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Calculating Dissolved Oxygen Levels in Ponds & Lakes Understanding
the rate of oxygen transfer a diffuser can deliver
Buy a Cheap Portable Dissolved Oxygen Meter
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Whenever the question of installing
an aeration system comes up I am inevitably asked how much oxygen will be delivered
by the aerator. Of course this is a standard question because the amount of oxygen
being delivered in to the water is critical if there are fish in the pond or if
it is an aquaculture system with a certain number of pounds of fish per tank or
per square meter. Each diffuser has a different transfer of oxygen level and if
we are installing diffuser discs with medium sized bubbles or are using airstones
with micro-bubble sizes that are less that 1 mm per bubble then it can make a
huge difference!

Extech
407510 Dissolved Oxygen Meter
$399.00
Dual display provides O2 or dissolved
oxygen and temperature readings Measures dissolved oxygen in water from 0 to 20.00mg/L
and oxygen in air from 0 to 100% Resolution: 0.1mg/L DO, 0.1% O2 Automatic temperature
compensation Min/Max/Average record/recall
Includes 4M (13 foot) cable
for probe. |
Dissolved
Oxygen (D.O) Meter For Ponds & Lakes - $395
Includes shipping
within continental USA. Item
# PR-DO621 (Meter, Probe w/ 5' cable & Battery)
This
inexpensive meter is a good value but don't call it cheap! It has a limited two-year
meter and probe warranty. Featuring a high-performance oxygen probe on a 5 foot
cable to allow for depth-readings of O2 levels that are not deep but will suffice
for most ponds since the levels measured will provide a good indication of the
overall oxygen levels of the pond. The meter is temperature-compensated from 0–50ºC
(32–122ºF) with an accuracy of .2 ppm and measures 0-20 ppm or percent saturation.
Each meter comes with a replaceable probe on a 5' cable.
Uses one 9V battery
(battery included). Meter measures only 3" x 5". The two-year warranty on the
meter and probe does not cover mishandling or water damage to the meter so be
careful if you plan to submerge the probe in from the edge of your boat...we've
found shore based measurements are less likely to cause dunking of the main unit
but that is dependant on the user and the way they take care of their tools! We
like this unit because it is reliable but not too expensive so if we get 2 or
4 years of usage from it we are happy! Replacement parts, replacement probes and
membrane kits are readily available. Please contact us by email for replacement
prices.
Know
your Dissolved Oxygen levels. It really helps Monitoring
dissolved oxygen is a key to pond & lake health If you are considering
one of the many commercially built pond aerators then you will, if you are using
a quality reviewed system, be using one that has been evaluated and tested for
what is called the "Standard Oxygen Transfer Rate" or SOTR which is
the reliable measure of gaseous transfer that is particularly useful for engineers
and scientific types who insist on understanding the minute details of how bubbles
can rise and conquer!
Warning: This next
section is the kind of scientific, engineering talk that makes most of my friends
fall asleep in their bowl of chili...if you continue beyond this point I am not
responsible for any of you who nod off and wake up tomorrow with your forehead
stuck to your computer keyboard!
If your water is literally "void"
of any oxygen then any sort of aerator, surface aerator, impeller system, bubbler
or bottom-mounted, lake-bed system will rapidly show performance of adding dissolved
oxygen at a rate that is ypically 10 pounds per horsepower per hour.
Many
surface aerators provide excellant aeration and don't break the thermocline which
can be a problem in certain ponds and lakes and such surface aerators are typically
rated at closer to 2 to 3 pounds of oxygen per horsepower per hour. I am sometimes
asked why are there these difference and these descrepencies in data?
Mainly
it is because advertised and stated SOTR rates are based on waters that are delibrately
as close to eutrophic or 0m/per liter as possible thus making the device seem
extremely effective at providing the most pounds of oxygen per hour per kilowatt
or HP.
Despite the rated SOTR of any system it is rare that the maximum
rate will be achieved because the rate of O2 transfer is extremely temperature
and concentration dependant. What does this mean? It basically states that any
aeration system will only be able to deliver the measured advertised maximum oxygen
level when the baseline levels are close to zero. It is rare that any body of
water will have D.O. levels approaching zero so often the listed parameters can
be erroneous. The following chart can help estimate the oxygen transfer that your
aerator will provide.
