GPH for Bog Filter..?

[Meyer Jordan]

What I'm reading is your 1 to 1 ratio (equal size) for grow bed and fish tanks size is correct, but I'm also reading that you should be cycling, or turning over, the water every hour minimum. So a the flow rate of a 100 gallon grow tank should be 100 gph. Pretty much the same as what is recommended for standard ponds. I'm not sure how you came up with 5-10 gpm? That would work for a 300 growing tank, but it would be below the recommended flow rate for anything bigger.

One major item to consider here is that a fish tank and grow tanks of equal size will not have the same capacity in water. Depending on the substrate (if a gravel system is used) the capacity for water in the grow tank will only be 30% - 40% of total size.

Here is one of the sources for the quoted recommended flow rate of 5 - 10 gpm.--
5 gpm: http://www.friendlyaquaponics.com/2015/08/02/water-pumps-and-flow-rate-in-the-vegetable-troughs/

And this from the FAO:
The flow rate of the water entering each canal is relatively low. Generally, every canal has 1–4 hours of retention time. Retention time is a similar concept to turnover rate, and refers to the amount of time it takes to replace all the water in a container. For example, if the water volume of one canal is 600 litres and the flow rate of water entering the container is 300 litres/h, the retention time would be 2 hours (600 litres ÷ 300 litres/h). Deep Water Culture Aquaponic Unit – Step by Step Description FAO

If the system utilizes towers, then the flow rate is 2 gph/tower. http://blog.brightagrotech.com/pumps-for-aquaponics-or-hydroponics/

On the Wikipedia Aquaponic page there is a diagram of a fairly large system. A little figuring using the date provided on this chart results in a retention time of almost 5 hours.

Also it should be noted that in aquaponic systems where the flow rate required for the fish tank size exceeds the flow rate desired for the grow tank, water is diverted away from the grow tank and returned directly to the fish tank.

All data involving flow rates in reference to the nutrient uptake efficiency of plants, whether from engineered wetlands or aquaponics, indicate low flow rates and ample retention time.

I feel that it is time to give this poor horse a break and quit beating it looking for answers that just aren't there.

 

[Mucky_Waters]

Here is one of the sources for the quoted recommended flow rate of 5 - 10 gpm.--
5 gpm: http://www.friendlyaquaponics.com/2015/08/02/water-pumps-and-flow-rate-in-the-vegetable-troughs/

All data involving flow rates in reference to the nutrient uptake efficiency of plants, whether from engineered wetlands or aquaponics, indicate low flow rates and ample retention time.

I feel that it is time to give this poor horse a break and quit beating it looking for answers that just aren't there.

Well some of the answers are there is you look for them.
This is a cut and paste from the link you provided above.
"We have a large aquaponics system with four separate sets of troughs. We noticed for a long time that growth in one of the trough sets was excellent, growth in another was good, in another barely OK, and growth in the fourth was poor: in that trough the vegetables were sickly with lots of bugs.
Susanne knew the problem must be connected to flow rate, so I got out there with a 5-gallon bucket and a stopwatch. I put the bucket under each of the trough inflows and timed it to see what the flow rate into the troughs was in gpm. It came as no surprise to see that the “excellent” trough had a flow rate of 5 gpm, the “good” trough had a flow rate of 1-1/3 gpm, the “OK” trough had a flow rate of 2/3 gpm, and the “poor” trough had a flow rate of 1/3 gpm! We have a WaterPik that puts out more water than that!"
What is basically is saying is that the trough with the greater flow rate produced better growth.

Now we can take a break.

 

[Meyer Jordan]

Well some of the answers are there is you look for them.
This is a cut and paste from the link you provided above.
"We have a large aquaponics system with four separate sets of troughs. We noticed for a long time that growth in one of the trough sets was excellent, growth in another was good, in another barely OK, and growth in the fourth was poor: in that trough the vegetables were sickly with lots of bugs.
Susanne knew the problem must be connected to flow rate,so I got out there with a 5-gallon bucket and a stopwatch. I put the bucket under each of the trough inflows and timed it to see what the flow rate into the troughs was in gpm. It came as no surprise to see that the “excellent” trough had a flow rate of 5 gpm, the “good” trough had a flow rate of 1-1/3 gpm, the “OK” trough had a flow rate of 2/3 gpm, and the “poor” trough had a flow rate of 1/3 gpm! We have a WaterPik that puts out more water than that!"
What is basically is saying is that the trough with the greater flow rate produced better growth.

Now we can take a break.

5 gpm or 300 gph being described as a higher or lower flow rate is comparative. In the example, compared to 1-1/3 gpm(80 gph), 2/3 gpm(40gph) and 1/3 gpm(20 gph)it is a greater flow rate.

