Installing UV Sterilizer ?

[DaneDad]

Due to my homebrew dual 55g biofilter, I would like to know if I can connect a 40W UV on the supply side rather than the return. Advantage would be ease of installation and maintenance.

Would like to know what the disadvantages are being that it would be installed prior to the biofilter?

 

[Mucky_Waters]

Would like to know what the disadvantages are being that it would be installed prior to the biofilter?

If your bio-filter is already established then there should be no problem at all. If your bio-filter isn't estabished and you hooked up your UV light, and left it on, it could kill a lot of benificial bacteria before it enters the filter, thus slowing down bacteria colonization.

 

[koiguy1969]

the only advantage to installing a U.V after the filter is the water would be cleaner as it passed thru.but thats pretty much limited to pressurized filters. the time that beneficial bacteria is free floating is minimal,basically, just long enough to find a home. and the bacteria that colonizes the filter will mostly form right there in the filter.like mucky stated it may extend the time it takes to fully colonize the filter, but not by a whole lot. that said, installing a U.V on a gravity return filter after the filter is not a realistic approach, unless youve got a very slow flow of water. a U.V. on the output will more than likely cause overflow prolems with the filters due to restrictions in output flow the unit will cause. i ran mu U.V before my filter for years, worked fine.however, i do use prefilters. so they minimize the amount of crud pushed thru.

 

[Waterbug]

A strong UV will kill 99.9% of bacteria (good and bad) passing thru it. However that this would interfere with getting a colony going in a bio filter has never been shown to be true. The problem is thinking the bacteria in the bio filter only come thru the UV. This is like irradiating food. It does kill all bacteria on the food, but that doesn't mean bacteria won't land on the food and start reproducing a second after the food was irradiated.

At least some species of Nitrosomonas and Nitrobacter do have a free swimming stage in their life cycle, but they can complete that stage within a bio filter. Remember they live in a much different world. These dudes are in the 1 micron range. If we were that size a 55 gal drum would appear to be 9x14 miles in size. At the 1 micron size there are huge dead spaces in a filter. Also not all species have been studied in that detail.

There's no down side to placing a UV before a bio filter. There is an advantage when placed after a good mechanical filter, like a sand filter, because the water would be cleaner and fewer particles to shield algae from UV rays. But that's a pretty small advantage imo.

The only other issue is controlling flow thru the UV. Often flow has to be reduced to get it right for conditions in the pond. The spec gives the max flow. But if water is cloudy flow has to be reduced. So generally a bypass is installed so rather than just restricting total flow through the pond only flow thru the UV is restricted. The excess flow is directed around the UV. But simply running a pipe around the UV isn't enough because water pressure on both sides of the UV would be the same and that makes a mess of getting water thru the UV. Instead you want the bypass and the UV outflow to be open, like each dumping into the pond or a waterfall or dumping into the top of a filter, not beneath the surface of a filter.

So to me you can place the UV before the bio filter but the water from the UV shouldn't go into the bio filter unless it flows into the top and the bypass also flows into the top. The bypass could probably go into the filter beneath the water surface but there could be flow issues in your specific system. They shouldn't both share the same pipe going into the filter.