Oxygen
Transfer Rate (OTR)
As a % of the Maximum Listed Transfer Rate of Your Aeration Device. | Initial
Dissolved Oxygen Level | 10°C
(50°F) | 15°C
(590°F) | 20°C
(68°F) | 25°C
(77°F) | 30°C
(86°F) | 0 | 89% | 90% | 91% | 92% | 96% | 1 | 82% | 82% | 82% | 82% | 82% | 2 | 75% | 73% | 72% | 72% | 67% | 3 | 67% | 64% | 62% | 58% | 56% | 4 | 58% | 55% | 51% | 47% | 44% | 5 | 52% | 46% | 41% | 35% | 31% | 6 | 41% | 36% | 30% | 24% | 17% | These
levels are approximate for fresh waters at sea level. SOTR (Standard Oxygen Transfer
Rate) are typically used to describe mechanical aerators such as paddlewheels,
surface aerators and sometimes fountains. With bottom diffuser aeration this science
is rarely used as the majority of oxygen transfer happens at the surface/atmosphere
interface where the aerator boil pushes waters to the surface where the oxygen
transfer occurs; thus depth and temperature and CFM of the system involved plays
a major role making the SOTR rate almost inappropriate for discussion.
Congratulations: You
made it through this section... which according to my wife was dryer than an Arizona
bullfrog on a July rock! | For
the creatures of the Earth that inhale and breathe air a level of oxygen that
is around 21 percent is required to support life but in ponds, lakes and aquaculture
waters aquatic life is often supported in water that containes less than 0.0001
percent oxygen, which is equal to 10 mg/l.
With such a small amount available
in even the best of aquatic eco-systems it is understandable why every aquculturist,
serious koi or gold fish owner, or even anyone interested in maintaining a fish
pond or a healthy water body should understand, measure and record the various
seasonal changes of the dissolved oxygen to ensure fish health and pond clarity.
If
the oxygen level is too low, get yourself a pond aerator if this is the case,
your fish may stop eating and become lathargic and will expend extra and un-available
energy trying to find their food...but at the same time if the oxygen levels are
too high then it can also be a catastrophic fish-kill. At both extremes there
can be extreme fish stress and even death to aquatic life if the O2 levels surpass
critical thresholds.
Using a dissolved oxygen meter will allow you to regulate
and understand how your pond is evolving and when changes need to be made to adjust
the pH, temperature or aeration efficiency of your system you will be able to
quickly react!
I always tell the municipal lake-managers, pond owners and
the home-owner associations that I work for that they must take ownership and
responsability of their pond or lake. It is the same with the small backyard fishpond!
The
daily 24-hour cycle, sometimes called the diurnal cycle, of oxygen addition and
reduction in a pond should be well understood because as you probably already
know there is a delicate and fragile balance between the existing dissolved oxygen
in any pond or lake or water-garden versus the absolute rate of oxygen consumption
and this fluctuating level can be altered by the shifting algae growth cycles,
temperatures and even the prevailing wind directions! In your outdoor ponds there
will be lower dissolved oxygen levels in the height of the summer months, during
June, July & August especially because during the warmer months the overall
rate of oxygen consumption in the pond will increase as temperature increases.
This is why the most important thing to monitor will be the oxygen level.
The combination of monitoring your oxygen as well as other chemical and elemental
paramaters of your pond combined with accurate record-keeping will provide extremely
useful and predictive knowledge for the years to come as you deal with changing
environmental systems and patterns.
If you want to really get technical
then the bottom line is that it takes way more than just bubbles to correctly
aerate a pond or lake. When the oxygen levels are low you should be able to expect
a transfer performance of up to 10 pounds of dissolved oxygen per HP per hour,
this is using the standard rate so coveted by engineers!
Most pumps, water
moving fountains and air bubblers are actually rated at less than 2 pounds per
horse power per hour. But as we have found these ratings are often inaccurate
becasue most O2 transfer happens at the surface and not in the mechanical mixing
or aerating.