I am baffled by your reluctance in accepting the fact that any wetlands filter's efficiency is directly tied to flow rate and retention time. HRT (hydraulic retention time) must be of sufficient duration to allow for plant's assimilation of nutrients and other pollutants. Document after document in scientific literature supports this with HRTs ranging from several hours to several days.
If you want further proof of this I would suggest that you search HRT (hydraulic retention time).

 

[Mucky_Waters]

5 gpm or 300 gph being described as a higher or lower flow rate is comparative. In the example, compared to 1-1/3 gpm(80 gph), 2/3 gpm(40gph) and 1/3 gpm(20 gph)it is a greater flow rate.

I am baffled by your reluctance in accepting the fact that any wetlands filter's efficiency is directly tied to flow rate and retention time. HRT (hydraulic retention time) must be of sufficient duration to allow for plant's assimilation of nutrients and other pollutants. Document after document in scientific literature supports this with HRTs ranging from several hours to several days.
If you want further proof of this I would suggest that you search HRT (hydraulic retention time).

The example I quoted from your link merely shows that in those specific troughs (of undetermined size and retention time), that a greater (faster) flow rate produced better plant growth, indicating that the plants in the troughs with the faster water flows absorbed more nutrients then the ones with less water flows. Are you now disagreeing with the link that you posted?
As for one pass wetlands filters, I have already stated that I agree you are going to need maximum retention time for the plants to absorb as much nutrients as possible before the water flows into the target stream or lake. But we are talking about recirculating systems here, not one pass wetlands systems. I am baffled by your reluctance too acknowledged the difference.
In a wetlands filter the objective is to try and reduce the nutrient load of the source water to as close to zero % as possible before it is reintroduced to some natural body of water. In a recirculating system it is not necessary to reduce the nutrient load to zero in one pass, all that is necessary it to continually supply the plants in the grow bed/bog with a relatively constant level of nutrients.

Read this: http://teca.fao.org/read/8397
Paragraph 3.
"The retention time for each canal in a unit is 1–4 hours, regardless of the actual canal size. This allows for adequate replenishment of nutrients in each canal. Plant growth will definitely benefit from faster flow rates and turbulent water because roots will be hit by many more ions; whereas slower flows and almost stagnant water would have a negative impact on plant growth. "

 

[Meyer Jordan]

The example I quoted from your link merely shows that in those specific troughs (of undetermined size and retention time), that a greater (faster) flow rate produced better plant growth, indicating that the plants in the troughs with the faster water flows absorbed more nutrients then the ones with less water flows. Are you now disagreeing with the link that you posted?
As for one pass wetlands filters, I have already stated that I agree you are going to need maximum retention time for the plants to absorb as much nutrients as possible before the water flows into the target stream or lake. But we are talking about recirculating systems here, not one pass wetlands systems. I am baffled by your reluctance too acknowledged the difference.
In a wetlands filter the objective is to try and reduce the nutrient load of the source water to as close to zero % as possible before it is reintroduced to some natural body of water
In a recirculating system it is not necessary to reduce the nutrient load to zero in one pass, all that is necessary it to continually supply the plants in the grow bed/bog with a relatively constant level of nutrients.

Read this: http://teca.fao.org/read/8397
Paragraph 3.
"The retention time for each canal in a unit is 1–4 hours, regardless of the actual canal size. This allows for adequate replenishment of nutrients in each canal. Plant growth will definitely benefit from faster flow rates and turbulent water because roots will be hit by many more ions; whereas slower flows and almost stagnant water would have a negative impact on plant growth. "

This is correct for the aquaponics system that this quote is in reference to....DWC or raft systems. There is no sub-strate in these systems. Even so, this quote plainly states that "The retention time for each canal in a unit is 1 - 4 hours, regardless of actual canal size."
It all still goes back to the assimilation or nutrient uptake rate of plants. This will vary based on the time of year (usually). When plants are in active growth, Spring and early Summer, the assimilation rate will be at its highest. After this growth period the assimilation rate will begin to decrease dropping to virtually zero in Winter. HRT is determined based on the higher rate.

In a recirculating system it is not necessary to reduce the nutrient load to zero in one pass

This is your interpretation and needs to be qualified. As stated before, If the "bog" is to be used as a phyto-filter strictly for polishing the water, ample retention time must be provided. Previous links have been provided supporting this. However, if the "bog" is to be utilized as a bio-filter then retention time is not an issue.

 

[MitchM]

So another aspect will be the density of plants in the bog and how "hungry" the specific plants are. I assume that faster growing plants will use more nutrients. Temperature of both air and water are also likely to have a major affect on nutrient absorption.

