If UV is designed properly it is very inexpensive in running costs and is often used.

I cannot think of anything less expensive in running costs other than solar methods, but these I believe are quite demanding in capital costs and with limited effectiveness.

I think we can try to use metabolites from biocontrol agents. May be I will/ can try to check this.

Ozone is also effective when the water is fairly clean of debris

Copper is also effective at very low rates (even 5 ppm) against Phytophtorae and it is used to clean water for irrigation of citrus

Somebody should offer a prize for the solution to solutions.

A second prize for cleaning seed in a novel and effective way.

David, I agree, of course without using of any pesticide...

Slow sand filtration is the best way to remove the pathogenic organism. may be the attached file useful for you. Also, I had asked some elder villagers to how to deal with water before potable water entered in their village. They only added some of sesame to the water container before use to drink.

 may its interesting foe some persons

Dave Sands, the question is about irrigation water not about seeds !

Alex you say 'expensive' and 'not applied in the field'. Expense is of course relative, particularly in relation to the value of the crop and the effect of losing customers - in the UK there are growers using chlorine dioxide injection of irrigation water for high value field crops. The main driver is concerns about  human pathogens and being seen to be doing something by their customers.

In UK SSFs tend to get used to treat rain catchment and recycling on nurseries. All the others also tend to get used in nursery situation.

I think a combination of Colloidal Silver and Nascent oxygen releasing compounds like Potassium Mono persulphate is a better option

I recomend that use a special device which combination of UV and ozone. If  water  through the device some pahogen and plankton  will be died.

Colloidal Silver and Nascent oxygen releasing compounds is cost effective and kills virus, bacteria, yeast, fungi and moulds.

A large range of plant pathogenic bacteria, fungi, oomycetes, nematodes and viruses has been reported from irrigation water resources, in particular irrigation runoff containment basins. Release of irrigation water with clean tools and production areas will help prevent many disease-causing microorganisms. Several kinds of disinfectants are used to treat greenhouse benches, pots, tools, and equipment used for planting and harvesting. These materials include products with peroxide, quaternary ammonium, and/or sodium hypochlorite (bleach) bases. Fruit growers use copper sulfate, introduced near the irrigation water intake, in an effort to reduce losses from sprinkler rot. Container nurseries recycle irrigation water and use a variety of chemical methods to disinfect it; chlorine gas, sodium hypochlorite, and ozone systems have been installed but with variable efficacy. Fumigating soil or media for control of weeds and insects will also control many fungi. Soil fumigation using methyl bromide with or without chloropicrin is effective but too expensive. It was phased out after being classified as an ozone depleter under the Clean Air Act. Other effective soil fumigants include metham sodium and dazomet products which break down in soil to isothiocyanate. Metham sodium can be applied with irrigation water.

Colloidal Silver and Nascent oxygen releasing compounds are GRAS and non-carcinogenic and possess long lasting effect

@All, thank you a lot for contribution to this discussion. I can summarize that application of:

1) Colloidal Silver or Nascent oxygen releasing compounds like Potassium Mono persulphate (Vijayaraghavan Gonuguntla);

3) combination of UV and ozone (Jeong-Yeol Lee), ozone (Parm Randhawa)

4) chlorine dioxide or use of rain water (Steve Roberts) @Steve, David, I have asked the same question about seeds regarding bacteria and viruses 

5) Slow sand filtration and sesame seeds (Fikrat Hassan)

6) Copper (>5 ppm) (Gianfranco Romanazzi)

7) metabolites from biocontrol agents (Naveen Arora)

8) UV (including solar methods) (Henrik Rasmus Andersen)

9) peroxide, quaternary ammonium, and/or sodium hypochlorite (OGESH CHANDRA TRIPATHI)

may be very useful.

I would suggest some more hypothetical methods that could be applied too:

10) low frequency or microwave electromagnetic fields, electric current through water.

11) bacteriophage cocktail (against bacteria)

12) biocontrol agents (bacteria)

13) cationic detergents 

From my experience – efficiency of any method depends on amount of solid particles, including eukaryotic cells in water. I believe that ideal method must kill plant pathogens and leave alive saprophytic microbes like hot water (50oC) treatment for seeds. 

I go with Dr Alex.

A beautiful summation and new suggestions.

Silver is an intelligent biocide. It is selective. It kills alkali loving pathogens and promotes acid loving beneficial microbes.

Regards

VIJAY 

Vijay, 

Silver and copper are good synergists  in combination with other antimicrobic agents - in our experiments colloid silver could “fix” the problem of antibiotic resistance in bacteria.

Alex

WE offer Colloidal Silver and copper combination for use in Agriculture for Soil Sterilization since about four years where the crops are more prone for virus and it is showing very satisfactory results.

In animals we are using only Colloidal Silver and avoiding copper.

Regards

VIJAY

We found with wheat  that 11 days of dry heat (70C) was a surprisingly good way to get rid of Xanthomonas and Pseudomonas (for foundation seed).. Seed must be put in envelopes and care must be made to avoit their contact with metal. Also we found that tobacco seeds could survive microwave ovens for 10 minutes. This too cleaned the seed of Erwinia aroidae. If you want refs  email me  [email protected]

Nature uses acids and acid fermentation of seeds are interesting. Tartaric acid at 50 mM  pH 3 is a good spray for bacteria.  Most pathogens give up the ghost at pH 3.5

I think we need to look at prices for disinfection of water at scale and per m3. From my experience with water and wastewater nothing can compete with UV. Some years ago I ran some full scale experiments on disinfection of a wastewater treatment plant effluent at the 100-700 m3/h scale and achieved running costs of about 0.03 €/m3.

If one add a chemical disinfectant (other than ozone) one needs to consider the effect on the crop and the long term soil chemistry.

I mentioned solar based disinfection as being cheaper in running costs than UV in my first comment. My point with that was that it is not realistic to use due to the high capital cost of such systems.

have you thought about hydrogen peroxide?

Briceida Covarrubias Thank you your answer. H2O2 is commonly used in greenhouse production, and will be too expensive for field application. Some pathogens can rapidly get tolerance to this agent, like Agrobacterium bv1 that can multiply up to 600 ppm. I think it should be an efficient mix of several active ingredients.