Author Topic: Best Practice, the Water Pump.  (Read 7858 times)

Dillon

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Best Practice, the Water Pump.
« on: September 18, 2013, 04:29:07 16:29 »
Best Practice, the Water Pump.

So what exactly is best practice? first of all, the water pump, why did the aquaponic industry originally select, and why are submersible pumps still preferred over a standard centrifugal pump installed in an accessible location when it is clearly understood that the submersible is not the preferred option for recirculating aquaculture systems or any other fluid handling application for that matter, no engineer worth his salt would entertain the design of a submersible pump over any other pumpset when there is no specific requirement for a submersible.

A water pump will function just as well submerged than if it wasn’t, an electric motor doesn’t, the electric motor has to be sealed against the ingress of water and the favoured method of achieving this in the readily available range of submersible pumps in use in aquaponics is to encase the stator and connections to the flexible supply cable in a resin of some description thereby rendering any maintenance or repairs impossible and apart from the more expensive models of submersible there are no spare parts for the rotor, impeller or casing components either, so in effect the majority of submersibles on the market today are simply disposable items as there is no remedy for electrical or mechanical breakdown after any initial manufacturers warranties.

But the close coupled pumpset installed outside the water tank is not only accessible without unnecessarily stressing the fish every time you have to access the pump, every component part of it can be readily accessed for maintenance or breakdown purposes, bearings and impellers can be replaced, windings rewound and electrical connections accessed in a safe environment away from the water.

Motor Control

As I mentioned earlier, it is common practice to oversize a pump then choke the feed down to each media filled GB in order to fine tune an Affnan design autosiphon, it is also good practice to design additional capacity in the pump for the future development of adding additional capacity to the entire system or modifying pipe runs and increasing the static head creating entirely new operating parameters for the pump so the installation of an oversize pump isn’t necessarily a bad thing… but running it at full speed in an installation that requires less than 100% of its capability most definitely is.

In plain and simple terms, with a constant load, a slower motor does less work than a faster motor.  So you can only save energy in applications where you need less work done.  Variable Speed Drives, Inverter Drives or Frequency Converters save energy by making the motor do less work.  They are designed to reduce speed and save energy in applications where the main opposing force is drag, so this is especially true in air handling and centrifugal pump applications.  Due to the physics of drag, a small reduction in motor speed will result in a larger reduction in the work done and the energy consumed.  So there is certainly scope for energy efficiency improvements in general aquaponic installations.

So in an effort to locate a suitable piece of kit that meets all the requirements of best practice in an energy efficient circulating pump, manufactured from materials compatible with aquaculture use, mounted outside a Sump or Fish tank and a matched with a speed controller of some description, I found what is proving to be a most reliable candidate.

The Wilo Yonos-PICO is marketed as a glandless circulation pump with threaded connections, a blocking-current proof EC motor with integrated electronic performance control for all hot water heating systems, air-conditioning applications and industrial circulation systems.  It has a cast iron body and pump casing, a PP impeller, an operating ambient temperature range of -10 to +40°C.  The electronic performance control is in the form of an integrated frequency converter with a front mounted variable or constant differential pressure speed selector dial with a bleed function for the pump chamber, integrated protection against thermal overload, transient voltages and cavitation within the pump and a LED display for setting the static head and indication of running power consumption.

Continued...


Dillon

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Re: Best Practice, the Water Pump.
« Reply #1 on: September 18, 2013, 04:35:37 16:35 »
Continued...

The pump curves of the two models shown below I found would be appropriate for systems with fish tanks up to around 2m³ assuming there is a combined static head and average pipework resistances associated with installations of that size, I chose the 15, 25, 30/1-6 for my trials and so far, the only drawback I have encountered is that with it not being a self-priming pump and I have it installed at chest height which is around 1m above the sump water level from where the pump takes its water supply, I have had to install a foot valve on the suction pipework to prevent the water draining from the pump chamber in the event of a power failure, additionally I have installed an injector point just above the foot valve where I am able to connect a garden hose to charge and purge the pump circuit of any air if the need arises.

I have a couple of submersible pumps left over from previous trials, both are nondescript disposable cheap non-branded Chinese imports bought from garden centres and matching the flowrates of these pumps with the Wilo pump I can comfortably estimate savings of between 8 and 12% in power consumption figures, these savings are indicated by the power consumption display of the Wilo pump controller and confirmed by a separate power meter, a Metrel Eurotest 61551 for those interested.

