Wastewater Treatment

[GaryD]

Hi,

In a BYAP discussion that started out comparing the efficiency of swirl filters versus radial flow filters, RupertofOz asks the following:

Why do people feel it is so valid to transpose waste water treatment techniques & equipment.. to aquaponics...

The simple answer to the question is that people use such processes because they work.

As a former wastewater treatment operator, I offer the following:

• Recirculating aquaculture is wastewater treatment.....inasmuch as it involves the removal/conversion of volatile/toxic substances from water.
• The micro-biology and water chemistry for both disciplines is virtually identical.
• Wastewater treatment (in terms of the fundamental processes involved) came long before recirculating aquaculture.

I found that the further I got into aquaculture the more I understood the similarity between the two disciplines.

Rupert then goes on to say.....

But I'm not sure what people are attempting to acheive... and if it's to stock more fish... then it worries me a little... as many are already overstocked..

This is a strange comment......overstocked compared to what?......and according to who?

The major limitations to the number of fish that you can stock in any situation are:

• your ability to convert the toxic substances generated by the fish.
• your ability to retain acceptable levels of dissolved oxygen.
• your ability to maintain carbon dioxide levels with acceptable limits.
• cultural factors associated with the fish species - some fish (relative to others) just don't like to be crowded.

The basic flood and drain AP system, while useful in some respects, is limited in its scope.

When something goes wrong with a basic flood and drain system, advocates of the model insist that the system is overstocked or that the operator has been over-feeding.....when what might just as easily have happened is that a convergence of events........water temperature, oxygen levels, time of day, etc.....has exposed the limitations of the Speraneo model.

If the incorporation of filtration equipment allows one to carry more fish for the same inputs....in greater safety....why not do it? And what does it matter where the equipment or processes come from?

In fact, from a sustainability perspective, getting the best bang for every buck invested in electricity or fish food is essential....and you won't do that with a basic flood and drain system.

In a subsequent post in the same thread, Rupert says.....

Sorry, but trickle towers aren't particularly great at nitrification... they're very effective at oxygenation... which can assist in nitrification...

Notwithstanding the fact that I've already addressed Rupert's failure to understand the difference between trickle towers and trickling bio-filters, his confusion continues.

Tricking bio-filters, which I've used in aquaponics since I began, are derived of the wastewater treatment industry where they've been used (principally for nitrification) for over 100 years.

In the case of trickling bio-filters, the word "trickling" refers to the way that the water percolates through the media rather than to the volume of water. The very large bio-filters that I worked on had 32 megalitres per day go through them - hardly a "trickle."

Aquaponics is aquaculture......and aquaculture is wastewater treatment.

Had Rupert been a wastewater treatment operator, it's possible that none of this would have been a surprise to him.

Gary

[Pseudoreality]

After sitting through a millon talks on wastewater treatment I could not agree with you more. A lot of the skills and knowledge are transferable. Water chemisty is all the same no matter if its lakes, potable water, wastewater, mine water. In both watsewater and AP systems you are trying to remove solids and promote the nitrogen cycle. The only major different I see is you are not as concerned about pathogens or BOD removal in AP. I would be currious to see how BOD changes throughout an AP system.

[Cecil]

Gary,

As always you are spot on. The only thing, is isn't the following also a limitation in an aquaculture RAS?

* your ability to remove settleable and suspended solids

regarding your following bullet points:

* your ability to convert the toxic substances generated by the fish.
* your ability to retain acceptable levels of dissolved oxygen.
* your ability to maintain carbon dioxide levels with acceptable limits.
* cultural factors associated with the fish species - some fish (relative to others) just don't like to be crowded.

or perhaps that is actually part of the first bullet point? I don't think of the solids as being "convertable" and toxic like ammonia and nitrites until they are high enough. Perhaps I'm wrong?

[GaryD]

Hi Cecil,

In a pure aquaculture sense, it comes down to separating the fish from their wastes.....period!

