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Noahsnana
05-17-2005, 02:17 PM
Tell an novice what this is ...increase my knowledge :thinking:

What is it?
How does it effect water quality?
What levels are desired?
How do you use an ORP Meter?

Thomas T
05-17-2005, 02:25 PM
What is ORP?
ORP is a term used frequently in the water treatment & food processing industry. ORP stands for Oxidation-Reduction Potential. So what is that? The best definition I can give is that “ORP is a measure of the cleanliness of the water & its ability to break down contaminants”. It has a range of –2,000 to + 2,000 and units are in “mV” (millivolts). Since ozone is an oxidizer, we are only concerned with positive ORP levels (above 0 mV).

ORP Level (mV)
Application

0-150
No practical use

150-250
Aquaculture

250-350
Cooling Towers

400-475
Swimming pools

450-600
Hot Tubs

600
Water Disinfection *

800
Water Sterilization **

ORP sensors work by measuring the dissolved oxygen. More contaminants in the water result in less dissolved oxygen because the organics are consuming the oxygen and therefore, the lower the ORP level. The higher the ORP level, the more ability the water has to destroy foreign contaminants such as microbes, or carbon based contaminants. The chart on the left identifies ORP levels for various applications.



ORP level can also be viewed as the level of bacterial activity of the water because a direct link occurs between ORP level and Coliform count in water. The chart to the right lists ORP levels and relative Coliform counts.


200 mV 300 Coliform count in 100 ml of water
300 mV 36 Coliform count in 100 ml of water
400mV 3 Coliform count in 100 ml of water
600mV 0 Coliform count in 100 ml of water



How does an ORP meter work?

An ORP meter measures very small voltages generated with a probe placed in ozonated water. The electrode is made of platinum or gold, which reversibly looses its electrons to the oxidizer. A voltage is generated which is compared to a silver (reference) electrode in a silver salt solution, similar to a pH probe. The more oxidizer available, the greater the voltage difference between the solutions.


Disadvantages
ORP cannot be used as a direct indicator of dissolved ozone residual, except in very clean water applications.

Advantages
ORP is a convenient measure of ozone’s ability to perform a chemical task. ORP is valid over a wide pH range, and ORP probes are rugged enough to be place into processes for in-line measurement. The probes can withstand process pressures in excess of 30 PSI.

ORP and Ozone
In a clean water system, using ORP to measure the dissolved ozone status works well. In our experience, however, even the strong oxidizing power of ozone in moderate turbidity (cloudiness) systems can result in ORP values far below expected and even negative (reducing) values. In general, monitoring ozone with ORP at the generator source works well but measuring dirty water becomes unreliable. Ozone detection kits are available and work well at the limit of approved concentrations for your application.

Noahsnana
05-17-2005, 02:35 PM
What about for normal pond usage? Can we elaborate?

Thomas T
05-17-2005, 02:37 PM
How does it effect water quality?
What levels are desired?

At 250 - 300mV, the nutrients (DOC) as well as single cell algae are being oxidized into water & CO2. This is the one of the reasons why your water clear up so fast when PP is added to the water. In the nutshell, water quality improves. However above 500mV, you'll kill everything including fish & bio-filter.

How do you use an ORP Meter?
I have the probe & meter hardwired to my settling chamber on the Nexus. It monitors the water 24/7. The probe requires cleaning every 4-7 days using a wet tooth brush. See pics.

CarolinaGirl
05-17-2005, 02:47 PM
Very informative Thomas, thanks! I like the idea of having the ORP meter mounted for constant use. Very fancy housing too, I might add :p: . How long do the batteries last when you run it 24/7?

Thomas T
05-17-2005, 03:07 PM
The battery is a single 9V cell and should last 3-4 months on continuous use. The plastic tuberware housing is velcro'ed to the Nexus.

