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High Nitrates Level? Try This!

 




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doug
Novice

Oct 15, 2000, 9:48 AM

Post #76 of 312 (127790 views)
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I have read with great interest the three long pages of research done on the trickle tower filtration system and are very impressed and appreciative of the information. Would you please clarify or answer the following.
1. When a drip tray is used to distribute the water, what is the relationship between the size and number of holes to the flow rate of water?
2. Twice Mark has mentioned that a slow flow rate is best or at least not detrimental but suggests a rate of 1.5 Ė 2 times the pond volume per hour. To me, this is a fast flow rate when wet systems are often only 0.5 times the pond volume per hour. Am I wrong on this?
3. If the object is to supply as much air into the system as possible why put it in a container? Why not just set up a fountain right in the pond cascading water over bio balls in a perforated tray at itsí base just above the water level of the pond? If the water supply to the fountain was mechanically filtered what would be missing?
4. When the filter size is referred to in tonnage, what is meant? The water is not accumulating in the Ďdryí filter system, so what is being referred to? Is it the potential volume of water the container could hold? Shouldnít filters be rated by the amount of surface area they supply?


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Mark
Veteran

Oct 15, 2000, 10:45 PM

Post #77 of 312 (127790 views)
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Let me try to answer your questions.

1. When a drip tray is used to distribute the water, what is the relationship between the size and number of holes to the flow rate of water?

First of all, allow me to define the word trickle from the dictrionary as :
1. to issue or fall in drops;
2. to flow in a thin gentle stream;
3. to move or go one by one or little by little;
4. to dissipate slowly.

The efficiency of the system does not solely depend on the no. of holes or the size of the holes appearing on the drip tray or PVC pipes. It does however, depends alot on the the way the water is delivered to the surface of those bioballs. Hence a too slow a flow rate will cause all the water to comes together after passing thro' the drip plates and defeat the whole purpose of using a drip plate. However, if the flow rate is too fast, there will be little time for exposure before the water returns to the pond hence depriving the trickle intake of oxygen. That goes the same with holes. Too small a hole, water will be diff. to pass thro' and too large a hole, it defeats the whole purpose. My consideration will therefore be the *break point or at the balanced point where water drip thro' the holes in the drip plate. In order to do this efficiently, you need to have a valve to control the flow rate and a water level of at least 3 inches or more above the plate.

2. Twice Mark has mentioned that a slow flow rate is best or at least not detrimental but suggests a rate of 1.5 Ė 2 times the pond volume per hour. To me, this is a fast flow rate when wet systems are often only 0.5 times the pond volume per hour. Am I wrong on this?
You can achieve this by either expanding the surface area of the filter and the drip plates or cutting down the flow rate with slower pump.

3. If the object is to supply as much air into the system as possible why put it in a container? Why not just set up a fountain right in the pond cascading water over bio balls in a perforated tray at itsí base just above the water level of the pond? If the water supply to the fountain was mechanically filtered what would be missing?
Water trickling need not confine to only bioballs sitting in a filter tower. High Waterfalls and fountains are another form of trickle system. The whole idea is to exposed the water to as much oxygen as possible before returning them to the pond. Unfortunately not many of us have big area to install these. Noise another consideration as we do not want to disturb our neighbours. Hence trickle tower seems to be the answer and besides its easy to maintain.

4. When the filter size is referred to in tonnage, what is meant? The water is not accumulating in the Ďdryí filter system, so what is being referred to? Is it the potential volume of water the container could hold? Shouldnít filters be rated by the amount of surface area they supply?

Surface area has our main consideration when coming to size of a filter system. And we usually take 30% or more of pond surface area as an indicator. If we calculate the total surface area of the bioballs, we will quickly realised that how small our filter tower is as compared to the normal wet system.

Hope these help.


(This post was edited by Mark Richman on Apr 10, 2001, 9:00 AM)


doug
Novice

Oct 16, 2000, 2:54 PM

Post #78 of 312 (127789 views)
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Thanks for getting back to me Mark. I think you hit it on the head when you considered the problem of maintenance with setting up a fountain (not enclosed) as a trickle tower. Keeping leaves and nettles out of the system would be a constant pain.

