Oxidation Reduction Potential (ORP)

What is oxidation-reduction potential?

Oxidation-reduction potential (ORP) measures the ability of a lake or river to cleanse itself or break down waste products, such as contaminants and dead plants and animals. When the ORP value is high, there is lots of oxygen present in the water. This means that bacteria that decompose dead tissue and contaminants can work more efficiently.

In general, the higher the ORP value, the healthier the lake or river is. However, even in healthy lakes and rivers, there is less oxygen (and therefore lower ORP values) as you get closer to the bottom sediments (mud; see the picture below of a lake bottom). This is because there are many bacteria working hard in the sediments to decompose dead tissue, and they use up a lot of the available oxygen.

In fact, oxygen disappears very quickly in the bottom mud (often within a centimeter or two) and ORP falls quickly.Oxidation-Reduction Potential (ORP) is measured in addition to dissolved oxygen because ORP can provide scientists with additional information of the water quality and degree of pollution, if present. Also, there are other elements that can function like oxygen (in terms of chemistry) and contribute to increased ORP.

Why does oxidation-reduction potential matter?

ORP depends on the amount of dissolved oxygen that is in the water, as well as the amount of other elements that function similarly to oxygen. Though not technically correct, oxygen and other elements that contribute to high ORP effectively help ‘eat’ things that we don’t want in the water – such as contaminants and dead tissues.

When ORP is low, dissolved oxygen is low, toxicity of certain metals and contaminants can increase, and there is lots of dead and decaying material in the water that cannot be cleared or decomposed. This is obviously not a healthy environment for fish or bugs. In healthy waters, ORP should read high between 300 and 500 millivolts. In the North, we might expect low ORP in waters that receive sewage inputs or industrial waste.

How do we measure oxidation-reduction potential? It is measured directly in the lake or river water that you are investigating using an ORP sensor or ORP Meter. ORP is measured in millivolts (mV) and the more oxygen that is present in the water, the higher the ORP reading is. ORP can either be above zero or below zero.

References/For More Information

Horne, A. J., and Goldman, C. R. 1994. Limnology, 2nd edition. McGraw-Hill, Inc. 576 pp. Wetzel, R. G. 1983. Limnology, 2nd edition. Saunders College Publishing. 760 pp. wikipwdia

RO vs UV Purifier: Which One is Right for You?

RO vs UV Purifier: With pollution levels increasing over the globe, access to clean drinking water is becoming exceedingly difficult. However, thanks to water purifiers and continuous advancement in them, it is getting easier to get clean drinking water to your home. While water purification technology has gone through many improvements in the recent past, two types of water purifiers that stand out are RO and UV water purifier.

As per our Topic “RO vs UV Purifier: Which one is right for you?” we can see that Both come with their own pros and cons. This often creates confusion among consumers when thinking of buying a new water purifier. Understanding the difference between RO and UV purifiers can help you in evaluating which fits your requirement the best. Read on to find pointers that sheds light on the difference between the two.

  • The Working Principle

Reverse Osmosis (RO) systems use a semi-permeable membrane that removes dissolved salts, large particles as well as most types of bacteria and germs. This is done by moving molecules from a region of high concentration to one of low concentration, using pressure to push water across the membrane, leaving the impurities behind in each stage.

Ultra Violet (UV) systems use UV rays to perforate the harmful pathogens in the water. By directly attacking the genetic core of bacteria, it kills the bacteria.

Verdict: RO purifiers can reduce the total dissolved salt content of the water and remove most bacteria but may not be as effective in killing some types of bacteria. UV purifiers, on the other hand, maybe good to kill the invisible bacteria but may not be as effective for lowering the dissolved particles in the water.

  • Maintenance Hassles and Costs

The quality of RO determines its maintenance costs. A low-quality RO compromises on its filters which thus require regular replacement for effective results. Whereas a good quality RO is certain to give 100% pure water and thereby less maintenance hassle. However, even the good RO systems would need at least some or all of the filters being changed after one year.

UV water purifier, on the other hand, functions using a UV lamp. While there is no definitive way to find out if the UV lamp is working or not, most experts usually recommend changing it after one year. Some purifiers also come with UV alarms that let you know when the lamp is not working.

Verdict: Both RO and UV purifiers have a similar maintenance cost. Buy a machine that uses good quality filters and always use company recommended filters when replacing them to ensure the efficacy of the purifier. 

  • The Water Source

As already mentioned above, while RO systems remove the bacteria and other impurities, UV kills them. Thus, RO purifiers also use a pre-filter in most cases which can handle highly impure water with high levels of dissolved particles. UV purifier, on the other hand, does not use a pre-filter to remove physical impurities.

Verdict: While a UV purifier is great for killing invisible bacteria that may pass through the membranes in the RO systems, it cannot remove dissolved salts from water. For that, you need an RO purifier.

  • Water Consumption and Wastage

Since UV purifiers kill bacteria by passing water through UV lamps, it results in zero wastage of water. However, an RO purifier eliminates contaminated water at every stage of purification. This leads to a considerable loss of water.

Verdict: RO purifiers waste more water than UV purifiers. While this wasted water may not be fit to drink, you can use it for other chores of the house such as cleaning the house, washing clothes, and watering the plants.

Choosing the right type of purifier may be challenging. Consider factors such as type of water supply, level of contamination and other factors to select the right type of purifier. Whether you buy RO water purifier online or a UV purifier, make sure you choose one that promises good quality water and least maintenance hassles. You can also select a RO+UV purifier to get the advantages of both the technologies.