Windmill Aeration Questions

Question and Answer from Australia on Windmill Aeration

Dear Pond Owner Magazine,

We haven’t gone to sleep, in fact we have been doing some research into where we might best make an early breakthrough for multiple systems. It seems that prawn and fish farms may be the answer. We are still early in the “blue-green algae season” and although dire predictions are being made about the severity of blooms this summer, they haven’t happened yet, so they are not on the radar of many.

An example – although we may be too late for this one – is a prawn farm in Queensland with 31 grow-out ponds. Each pond currently has up to 10 surface aerators. The Queensland EPA quite rightly stated that efficient aeration is a key issue for aquaculture farms. However, a study they arranged concluded that surface floating paddle wheels have higher standard aeration efficiencies compared with, “aspirators, leaky hoses and airlifts”.

To cut a long story short, the eco-efficiency assessment was to spend A$123,000 to install variable speed drivers (lower speed during daylight hours) on some aerators and weights on aerator floats to improve aerator efficiency. This would save [electrical] energy costs. We did some simple arithmetic and estimate that if they installed windmills on all ponds, it would cost around A$93,000 and, of course, zero energy use and costs from then on. So 100% energy savings.

We’re awaiting responses from our brief contacts (to date) with the Queensland EPA and the Australian Prawn Farmers Association. We might need to be persistent, since people hate to be told they might’ve made a wrong decision based on false premises. Of course, they were unaware of your products and obviously didn’t go looking for them.

We’d appreciate your comments on the QLD EPA’s conclusion on aeration efficiency, (I think they are wrong), and would also appreciate references and testimonials from users of the products in the aquaculture industry.

Lack of winter and spring rains means that a number of rivers and streams in drought area are likely to flow very slowly and will be subject to algal blooms. What is your opinion about the effectiveness of deep aeration to combat blooms under these circumstances? It is not unlikely that if the current rainfall patterns persist, algal blooms in slow moving rivers will become endemic. Would strategically place diffusers prevent or mitigate blooms in rivers? Because the windmills are intrinsically inexpensive, they could be permanent fixtures, although it may be necessary to remove pipes and diffusers when floods are likely in winter and spring (assuming it rains!!).

Best regards
Harvey Gough MRACI CChem
Novasys Group Pty Ltd

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Harvey,

Thanks for your note, as you know there are tens of thousands of these windmill aeration systems installed in North America. Superior Windmill, for example, is one of the leading manufactures of these units in the USA and Canada.

It strikes me as odd that a scientific body in Australia would consider surface aeration more effective than bottom up aeration. There are Canadian government bodies that have found bottom up aeration to be 8 times more effective than surface aeration (compared to Paddle wheels or Fountain aeration systems).

Surface aeration only aerates the top 2 feet of a pond surface where as bottom up aeration aerates from bottom to top of the pond. Depletion of oxygen starts at the bottom of the water where the decomposition of organic matter takes place.

Providing more oxygen from the bottom of the water accelerates the decomposition process of all sediment, waste matter, etc. From the bottom the oxygen rises up through the water column – it helps burn off the excess organic matter that is suspended in the pond body.

You need to find yourself a case study example or customer that understands the logic behind this – install a few systems and watch the water quality results. They will all be impressed and then you will be able to invite the local media to view the results as well. Local in Country testimonials is the way to go. Even if you have to invest in the first few units to show case the example. This is what they are doing in Japan right now.

The reason farmers in North America install these units on their farm ponds is to prevent blue green algae from forming on their ponds. If their cattle drink blue green algae they will get very sick and can even die from it. Studies show that cattle drinking from clean aerated water gain 1/3 more weight in the same period of time so there is a strong ROI for this as well.

So we are well aware of blue green algae in North America and there is not one farmer that uses surface aeration – they all use bottom up aeration.

Sincerely,
Pond Owner Magazine