With regards to your comments on the sizing of the holes verses flow. I agree with your reasoning that the rate of flow that we are trying to achieve is that point where the water breaks the surface tension of the plate and falls cleanly away at each hole. This can be achieved with an oversize pump and control valve but it would be good to refine this somewhat in the face of the initial capital expense of the pump and itís energy consumption. First of all, there must be a minimum size for the holes since we all know that with the growth of any algae a tiny hole is going to fluctuate in size too much to the point of restricting any flow at all.

Generally speaking the following is what I think is needed by the people following this discussion group who are about to build or improve their trickle tower. We need numbers for the following.
1. Hole size in drip pan. There must be an ideal hole size regardless of filter size. I would think the size of the drip onto the bio media would be a constant regardless of the overall size of the filter, for a depth of bio media of 18 inches (a depth which has been referred to as sufficient throughout the discussion).
2. Spacing of the holes This would depend on the bio media but wouldnít very much.
3. Flow rate per hole. From this we could determine the total flow rate to the filter.

Can you help with this info?


Mark
Veteran

Oct 17, 2000, 3:13 AM

Post #79 of 312 (127787 views)
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Most trickle system are self-made (I think) and comes in various designs. Honestly, I don't have an answer for standard hole. However, I experimented with 1/4 and 3/16 inches dia spaced 1 inches apart and they seems fine with all the pumps.

Hope this help.


FrankChong
User

Oct 17, 2000, 9:16 AM

Post #80 of 312 (127786 views)
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Doug,

Mark is correct, I have tried using 3/16 inch holes spaced at about one inch square. I obtain good flow over the filter material.

As for the pump size selection. Eventhough there are calculations one can make. I have not used the formulars since I left engineering school 20 years back. Anyway the calculations are only approximations and never right to the dot because of a number of approximations we have to make on the pipe losses. What is most frustrating is, even when one knows exactly the static head and delivery volume required. You cannot find one pump exactly matches your requirement. The pump manufacturers do not even include the pumps performance curve. In most instances it only states the current (electricity) consumption and maximum flow rate. Very little use, one has to extrapolate and make an intelligent guess when you have to deliver the water to certain height.

The most practical approach would be to construct the drip tray. Then using a pail of water to pour over the drip tray and measure the flowrate. You could get an idea of the flowrate required.

There is no magic number of flowrate for trickle tower to work. Certainly one would want to avoid a gush of water that could flush out all the solid waste. On the other hand you want to have enough flowrate so that sufficient volume of water could be treated over 24 hour period, this could involve multiple units of trickle filter. This flowrate is dependent on whether the trickle filter is the only filtration system or they are supplementary filter working in conjunction with other filtration systems.

If you are feeling more confused, it is a good sign. You are on the right track. Do ask more the haze would clear.


doug
Novice

Oct 17, 2000, 8:57 PM

Post #81 of 312 (127785 views)
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The suggestion of building the drip tray and testing the flow rate is a good idea. I think Iíll start with 3/16 holes at 1 inch spacing like you suggest. 3/16 seems big enough not to get plugged and not too large to cause excessive flow onto the biomaterial. Iíll experiment with 1 sq ft. and see how much water flows through per hour. Iíll then need to decide on the flow rate and then I can calculate the area Iíll need in the drip tray. Question. The pond will hold 2000 gallons. How much water should pass through the trickle tower (not the pump rate) per hour. The only other filter will be a mechanical filter in line with the trickle tower. Please donít write back and ask me how many pounds of fish Iíll have in the pond because I donít know. So far, if I add up the weight of all my fish they wonít tip the scale at 2 lbs. Iím obviously knew at this but have been warned that I should think big when it comes to the filter because who knows how many pounds of fish will depend on it in a few years. What I can tell you, is that Iíll have 720 scrub pads (about 4.5 cu. ft) for the biomaterial. I know, bio balls are best but economics took precedence on this one.
Iíll post the flow rate per hour for 1 sq. ft. drip tray with 3/16 holes at 1 inch spacing with a 3Ē head when I have the answer.


