Ok, what's your take on microscreen filters - disc or drums?
The first thing to understand is that all solids within the pond will NOT settle under any circumstances. Why you ask? Well, its all a matter of bouyancies. Only negatively bouyant solids will sink and seperate out given the right circumstances. Vortexes work very well on these types of solids. But neutrally and positively bouyant solids will not seperate out and sink to the bottom. Micro screens act as a physical barrier that will prevent these solids (dependent on the micro screen's size) from passing on to subsequent chambers.
Sure does, Steve. Thanks. What micron size (sizes) would be best to employ? Do you think these systems are as good or better than the ones I mentioned? My research gives me a price about the same as the big Nexus w/Answer.
Billy! Thanks for starting this thread. Anything to do with filtration and I'm there!
I've thought about this quite a bit. A DIY microscreen with extra pump, etc. is an intimidating project to me at this time, but I like the concept.
However, in my mind - why does it have to be a pseudo answer? The screen area seems quite small whereby necessitating the need for sprayers.
If one has a large enough diameter tank, why couldn't a horizontal sheet of screen across the entire chamber between input & output pipes work? If the tank is large enough, I would think it would take quite a while before such a large surface area gets gunked. I.e.; either the output pipe would be over the entire screen, or output pipe coming up through a sealed hole through the screen.
In such a situation, assume the screen would get gunked nearest the output pipe (center). OK - but if said tank is 3.5 feet or so square - & with basic maintenance (draining) - wouldn't it take a hell of a long time to get to the point where the entire screen is blocked from water? Even if there's an unblocked area 3" around the rim - I assume it would still function properly.
Heck - I even think a regular window screen would be helpful to some people.
So - would this horizontal method negate the need for a spray system? FURTHER - would the addition of a mere pissy airstone in the corner of the tank help push away solids so some semblance of a clear area is ensured?
I'm really thinking of doing this so I'd love opinions on if this would work or if my thinking is flawed.
Last edited by Meagain #1b; 06-10-2004 at 04:49 PM.
The rotaing drum filters work on the principles you're talking about. bil has a design he's worked on for a while. I'll see if I can get him in on this thread. Meanwhile, back at AES:
I use micron bags (18 x 24) in my strainer tank prior to the pump. Even with the suction of the pump the 250 micron bags wouldn't last a day. I now use a 800 micron bag and it will last for a few days. Haven't tried to see how long it will go. I just clean it every other day as maintenance.
So Meagain, your idea of gravity flowing over a large area probably wont work well. It will plug quickly as the mesh clogs with the fines. Figure on mine 18 x 24 is 864 sq inches of area and with a fine mesh with suction it clogged quickly. Nicco just set up his from W. Lim and I will check it out. I'm sure he'll post results also.
Garret - but isn't yours pressureized in a pressure system in a relatively small area? I'm talking about a gentle gravity system (settle chamber or vortex) with upflow to an output pipe to mechanical filter or something. Most of the solids will settle out.
You would feed from below with a screen blocking the the output pipe. Heavies will settle and floaters and fines would be stopped. Correct?
Gravity flow wouldn't work because even the slightest clogging of the screen would stop flow. I think you'd have to have a pump feeding it and then it would be a pressure system once it started clogging. Wasn't Bil working on a system to flow water over the top of a flat screen pushing the stuff to the end? I don't remember if he worked the clogging bugs out of that or not.
Order AES's pond supplies catalog. They have a pic of the internals of one of their gravity fed screen systems. That looks like it may work. Problem is the water wasted flushing the crap out. Over on Koivet someone has a thread running on a rotating screen one he made. Slick set up using computer logic etc. Even this one needs a rinse cycle, but mad does it pull the fine crap out. Keep working on one that's cheap to build and run and make your first million.
Garrett - Do you know if AES online has what you are talking about? I'd like to see but haven't a clue what I'd look under.
What I'm thinking of - Say you have a Rubbermaid stock tank as a settle tank. It's gravity fed meaning it's dug in the ground. Bottom drain feeds it in the bottomish area. Crap flows in and settles out. Smaller particles continue to fly around. Above their head is a flat horizontal screen. Above the screen's head is a pipe to the mechanical filter, bead, what have you.