But the real savings in my best practice pump of choice is being able to control the optimum flowrate appropriate to exchange the volume of water in the fish tank exactly once every hour and delivering that water equally to the grow beds without restricting the flow with isolating valves, having a pump installed in an accessible location where it can be freely accessed without getting wet and stressing the fish and in the knowledge that the combined pump and controller is afforded comprehensive protection against transient voltages, overheating and cavitation creating air and water vapour particles and that all the components of the pumpset can be either maintained or replaced and are supported by a worldwide network of agents for the manufacturer.

In ball park figures, every 100w load run for 24/7 will extrapolate to an additional £10.00/month on your electricity bill so any savings on the consumption figures we’re talking about here aren’t going to pay for an extra holiday in sunnier climes but the bigger your installation the more savings there will be to be had, the cost of comparable 6m head with 4m³ flowrate submersibles I have seen range from just under £100 up to over £200 rated at between 65W and 85W and including the dreaded VAT, these come with a supply cable and a selection of  hose tails, but without any switching device, the Wilo Yonos-PICO 15, 25, 30/1-6 has a min/max rating 4W/40W running at full speed costs £79.16 + VAT complete with a soft start speed controller and all the added protection expected from such a unit, surprised? I was! And very pleasantly too  :)

Regards
« Last Edit: September 18, 2013, 04:39:57 16:39 by Dillon »

Craig

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Re: Best Practice, the Water Pump.
« Reply #2 on: September 18, 2013, 09:07:50 21:07 »
Thank you Dillon, this is  very informative, I have been looking at submersible pumps because my system is nearly complete and I will be needing one soon, I did think about an external pump because I use to use one when making bio diesel and it was a good piece of kit. I do not know why I was going to opt for the submersible, I think it may be due to watching to many U tube videos where the submersible seems to be the standard.  I have also been looking at aerators do you have any words of wisdom for them. Thank you Craig.

AquaVeg

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Re: Best Practice, the Water Pump.
« Reply #3 on: September 19, 2013, 06:03:50 18:03 »
Nice topic Dillon.
I have been running on my pilot system a Hailea 8830 for 18 months located in the FT. On for 15mins off 30mins. I have started working on the next system and it will be using two 8830 feeding a DWC raft 30ft by 4 and 3 F&D IBC beds. Total power less than 100w. Have read in several forums that a flow rate of 5gal/min is adequate for the DWC and that is what I am going to try. Will be mounting the pumps outside the tank for convenience. It all comes down to cost and how much you want to spend. I am trying to make AP pay for itself. Time will tell. Oh, Hailea say you can purchase a spare impeller.

Rgds John.

Dillon

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Re: Best Practice, the Water Pump.
« Reply #4 on: September 20, 2013, 12:04:51 12:04 »
Thank you Dillon, this is  very informative, I have been looking at submersible pumps because my system is nearly complete and I will be needing one soon, I did think about an external pump because I use to use one when making bio diesel and it was a good piece of kit. I do not know why I was going to opt for the submersible, I think it may be due to watching to many U tube videos where the submersible seems to be the standard.  I have also been looking at aerators do you have any words of wisdom for them. Thank you Craig.

The power of suggestion Craig, subliminal recommendations, when all you see are submersible pumps, even from the industries gurus why would anyone who didn’t know any better question it?

While some submersibles are capable of working in-line, I haven’t seen a dedicated inline pump on sale from any aquaponic supplier yet and no mention or discussion of high efficiency pump motors and pump motor controllers and Wilo aren’t the only manufacturers of this equipment there are many more out there, the model I chose for my little test unit simply fitted the bill at the time, I fear there’s a larger element of profiteering at work by selling cheap disposable Chinese imports expensively than providing cost effective, reliable and efficient solutions for the end user.

I don’t know about ‘words of wisdom’ Craig? I believe that’s perhaps one accolade too far, I guess my M&E background has given me a head start with the Electrical and Mechanical design aspects of aquaponic systems and my work in the water treatment industry and Sewage Treatment Plant in particular has given me an in depth understanding of the principles adopted by the aquaponic industry as every single process of solids separation, treatment, aeration, nitrification, settling, sludge treatment and weir technology has roots in established STP technologies.

Which leads me on to your question regarding aeration, I have it on my agenda to look further into but I haven’t got around to it yet, what I do know is that in STP, venturi technology is used extensively at just about every stage of treatment, they are known as Ozone Injectors and a Company called Mazzei, http://mazzei.net/ are recognised as one of the industry leaders in venturi technology, venturis are employed in industry as a cost effective means of aeration or the introduction of ozone, there are no working parts and are virtually maintenance free with the cost of operation being a minor compromise in flowrate.

