TESTING THE WATER BASIC WATER QUALITY TESTING FOR AQUAPONIC SYSTEMS - GOFARM ...
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Testing the water…
Basic Water Quality Testing for
Aquaponic Systems
GoFish Workshop
January 10, 2021
RuthEllen Klinger-Bowen
rckb@hawaii.edu
What parameters to test? v What water parameters affect my plants the most? v What water parameters affect my fish the most? v How much do I want to spend, without compromising how “accurate” I need to be?
Water chemistry parameters
important in aquaponics
v Temperature (⁰F or ⁰C)
v Dissolved Oxygen (ppm or %)
saturation)
v pH (range of 1 – 14)
v Ammonia (ppm)
v Nitrites (ppm)
v Nitrates (ppm)
v Conductivity (µSm/cm or mSm/cm)
v Total Dissolved Solids (TDS)
Temperature v Affects whole aquaponic ecosystem v Ammonia toxicity increases with increasing temperatures (fish) v Increased temperature decreases oxygen solubility (D.O.) (fish/plants/bacteria (nitrifiers)) v As temperatures decrease, the fish’s immune system to ward off diseases is compromised. v Growth, physiology, reproduction and health of fish/plants/nitrifiers heavily influenced by temperature. v Rapid temperature shifts most influential stressor rather than the temperature itself
Dissolved Oxygen
v Definition – amount of
oxygen dissolved in water
v Important to fish survival,
plant growth, and
nitrification
v Maintain ≥6.0 ppm for
optimal aquaponics (>80%
saturation)
v Oxygen levels decreases
with higher biomass and
increasing temperatures
During a low (
Nitrogen cycle in an
aquaponic setting
v Three Nitrogen (N) parameters
that are tested: Ammonia,
Nitrites, and Nitrates.
v Nitrogen (N) enters system in
feed (as protein)
v Fish eat, metabolize, then
excrete waste products as
ammonia (also excretes
ammonia through gills)
v Bacteria convert to nitrites
and then to nitrates
v Plants can utilize all nitrogen
forms but prefer nitrates
Source: http://www.liveaquaria.com/PIC/article.cfm?aid=78
Nitrifying Bacteria
v Ammonia Oxidizing Bacteria (AOB): Nitrosomonas
Converts ammonia to nitrites
Ø
55 NH4+ + 5 CO2 + 76 O2 → C5H7NO2 + 54 NO2- + 52 H2O + 109 H+
Nitrosomas
Nitrobacter Nitrospira
v Nitrite Oxidizing Bacteria (NOB):
Nitrobacter/Nitrospira
Converts nitrites to nitrates
Ø
400 NO2- + 5 CO2 + NH4+ + 195 O2 + 2 H2O → C5H7NO2 + 400 NO3
- + H+
pH (Power of Hydrogen)
v Based on the amount of
hydrogen ions (H+) are
present (acidic/basic)
v Scale 1 – 14 (no units)
v Negative scale so pH 7 has
less H+ ions than pH 6
v Logarithmic scale so pH 7
has 10x less H+ ions than
pH 6 and 100x less than pH
5
Why take pH measurements?
v Too low or too high pH affects
fish/bacteria health and
nutrient availability to plants
(nutrient lock-out)
v High pH increases ammonia
toxicity to fish
v Through natural nitrification
process, pH in aquaponic
systems trend towards being
acidic – typically need add a
buffer (crushed oyster or
coral)pH optima for various biota
in an aquaponic system
pH
Crop 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0
Beans
Cucumbers From: Hydroponic
Lettuce Food Production
(Resh, Woodridge
Peas Press, 1987)
Strawberries
Tomatoes
Radish
Timmons et al (2002)
Fish
Tyson et al (2004) Hochheimer and Wheaton, (1998)
BacteriaImpact of pH on nutrient availability in plants
http://www.rivendelldistribution.com/docs/availability_vs_pH.pdfAmmonia
v What is measured is the total
ammonia nitrogen or TAN
v TAN = Ionized (nontoxic) form NH4+ +
un-ionized (toxic) form NH3¯
v Both forms are constantly moving
back and forth, and is highly
dependent on pH and temperature
NH4+ ↔ NH3¯Ammonia effects on fish
v Essentially disrupts function/structure of
fish tissues
v Affects central nervous system, internal
organs, and gills
v Toxic ammonia as low as 0.02 ppm can damage
gills
v Fish will “spin” in the water column
v Causessecondary infection due to stress,
physical damage, mortalityHow to calculate toxic ammonia The higher the temperature and/or pH, the higher the toxic form ammonia will be present
Nitrite (NO2) effects on fish v Acute high levels are toxic v Prolonged low levels toxic v NO2 should always measure ZERO! v NO2 acts like carbon monoxide, prevents oxygen from binding to the fish’s blood hemoglobin (called brown blood disease)
Nitrate (NO3)effects on fish
v Least toxic of nitrogenous
forms
v Most fish can tolerate
prolonged levels of >400
ppm
v Target for aquaponic
systems is 50-150 ppmLet’s Test the Water!
v pH
v TAN API Freshwater
Master Kit
v Nitrites
v Nitrates
ü Rinse tubes with sample water prior to testing
ü Childproof caps (Press red tab and twist)
ü Use the vial tops when mixingAmmonia
How fast this cycle occurs
is highly dependent on
Nitrites
oxygen, temperature, pH,
and buffering capacity of
the water.