In ideal world (from a fish' perspective), this might mean living in flowing waterway or a body of water that is large enough that they will never come face to face with their own pee or poop.

Aquaculturists achieve that by using creeks, rivers, lakes or seas wherever they are allowed.

Fortunately, not all aquaculturists have access to these chunks of water so they use ponds and tanks.

Cost-effective aquaculture requires that we minimise our use of water and that means that we have to manage the pee/poop contact thing using what we know about micro-biology and water chemistry.

RAS operators use a variety of hardware options to convert the wastes to less harmful substances.....and water replacement to limit the build up of nitrates.

Aquaponicists use media grow beds to both convert the wastes and to limit the build up of nitrates.

Smart aquaculturists and aquaponicists use some of both......a safe way to deal with wastes and an efficient means of controlling nitrate levels....by extending the scope of integration to include plants.

Cecil, I guess what I'm trying to say is that cost-effectvely keeping the fish as far away from their waste as possible (by whatever means) is a given.

Gary

[Earthan Group]

I think Rupert is looking at the filtration and stocking side of things from the point of view of the plants and the fact you need very little fish (feed) to deliver adequate maco nutrient to a very large area of plants. Hence the "many are already overstocked" comment. But who really knows?

My point of view, many of you will know I wear aquaculture goggles for good reason, is if you want to have the best fish growth in a small space, filtration is neccessary. A debate will no doubt start on what is the best. Simply the best is what will grow you the most amount of fish for the smallest cost over the life of the system, not just the start up. Instead of having a 2000 liter tank running 20kg of fish in it, you can run a 1000 liter fish tank with the same amount of fish which will use less power and water.

Is filtration entirely critical? Well yes it is, however it can take many forms within your systems. For example, our recent build has a very low fish to plant ratio and I designed the filtration within the beds.

[GaryD]

Hi Paul,

Where you been, man?

I think Rupert is looking at the filtration and stocking side of things from the point of view of the plants and the fact you need very little fish (feed) to deliver adequate maco nutrient to a very large area of plants. Hence the "many are already overstocked" comment. But who really knows?

The relatively recent realisation that you can run a lot of plants on relatively few fish has been the saviour of both raft and basic flood and drain "closed loop" systems (in that advocates of the system can retreat from their previously inflated stocking rates).....but they are still something of an agricultural absurdity - in my view.

Regardless of how many fish you have, if you don't have the capacity to isolate fish from plants, you are still required to make too many compromises.....and you're always going to be hamstrung when something goes wrong.

From a commercial perspective, it makes more sense to set up an efficient hydro system (be it raft tanks or NFT) and simply rely on the fish system to provide water (appropriately adjusted) for the hydro system. That way, you achieve AP's biggest benefit (two crops for the amount of water previously required for a single crop) but you are not limited in the way that you manage your plant crops......or your fish.

Gary

[Earthan Group]

Hi Paul,

Where you been, man?

Trying to get some rest Gary. Happy new year to you mate. I am off up the coast with the family for a few days, visiting underwater world and all those fun things. Great to have some time home with the family, be is short lived. Then Friday, off again...

The relatively recent realisation that you can run a lot of plants on relatively few fish has been the saviour of both raft and basic flood and drain "closed loop" systems (in that advocates of the system can retreat from their previously inflated stocking rates).....but they are still something of an agricultural absurdity - in my view.

That may be true Gary. Many have been running their nutrient loads based on the information out of the UVI result (eg:100grams feed per m2), but not many are removing the solid wastes out of the systems so have the capacity to gain an additional 25% to 35%.

Some of the UVI numbers suggest 65 grams per M2 this would give you 15m2 per kg of feed (at the lower protein level). Raise the protein level to Australian species and it looks more like 20m2 maintain the solids for processing it may look like 26m2 to 30m2 per kg of feed. I am surprised it took them so long.

Regardless of how many fish you have, if you don't have the capacity to isolate fish from plants, you are still required to make too many compromises.....and you're always going to be hamstrung when something goes wrong.