FrankChong
User

Oct 18, 2000, 9:39 AM

Post #82 of 312 (127785 views)
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DOUG,

The size of filter as I learnt from this site is 30% of pond area. No reason to dispute this rule of thumb as it has been tested by more experience ponder. My personal thought is, size alone do not determine the effectiveness of filtration. More crucial aspect is what you use as filter media. I am currently writing an article on this aspect where I will explain in greater detail.

In my opinion 4.5 cu ft of filter media is way too small. Based on the rule of thumb total volume of filter should be 600 gallon, 30% of pond size. It is possible to reduce the filter size provided you make it up with more frequent maintenance.

My thought is :

1) Bacteria do not require a filter media to roost and process waste. The biological process goes on with or without the filter media (assuming the pond water is mature). Think about it and let me have your thought on this. Why then we put in filter media ?

2) We put in filter media solely for the purpose of trapping solid waste, so it would not cloud the water. So that you and me can appreciate our koi.

3) If we could effectively trap all the waste and flush it out in good time. Why do we need the rest of filter material for ?

Back to your filter design. I am not very sure whether the scrub material you use is same as what I have here. But I can be very sure bio ball is definitely not suitable as your mechanical filter media. Not unless you have 600 gallons of them. This is because the filterbility (the ability to filter) of bio ball is very low.

The logic is, supposing you settle for a 300 gallon filter material and you need to trap 150 gm of waste from your koi. Japanese fibre matt would probably be sufficient. However, if you intend to use only 100 gallon of filter material to trap the same amount of waste. Bio ball or Japanese matting would not do the job, they are just too porous. There is no magic here, if you intend to trap the same amount of waste with less filter media, you have to use more dense material. The other effect of trapping waste with reduced filter material would obviously cause the filter to choke up much faster. This you could overcome with more frequent flushing.

The only way for 4.5 cu ft of filter material to work for a 2000 gallon pond is to use sand filter with daily backwash routine. Plus the trickle tower to take care of whatever debris left. If you opt for sand filter make sure a bigger grain size of 2 to 3 mm is use. The fish waste is likely to cake up the sand if the grain size is small.

In my case the main filter is about 15% of the pond volume. My trickle tower is 1000 litre stainless steel water storage tank of five feet high. About 30% percent of water from the main filter is fed to the trickle tower.

I am now working on a more effect way of trapping the solids before it goes to my in ground main filter. Too labour intensive to clean out in ground filter.


dttk
Veteran

Oct 18, 2000, 7:13 PM

Post #83 of 312 (127784 views)
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Dear Frank, I hope I'm not hearing wrong or getting the wrong impression but as far as I know, it is a well known fact that for effective filtration we need to achieve a bio-media surface area of 30% of the pond surface area. This does not include mechanical filtration. The biological filter media were meant to support the growth and maintenance of denitrifying bacteria rather than mechanically filtering water. Of course the other surfaces of the pond in contact with water will also support some bacteria but this is way too little to be able to effectively remove ammonia. Similarly the trickle tower filter media should be used as a biological media rather than for mechanical filtration. However I do agree with your points on mechanical filtration. That's the reason why hobbyist till today still strife to create an effective mechanical filtration system that removes all suspended wastes so that only clear water goes thru for the biological filtration process.


Mark
Veteran

Oct 19, 2000, 2:30 AM

Post #84 of 312 (127785 views)
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In all wet/mechanical system, please remember to consider all the surface area of a f/media used within a chamber. For example, if the f/media used is 2 x 2 feet we should have 8 sq ft.(each side is 4 sq ft) of surface area for good bact. to grow. And if we use 2 of these, the total surface should therefore be 16 sq ft. Generally most of us will consider only the top side (ie 2x2=4sq ft) of the f/media and we lay them horizontally. What if we lay them vertically? Will it change your understanding to the surface area? Do we get a total surface area of 8 sq ft per f/media instead?

Please give some thoughts to the vertical arrangement. However if you can, please consider a trickle system instead of a wet/mechanical filter.


FrankChong
User

Oct 19, 2000, 5:08 AM

Post #85 of 312 (127784 views)
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DTTK,

You are right, most of the recommendations for filter size is filter material surface area = 30% pond area. Some recommend filter size = 30% pond area.