Bubbles from diffusers tend to expand and spread out as they
rise from the bottom to the surface. The volcanic like mounting of water that
is pulled within the bubbles from one of our synergystic diffusers rise at a rate
that avages about one foot per second moving around 2,000 gallons per minute from
the area above the diffuser assembly. In comparison, a simple PVC pipe drilled
with 1/64" holes will only move 200 gallons per minute on average with the
same 1/3 HP piston compressor that delivers 3 CFM!
Email
us with your questions We
will respond within 24 hours GAURANTEED!
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pond aeration systems
Ratings
and Reviews of Disc Diffusers & Airstones
For
more information on pond aeration visit the following ten pond aeration websites.
Please note that we are not specifically endorsing any particular way of treating
ponds or any particular business. Due dilligence in all things!
1.
Water Qaulity - Calculating the percent saturation is another way to analyze dissolved
oxygen levels. Percent saturation is the measured dissolved oxygen www.cotf.edu/ete/modules/waterq3/WQassess3f.html
2. Dissolved Oxygen and Water Quality - A good level of
dissolved oxygen Is essential for aquatic life. ... As dissolved oxygen levels
in water drop below 5.0 mg/l, aquatic life is put underwww.state.ky.us/nrepc/water/wcpdo.htm
3. Dissolved Oxygen and Nutrients - Key Findings Report - NREI - Aquatic
animals need dissolved oxygen to survive. If levels of dissolved oxygen become
too low, many types of fish and other animals could www.mb.ec.gc.ca/nature/ecosystems/nrei-iern/dg00s06.en.html
4. Major Findings - Dissolved Oxygen - Northern River Basin Study
- Winter is a critical time for dissolved oxygen levels. ... Dissolved oxygen
levels rarely dip below the Alberta surface water objective of 5 www3.gov.ab.ca/env/water/nrbs/sect3/sect38.html
5. Science Junction - Water What Ifs - Dissolved Oxygen
Lessons - Decreases in the dissolved oxygen levels can cause changes in the ...
Dissolved oxygen levels change and vary according to the time of day www.ncsu.edu/sciencejunction/depot/experiments/water/lessons/do/
6. Canadian Water Quality Guidelines for the Protection of Aquatic - Dissolved
oxygen levels in aquatic environments can. affect the persistence and bioavailability
of some. chemicals. For example, the persistence in water of ceqg-rcqe.ccme.ca/download/en/178/
7. Dissolved Oxygen Meters, Portable Meter - Cole-Parmer Catalog
- METTLER TOLEDO's Dissolved Oxygen Sensors to monitor your processes.- Dissolved
oxygen meters are analytical instruments that are used to measure the amount of
oxygen dissolved in a liquid sample. www.coleparmer.com/Catalog/product_index.asp?cls=46612
8. Hanna Instruments Dissolved Oxygen Meters - Meters for Laboratories
· Meters for Schools & Colleges · Swimming Pools Spa's & Hot Tub Testing ... You
are here: Hanna Catalogue > Dissolved Oxygen Meters www.hannainst.co.uk/acatalog/Dissolved_Oxygen_Meters.html
9. Pond and water garden test kits, test ammonia, pH, nitrites
... - Pond Test Kits testing pH, Salt, Dissolved Oxygen, Ammonia, Nitrites, Nitrates,
& More ... They're made in the USA, Available meters are oxygen meters - Dissolved
oxygen concentration in ponds fluctuates on a 24-hour basis. .... Dissolved oxygen
can be monitored using an electronic oxygen meter or chemical www.pondsolutions.com/test-kits.htm
10. Pond Aeration For Healthy Koi Ponds - In smaller fish/ koi ponds aeration
is usually achieved when water ... Although a bit pricey, a dissolved oxygen meter
is one of the best - Dissolved Oxygen Meter - Waterproof pH tester - Salinity
Meter ... The meter is extremely easy to use; simply turn it on and dip into your
Koi pond - Disolved Oxygen Meter Dissolved oxygen metering is an important application
test if efficiently maintaining koi ponds where oxygen levels are important to www.pondbiz.com/home/pb1/smartlist_323/h2o_test_kits__meters.html
Buy
The Best Oxygen Meters
Dissolved
Oxygen (D.O) Meter For Ponds & Lakes - $395
Includes shipping
within continental USA. Item
# PR-DO621 (Meter, Probe w/ 5' cable & Battery) This
inexpensive meter is a good value but don't call it cheap! It has a limited two-year
meter and probe warranty. Featuring a high-performance oxygen probe on a 5 foot
cable to allow for depth-readings of O2 levels that are not deep but will suffice
for most ponds since the levels measured will provide a good indication of the
overall oxygen levels of the pond. The meter is temperature-compensated from 0–50ºC
(32–122ºF) with an accuracy of .2 ppm and measures 0-20 ppm or percent saturation.
