Hi all,
Most who have used both and been in a position to develop a preference, go with the Sera. 34% greater ability to house biological bacteria. That has to be worth something. I know what I would prefer
&
I have spoken to several people at the top of their field, including a cutting edge aquatic retailer and aquascaper who stocks EHEIM filters but will not stock their media in preference for Sera Siporax.
Don't get me wrong I like Siporax as well, but honestly it is just personal preference. I haven't got a product to sell, I like all the ring shaped media, and if some N2 out-gassing happens from a porous media, so be it, but that isn't my primary interest.
To go down the car analogy I drive a "
W reg 1 litre Vauxhall Corsa with 105,000 miles on the clock, that I bought 7 years ago for £1800", so that might tell you where I am coming from.
We have some kit (if I can find it) which allows you to measure DO2 in a chamber, but it won't tell you anything different. We used to do a lot of work in the lab with landfill leachate, which you can think of as uber polluted tank water, and the only reason you would use a sealed vessel (like a external filter) is for anaerobic fermentation. Honestly gas exchange and oxygen are the key, and after that everything else is just "
re-arranging the deck-chairs".
Calzone wrote:
Thinking about it, my question now would be, would I be better taking say 50%of the media out to improve flow as the surface area will still not be limiting but better flow will decrease boundary layer thicknesses and therefore improve new gas/nutrient diffusion into the pores?
Yes it would, with most canister filters performance actually improves as the amount of media is reduced, or if you change to a media which clogs less easily. This is why I have a regularly cleaned coarse PPI10 pre-filter sponge on the filter intake, and 1/2 fill with media that won't clog (like ceramic/sintered glass rings, alfagrog or "coco pops"). You can then direct the flow from the venturi straight at the sponge, the intake can't suck in the large air bubbles and the pre-filter sponge stops any bulky organic debris from getting into the filter, I just want the NH3 in there and the flow speed to remain quick through the filter. All this "
you need the flow speed to be low enough for the bacteria to be able to absorb the NH3 is a fundamental misunderstanding (or attempt to confuse?) about the processes involved. Both plants and fast linear flow help ensure water oxygenation, water plus NH3/NO2 and O2/CO2 is then re-circulated through the filter media as frequently as possible, the NH3/NO2 is consumed, the gases diffuse in/out along their diffusion gradients at the waters surface and the plants assimilate the NO3. It is KISS solution to bio-filtration, compare this to this set-up suggested by Sera: <
http://www.sera.de/uk/hauptseiten/s...-siporax-what-kind-of-filter-is-suitable.html>.
The other thing to think about is if all the water in the filter becomes de-oxygenated you continually return NH3 to the tank, but if you have a high flow system that doesn't allow any denitrification, you return NO3 to the tank, and I know which I'd prefer.
Foxfish has written the important bit:
.......No I am not saying that, I am saying there is a limit to the effectiveness of porous media inside a plastic box with limited oxygen. You can have 10 billion holes per square inch of media or 20 trillion holes per square inch but only a fraction of the surface area will be effective. If you expose the media to air then the only limiting factor is bacteria food! On that basis there is no need for a porous media in a trickle tower because the non clogging plastic bio balls will be effective enough."
There is some work being done on re-circulating systems using biofilters (RBFs), obviously they tend use cheap bulky substrates, but this one should be available and is quite interesting. This paper (Hu & Gagnon) found crushed glass (not sintered, but just crushed re-cycling glass) is a very effective medium, and there is now a lot of work on crushed glass as a filter material (See Horan & Lowe).
Hu & Gagnon (2006)
"Impact of filter media on the performance of full-scale recirculating biofilters for treating multi-residential wastewater".
Water Research 40:7 pp. 1474–1480.
Abs. "
The average influent 5 d biochemical oxygen demand (BOD5) and total suspended solids (TSS) concentrations into the field filter system were 381±64 (mean±standard deviation) and 46±21 mg/L, respectively. The results showed that crushed glass could be an effective medium in RBFs since the crushed glass filter produced stable effluent BOD5 and TSS concentrations of less than 20 mg/L. Geotextile was found to be another successful alternative filter medium with the effluent BOD5 and TSS of 18±11 and 11±7 mg/L, respectively, even though the porosity of geotexitle filter was as high as 0.90." <
http://www.sciencedirect.com/science/article/pii/S0043135406000819>
Horan & Lowe (2007) "Full-scale trials of recycled glass as tertiary filter medium for wastewater treatment".
Water Research 41:1, pp. 253–259.
Abs. "
Pilot-scale trials at a domestic wastewater treatment works compared the performance of three grades of recycled glass (coarse, medium and fine) when used as tertiary filter media for total suspended solids removal (TSS). Fine glass produced the best effluent quality but blinded rapidly and coarse glass could process three times the flow but with a reduction in final effluent quality. The medium glass offered a compromise with similar flow characteristics to the coarse glass, yet still achieve good solids removal, albeit less than the fine glass. Full-scale studies compared the performance of medium glass with the sand medium that is typically used in this application. There was little difference between them in terms of TSS removal, and they both removed around 75% of TSS from the influent, provided that the solids concentration did not exceed 70 mg/l. However, the glass media had superior flow characteristics and was able to treat an additional 8–10% of the influent following the backwash cycle." <
http://www.sciencedirect.com/science/article/pii/S0043135406004702>
cheers Darrel
