Setup for Optimal Flow in a Moving Bed (K1) filter

[InfinityARch]

Hey, so after a bit of a false alarm with my secondhand 120 gallon tank's seals (it's been holding water for a little less than a week with no incident), I'm back to the task of figuring out how I'm going to handle the filtration and plumbing.

While it's by no means necessary for a tank of this size, I'm a fan of moving bed style filtration because of the low maintenance requirements, the high efficiency, and the high ratio of atmospheric oxygen vs dissolved oxygen the filter uses.


Below is my current plan for my sump. It's a somewhat unorthodox design in that the mechanical filtration comes after the biological filtration, but I've seen other people with moving beds doing in like this since it won't get gummed up with detritus like a wet/dry or submerged biofilter would, and the flow of water coming down from the tank can apparently help drive the motion of the media, reducing the size of the air pump you need to run the system. I'm planning on having a final flow rate of 720 GPH, well within the recommended limits for K1 to ensure good contact time, and I've sized the chamber for a capacity of around 16 liters of media (forgive me for mixing metric and imperial units) based on a 60:40 K1:Water ratio. The air pump I'm planning on using is a high-end 16 LPM pump that's supposedly extremely quiet for a pump of its size, and I've heard you want about 1 LPM of air for each liter of media.


Can anyone with experience using this style of filtration offer advice on how I can further refine this design, and how I should set up the air lines to achieve the best results?

 

[Oughtsix]

My theory on filtration, especially sump filtration is to remove the waste before it has a chance to break down into nitrogen compounds.

I do not understand why you don't move compartment "D" in front of compartment "A" so the waste gets filtered out first thing? I understand the K1 is very good at shedding gunk when used in a moving bed... but in my experience a lot of the gunk will end up at the bottom of the compartment requiring a much more involved cleaning process than just pulling the filter socks and cleaning them.

I have not experimented with K1 moving bed media filters... my concern has always been the noise. Is the sump going to be located where the noise will not be an issue?

I agree with you on the advantages of moving bed K1 filtering for its capability of adding huge amounts of oxygen to the water while promoting off gassing of compounds from the water!

 

[InfinityARch]

My theory on filtration, especially sump filtration is to remove the waste before it has a chance to break down into nitrogen compounds.

I do not understand why you don't move compartment "D" in front of compartment "A" so the waste gets filtered out first thing? I understand the K1 is very good at shedding gunk when used in a moving bed... but in my experience a lot of the gunk will end up at the bottom of the compartment requiring a much more involved cleaning process than just pulling the filter socks and cleaning them.

I have not experimented with K1 moving bed media filters... my concern has always been the noise. Is the sump going to be located where the noise will not be an issue?

I agree with you on the advantages of moving bed K1 filtering for its capability of adding huge amounts of oxygen to the water while promoting off gassing of compounds from the water!

The noise from a moving bed filter largely comes from the air pump; the sound of the media knocking against itself isn't really audible with the stand doors shut, so if you're willing to splurge on an air pump you can apparently cut down on the noise a lot. That's also the reason for having the outflows right there; flowing water further cuts down on the amount of air you need to keep the media flowing properly.

Though if that's going to result in gunk building up in the media chamber that would otherwise be caught in the filter socks, I tend to agree it isn't worth it.

Since I'm using two herbie style drains, the outflows need to be below the water level. otherwise that completely defeats the point of using a full siphon drain in the first place. How would I even be able to access the socks in that event though? The shortest you can get them is 8", and since the outflows need to be an inch below the water level that gives me about 2" of clearance between the socks and the pipes to somehow maneuver them in or out. I suppose I could add a dedicated chamber for the pipes to drain into (and abandon the idea of having a dedicated equipment chamber), but wouldn't the gunk just end up accumulating there instead of in the biomedia chamber?

 

[Oughtsix]

Just blue skying here... how about a PVC slip coupling?

I have used these several times to repair broken sprinklers. The smaller tube slips in/out about 6"... depending which model you buy. There are a couple O rings to seal them and still allow the piece to move. They will hold full household water pressure without issue.

I would mount this coupling upside down so to speak. Cement the smaller sliding piece to your outflow tube suspended above the sump / sock. When in normal operation slide the outside part down into the sock below the water line giving you full siphon. To clean the sock filter slide the outside piece up, remove the sock filter, replace it with a clean filter sock, then slide the outside piece back down to under the water level. The only reason I recommend mounting it upside down is that it will be easier to slide the outside piece up and down than to try to slide the little inside piece up and down.

What do you think?

 

[InfinityARch]

Just blue skying here... how about a PVC slip coupling?

I have used these several times to repair broken sprinklers. The smaller tube slips in/out about 6"... depending which model you buy. There are a couple O rings to seal them and still allow the piece to move. They will hold full household water pressure without issue.

I would mount this coupling upside down so to speak. Cement the smaller sliding piece to your outflow tube suspended above the sump / sock. When in normal operation slide the outside part down into the sock below the water line giving you full siphon. To clean the sock filter slide the outside piece up, remove the sock filter, replace it with a clean filter sock, then slide the outside piece back down to under the water level. The only reason I recommend mounting it upside down is that it will be easier to slide the outside piece up and down than to try to slide the little inside piece up and down.

What do you think?

It's a nice sounding idea, but the issue is I don't think I have enough space for those kinds of couplings given how I'm laying out the piping, the bottom-most one has like 1" of clearance between it and the lid of the sump.


Here's my current revision with the mechanical filtration first.

 

[Oughtsix]

Looks good!