For instance, a 70g stock tank is 40.5" x 32" oval. The screen would be that size. So depending on the screen - I find it hard to imagine there wouldn't be an area in that screen that will still provide water to feed the output pipe. or be gunked so thick to stop water.
Large surface area spreading the joy. Said screen would have a frame around it & easy to remove. Hopefully able to smack against something in a pinch. Same page?
Course I suppose a sheet of Matala might suffice but things get stuck in the nooks/crannies.
Edit: Ah! I remember Bil's concept. It was opposite of mine and a bit different in theory whereby dirty water exited the top to drop down on a screen & the outtake pipe was below.
Last edited by Meagain #1b; 06-10-2004 at 09:28 PM.
But in the catalog they have extra pictures of the "insides"!
I told you last year to order this cat!!! GOOBER!!! :p
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I am convinced that the RDF is the only efficient prefilter device on the market. I have researched the designs and have combined attributes as well as improvements to the system. My design is in operation and working quite well. Please check out my website www.koipondfiltration.com. The most recent update is located at http://www.koipondfiltration.com/May...4%20Update.htm. The beauty of the system is that it is automatic, it discharges waste on demand, it only uses a small amount of water for backwash, screen size is 60 uM or smaller. No other microsceen is effecient as this one. The answer has several inherint design flaws. If interested, I will elaborate. Funny thing, about a year and a half ago, I presented my concept and design on the NI board. People held there ground and said that the answer was the best there was. In fact some people even said that all the RDF was good for was for leaves and twigs. I believe I have proven that person wrong by a long shot. Please feel free to e-mail me or ask any question that pertains to this system. I will be glad to share my experience and two years of development. Be careful purchasing one off the shelf. There are two types of RDF's on the market. One that flows through the drum and the other that flows through the shaft of the drum. My system flows through the drum. I can filter over 10,000 GPM with ease. If you would like more details and design considerations, please ask. Stephen Castel.
Thanks, Stephen C! That's why I asked you to come over here, but as long as you're here, I sure hope you'll stick around for a while. I expect you'll get lots of questions on your creation. The folks on this board are very open to new ideas and eager to learn!
I have a wealth of knowledge on this subject. As you are aware, I designed, fabricated and installed my system. I was not satisfied with the same old technology (vortex, answer VMS). They do not perform to my expectations. RDF technology has been around for years, it just has not been used in koi ponds. In fact, I don't know anyone using one today in a koi pond. I am pleased with the initial results. The RDF from AES in this thread will not last outdoors. Its plastic and must be installed under cover. As I said in the above post, throgh the drum flow and throgh the drum shaft flow are another main difference. Huge in my opinion. Food for thought, Stephen Castel.
My first post had a typo. Said system can filter over 10,000 GPM meant 10,000 GPH. Sorry, Steve.
When you say the best available on the market it is decieving. Your set up is not available on the market and from what I've read you have no intention of doing so. Yours is a one of a kind.
That aside, I marvel at the engineering you put into this. Having the logic to only backwash as needed and saving water in the process is what makes yours really shine. I look at the one AES has available and think it may be possible to modify it but the price is over what you say yours cost to make. I understand business and if you did produce it the costs for engineering manufacture, shipping etc would drive the cost of yours up considerably also. At least at first.
Thank you for sharing with the people your design and engineering.
Meagain, the AES one I was talking about is called a Parabolic screen filter. It works on a gravity feed. Only problem is it constantly takes water to keep removing the crud. Their web site only has a picture of the box. The catalog breaks it out and shows the inner workings.
I did not mean to imply that my system was the best. I meant that the RDF with flow throgh the drum design is suppirior to all other RDF's or microscreens on the market. I am working on a design that will be far less expensive to manufacture but not sure when I will be able to share that info. Thanks for the kind words, Stephen.
I recently reviewed what's available to us.
Microscreen uses in it's various guises is a boon to clean water. Settlement chambers on their own cannot clean everything out, particularly stuff that floats or is neutrally bouyant.
