An Innovative Wetland for Innovation Day

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Did you know February 16th is Innovation Day? Perfect timing again! I mentioned an “innovative” use of Eco-Blox in a blog celebrating World Wetland Day February 2nd. I think it only appropriate that I expand on that innovative use this week.

To start with, let’s look at the word. According to Oxford Languages, the group that publishes the Oxford English Dictionary (my mom’s favorite), “innovation” means ‘featuring new methods; advanced and original’. Water matrix blocks were themselves the very definition of innovative when they were invented by Humberto Urriola, who came up with the idea of a modular drainage cell back in 1984. His Flo-Cell® was a flat three-dimensional mat that, in various configurations, captured, transported and held stormwater long enough for it to percolate back into the ground, recharging fragile aquifers, critical given the climate and erosion issues Down Under.

Almost four decades later, water matrix blocks are still used for stormwater mitigation and rain harvesting, but the latest innovation involves using their storage capacity to capture and remove even the finest sediments suspended in pond water. They’ve been used to trap sediments in dual chamber rain harvesting systems before, but this is a different application, one that combines the physics of sedimentation with the advantages of upflow bogs.

The idea is simple. First, the physics in a nutshell, because the math is beyond me. When velocity drops, solids drop out. Pump solids-laden water into an Eco-Blox chamber that’s only open at the top, with lots of partitions, and cover the top with a thin layer of gravel. The water slows to nothing if the chamber’s big enough, and forcing the water to exit upwards, through the gravel, ensures that virtually all sediments will drop out of suspension and stay in the chamber.

And sediment is only half the issue. Dissolved organics and minerals in the water, which would have fueled algae blooms, pass through that same gravel bed. Billions of bacteria thriving in the well-oxygenated nutrient-rich water strip out ammonia and nitrites, excreting nitrates right where the roots of plants spreading through the gravel can absorb them. The plants will also thrive, the water will be stripped of all organics and algae will never get a foothold.

Standard stuff, but the innovation is in the details. The appropriate number of Eco-Blox for the volume to be cleaned, the correct flow into the chamber, the right thickness to the gravel bed, the optimal plants for the artificial wetlands –that’s all pretty straightforward. The innovation is in the delivery of the sediment laden water, and the flushing of the accumulated solids in the chamber.

The delivery is a matter of shaping the bottom to accumulate solids near bottom drains, and plumbing the skimmers to pull water off top and bottom to deliver wastes to the chambers. But, you may say, there are lots of ways to gather sediments, and any gravel bed will trap them, both valid points. The trick is keeping the gravel from clogging, channeling and going septic when oxygen can’t penetrate the accumulating goop. That’s the huge advantage to creating these Eco-Blox bogs, and upflow is the key. 

Traditional downflow bogs pull water through a large volume of gravel, often feet thick, to trap organics for years, but over time channeling renders them less effective. Anaerobic zones build up with no easy way to clean them out. Downflow grids of perforated pipe, covered with a thinner layer of gravel at the bottom of ponds, address these issues, but the grids tend to clog over time and are relatively inaccessible.

Eco-Blox sediment traps are designed to efficiently collect both top and bottom water via skimmers and bottom drains, separate out solids as water passes up and out, then clean easily, flushing sediments out onto grade by turning a valve. The continuous automatic capture and easy removal of solids is the innovation. Monthly maintenance consists of turning a valve or opening a threaded cap for a couple of minutes, to flush the accumulated wastes out where they can be dried and collected – that’s some black gold there.

It’s no wonder that Botanical Gardens appreciate the idea. A filtration system based on plants that cleans and clears vast volumes of water, with no moving parts except multiple magnetic induction pumps, powerful and efficient, inexpensive to buy and run, housed in easily accessed skimmers that require only to be emptied of leaves on a weekly basis? And the system can collect the fertile organic sediments and dry them in a free-draining gravel bed at grade, whenever compost is needed?

Eureka!

Case in point: the Botanical Garden in Culiacan Sinaloa Mexico used riverwater to feed their Victoria Pool, where they showcased the leaves and blooms of the world’s largest waterlily and other aquatics. The 225’ x 30’ pool, about 3’ deep, had a number of serious leaks, so it was constantly being refilled with muddy water that never cleared. The water was so turbid from both mud and algae that you couldn’t see your hand with your arm in up to your elbow. Two 8” weirs that spanned the width of the pool upstream and downstream of the angular bridge provided the only circulation. They had installed a 10hp irrigation pump drawing about 8000 watts an hour, but had to valve it back because the high-head pump cavitated otherwise, so they couldn’t keep the whole weir covered with water. (If that sounds like a foreign language, check out this article I wrote in POND Trade Magazine, Flow, Friction and Total Dynamic Head: A Pump and Plumbing Primer for Ponds)

I’ll tell you what we did – next time.


About the Author:

DEMI FORTUNA

Demi has been in water garden construction since 1986. As Atlantic’s Director of Product Information, if he’s not building water features, he’s writing or talking about them. If you have a design or construction question, he’s the one to ask.

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