TT

MCA
05-17-2005, 05:05 PM
I think the values should be more for ~250 for the average pond. Over 300 for very good water quality, over 350 for fantastic water quality. I know who koi keeper who's pond water is near 400 and he does not use ozone or PP....just fantastic filteration and aeration.

I try to keep our pond in 300+ range...it aint always easy.;)

Noahsnana
05-17-2005, 05:24 PM
Thanks for taking the trouble to post a pic to demonstrate application Thomas.

So the ORP meter is measuring Disolved Oxygen in the water... this replaces the kit test w/drops. How accurate are the meters... How offten are they calibrated or do you calibrate these meters?

nicco
05-17-2005, 07:25 PM
Umm. Nope. ORP does not measure dissolved oxygen directly, nor is it a measure of dissolved oxygen content in the water. You use a DO meter to measure dissolved oxygen. ORP is a measure of the potential of the water to oxidize substances in it. To us this usually means the decay of waste products. How much potential the water has to carry out this decay is dependant on many things, dissolved oxygen, temperature, pH, amount of contaminants, the presence of other oxidative chemicals (such as chlorine or potassium permanganate) and so on.

The chances are that if you have a high value of ORP (say 300 and above) and you do not have any oxidative chemicals in the water then the water is probably quite clean. In this way, the value is being used as an indication of how well your filtration system is working and how healthy the water is.

Some folks clean and calibrate their meters very regularly. I find that mine only need calibration at most once a month. Once I left a probe in the pond for four months and it still calibrated correctly. Some meters cannot be calibrated.

Thomas T
05-17-2005, 07:51 PM
The easiest way to build up your ORP to 300+ is installing a large trickle Tower or Bakki Shower like Carloskoi's. If you have a submerged medium filter system, it'll be tought to break the 300 mark without ozone or PP.

TT

MCA
05-17-2005, 08:58 PM
http://www.koiclay.com/page6.htm

Noahsnana
05-18-2005, 12:01 AM
Thank you nicco for politely correcting me I really appreciate it.

Noahsnana
05-18-2005, 12:17 AM
http://www.koiclay.com/page6.htm

Thank you MCA explained everything.

Measure of pollution... boy was I going I the wrong direction.

MCA
05-18-2005, 06:19 AM
You are welcome. :D:


While we should all target our pond water to be around 400mv, the reality is most of us are doing good to be in the 300 range. But everyone should have water that greater than 200.

Blammo
05-18-2005, 06:41 AM
You are welcome. :D:


While we should all target our pond water to be around 400mv, the reality is most of us are doing good to be in the 300 range. But everyone should have water that greater than 200. Right, Mike.
To elaborate..
ORP, if used at all, should be to get an AVERAGE measurement of water " quality"
This means measure a couple times a day over a MONTH to get an average.
Feeding, rain, water changes, leaves(leefz ?) in the pond all DRASTICALLY change ORP.

There are SOME :rolleyes::rolleyes::rolleyes: who chase it hour by hour... Idiocy ! :p:

The meters best job is in doing "prolonged" PP treatments :rolleyes::rolleyes::rolleyes:
I wont elaborate on "prolonged", at this time... :no:

Noahsnana
05-18-2005, 08:18 AM
Is there any other way to measure DOCs levels?

Noahsnana
05-21-2005, 09:43 AM
Is there any other way to measure DOCs levels?

Anyone?

allen42
05-21-2005, 09:55 AM
Thanks for starting this Thread Nana , I sho nuff learned something from this & now i want a ORP meter !!

Noahsnana
05-21-2005, 09:58 AM
Me too Allen. Just curious as too any other way to measure the pollutants on the water beside sight and ORP.

koiingaround
05-21-2005, 11:42 AM
Me too Allen. Just curious as too any other way to measure the pollutants on the water beside sight and ORP.

I have been wanting one for a year now...
hehehe but there are soooo many other things that are always needed too...sigh... :rolleyes: ;) :rolleyes:

nicco
05-21-2005, 12:31 PM
Is there any other way to measure DOCs levels?