NitratesBuffering Capacity
Total Alkalinity
v Ability to withstand changes in pH.
v Expressed as ppm CaCO3, meq/L, or dKH
(KH)
v Total concentration of bases (reacts with and
neutralizes acids)
v Carbonates and Bicarbonates are the most
important
v Hydroxides, Phosphates, and Borates are minor
contributors
v FW Range 50 – 200 ppm; 100 ppm idealBuffering Capacity of Natural Buffers at Different Concentrations of Vinegar
Carbonate (KH) at Different Concentrations of Vinegar
Nitrogen, Phosphorus, Potassium
Extract from CaCO3 Sources
Coral
Chips
Egg
Shell
Oyster
ShellpH versus Size of Coral
(Vinegar 1:100, Coral 10 Grams) Sand
Small
Medium
LargeImpact of Buffers on pH
8.00
7.50
7.00
6.50
6.00
pH
5.50
5.00
4.50
4.00
3.50
3.00
1 13 24 30 35 40 45 50 55 60 65
Days in Culture
Control Sand CoralIs my pH going to change so much
that I have to worry about it?
Greenwater tank
CO2 spontaneously combines with H2O phytoplankton
and makes carbonic acid (H2CO3 ). In a
greenwater system CO2 is removed by
phytoplankton to make starch and
sugars via photosynthesis. Less CO2
means less H2CO3 resulting in
fluctuations in pH.Aquaponics = Tank
Cover
v 70% shade cloth
v Prevents algal growth
v Optimal conditions
for desirable plants in
the grow bed
v Caveat: CO2 through
respiration will
increase over timeWhat Happens to Carbon
Dioxide in Water?
Carbon Dioxide + Water = Carbonic Acid
CO2 + H2O = H2CO3
H2CO3 ↔ HCO3- + H+What is the pH of Water Before
and After Blowing Bubbles?
n Measure pH of the sample water
n Use a straw and blow into the water
bottle for 2 minutes (releasing your
CO2)
n Measure pH
n Did it change?What Happens to Baking Soda in
Water?
Baking Soda + Water = Sodium Ion
+ Hydroxyl Ion + Carbonic Acid
NaHCO3 + H2O ↔ Na+ + OH- + H2CO3
OH- + H+ = H20What is the pH of Water with Baking
Soda Before and After Blowing
Bubbles?
n Add approx. 1 to 2 tsp baking soda to
water bottle.
n Mix well
n Measure pH
n Using a straw, blow bubbles in the
water, releasing your CO2
n Measure pH
n Did pH change?Conductivity v Conductivity most important
for plant production
v Measure of ability to
conduct an electrical
current
v Direct measure of all ion
content of the water
v Higher ion content,
higher conductivity
v Measured in
microSiemens/centimeter
(μS/cm) or
milliSiemens/centimeter
(mS/cm)
v Need an battery operated
meter to measureTotal Dissolved Solids (TDS)
v Measure for good plant
production
v Measure of all inorganic
solids (minerals, salts,
metals) dissolved in
water
v TDS meters less
expensive than
conductivity meters
v 1 ppm TDS = 2 μS/cm
conductivityConductivity vs hardness vs TDS Conductivity TDS (ppm) Hardness (μS/cm) 0 – 140 0 – 70 Very soft 140 – 300 70 – 150 Soft 300 – 500 150 – 250 Slightly hard 500 – 640 250 – 320 Moderately hard 640 – 840 320 – 420 Hard Above 840 Above 420 Very hard No matter what parameter you measure, what levels are ideal is dependent on the crops you grow
Water test methods
“Aqua” Strips v Easy to use v Inexpensive v Inaccurate v Locally available v TAN maximum 6.0 v Most tests in one ppm strip v No DO strip v Nitrate up to 200 ppm
Aquarium kits
v Easy to use
v Locally available
v Relatively
inexpensive (online)
v pH minimum 6.0
v Nitrate up to 160 ppm
ppm (Hydroponic
v Precise among
kits go lower)
testers
v No D.O.
v Individual and
multiparameter test
kits availableAPI kit vs. Hydroponic kit Compare the 2 test kits on the water sample
Aquaculture
kits
v Multiple of common
parameters can be v Generally not locally
measured available (must be
mail ordered)
v Inexpensive over the
v Shipping & Handling
range and number of plus hazard charge
tests
v TAN limit 3.0 ppm
v Accurate and precise v Nitrate individual test
among testers that must be ordered
separatelyElectronic
Meters
v Fairly easy to use
v High range values v Some can be
for all parameters expensive
v Highly accurate v Must be mail
ordered
and moderately
v Probes/standard
precise
separate cost
v Special care
v CalibrationDecide what is right for YOU
v How many systems/tanks will be tested?
v How often will they be tested?
v What is the life expectancy of my water
chemistry method and will I use it effectively
and efficiently?
v How much do I want to spend?
v Local vs. mail order/internet
v Shipping/handling/HAZMAT charges
v How accurate do I need to be?Water Chemistry
Example of a Water Chemistry Data Log
Tank Method Temp D.O. pH TAN NO2 NO3 TDS
Date
Temp = temperature recorded as ºC or ºF
D.O. = dissolved oxygen (parts per million (ppm) or % saturation
TAN = total ammonia nitrogen (ppm)
NO2 = nitrite and NO3 = nitrate (ppm)How often do I test?
v Temperature, D.O., pH, TDS –
Daily
v TAN, NO2, & NO3 – Every 2 to
3 days if new system; after
one month, 1x/week
v Good exercise for students to
Photo courtesy of Dr. Clyde Tamaru learn chemistry and
ecosystem health
v Most importantly, record all
measurements! If it isn’t
written done, it did not
happen!Publications of interest FAO Small-Scale Aquaponic Food Production http://www.fao.org/in- action/globefish/publications/details- publication/en/c/338354/ Testing your Aquaponic System Water: A Comparison of Commercial Water Chemistry Methods http://www.ctsa.org/files/publications/ TestingAquaponicWater.pdf
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