Never a truer word said Gary. The recent build I mentioned in my previous post has the capacity to isolate parts or all of the garden from the aquaculture system without risk to the fish. At a very small cost in comparison to the entire system. This is something that is very easy for those at home to do. Very handy for many that treat with salt and worry about thier plants.

From a commercial perspective, it makes more sense to set up an efficient hydro system (be it raft tanks or NFT) and simply rely on the fish system to provide water (appropriately adjusted) for the hydro system. That way, you achieve AP's biggest benefit (two crops for the amount of water previously required for a single crop) but you are not limited in the way that you manage your plant crops......or your fish.

We have talked about that before Gary. That is how the recent fish farm we built is set up to operate. However, I think the main issue with that is the interpretation of aquaponics in the current market changes to suit what will sell. Many are of the popular belief, if you are not running from fish tank directly back to the plants and back, you are not doing aquaponics. Example, a fish farm utilizing a waste stream through NFT may not be considered aquaponics by those not selling NFT. Perhaps in time folks will change their perspective, like they have with filtration and stocking levels, feed loads etc.

[GaryD]

Hi Paul,

Happy new year to you, too. I hope you enjoy that break with the family.

I think the main issue with that is the interpretation of aquaponics in the current market changes to suit what will sell. Many are of the popular belief, if you are not running from fish tank directly back to the plants and back, you are not doing aquaponics.

I think most people are aware that aquaponics is the combination of recirculating aquaculture and hydroponics - in all of its forms. Having said that, there are always people who want (for a variety of reasons) to define things to suit themselves.

One of the stated aims of the Aquaponics Association is to define aquaponics.....and to eliminate the "myths" associated with aquaponics. As far as the "myths" go, the folks behind the association are those principally responsible for the myths - so it will be interesting to see which way they go with that.

They have already begun to describe aquaponicists as aquapons, so we can probably anticipate similar efforts to limit the definition of aquaponics to whatever suits their marketing. Fortunately, there are enough of us around to remember the way that it really is.

Gary

[ande]

He he
To me AP is part of the wastewater treatment

cheers

[tpilk]

This is an interesting discussion.

I recently posted an inquiry about nutrient levels/depletion for a given system system, specifically NFT. I am planning to pull "fish water" from the main AP systems (I have two), to circulate through an NFT system. I do not want it to return to the main system for a few reasons, one is it will allow for more aggressive pest control (Thailand has bugs to no end). My question has to do with depletion of nutrients while the water circulates, basically, how can I determine when the water needs to be replaced? Or, possibly recharged, say if I were to supplement with either Hydro Nutrients or even a seaweed-type product if that's possible? The water would then move to the next phase, which will be the wicking beds. So basically it will go from FT to NFT to wicking beds.

I'm also trying to understand what will be the driving factor for advancing the water from one system to the next....what will come first - depletion of nutrients in the NFT circuit or possibly wicking bed demand. Can water stay in the NFT system for up to a week (which is about the watering cycle for the wicking beds)? If not, how long? Regardless, I will always use the same amount of water as I would by not "sharing" it's use so this does not present any conservation or efficiency loss. One additional concern is if I pull too much water from the main system in a short period to feed the NFT and wicking beds, could it affect the health of my main system, which is well stocked, highly oxygenated and filtered. I read all the time that water changes are discouraged in AP and aggressive use could have a similar result, right?

I know all of this is subjective - I need to specify the size and specifics of my main system, size of the NFT system, as well as how many wicking beds will be supported. I guess I'm really looking for input as to my thought process here. Back to this thread, I see diversity as a key element in being successful and productive. Currently, I would lean towards adding additional wicking beds over growbeds, if for no other reason than the limitations a non-isolated system presents. I have no desire to ever go commercial, but a nice, self-sustained mini-farm would sure be a great endgame and for that I see diversification becoming more and more critical.

Any thoughts?

Cheers