Microscreens commonly in use seem to be between 200 and 500 microns. The smaller screens are probably suited to drinking water use and would have a tendancy to clog at lower flow rates since it is small enough that a biofilm can span the gap.
Microscreens are used in a number of active and passive forms, some rotating, some stationary, some using curvature to self clean.
Rotating drum filter (RDF) technology certainly is the leader in terms of providing clean water with very little waste. But it requires a high level of technology to function. It needs a motor plus power supply, various sensors and a controlling device of some sort. For this reason installed cost is high. If cost is no object, or if you have Koiboy's (you da man) knack, definitely a way to go. Debris is automatically removed by backflush which occurs when the controller detects a rise in internal water level indicating that the screen is getting clogged. Just remember that this is similar (simpler but similar) to dishwasher and laundry machine controller technology. How often have you had to replace a machine like that because the electronics died on you? A commercially available for just under $6K here...
Rotating disc filters turn RDF's on their side and operate using a microscreen disc rather than drum and operate in much the same way. Same pros and cons as RDF but I thing RDF probably works better since you don't have the issue of the outside of the disc moving faster than the center. Commercially avialable here for under $4K....
Then there are passive microscreen devices, probably one of the best known ones (and possibly one of the best debugged ones) being the Answer sold as an attachment of the Nexus filter or for your own attachement to a vortex chamber. Self cleaning and no power needed. It blocks particles and causes them to be deposited in the settlement tank. Debris is removed by draining the filter. Available for between $800 and $1.5K depending on size (not including the Nexus filter), here....
There are other passive microscreen devices. This one by Sweetwater uses a water spray using partial return from your final filter stage to self clean. The water flow in the vortex causes the VMS to rotate. It must be used with their vortex tub and be positioned just right or it will not work well. Apparently it is fairly sensitive to the goemetry of the container and does not suit DIY liner vortex chambers. Dirt is removed by draining the vortex chamber. So by the time you have bought this device and the chamber you'll be out $1.2K to $1.5K. Available here....
More passive technology.... Parabolic screen filters, place a microscreen in a curve relative to the water inlet. This arrangement causes the water to pass through the screen and self clean the screen at the same time. The waste tank has to be manually drained and I suspect that the screen clogs from time to time. Available here for $1.1 to $1.3K
The something relatively new on the market. After looking around I decided to give it a try. A pressurized VMS settlement chamber. It puts a VMS inside a container that looks like a bead filter. The water flow causes the VMS to rotate and internal recycling jets keep the screen clean. Particles are collected in the tub and must be periodically drained manually much the same way a bead filter is operated. It's not entirely something for nothing, you do need a pump that is man enough to push water through this device and your bead filter. It is very compact compared to a vortex chamber and works above ground. Available here for $1.3K to $1.5K ....
I opted for the pressurised VMS with a 500 micron screen. It suited me because I already had a bead filter and while I had a settlement chamber is was a liner chamber and unfavorably situated after the pump (uphill from the pond). Purchasing a vortex tank and VMS would have cost more than this little gadget. I did have to buy a bigger pump but, then I'd intended to use my existing pumps to drive some new skimmers. I have plans to convert my settlement tank into a foam fractionator or perhaps leave it as a vegie filter (which it already was). It's early days (installed yesterday) but the water does look cleaner already.
Hope this helps.
Thanks for the great post Nicco.
I do believe the answer needs power though. It's driven by a motor.
The parabolic looks more like something that could be home made if you had time to play. It's kinda like Bil's filetr he was trying only with a curve and a waste pipe at the end of the curve. That's what makes me think it will constantly purge water from the system.
Have you cleaned the new filter yet? I'd be curious to see what it takes out.
I did do some thinking before plonking down my dollars!
Here's another series parabolic screen filter supposed to go down to 30 micron.
Cannot help but feel that the snails that clog up our bead filters would do the same for these.
This is a good site for foam fractionators (aka protein skimmers). Shows a cut away view of a couple of designs. They seem fairly affordable too.