No matter which aquaponic forum you look at, I guarantee you will see two current discussion threads, the first will be a discussion on a reworked autosiphon that works better than the one posted previously, but they’re not entirely sure how they achieved it! And a second thread on home made venturi designs that produce an unspecified volume of air in a further unspecified flowrate.  Now, if you’re like our AUS and US cousins and take some sort of personal gratification in attempting to copy an established, tried and tested, patented technology device that has had papers published about it and is manufactured to BS and International approval standards, then gather your bits of PVC tubing, chewing gum and sticky back plastic and knock yourself out.   :)

Continued...

Dillon

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Re: Best Practice, the Water Pump.
« Reply #5 on: September 20, 2013, 12:11:37 12:11 »
Continued...

Or if you’re like me and don’t see the need to reinvent the wheel and end up with something not quite perfectly round then you could do worse than visit http://www.ebay.co.uk/itm/2-4-6-1-1-5-2-4-Venturi-Injector-Ozone-Mixer-Hot-Tub-SPA-Pool-/221228195784?clk_rvr_id=522455504711 and select the size of Mazzei designed ozone injector you require, add a valve to the air inlet port to fine tune the amount of air you need to inject and there you have it.  I’m again amazed that no-one involved in aquaponics has identified the availability of these cost effective freely available items that meet the criteria perfectly as fit-for-purpose! Did no-one ever wonder where the bubbles came from in their Jacuzzi?  :)

While it is often said ‘you can never have too much oxygenation in your system’, once your system water is saturated and that is dependent upon consumption and water temperature, you’re simply wasting energy pumping more air in regardless, your oxygen levels will fluctuate throughout the day affected by temperature and feeding fish, the more fish feeding in warmer weather you have the more oxygen you will need to introduce, if you were to calculate your total oxygen requirements you would need to consider far too many variables to be confidently accurate and would need to confirm your DO levels occasionally anyway so it is my personal opinion that it is better practice to test your water periodically and provide at least the minimum required for your fish as they are the biggest consumers in a system of just GB’s, DWC however needs saturation levels of DO and tests have shown the more bubbles of air mixing with the roots produces considerably more growth, saturated DO levels of water @10°C = 10.27mg/l or ppm, 20°c = 9.07 and 30°C = 7.54 using aeration methods from ambient air which contains just under 21% oxygen which is >200,000 ppm so it is understandable that plants show better growth when their roots are surrounded by air bubbles.

Whether you use a venturi device, dropping water, mechanical means or a mixture of the three aeration methods, they should be considered and form part of your overall systems backup plan in the event of an electrical or mechanical failure and if you subscribe to sod’s law as I fervently do, then the one device or scenario you haven’t formulated a backup plan for is the same one that the gremlins are already plotting to exploit.  :)

Regards

Dillon

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Re: Best Practice, the Water Pump.
« Reply #6 on: September 20, 2013, 12:18:46 12:18 »
Nice topic Dillon.
I have been running on my pilot system a Hailea 8830 for 18 months located in the FT. On for 15mins off 30mins. I have started working on the next system and it will be using two 8830 feeding a DWC raft 30ft by 4 and 3 F&D IBC beds. Total power less than 100w. Have read in several forums that a flow rate of 5gal/min is adequate for the DWC and that is what I am going to try. Will be mounting the pumps outside the tank for convenience. It all comes down to cost and how much you want to spend. I am trying to make AP pay for itself. Time will tell. Oh, Hailea say you can purchase a spare impeller.

Rgds John.

Hi John, There’s another adage I often use and that is ‘If it’s not broken then don’t try to fix it’ it just wouldn’t do for us all to be the same would it? And if you’ve found a pump you’re happy with then it’s my opinion there is no better pump!

When reviewing the performance of a pump, the pump curve shows us a rate of flow l/h against a known head of water in m so with one pump in the system and against a combined head of water plus any pipework losses in the suction and delivery pipework, that flowrate will progress through the entire system.

The only hard and fast rule there is regarding flowrates in an AP installation has come from the Aquaculture industry and that is that you should change the water volume of your fish tank over completely, at least once every hour, this is ‘best practice’ so at least, minimum flowrates are in fact dictated by existing protocol.

