Some of my thoughts. I endorse Bean's suggestions. (It's nice to get consensus in threads. It makes people more confident that a given suggestion is well founded instead on just one guy's opinion)
1) For the question about o-u-o or u-o-u it depends on the source of the water that contain micro bubbles. I once had a baffle arranged in u-o-u fashion which didn't work well since my drain line was aimed right at it. The directed flow pushed a significant amount of bubble filled water right under my first baffle. On the other hand if you don't have a lot of directed water flow where intake on the box you're making is going reside, then u-o-u may work better. Look at your existing sump. If there are a lot of micro bubbles making it down to the lowest levels, go o-u-o otherwise u-o-u. That's my suggestion on that issue.
2) When you do decide which way to make your baffles, think about baffle spacing. Bubble filtering takes place when the rate that bubbles rise is faster then the downward flow rate of the water surrounding them. In other words you've got to make the downward flow compartments as large a possible to slow down the water to get better bubble filtering. Smaller bubbles rise slower.
That being said, you don't get any bubble filtering from the compartments between baffles that create upward flows. Make these as small as possible, but still large enough to easily allow your maximum flow rate.
The mistake most people make is to evenly space the u-o-u or o-u-o compartments. What I'm suggesting is don't center that middle baffle in the bubble trap. Move it over as far as you can to make the down flow slower and the up flow faster. That way for the same given space, you will maximize your bubble trapping capability.
3) Consider the evaporation of the water in the return section. If you don't have an ATO (auto top off) you are going to get a water fall in one part of the bubble trap when your water evaps. This will create microbubble at the worst possible place, right next to your return pump. Also consider making it large enough to handle a full days worth of evap so you don't go crazy all day keeping that compartment full. Definitely implement some ATO system if you haven't yet. It's very worth it.
Hope this helps.
Kyle
