flat sheaves, or stuff it into net bags. Weight or stake them to the bottom in an area with water movement.

Did you know that for every pound of oxygen consumed by fish, they exhale one pound of carbon dioxide? Carbon dioxide can, therefore, cause a problem in recirculating systems where aeration or agitation or some other form of degassing is not done. This can be the case, for example, where pure oxygen is used in place of aeration. Somewhere in the system, carbon dioxide must be removed, or it can build up to dangerous levels. Dangerous to the fish, and to you if you are in a closed building. Here are some numbers to keep in mind.

Oxygen is about 20.9% of the air and, because it is only slightly soluble in water, it becomes saturated at a level of about 9 ppm at 68F (20⁰C). Carbon dioxide is 0.033% of the air and is saturated in water at about .5 ppm because it is much more soluble in water than oxygen. The comparative solubility of these two gasses in blood is similar to that of water. Therefore, if there is a lot of carbon dioxide in the water, there will also be a lot of carbon dioxide in the fishs blood so they will be able to hold that much less dissolved oxygen. 

If there is in excess of 5 ppm carbon dioxide in the water,
it is significantly affecting the fishs ability to breathe oxygen.

If you are conducting intensive aquaculture operations outdoors, a splash aerator or aeration with air diffusers will drive off the carbon dioxide into the air. If you are indoors in a closed building, very high levels of carbon dioxide can accumulate in the air. Since carbon dioxide weighs almost twice as much as air, it lays in the bottom of the portion of the indoor air space similar to the "fog" generated from dry ice used for theatrical purposes. It then has to be removed from the building, which requires air ventilators. In the winter, air ventilators can remove a lot of heat along with the CO₂.

We suggest that you strip CO₂ with a degassing column which is ventilated to the outdoors. To keep from causing a negative pressure inside the building, outdoor air could be drawn from the outside of the building directly into the bottom of the degassing tower and forced up through the down flowing liquid then directed back outdoors separate from the inlet. In cold weather you will have a significant cooling effect on the water because it is being degassed through cold air. To save this energy, use of an air to air heat exchanger.

Packed columns are often used for the purpose of adding oxygen or removing nitrogen, hydrogen sulfide or carbon dioxide. In most areas of the country, well water (ground water) needs both aeration and degassing. The packed column is usually the best way to do it. Oxygen can be taken up to near saturation levels as the undesirable gases are stripped out.

Segmented packed columns are the result of extensive research and development 
by the Canadian Government. No energy input and no moving parts 
give this equipment it simplicity and low cost.

Each segment is made of durable UV inhibited high density polyethylene for out door use. It has been engineered and molded with a series of internal angles to produce the ideal flow pattern to prevent wall channelization. Install the proper number of segments to give the water quality you need. You can feed the top segment as much as 150 gpm with excellent aeration and gas stripping results. Each segment has a heavy bracket molded in which fits on to an optional hanger. Snap the segments onto the beam and either hang it from the ceiling or support it on the tank wall or to a post. The water to be treated is "dumped" in the first segment and exits directly into your tank. Each segment should be filled with .6 cubic feet of bio-media.

How Ozone Generators Work

Ozone is generated by passing air or oxygen through a reaction vessel, where either an electric arc, corona discharge (CD), or an ultraviolet (UV) lamp excites the oxygen. In this reaction oxygen molecules separate into atoms of oxygen which then temporarily recombine with each other to form ozone. When ozone oxidizes organics only one atom of oxygen is used, leaving one molecule of oxygen. What could be better for aquaculture?

• Ozonization is highly effective in removing organics, pesticides, and color.
• It reverts back to oxygen quickly. Unlike chlorine, there are no detrimental residuals.
• It is produced on site, with no electricity near the water.
• It is economical and nonpolluting, when used correctly.
• It can be used as a sterilizer, before, during and after water is used for aquaculture.
• Ozonization also improves biological filtration and particulate filtration.
• It can remove the biological oxygen demand in the water.
• It oxidizes long chain molecules, which biofiltration cannot do.

• Ozone is very unstable. It will revert back to oxygen within an hour, even if there are no organics for it to oxidize.
• Temperature, pressure and sheer cause it to revert back to oxygen. When ozone molecules collide, they recombine as oxygen, which is why it is virtually impossible to get ozone to the tank above 2% (by weight). If it is under pressure or goes a long distance in the air line, it will go down below 1%.
• Use dry air or oxygen to produce ozone. Humidity can reduce ozone production by 70%, form scale in the CD reactor, and produce nitric acid.
• To insure sterile (germ free) water for drinking or other purposes, there is nothing better than ozone. Ozone can also remove THM_s, PCB_s, and most other organics, including color.
• OSHA says that it is harmful to breath ozone above 0.1 ppm in the air. However, many companies are selling ozone generators for air purification that produce levels much higher than that. Most people can smell ozone above 0.05 ppm. Vent off gas outdoors or into an ozone destruction device, such as a UV light or activated charcoal.

Ultraviolet lights with a specific ozone generating wave length are generally used to produce the lower levels of ozone; that is the percent of ozone by weight of the air or oxygen it was produced from. The slower the gas moves through the reaction vessel, the higher the percent of ozone. The corona discharge (CD) type of ozone generator uses an electric arc similar to sparks or lightning to produce higher percentages of ozone by weight. A relatively small CD reaction vessel can produce a relatively large volume of ozone. The greater the percentage of ozone, the raster the oxidizing reactions take place.

