Fenton's Reagent for Disinfection

[Papa]

i need a little help from our chemistry gurus.

i'm curious about how i would go about utilizing Fenton's reagent to disinfect a dwc system.

i have 30% H2O2.
i was looking at this for the iron sulfate:

will it work alright?
i'm wondering if i could use muriatic acid to lower the pH (which i have) or if it's better to use sulfuric acid?

now, after i have the proper chemicals, what amount of hydrogen peroxide and iron sulfate should i use per 100 gallons of water?

i found this paper interesting:
http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1152&context=usepapapers
but i know that e.coli is relatively easy to kill compared to other things we may be after in a system, so any knowledgable recommendations regarding dosages would be much appreciated.

 

[straincreation]

Hit up squiggly on his chemestry thread he will most likely have thee answer your lookin for. Im on my tablet so its a bitch to link. Your a mod so you should be able to find it rather quickly.
Happy farmin;)

 

[seebobsled]

This is a cut n paste but all info on the subject!
Iron
Truly Cleaning Your Hydroponic System : The Fenton Process and Chemistry

When most people clean their hydroponic systems they use a hypochloride or hydrogen peroxide wash that they think kills all the bacteria and potentially hazardous substances within their setup. However few people realize that – although the system is indeed sterilized – the bast amount of harmful substances and chemicals (even those coming from the plastics themselves) remain intact after the attack of either hypochloride or peroxide. For example, many of the harmful plasticizers and complexes used for the making of PVC and other polymers remain intact after a rigorous wash with these two cleaning agents. So what can we do to truly clean our hydroponic systems and get rid of all the bad things that may be quietly waiting their turn to get into our plants ? The answer comes in the form of a very well known process used world-wide to clean water supplies from toxic chemicals : the Fenton process.


In the late 19th century, Henry John Horstman Fenton discovered a chemical process which was able to oxidize the most resilient organic molecules and turn them into harmless chemicals. As a matter of fact, Fenton’s process was so revolutionary that it sprouted a whole new area of research called Fenton chemistry in honor of its discoverer. What was this wonderful discovery ? Within the next few paragraphs you will learn what the Fenton reagent and process are all about and – most importantly – how this process can help you clean, I mean REALLY clean, your hydroponic system between growth cycles.
-



-
If you have been preparing your own hydroponic solutions and you have been using hydrogen peroxide then you already have most of the things you need to do some Fenton chemistry. The process basically works by adding a source of iron ions (they must NOT be chelated, like iron (II) sulfate) and hydrogen peroxide to a water solution. The iron ions then catalyze a series of reactions that generate powerful oxidizing radicals that destroy almost all harmful organic substances within your system. The iron ions are KEY to the Fenton process since they allow peroxide to generate this extremely reactive substances that are never present when peroxide exists on its own (reactions shown above). Research has found – for example – that phenol (a common chemical used as a model contaminant) remains unchanged in the presence of large concentrations of hydrogen peroxide while it is quickly destroyed in the presence of the Fenton reagent (Iron ions plus hydrogen peroxide). So what do you need to do ?

• First of all you should add about 0.2g of Iron (II) sulfate per liter of solution you will be using to clean your system.
• Then you should set your pH to a level between 3 and 3.5 using a STRONG non-organic acid such as nitric or sulfuric acid. You should NOT use citric, acetic or phosphoric acids since they lower the effectiveness of the Fenton reaction.
• Add as much peroxide as you would add to regularly clean your system. About 70mL of 50% hydrogen peroxide for each liter of solution works very well.
• Circulate the Fenton cleaning solution for at least 6 hours.
• Wash your system with water until no Fenton solution remains.

It is key for you to use a non-chelated iron source since chelated iron sources such as FeEDTA or FeEDDHA do NOT work well since the chelate does not allow the iron ions to properly react and participate in the Fenton chemistry that should be going on. The pH adjustment step is also vital since a pH above 5 would cause the formation of FeOH3 instantly upon the addition of H2O2 with the subsequent catalytic decomposition of all the H2O2 by the iron hydroxide (this is NOT something we want !). After you use the Fenton reagent to clean your system you will be certain that a lot of the harmful organic molecules that were present have been destroyed and your system will now be able to play as a sterile and harmless host to your new set of beautiful plants.