Since each pond and the variables will be different, a large, heavily planted bog to pond size ratio is the surest bet. (I guess).

Hungry plants won't stay hungry for long, as their root systems will stop growing if there are insufficient nutrients to maintain plant growth.

The goal of a wetlands filter should be to supply the plant roots with as much nutrients as possible from the main pond. The nutrients must be balanced with a proper mix of organics and minerals that the plants need. That's the tricky part - how to balance the nutrient mix and how to make sure the water flow allows for the deposit of nutrients to where the plants need it.
The wetlands filter design should take into account all turbulence, obstacles in the water path and whether or not the water flows over or through the root zone.
That what makes wetlands filters so interesting, imo.

The thing that will limit plant growth will be the nutrient which is in the least supply that the plants need. Any extra nutrients will be taken up by algae and moss.

.

 

[MitchM]

So what is the difference between Addy's bog, and the OP's bog that you were originally applying those wetland guidelines to? This is how we got on the topic in the first place.
...

One difference that stands out to me is that the OP's pond is 20X larger than the proposed "bog"
Addy's pond is only 5X larger than than her "bog"
Addy has a much greater relative capacity for filtering than the OP's setup.
Any filter system must be sized properly or it will fail. The design won't matter.

I'm estimating the OP's pond to be 1800 gallons, the "bog" to be 90 gallons.
Addy's pond is about 12,000 gallons with a 2100 gallon "bog"
- of course stocking and feeding levels will play a part in all this as well.

.

 

[Mucky_Waters]

In a recirculating system it is not necessary to reduce the nutrient load to zero in one pass,

This is your interpretation and needs to be qualified. As stated before, If the "bog" is to be used as a phyto-filter strictly for polishing the water, ample retention time must be provided. Previous links have been provided supporting this. However, if the "bog" is to be utilized as a bio-filter then retention time is not an issue.

Would you like me to quote one of the links you provided again?

Any "bog" that has plants growing and flourishing in it will be functioning both as a "phyto-filter" AND a bio-filter regardless of retention time or flow rate. (Eg, if Addy's has plants flourishing in her bog, that is proof that they are getting the nutrients they need). It's really that simple.

One difference that stands out to me is that the OP's pond is 20X larger than the proposed "bog"
Addy's pond is only 5X larger than than her "bog"
Addy has a much greater relative capacity for filtering than the OP's setup.
Any filter system must be sized properly or it will fail. The design won't matter.

I'm estimating the OP's pond to be 1800 gallons, the "bog" to be 90 gallons.
Addy's pond is about 12,000 gallons with a 2100 gallon "bog"
- of course stocking and feeding levels will play a part in all this as well.

.

Thanks for trying to answer the question Mitch, but size difference wasn't really what I was talking about. The point was one of function.

 

[Meyer Jordan]

Any "bog" that has plants growing and flourishing in it will be functioning both as a "phyto-filter" AND a bio-filter regardless of retention time or flow rate. (Eg, if Addy's has plants flourishing in her bog, that is proof that they are getting the nutrients they need). It's really that simple.

Then why is retention time mentioned and emphasized by both wetlands engineers and the Aquaponics community? They certainly must have a basis for believing its importance and necessity.
I understand their rationale and will side with them. Others may form their own opinion.

 

[Mucky_Waters]

Lets back up a bit and discuss Addy's bog. In speaking about her bog you said,,,,

because of your flow rate is more of a biofilter than a phyto-filter thus, as you say, not really a true wetlands filter.

I agree it is not comparable to a wetlands filter, not because of the flow rate bug because the water going through her bog recirculates back from where it came from (the pond). Wetlands filters don't do that, they only go in one direction. (seems like we've been here before???)
But as for it being more of a biofilter than a phyto-filter, that is a little more hazy. We can all agree that her bog likely has plenty of biological action going on, but she also say her bog is "full of plants". This is where we have to ask what exactly is phyto-filtration? My understanding is that phyto-filtration simply means "Using plants and trees to filter impurities or excessive levels of nutrient from water." And yes, I looked it up.
Now I have to ask, do you not think all those plants in Addy's bog are "filtering impurities or excessive levels of nutrient from her water"?
If your answer is yes they are, then she has a functioning Phyto-filter.
If your answer is no they are not, then I have to ask you where those plants are getting their nutrients from?
Of course, if Addy pipes in here and tells us that all her bog plants are wilting and turning yellow then we can probably end this discussion right now.