Ozone can be used in a protein skimmer (foam fractionation device), where it helps the process while the vessel allows capture of the off gas for venting or ozone destruction. Ozone works very well in oxygen saturators for the same reasons. Ozone can also be injected directly into degassing towers.

In a small home aquarium, 0.1 mg/L may be used. A sterilizing system for drinking water may need 1 mg/L with a 10 minute contact time. In recirculating aquaculture, with a high BOD and COD load, the ozone requirement can be more than 20 mg/L. The dosage is hard to determine because aquaculture conditions are always changing. We recommend the use of a side stream, wherein the water is treated as much as possible with ozone before it is mixed back into the main water body, or a redox controller. We strongly recommend the use of a redox controller because it will self adjust to the changing conditions in recirculating aquaculture.

Ozone is a very strong oxidizer and must be handled with special materials. The best is stainless steel for tubing, valves, and other components. Sweetwater air diffusers are made specifically for use with ozone. The second best material is pure teflon, then Kynar, CPVC, and HDLPE, in that order. Be careful using vinyl airtubing, as the ozone will leach out the potentially toxic plasticizer (it will look like oil on the inside of the tubing).

A good whiff of ozone will not kill you! If you smell ozone in the air in your building, turn off the ozone generator and vent the air space.

At Aquatic Eco-Systems we hear from a lot of people who have UV sterilizers and are still experiencing disease problems. This can almost always be traced back to inadequate UV irradiation. Because it is so difficult to measure the intensity of UV energy hitting your water, many UV buyers have improperly sized their UV sterilizers by simply following the maximum gpm flow rate published for 15,000 mws. (Who said aquaculture was easy)?

Be careful! You cannot compare UV Sterilizers by the watt ratings alone. That would be like comparing cars by their engine size alone. The watt rating is just the starting point for comparisons. The full amount of UV energy required to kill a microorganism must hit the organism after it leaves the lamp, after it leaves the quartz sleeve, after the lamp has aged, and after it has passed by any turbidity and particulates that is blocking the light.

Ultraviolet light can be very effective at eliminating viruses, bacteria, algae and fungi. Since it is the intensity of light that is doing the killing, we must know how much light energy to use and how much is reaching the target. Just as some sunglasses reduce UV intensity, so does discolored water, temperatures, turbidity, dirty quartz sleeves, and even some dissolved salts such as sodium thiosulfate. Old run down lamps also affect the intensity. Even lamp temperatures can reduce output when operated in cold water temperatures (110 F give maximum UV output).

To insure sterile water using UV light, you must first start with clear water, have a lamp and flow rate that are sized to deliver the correct amount of irradiation for the target organism. If a UV light is flow rated for 15,000 mws and you want 30,000 you can either double the amount of lamps or reduce the flow by half and so on for higher dosages.

Be aware that some lamps age rapidly and the manufacturer probably states the watts produced when the lamp is new. This wattage can be reduced by as much as 40% in as little as six months. We suggest that you further oversize your UV sterilizer by at least 40% so that you can be sure you are getting the killing power required when the lamp has aged. We suggest that you change lamps at six month intervals.

If you are bringing water into your facility which must be heated, you can use an electric heater for all or just a portion of your heating. For instance, you may use warming ponds, solar or waste heat when available and use thermostatically controlled electric heaters as the final temperature control. To determine the approximate size heater to order, choose one of the three categories.., then follow the calculation.

1. Flow Through System:

A flow through system has cool water entering and warmer water leaving. Determine the maximum gallons per minute that you expect to add. Determine the greatest temperature difference you expect to have (subtracting the incoming temperature from the desired temperature = temperature difference).

• 1000 watts (1 kw) will raise the temperature of 6 gallons of water (23 liters) one degree F per minute. Example: 6 gpm with a 10⁰ F difference = 10kw.

2. Non-Flow Through Calculation:

In a non-flowing system heat is only lost to the surrounding air. The temperature difference between the air and the water is the biggest factor. Also, the open area of the tank, the amount of agitation and the heat loss through the tank walls should be considered.

• For every 9⁰F difference you should have 4 watts per gallon (3.8 liters) of water. (With elevated non-insulated tanks with a large amount of surface agitation you could require as much as 12 watts per gallon per 9⁰F. For small glass aquaria use 8 watts per gallon per 9⁰F).

3. Temperature Raising Calculation:

Cool water is used to fill tank and the water must be warmed before the fish are added. Time will be a consideration. For every 1,000 gallons (3800 liters) you will need 1,200 watts (1.2 kw) to raise the temperature 10⁰F in 24 hours.

Heater Sizing

Its difficult to simplify something that is complicated but you can use this quick reference chart to estimate the size of an electric heater. A tank with 1000 gallons sits in a room that will stay around 60⁰F and you want the water temperature to be 87⁰ F. If for every 9⁰F you need 4 watts per gallon then: deltaT= 27⁰, 27 9 = 3, 3 x 4 watts = 12 watts per gal., 12 watts x 1000 gallons = 12,000 watts. Assumes one large non-insulated uncovered fish tank plus one peripheral (such as a sand filter) and a pump with no extreme water/air interface (such as a splash aerator or degassing tower). Minimize heater size and power use by insulating and covering.