Organically Bonded Mg Clogging UF

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For the past years we are struggling to solve the algae and organically-bonded magnesium problems in a lake in ​Saskatchewan, ​Canada.

We use 3 banks of ultrafiltration (UF) filters followed by 0.5-micron filters before nanofiltration ( NF).

The algae form even in winter months, under 3-feet-thick ice.

The organics in water are non-biodegradable and Mg has bonded to them. This makes Mg basically impossible to oxide with any oxidizing agent that we have tried. Mg stays in a dissolved state so the NF has to remove the  Mg instead of the UF.

That is why our reject rate is incredibly high (67% waste and it was designed to be 35%). And we need to replace the UF filters every 2 years while they should last 5-10 years.

How can we prevent algae blooms, oxidize the organically bonded Mg and prolong UF life?

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17 Answers

  1. I would replace the UF filters altogether with an Activated Filter Media which will last over 20 years as it is self-cleaning, self-charging and self-sterilising filter media. It won't clog up because it is an electro-static filtration method rather than a physical barrier. Biofilm will not grow on the surface of the media bed to clog it up either. At my company, we typically use this as pre-treatment to any ro or uf system to protect the membranes.

    In terms of algae control, you can manage this with mechanical aeration, I have experience in reducing algal counts of 1.2 million to less than 80 using fine and ultrafine bubble aeration here in Australia. Passing the water through a static mixer will raise the oxidation potential up to 200 mV to help with oxidation. This will also result in intense flocculation to help pull out the dissolved organics through the hydrodynamic cavitation reactions.

    If you would like to know more, please email me at andrew@waterandoilsolutions.com.au

     

  6. Baleen with CAF offers an alternative to UF.

    If UF quality is still sought, then Baleen plus media-filtration (to remove any ‘residual’ flocculant) is the ultimate solution i.e. UF problems will then disappear.  Call me 780 803 6934 (Alberta)

    www.baleeninternational.com

     

     

  7. In natural water Mg is always present as Mg2+ and cannot be further oxidised. May be you are confusing it with the removal of manganese which is in reduced form in natural waters and should be oxidised to form MnO2 which is a solid. Mg2+ can be partly complexed by the natural organic matter in the water but it contributes together with Ca2+ to the hardness of the water. If you concentrate hard water in an NF or an RO this will cause scaling. So probably this is the reason for the low recovery in the NF. You can increase the recovery by: 1) acid dosing 2) antiscalant dosing 3) removing multivalent positive ions before the NF by IEX

  8. Bonjour,

    We reduce the algae production in small lakes for storing water for irrigation by installing ahead a smaller dam for reducing the speed of the river flow in a larger bassin with 0.50 to 1 m depth maxi. It allows bacterias at the bottom of the small bassin to feed on the coming nitrates with the flow. It reduces the nitrates from 0.35 mg/l to 0.11. Then in teh main lake we have less nutrients as they have sedimented whyle crossing the small bassin we call bassin de décantage

  10. Варианты удаления Блум или два . Но наиболее эффективную поставку разработан в Сколково ( Россия) фильтр, который не требует замены в течение 10-12 лет и он удаляет практически все примеси.

  11. You simply do hypo dosing (10% chlorine concentration ) before UF inlet @ 1 PPM by positive displacement pump , It should be continous during operation but should take care b4 RO/ Nano membrane ,use SMBS b4 RO feed for decholorination.

    1 Comment

  13. I don't understand the problem.

    Algae blooms are associated to the N and P levels. Could you control them?

    I think that you must install a DAF before UF to discharge the amount of SS.

    1 Comment

    1. At Griffith New South Wales Australia, Biosol has been shown to reduce incident P at the treatment plant by 75% when compared with Ferrous Chloride and Magnesium hydroxide dosing in the sewer catchment.  This P is forming an insoluble Calcium / phosphorus microfine sediment that is not available to the algae.  Dropping N or P will reduce the algae as Jose Martinez suggests.  Biosol treats the cause of the problem and not the symptom.

  15. The Mg will be in oxidized form already, independent from it´s solubility or binding to organic. Applying oxidants you rather destroy that organics and set the Mg free. Is there a chance to eliminate the phosphorous needed for plant growth by adding a precipant? Products will easily be retained by the UF.

  16. The central metal ion in plant chlorophyll is Mg++, so you should prefilter the water to remove cells before adding any oxidant.    Your statement is somewhat confusing since you refer to organically bound Mg++  and soluble Mg++.  The former would be mostly removed by the prefiltration (conventional treatment with sand filter) and the latter would be removed by an  NF or RO membrane. Certainly the UF would clog rapidly if the cells have not been removed.   Algae grow under conditions of slow moving shallow water, warmth and sunlight plus nutrients. Reducing algal growth in source water  is primarily managed by reducing the nitrogen and phosphorus nutrient input. Sometimes aeration of a small body of water will also control algae growth. The other concern about algae is the possibility of cyanotoxins and geosmin and isoborneol production. That's why it is essential to filter out the cells before adding oxidant which will lyse the  cells and release toxins.

  17. Algae need nutrients and light, if you can limit either of these you can limit algal growth.  

    Other than the obvious pontoons, floating balls, surface growing plants, etc. if your lake is deep enough, circulation could be used to draw the algae down below the growth depths.  I'm amazed to hear that algae is growing even under 3 foot of ice, can you see it through the ice?

    Otherwise you're easiest assessing the rate limiting nutrient & then determining if you can control its concentration.

    Or you could consider predation.

    Have you tried varying concentrations of ozone and AOP's for the oxidation step?