OVERVIEW 1. Bioconverter Basics 2. BioConverter Design 3. Water Flow 4. Oxygenation 5. The Ideal BioConverter 6. Things that can go wrong 7. Summary
1. BIOCONVERTER BASICS The purpose of the BioConverter is to convert nitrogenous waste (ammonia excreted through the gills) to relatively harmless compounds via the nitrite / nitrate cycle. In addition, the ideal bioconverter will convert organic (carbon containing) compounds in solid fish waste to an oxidized state - ultimately carbon dioxide - which will then gas off to the atmosphere. Its job is NOT to remove solid waste (fish or otherwise) from the water.
Bioconverters work because of the actions of hard working, middle class bacteria, which, like koi, have basic needs: a) A home (usable surface area): - gravel - matting - ribbon - beads b) Food: exposure to nitrogenous & organic compounds 1) stuff in water 2) exposure to water 3) appropriate flow rate - fast vs slow c) Oxygen: supplied by O2 dissolved in the water
2. BIOCONVERTER DESIGN A) Pre-Filter: Catches the big chunks to help avoid clogging bioconverter media - Settling chambers - Coarse matting - Should not be relied on for bioconversion - Should be easy to clean / flush The pre-filter is the first line of defense for the bacteria in the bioconverter, to keep them from being smothered in solids.
B) BioConverter Media: Home, home on the range … Where the Nitrosomonas and Nitrobacter (and Aeromonas) play … - Adequate total surface area? - Flow capacity - Maintenance of design flow - will media settle together, plug easily, or clump? - Contact time with water - Biggest possible for space and budget - No such thing as over - filtration
BIOCONVERTER TYPES Maximum O2 level possible: 9 ppm The DO concentration for 100% air saturated water at sea level is 8.6 mg O 2 /L at 25°C (77°F) and increases to 14.6 mg O 2 /L at 0°C. Maximum O2 level possible: 9 ppm Maximum O2 level possible: 9 ppm Moore, M.L. 1989. NALMS management guide for lakes and reservoirs. North American Lake Management Society, P.O. Box 5443, Madison, WI, 53705-5443, USA (http://www.nalms.org).(http://www.nalms.org) Bead Filter Fluid Bed FilterMatting Filter
OTHER POSSIBILITIES … Maximum O2 level possible: 9 ppm AquaScapes type filtration - gravel / rock surface area & matting
Flow rate: Turnover time (all pond water passes through bioconverter) of at least once per hour General plumbing considerations: - Pump size (design flow rate) - Actual flow rate = design flow rate minus back pressure due to height and back pressure due to friction in plumbing, fittings, and other restrictions - Pipes never get bigger, they get smaller with buildup - Pressure of media (draw through or pressurized filters and bioconverters) 3. WATER FLOW
Bioconverter plumbing and flow considerations: High flow rate is OK and even great if: a) the water is clean and won’t plug up the front line of the media, and b) bacterial colonies won’t be mechanically knocked off by excessive turbulence, and c) there is a large frontal cross section of media (water can flow through gently and equally as opposed to being pushed through a small opening through multiple layers)
Consider trying to push a certain volume of water through a certain amount of filter media, represented by the media filled cylinder, open at the ends. All of the water needs to go through the first layer of media (shown in green). If it plugs, all water flow ceases.
Now consider trying to push that same volume of water through the same amount of filter media, but the water is flowing through the sides. The water has a much larger surface area to spread out over as it passes through the media. This filter design will flow with less pressure, and will be much more difficult to plug up.
4. OXYGENATION Oxygen is our friend. - Higher levels of oxygen can support higher densities of bioconverter bacteria. - Goal of water flow is O2 saturation at all levels of pond activity (top, bottom, in bioconverter) - Bioconverter bacteria, even more than koi, function best at high O2 levels. Oxygenation of pond water: - Bring the water to the oxygen (“flooming”, streams) - Bring the oxygen to the water (waterfalls, air pumps, turbulence)
Water, when cold and highly tumbled, holds, at best 9-10 ppm of dissolved oxygen. Air, by contrast, holds about 21% (21,000 ppm) oxygen. If we can get the media (and thus the bacteria) into the air, and still provide the bacteria with food and moisture to do their duties (or is that doodies?), they stand a much better chance of being at O2 saturation, and their populations and therefore productivity should be much greater.
5. THE IDEAL BIOFILTER What Kind Of Bio Converter Enables Maximum Oxygenation; Can Handle Huge Water Flows; Has A Huge Media Surface Area; Has Little Or No Restriction; Has Rapid Biological Start Up And Recovery; And Will Not Go Septic After A Day Without Water Flow?
3” pump outlet to 2-2” valves Cover (evaporation, shade, and splash) Free flow water returnFour 1-1/2” spray bars per tray set
You’ll also need huge plumbing, lots of space above water line (this is a gravity return system), a BAP (large pump), and... A means to hide the Shower Filter This is a temporary pond, above ground, built to avoid the trouble and expense of dealing with a built-in in a few years. The filter cover is for water loss, and does little to camouflage the filter. The screen in front helps a little.
Lava Rock Tray after six monthsSpray Bar after six months
Shower Filters are large. They are gravity return, so they need to be above the water level of the pond. They require massive water flow. They splash a fair amount. They lose water to evaporation. They can cool the water too much in winter. They are loud (a pleasant sort of loud). Potential Drawbacks
Hide the Filters behind a screen or a faux rock waterfall. Use the gravity return to further direct water flow in the pond. Use large plumbing to flow huge water and minimize friction and power losses. Cover to minimize splashing, water loss, and excessive cooling in winter. Install an autofill. Enjoy the extra water noises. Potential Solutions
7. SUMMARY Efficiency of oxygenation. Great water movement. Organics and nitrogens are broken down very rapidly. Cooling effect in summer. Soothing effect on fish. Except for “Bakki Shower”, each pond / filter setup needs to be specifically engineered.