 

[Meyer Jordan]

Seems like we have gotten off track, again.
I am trying to stick to the subject of this thread as presented by the OP which is: "....Will 1700ish gph be to fast water for my bog plants?"
I take this to be a question of which flow rate will maximize the ability of plants to assimilate nutrients and pollutants. At this point, the OP has not advised any differently.
That being said, any subsequent question has been answered with this in mind. That there are different degrees of any filtration, mechanical, chemical, bio or phyto, but there will only be one set of conditions for each that will elicit optimal results. You have been discussing degrees of efficiency whereas I have been discussing optimum efficiency.
Yes, Addy's "bog" may produce a certain level of phyto-filtration, but it is not a pure phyto-filter. The percentage of Nitrate and Phosphorus removed from the water column is considerably less than in a dedicated phyto-filter. An engineered wetlands employs phyto-filtration but it is not called a phyto-filter because it is much more. A phyto-filter, depending on design, may also provide some biofiltration, but not on the level provided by a dedicated biofilter unit.
The one flaw that I have found in the hobby of Water Gardening and garden fish ponds is using 'one-size-fits-all" terminology. And that is exactly what has been occurring in this discussion.
Returning to the discussion of flow rates, Hydroponics has not been referenced. Just a quick check of a few sources reveals that even though aquaponic suggested flow rates are low, hydroponic flow rates are even lower. Just more evidence that HRT is all important in the nutrient assimilation efficiency of plants.
Since the OP has been provided all the information that they need to make an informed decision, I see no reason to continue this discussion any further in the direction that it has been going. I am weary of providing additional sources and explanations to support what has already been established by the scientific community and are just duplications of what has already been presented.
If some refuse to accept scientific data, that is entirely their option.

 

[addy1]

One difference that stands out to me is that the OP's pond is 20X larger than the proposed "bog"
Addy's pond is only 5X larger than than her "bog"
Addy has a much greater relative capacity for filtering than the OP's setup.
Any filter system must be sized properly or it will fail. The design won't matter.

I'm estimating the OP's pond to be 1800 gallons, the "bog" to be 90 gallons.
Addy's pond is about 12,000 gallons with a 2100 gallon "bog"
- of course stocking and feeding levels will play a part in all this as well.

.

My main pond is around 9k, add all the extra ponds, deck, stream, loop, stock tank, we add around 2-3 k more water. I have very soft measurements on water volume. I don't treat with chemicals etc. so never worry about water volume to dosage.

 

[Mucky_Waters]

Seems like we have gotten off track, again.
If some refuse to accept scientific data, that is entirely their option.

Actually I felt it went off track with your persistence in trying to apply one pass wetlands system retention times to recirculating planted bog systems in ponds. Trying to brush aside and ignore the obvious differences is hardly good science.
The links that you did post that were relevant to a recirculating aquaponic systems suggested retention times of 1-4 hours which corresponds to what I've read and posted, which if you take the low end of that, 1 hour HRT, is pretty much what is recommended for retention times in ponds. And when you consider the quotes from your links and my links I tried to bring to your attention like... "Plant growth will definitely benefit from faster flow rates and turbulent water because roots will be hit by many more ions; whereas slower flows and almost stagnant water would have a negative impact on plant growth. " (Which I notice you chose to ignore because it didn't fit with your necessary long retention times viewpoint) It seems like a good compromise between pond circulation and bog circulation.

We didn't even touch on the fact that adequate levels of DO are required in water for good plant growth and health, which is one reason many aquaponic growers often choose to use the ebb and flow system rather then constant flow systems which help ensure adequate levels of oxygen reach the roots. Very long HRTs in constant flow systems can, and sometimes do, lead to problems with low levels of DO at root level. (see the quote above in bold type)

You also do your best to ignore the fact that people are achieving good, even great, plant growth in their planted bogs (phyto-filters) with much lower HRTs then you say are necessary. Are they achieving the very best possible nutrient extractions they could in one pass? probably not. Could they get better nutrient extraction from a little longer retention times? Perhaps. But like most engineering designs, it is a good compromise. And if you can simplify the plumbing in your pond by using one pump to recirculate the pond and bog at the same ratio, and still achieve great plant growth and reduce the nutrient load in your pond, I say that is good practical science.

If some refuse to accept that people can still achieve great results with small compromises, that is entirely their option.

As for the OP, I disagree that a slower water flow will help much, I think what he/she will benefit most from is a larger bog.

 

[Meyer Jordan]

 

[crsublette]

@Mucky_Waters Here is some interesting material, better defines what is being talked about here...

and... NO where does it indicate flow rates, or hydraulic retention time, was determined due to "nutrient plant uptake" ability for phyto-filters or wetlands or bogs or whatever one want's to call them....

http://www.deq.state.or.us/wq/stormwater/docs/nwr/biofilters.pdf

http://home.eng.iastate.edu/~tge/ce421-521/ishadeep.pdf