Well perhaps you should go back and read the first few explanatory posts again. ORP meters do not measure DOCs directly either. Don't think anyone brought those up. Any decay or reduction process in the pond including the decay of solid materials affects ORP - say dead skin cells from fish.

DOC's are a separate topic and perhaps deserves a separate thread. How would you measure DOC’s? First you’d have to know what they are as they can be many things, then some combination of meters may help out – say TDS (since this measures total dissolved solids and is typically calibrated to one ion), ORP (because decay of DOC's will be a component of the total decay in the pond) and turbidity (for DOC's that stain the water) meters. Better to avoid the problem altogether by having a filtration system matched to your stocking level and doing regular water changes.

Noahsnana
05-21-2005, 01:51 PM
Well perhaps you should go back and read the first few explanatory posts again. ORP meters do not measure DOCs directly either. Don't think anyone brought those up. Any decay or reduction process in the pond including the decay of solid materials affects ORP - say dead skin cells from fish.

DOC's are a separate topic and perhaps deserves a separate thread. How would you measure DOC’s? First you’d have to know what they are as they can be many things, then some combination of meters may help out – say TDS (since this measures total dissolved solids and is typically calibrated to one ion), ORP (because decay of DOC's will be a component of the total decay in the pond) and turbidity (for DOC's that stain the water) meters. Better to avoid the problem altogether by having a filtration system matched to your stocking level and doing regular water changes.

Again thank you nicco... I am learning

Yes I believe it is time to start another thread concerning my last question.

Roddy Conrad
05-21-2005, 06:39 PM
A TDS (Total Dissolved Solids) meter is just a conductivity meter with a calibration to read conductivity as total dissolved solids. Conductivity meters are also sold with a slightly different calibration to read out as % salt in the water. The conductivity is "mainly" affected by dissolved salts, and only slightly affected by the DOC level, in most pond waters. There are exceptions for sure to any generalization about ponds!

ORP does more directly measure DOC content. But the ORP reading is affected by many variables, to name a few:

1. DOC content, higher ORP readings mean less DOC content, if the ORP reading is below 150, the DOC content is really too high to be healthy for the fish.
2. pH value, higher pH gives lower ORP readings, lower pH gives higher ORP readings. For example, dropping the pH from 8.3 to 6 without anything else changing but pH increases the ORP reading by about 100.
3. Temperature, lower temperature gives higher ORP readings, increasing temperature from 50F to 85F drops ORP reading by 50 to 75.
4. Lack of routine cleaning of the ORP electrode gives a slow drift upwards to the reading from the meter, if the probe has not been chemically cleaned for over a week, the usual behavior is the meter is giving a false high reading by about 100 points.

stephen
05-21-2005, 06:49 PM
Excellent post Roddy:yes: :yes: :yes:

Noahsnana
05-21-2005, 09:17 PM
When reading what MCA posted re: roddys link at KoiVillage on ORP I read it as ORP registers pollutants.... and I related it to DOC's

nicco
05-21-2005, 10:15 PM
Be aware that you can get low ORP and low DOC's too. So it's not the perfect indicator.

Some Brits have been using TDS meters to measure DOC's, but it's a little iffy. It's a bit like depending entirely on your ORP meter. What they do is they measure TDS of fresh water that they put in the pond after whatever treatment they employ. Then they keep track of the TDS readings in the pond. They set a threshold where, if an uppe value is reached they deem it time to refresh the water, or the continuously feed new water into the pond to maintain what they think is a reasonable reading.

The thought behind this rightly or wrongly is that any additional dissolved solids that turn up in the ponds is due to waste. It works for them.

The fact is that many top end koi keepers don't use either ORP nor TDS. So take it for what it's worth.

Stephen on the other hand has a couple of dozen of them and from his recent posts on his pond he doesn't trust any of them. Hey Stephen how about an update on that thread?