 

[seebobsled]

This is a another cut n paste but I have used this process to clean my ebbngrow ! It is similar to the first one but no iron and uses bleach for the disinfectant and low pH to get hard water and salt stains off. I thought it was easy and worked


Sterilizing hydroponics system between crops
Do not under-estimate the need for post harvest clean-up. Failure to do this properly can result in ongoing problems from disease, plumbing blockages and broken pumps.

Two separate precautions should be taken to ensure hardware is clean prior to replanting:

1. Disease preventative

2. Precipitate removal


Disease prevention

At the end of each crop it is necessary to sterilize the entire system to help prevent disease problems in the next crop.

Step 1. Remove plants and medium from the system then do as much manual cleaning as possible. External cleanliness of the system and growing area is as important as internal.

Step 2. Partly fill the reservoir with water. Lower the water’s pH to between 4.5 and 5.5. Then, after providing good ventilation for the area and subdued light conditions, add household chlorine bleach** (50g/L chlorine) at ~5ml per litre (4 tsp per Gal).

Step 3. Mix well, then soak system for 24 – 72 hours. While the system is soaking:

- Recirculating systems: Run the pump for at least 15 minute cycles every hour^.

- Run-to-waste systems: Run the pump for a short burst once every hour^.

Step 4. Discard this solution then flush the whole system several times with small volumes*** of fresh water to remove all traces of chlorine and dislodged material.

^ Note that there must be adequate ‘contact’ time (e.g. minimum of 24 hours) between the chlorine and all surfaces e.g. system sidewalls, pipes, etc. Pay particular attention to areas where there is usually zero water flow, such as dead-spaces in taps. ‘Flooding’ may be necessary to contact hidden surfaces e.g. underneath the upper surface of channels.

Also, note that chlorine bleach will not dissolve algae or general solid material. Only wet brushing will remove those contaminants.

*** Several small volumes are more effective than a single flush.

Step 5. Where fine drippers and sprayers are used, it may be necessary to individually dismantle and clean each unit.

For details on how to remove salt precipitates (build-up) from hydroponic systems click here

** Avoid contact with metal parts and ensure to follow necessary safety precautions. Use protective clothing (e.g. mask, goggles, gloves).



[Growers Guide Main Index]

Related topics:

"System & plant maintenance":

General hygiene | Discarding old nutrient solution | Flushing root zone | Nutrient disinfection | Nutrient deficiency symptoms

Disease control | Pest (insect) control | Pruning | Plant support | System clean-up between crops | Foliar Fertilizers

 

[Papa]

thank you seebobsled.
your first post had one of the issues i'm having trouble with . . . . "Add as much peroxide as you would add to regularly clean your system. About 70mL of 50% hydrogen peroxide for each liter of solution works very well."

for a 100 gal system, that's a recommendation of 26.5L of 50% hydrogen peroxide. or 7 gallons. i can only get 30% H2O2 here, so I would need 11.6 gallons of 30%. that's a hell of a lot of hydrogen peroxide . . . a LOT more than i've ever used alone to sterilize. the paper that i linked to demonstrated total extermination of e.coli at every dosage tested . . . . so understand my question about having to use 11.6 gallons of H2O2.

what was the dosage that you found effective?

 

[seebobsled]

I have only used the last process with low pH and bleach. That looks right on quantity but dam that rate it is expensive. I had battery acid and bleach so I used that process to clean. It worked well. The biofilm was removed from tubing and not much scrubbing. I think it might be a good for the Fenton process for a new plastic system clean for plastic leaching. That is the only reason I see to use Fenton's. Bleach can kill ecoli and cheap ! H2o2
is not.

 

[seebobsled]

You could isolate each module and drop a pump in to circulate. That would reduce volume! This is a rdwc right? Home depot has rubber plugs for most PVC size pipes. It would be a bit labor intensive but a lot less h2o2. Get three plugs. 2 to plug module and one more to plug next module and pump from the module that is done to next module.