Once the water has left the fish tank it enters the domain of STP principles, flowrates are used in sizing the sewerage network but in the determination of tank sizes, Hydraulic Retention Times (HRT) are used, HRT, (the amount of time in h, 1l of influent is retained) gives the designer a handy tool to determine the size of tank required for any particular process i.e. aeration chambers, clarifier, settling tanks etc, for in STP design HRT are already established.

So specifying a flowrate through a DWC tank will extrapolate to a specific HRT for that tank and if you were to install an additional tank of the same dimensions without any further modification to the system, the flowrate would remain the same but the HRT would double.  With the flowrate and tank size you mentioned earlier you would have a HRT of c2.5h for US gallons and c3h for Imperial gallons, The HRT published by James Rakocy in his Update on Tilapia and Vegetable Production in the UVI Aquaponic installation are: Fish Tank, 1.37h, Clarifier, 0.33h and the hydroponic tanks 3h.  So the retention times you are aiming for would certainly conform to Dr Rakocy’s UVI model, but the question arises ‘what is the optimum HRT for a DWC tank? I personally don’t think it matters that much whether it’s 1h or 10h, the nitrification process is taking place on every surface the system water is in contact with and considering the complete nitrification of fish waste takes up to 4 weeks I don’t see any reason why the nutrient bank in an established aquaponic system wouldn’t remain stable for at least 24 hours anyway.

It is my considered opinion that DO being maintained at saturation levels with lots of air bubbles mixing in with the roots and the amount of protein entering the fish at one end is equal to the amount of nutrients being converted and taken up by the plants at the other is far more important to balance in DWC tanks!

Regards



Craig

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Re: Best Practice, the Water Pump.
« Reply #7 on: September 20, 2013, 09:08:19 21:08 »
Thank you again Dillon, very informative and interesting.
 I will have two IBC's for fish tanks, a sump 700 litres, a DWC 2 x16ft and GB 3 x 18ft. The pump I had in mind was a submersible 3500 l/ph but now you have put doubt in my mind and an external pump does make sense, can you please advise me if the pump size is correct. I was advised by another friend that It would be ok for the system if all the water was circulated around the system every two hours. Please tell me your thoughts. Thank you Craig

Dillon

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Re: Best Practice, the Water Pump.
« Reply #8 on: September 21, 2013, 01:10:17 13:10 »
Thank you again Dillon, very informative and interesting.
 I will have two IBC's for fish tanks, a sump 700 litres, a DWC 2 x16ft and GB 3 x 18ft. The pump I had in mind was a submersible 3500 l/ph but now you have put doubt in my mind and an external pump does make sense, can you please advise me if the pump size is correct. I was advised by another friend that It would be ok for the system if all the water was circulated around the system every two hours. Please tell me your thoughts. Thank you Craig

Hi Craig, I have no intention of attempting to teach anyone how to ‘suck eggs’ but rather than make assumptions about any other readers current understanding, I need to just confirm what some may or may not already know.  When pump manufacturers declare a maximum head and flowrate for a pump, it is a maximum performance statistic assuming the other doesn’t exist i.e. take the pump curve I posted for the Wilo pump, the advertised flowrate the pump is capable of is 3.5m³/h and the maximum head it will pump against is 6m but when you look at the pump performance curve you will notice that against a 6m head you will have a negligible flow of water and conversely, the pump will only achieve a flowrate approaching 3.5m³/h when pumping virtually horizontally.

As a side note, I’ve found that you need to log in to see any posted pictures!

I can’t advise you whether I believe your pump is correctly sized for your system as I have no information on the specific pumps’ operating curve, (and they can vary considerable from pump to pump and call me a cynic, but if a manufacturer doesn’t publish a curve let alone an accurate one, then it’s probably not worth investing in), the overall hydraulic design, the static head of your system and the losses in your pipework, every metre run, diameter and type of pipe, every fitting or accessory fitted to the pipe will affect the flowrate.

There’s always more than one way to skin a cat! And the same goes for designing an aquaponic installation, as I see it, there are initially three components that need to be reconciled;

•   The amount of growing surface area
•   The daily feed rate and the fish biomass for feed conversion for that growing area
•   The fish tank volume to support the fish biomass

So dependent upon where your priorities lie, whether you want to prioritise fish or plants is where you’ll start to design your system, you’ve stated quite specifically that you have two IBC fish tanks so I am assuming that this is where you want to start your design, with a combined fish tank size of around 2m³ and as I stated earlier it is ‘best practice’ to completely exchange the fish tank volume around once every hour, and this will dictate your system design flowrate, which will be 2m³/h, spray bars, venturis etc would add additional head to your pump and with a CHOP 2 design you would also need to add the hydroponic section separately.