Each meter comes with a replaceable probe on a 5' cable.
Uses one 9V battery
(battery included). Meter measures only 3" x 5". The two-year warranty on the
meter and probe does not cover mishandling or water damage to the meter so be
careful if you plan to submerge the probe in from the edge of your boat...we've
found shore based measurements are less likely to cause dunking of the main unit
but that is dependant on the user and the way they take care of their tools! We
like this unit because it is reliable but not too expensive so if we get 2 or
4 years of usage from it we are happy! Replacement parts, replacement probes and
membrane kits are readily available. Please contact us by email for replacement
prices.
Compare
Pricing of Dissolved Oxygen Meters For Ponds and Lakes When
comparing oxygen it is a good idea to look for forums and reviews that discuss
the pros and cons of various battery operated and AC supply dissolved oxygen meters
and check to see if they include a deep-water probe or any probe with a 6 to 12
foot cable or more. Since the principals of oxygen measurements are scientific
and many companies offer products that do basically the same thing to various
degrees of efficiency then it is up to us as consumers to use our due-diligence
before buying a oxygen meter or DO meter. To compare prices with our recommended
meters we have grouped some of the more popular scientific and hobby dissolved-oxygen
meters brands together for comparision with ourown most used systems.
BUY
HANNA OXY-CHECK WATERPROOF DISSOLVED OXYGEN METER $459 Shipping Extra Measurements
in the field can subject the instrumentation to the inclemency of the weather.
Cold, rain, snow, dust and humidity associated with use in the field can cause
condensation, which may damage the meter, rapidly deteriorating its performance
and life. HI 9147 is designed for outdoor applications, especially wastewater
treatment and fish farming. Quick response through the galvanic D.O. probe. Backlit
Display. Simple on-site calibration requires no chemical solutions. HI9147 also
supplies the user with compensation (manual) of salinity and altitude factors
and automatically compensates for the temperature effect.
Range 0.0 to
50.0 mg/L (ppm) O2 0-600 % O2 -5.0 to 50.0°C Resolution 0.1 mg/L or 1% O2 0.1°C
Precision +/- 1% of the reading O2 +/- 0.2°C Typical EMC Deviation +/- 2% of the
reading O2 +/- 1°C Temp. Compensation Automatic from -5 to 50.0°C Calibration
Manual in Air Probe (Fixed) HI 76409/4 with 4m Cable or HI 76409/15 with 15m Cable
Battery 1 x 9V, Ni-MH, Rechargeable Battery Life 200 Hours of continuous use (without
backlit) Auto-Shut Off After 6 Minutes of Non-Use Environment 0 to 50.0°C, RH
95% Max Dimensions 164 x 76 x 45 mm Weight 511 g HI 9147-04 is supplied complete
with HI 76409/4 D.O. probe with 4 m cable, 5 spare membranes, 2 O-rings, protective
cap, HI 7042S electrolyte solution (30 ml), Protective Rubber Boot, Screwdriver,
rechargeable 9 volt battery and instruction manual in a rugged carrying case.
. Available
at: http://www.dynamicaqua.com | Buy
9200 Dissolved Oxygen Meter IP67 $1500 Shipping Extra The
Model 9200 is a fully specified unit combining ease of use and robust construction.