I have written an article in microsoft word format, had requested webmaster to post it for me. Let me have your thoughts after reading it.


doug
Novice

Oct 19, 2000, 7:50 PM

Post #86 of 312 (127784 views)
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Mark. From the drawing at the beginning of this discussion I assume you recommend a series of filter mats for a mechanical filter before the trickle tower. Iím sure we all agree that mechanical filtration is nesesary to keep the debris out of the bio filter, and I like your design but would appreciate your comments on settling tanks. I reason that we want to remove the debris from the whole water system and not just move it from the pond to another tank but still in the same water system, which is what happens in a settling tank. At least with the filter mats weíre forced to clean them. Do you agree?


dttk
Veteran

Oct 19, 2000, 7:57 PM

Post #87 of 312 (127784 views)
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Dear Frank, after reading your earlier posting(18-10-2000)again, I realise I may have missed the point you were trying to make. I quote, "Bacteria do not require a filter media to roost and process waste. The biological process goes on with or without the filter media (assuming the pond water is mature)". Were you implying that the concentration of bacteria in mature pond water is sufficient to biologically convert ammonia to nitrites to nitrates? I doubt even mature pond water without a filter has enough bacteria to process the ammonia unless the pond is large enough and the number of koi very few, like what you find in nature. But this is not practical in real life. Bio-media are used to support enormous colonies of bacteria in a small, undisturbed enclosure like the filter. An interesting topic was discussed sometime ago about whether the brownish-grey substance we find on the surface of matured bio-media are actually made up of bacterial colonies. Will be looking forward to read your article. Cheers!


Ben
User

Oct 19, 2000, 8:30 PM

Post #88 of 312 (127784 views)
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Hi doug,

A good settlement chamber must have opening at the bottom to flush out the trapped waste every few days. I personally feel that green matting is not a good material for the settlement chamber as all waste trap by the matting will be stuck within the matting and cleaning is very difficult and time consuming. Carlnet on the other hand will be more suitable as the fish waste hitting the net likely to settle to the bottom of the settling tank for flushing out. Cleaning of the carlnet is also so much easier.

A proper settlement chamber with flushing facility will make pond maintenance an easy job and allow you to have more time enjoying your koi.


FrankChong
User

Oct 20, 2000, 6:21 AM

Post #89 of 312 (127784 views)
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Oops, it looks like our webmaster may have the same problem in posting a message in word format. Give him a bit more time. My rational for concluding that biological process goes on with or without filter material is well illustrated.

To doug, Ben is right, you must have a discharge outlet at the bottom of settling chamber for you to flush out waste frequently.


Mark
Veteran

Oct 20, 2000, 7:55 AM

Post #90 of 312 (127786 views)
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In the first drawing, it was original a wet system having the last chamber modified to a trickle chamber. The first chamber was filled with rolls of settlement brush standing vertically to trap the heavy waste. Although you can also use f/mats but I think its an overkill. If you see my later part of the drawing whereby the whole filter box is converted to full trickle system, I raised the outflow outlet by 6 inches from the bottom and I do away with the foam media which was originally used to trap the heavy waste before water falling on the bioballs. These heavy waste will settled at the bottom of the chamber which I back flush them away every 2 to 3 days. You will be amazed how little maintenance it can be as compared to the wet system.

Hope this help.


Khoobg
Webmaster


Oct 20, 2000, 5:32 PM

Post #91 of 312 (127785 views)
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Hi Frank,

I am still searching for your email to me. Please email again to hiley@po.jaring.my just incase I can't find it. Thanks



FrankChong
User

Oct 21, 2000, 1:36 AM

Post #92 of 312 (127785 views)
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Hi Khoobg,

First article posted this morning, second article, continuation of first posted just now to your email hiley@po.jaring.my.

Cheers


Khoobg
Webmaster


Oct 21, 2000, 2:29 AM

Post #93 of 312 (127785 views)
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Hi Frank and all, Frank's article is now at http://www.koi.com.my/frank.html . Please read through and tell us what is your opinion.