You asked, will circulating the system water over once every two hours work? Well you have 2m³ of fish tank and let’s assume CHIFT PIST or CHOP 1 and there is a further 2m³ of water volume in your GB and DWC, pumping at a rate of 2m³/h will turn over your fish tank water once every hour and the total water volume in your system once every two hours so the answer in this case is of course yes!

I started this discussion in the hope others would contribute with their opinions of best practices, I can also see some benefits of procuring a submersible pump sized at twice the volume of your fish tank in max flowrate/h as is the most popular advice I have seen on the various forums, but it has to be said that the bigger the system is, the stronger the argument will get for the benefits of a speed controlled inline centrifugal pumpset up to motor sizes exceeding 0.37kW where BS 7671 regulations impose specific requirements for the protection and control of such motors where it would be at least challenging to argue the case against.

Regards

AquaVeg

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Re: Best Practice, the Water Pump.
« Reply #9 on: September 23, 2013, 09:18:52 09:18 »
Tony,  Best practice depends on your restraints. Is the AP project a hobby or commercial.

My objective is to make the project pay for itself, then if I can see that it has a potential for profit to maybe enlarge. So with that in mind all capital and running costs must be kept as low as possible, hence why I am going for minimum flow DWC and F&D. To date pilot F&D has worked find but I know enlarging system will bring different problems. Most AP forums suggest starting small and working up unless you have spent a great number of years in the horticultural business.

I would like to use green power but at the present time its not economic unless its subsidised. ( I have fitted PV's as a subcontractor and presently looking into a micro Hydro system to power some of the AP system) The AP business is very young and there is not enough trusted facts and results around to help new starters in the business.

I am looking towards setting up a Aquaponics Co-op to purchase and market as a AP group “United we stand divided we fall” or at least we stand a better chance of success by pooling resources. Is this best practice ?

Rdgs John.

Dillon

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Re: Best Practice, the Water Pump.
« Reply #10 on: September 23, 2013, 02:25:27 14:25 »
Hi John, it is my understanding of Industry Best Practices that they are the commercial or professional procedures that are widely accepted or prescribed as being correct or most effective and are not subject to or dependent upon any particular application or constraints.

That is not to say that any procedure chosen over what is considered or accepted as best practice should be frowned upon as I’m sure in the design of every AP installation there will be unique challenges to overcome.

I have stated previously and I am sure most will agree that Electricity and Water are expensive commodities anywhere in the world today and the preservation and optimum use of these utilities should be a primary driver for everyone wherever they are located and should certainly be considered in a best practice design, being located adjacent to a stream or river that you have access to is a gift and in my opinion should be made mandatory to exploit such an asset particularly with the amount of support available from the Energy Saving Trust and the Environment Agency!

What you propose with a Co-Operative is the formulation of a business and there is no best practice for any legal structure of a business, they all have their strengths and weaknesses.  An AP Co-Operative will need a business plan and in a business plan the best practice will be to formulate a comprehensive plan structured around one of the successfully adopted philosophies of business planning such as the Five Pillars of Business.  People, Planning, Process, Performance and Profit, and due diligence performed throughout the formulation of the plan, I have another adage I like to use here as well, another 5 P’s, Proper Planning Prevents Poor Performance.  So whatever the structure of the business is, its success will be largely dependent on the development and successful implementation of such a plan.

Regards

Rufe0

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Re: Best Practice, the Water Pump.
« Reply #11 on: May 19, 2014, 10:45:27 10:45 »
Hi

I'd just like to make a comment of the whole cycle your fishtank once per hour rule. What this means is 'filter' your fishtank once per hour. This rule comes from the early days of backyard diy aquaponics with a fishtank and expanded clay ball media beds normally on a flood and drain cycle. In this system the media beds are the filter. However it's now fairly common place to have a separate moving bed biofilter. In a system where you have a moving bed biofilter, then only this needs to have the fishtank volume cycled through it once per hour. After that DWC beds or any other beds don't actually need anywhere near that level to function properly. I'd bet DWC systems could drop crazy low like 100 or 200 hours per cycle and remain just as effective(just guessing tbh but anyway it would be significantly less). This is of course assuming Dissolved Oxygen levels where maintained with air pumps.

Neill

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Re: Best Practice, the Water Pump.
« Reply #12 on: August 31, 2017, 03:33:51 15:33 »
Great articles Dillon thanks for posting, its given me so much useful info and answered questions I hadnt even thought of asking yet :)