Utilising a Clark type polarographic membrane electrode optimised for both speed
of response and the ability to withstand the rigours of portable use, dissolved
oxygen measurements can be made either as % saturation or as concentration in
mg/L (ppm). The DO2 sensor incorporates a precision temperature measuring device
which determines and displays the temperature of the analyte and automatically
corrects for the changes in membrane permeability and oxygen solubility which
occur with variations in temperature. Calibration is a simple push-button operation
carried out in the % saturation mode with clear instructions given via the graphics
display. The sensor measures the partial pressure of oxygen and the reported results
are influenced by atmospheric pressure and depth, unless appropriate compensation
is made. The standard 9200 allows these values to be entered through the menu
options.
The 9200 is equally at home in the laboratory environment and
is suitable for B.O.D. (Biolchemical Oxygen Demand dtermination. The optional
B.O.D probe and associated components are designed to faciltate the 5 day B.O.D.
test as defined in ISO 5815. The kit includes adaptors, allowing use with the
many B.O.D. bottle configurations commonly available. High quality waterproof
connectors (to IP67) allow rapid interchangeability of electrodes, whilst maintaining
waterproof integrity. The connector incorporates a locking ring to guard against
accidental disconnection or ingress of moisture. Power is provided by 3AA size
batteries giving typically 100 hours of use. An operator selectable auto shut-off
feature ensures battery life is maximised. Automatic low battery warning is given
when remaining battery life is approximately 5 hours (@ 20°C). . Available
at: http://www.hannainst.co.uk
| Buy
Oakton ® Waterproof DO 300 Meter Stones
$930 Shipping Extra
Dissolved oxygen (DO) readings are displayed in mg/L, ppm, or % saturation simultaneously
with temperature values. Adjustable backlit display makes it easy to view readings
in low light levels. Calibrate at the independent 100% and 0% calibration points
to achieve high accuracy over the entire range. Increase reading accuracy by entering
salinity and barometric pressure—meters automatically calculate offset. Setup
function displays electrode slope, zero offset, and millivolt values. Real-time
clock stamps stored readings and calibration data with date and time, making it
ideal for Good Laboratory Practice (GLP) standards. Additional features include
selectable °C or °F temperature units, HOLD function, ready indicator, and auto-off
for battery conservation.
IP-67 waterproof and dustproof housings float
Perfect for harsh, rugged field conditions Memory stores 50 readings with corresponding
temperatures and time Galvanic probe allows you to take measurements immediately
Percent saturation resolution 0.1% Percent saturation accuracy ±1.5% full
scale Temp resolution 0.1°F 0.1°C Temp accuracy ±0.5°F ±0.3°C Temp range 32.0
to 122.0°F 0 to 50°C Temp compensation automatic from 0 to 50°C Salinity compensation
manual from 0.0 to 50.0 ppt, 0.1 ppt resolution Barometric pressure compensation
manual from 500 to 1499 mm Hg/ 66.6 to 199.9 kPa; 1 mm Hg/0.1 kPa resolution
Available
at: http://www.coleparmer.ca/
| Buy
The Techne Range of DO2 Dissolved Oxygen Meters by Jenway $875
Shipping Extra Model
970 is a low cost hand held unit that is rated IP65 for portable use. The Model
9200 Dissolved Oxygen Meter is designed and constructed to resist the harshest
of field, laboratory and industrial environments. The whole system is waterproof
to IP67, and if dropped into water will float. These products are ideal for on-site
water quality measurement in a multitude of customer applications. The 9200 utilizes
a Clark type polarographic membrane electrode optimized for both speed of response
and the ability to withstand the rigors of portable use. The Model 9150 DO2 Meter
is part of our Premier Portable range. The Model 9150 Dissolved Oxygen Meter is
designed and constructed to resist the harshest of field, laboratory and industrial
environments. The whole system is waterproof to IP67, and if dropped into water
will float. These products are ideal for on-site water quality measurement in
a multitude of customer applications. The Model 9500 DO2 Meter is a bench top
laboratory Meter. The Model 9500 is a fully specified dissolved oxygen meter that
includes full support for the B.O.D 5-day test protocol. Powerful data logging
capabilities are included with the ability to store up to 250 results plus 20
B.O.D. tests (up to 10 samples per test) either manually, at timed intervals or
alarmed events. Remote monitoring and data collection is facilitated by the provision
of both analogue and digital outputs and in the event of power removal all user
defined parameters are retained. Available at: aeratorsaquatics4lakesnponds.com |
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