A link to the article will be created from the main page of the web site for all to read through and comment !


dttk
Veteran

Oct 21, 2000, 8:36 PM

Post #94 of 312 (127785 views)
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Hi everybody, I've read Frank's article and here are some points that I would like to make. Two types of bacteria exist in a mature pond filtration system, aerobic and anaerobic. The settlement or first chamber would probably support more anaerobic bacteria which breaks down large solid wastes to finer particles(sludge) which are harmless. In the process hydrogen sulphide gas is released. People staying around the vicinity of oxidation ponds do experience such a problem when the wind carries H2S towards their direction. So the fresh waste which settled has been 'eaten' by bacteria. Only the chemical impurities are left to be processed. Koi also excrete urine which has ammonia. Infact the amount of urine excreted maybe more than the amount of faeces excreted since the latter depends on the amount of food consumed. Ammonia is processed by aerobic bacteria in the aerated chambers. Aerobic bacteria will concentrate in filter media and process ammonia into nitrite and nitrate. I agree with Frank that even the bio-media performs some degree of mechanical filtration. But their main function is to process ammonia. The sewage system is to cater for huge amounts of wastes unlike the filter system for a koi pond. Like I mentioned before, space and affordability are important factors. Biological filter media are necessary in a koi pond filtration system. If you remove it from the filter, keeping the other factors constant, ammonia level in water will increase. Any comments?


FrankChong
User

Oct 22, 2000, 3:05 AM

Post #95 of 312 (127785 views)
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Hi Dttk,

The aerobic bacteria requires oxygen to survive and process waste. When dissolved oxygen is depleted the aerobic bacteria will die off. Another strain of bacteria the anaerobic bacteria which feeds off nitrogen will take over the anaerobic process.

I believe that aerobic bacteria will be present in all the chambers as long as there are food and oxygen present. Hope is read it right.


dttk
Veteran

Oct 22, 2000, 8:26 PM

Post #96 of 312 (127785 views)
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Hi Frank, you're right about the aerobic bacteria dying off when O2 is depleted. That's the reason why bio-media should be aerated to support more aerobic bacteria. We should probably look at waste processing in a koi pond filter at 2 levels. First one being solid waste processing and second one being liquid waste processing. The two processes usually occur at the same time. Aerobic bacteria do breakdown solid and liquid waste. About aerobic bacteria not being able to latch-on to bio-media, we have to ask the experts like people who have actually bothered to experiment with it. Any volunteers? Will be looking forward to read your other articles. Happy koi keeping.


doug
Novice

Oct 23, 2000, 8:40 PM

Post #97 of 312 (127785 views)
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Frank. I have also had some experience with sewage systems and think that the info may be useful in designing filter systems for our ponds. I should start by saying that my experience is in a much cooler climate, Western Canada. Your description of a septic tank is the same as ours but your description of a sewage treatment plant is somewhat different. Here a treatment plant usually exists of big discs rotating half in and half out of the water. The idea is that the bacteria grow on these discs and rotating or cycling them in and out of the sewage keeps them aerated. My own perspective on the trickle tower is that what they accomplish, is adding air to the system. Iím not sure if I agree with your logic that the bacteria don't need filter media (bio balls, scrubbies etc.) to grow on. Itís true that the bacteria grow on the waste itself but it seems to me that if we expect the bacteria to breakdown the waste completely we need additional surface area for them to grow. It would be interesting to pump emulsified waste through a chamber that was fully saturated with air and see what would happen to the ammonia. I have recently discovered that a garden soaker hose makes a great aerator. The bottom of a chamber completely covered by a coil of soaker hose with air pumped into it might make a very effective bio filter and may be enhanced with a loose supply of bio ball or scrubbies bouncing around in the bubbles.


FrankChong
User

Oct 24, 2000, 5:43 AM

Post #98 of 312 (127785 views)
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doug,

Your experiment should tell us something. Keep us posted with your result.


doug
Novice

Oct 25, 2000, 5:22 PM

Post #99 of 312 (127785 views)
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I"m not in a position to try what I suggested above at this time. I did how ever do a little experimenting that you may find interesting. I determined that a 1/8" hole with a 1/2" head of water discharges 1.80 US gallons per hour. This is usefull in determining the relationship between the pump discharge rate and the size of the drip tray in the trickle tower. At this rate the water flowed smoothly from the hole.


ngtpeng
Novice

Dec 8, 2000, 11:32 PM

Post #100 of 312 (127785 views)
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Where can I buy the brushes in Singapore?

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