How to attain desired air quality in aeration tanks?

Published on by in Technology

Recently, I came across a problem of irregular air supply in an aeration tank. Since one of the blowers is out of service, to maintain regular air supply, we connected a compressed air line to the aeration tank.

I feel that, compressed air is not giving satisfactory results compared to the blowers, but am not able to find any literature on the topic.

Is the use of "blower" or "Industrial Compressed Air System" appropriate for aeration systems, and how can it be adjusted ? Can compressed air in fact replace blower systems in the short and the long term?
 

Taxonomy

12 Answers

  1. Blowers x Compressors

    As some colleagues already said there is a difference between blowers and air compressors. May be you can share witu us dissolved oxygen content in the aeration tank, tank dimensions  and type and flow per diffuser. With this information we can help you.

     

    Regards

    Ademar

  3. Aptitude à la gestion des projets

    On peut utiliser préalablement de l'anaérobie avec absorption du gaz carbonique par les algues
     

  4. Hello Bruno, I really appreciate your insights on energy consumption. It clearly shows why one should get blower. From my little experience, I have seen that, financial aspect of any system plays a very important role. Thanking you for sharing insights and giving your precious time to this post. Have a nice day.

  6. Aeration pattern and minimal flux or specific airflow rate

     

     

    Hello, diffusers are a system of equal pressure. This means that any compressed air will expand immediately and get out into water if hydrostatic pressure and dynamic wet pressure was beaten. Prerequisite is: leveling of diffuser membranes and identical behavior of diffusers in terms of minimal pressure for opening pores

    Assuming unclogged diffusers, there is a minimal airflow rate per diffuser or a minimal flux (airflow rate decided to membrane surface) where diffusers will still deliver on whole surface. Below it the system will lose pattern.

    Blower capacity for continuous airflow must be above this value. If less was desired a modulated on/off impulse may deliver good average. 

    The reality is that all diffusers must be identical as type and age, and must be free of sediments and deposits. In time they  will start losing initial properties and system may lose pattern.

    Replacing some diffusers with new ones may also affect pattern.

    Sludge or condensate in the pipework may also obstruct air in portions of grid.

    One is clear: if blower capacity goes below minimal, the only solution is to add capacity in mass flow, and not in pressure, as all other colleagues mentioned. Do not mistake blowers with compressors. A blower delivers a huge mass flow at up to 1bar over pressure usually, and a compressor delivers huge pressures at low airflow rates. 

    There is plenty to write, and there are some different types of fine bubble diffusers: ceramic, epdm, silicone, polyurethane and different shapes: discs, tubes, panels, stripes. Each has specifics. 

    I am glad if I could help, and we can go into details anytime. I'm with one of the manufacturers of diffusers, and I might be able to support by sharing without advertising...  Regards!

     

  7. Bonjour En fait j'ai eu à résoudre ce genre de problème pour une micro station d'épuration dont la motorisation était hors service. j'ai fait la même chose, j'ai installé un compresseur qui insufflait de l'air dans le fond du réservoir. J'avais pris la précaution de faire une vidange du réservoir tellement le contenu dégageait une odeur pestilentielle qui d'ailleurs a gêné les occupants des lieux depuis la mise en fonction de cette micro station. Toutefois comme je pratique l'Assainissement biologique j'ai mis le site sous surveillance par prélèvement instantané. au début l'analyse était essentiellement visuelle mais très vite vu l'odeur je suis passé par le laboratoire. l'avantage du laboratoire c'est qu'il m'était possible de suivre tous les mois sur un graphique l'état de détérioration du milieu. l'air compressé n'était donc pas la solution et cette procédure a été stoppée. Par un concours de circonstance j'ai effectuée une expérimentation qui s'est vu positive puisque de suite les paramètres se sont stabiliser et sont revenus très vite correctes. Depuis les utilisateurs des lieux appliquent scrupuleusement cette nouvelle procédure dont ils sont tout à fait satisfait. l'expérience d'air compressé a duré presque deux ans, 4 mois ont suffit pour revenir à la normale. mes conclusions l'air insufflé agit sur le milieu comme un clou sous la pluie: il s’oxyde. En plus il ne faut pas négliger la présence des micros polluant chimiques qui réagissent sous l'apport d'oxygène. j'ai la solution mais je ne peux pas la communiquer tant que je ne suis pas protégé de sa propriété industrielle. lyseconcept jean Marius Hello In fact I had to solve this problem for a wastewater treatment plant whose engine was out. I did the same thing, I installed a compressor that breathed air into the tank bottom. I had taken the precaution of a tank drain so the content off a stench which also hampered the occupants since the function of this micro station. However, as I practice Bioremediation I put the site under surveillance by sampling instant. early analysis was primarily visual but soon saw the smell I went through the lab. the advantage of the laboratory is that it was possible for me to follow every month on a graph the middle of the state of deterioration. compressed air was not the solution and this procedure was stopped. By a combination of circumstances I conducted an experiment that has been positive since once the parameters have stabilized and returned quickly correct. Since users of the premises scrupulously apply this new procedure they are quite satisfied. compressed air experience lasted almost two years, 4 months were enough to return to normal. my conclusions the supply air is on the middle like a nail in the rain: it oxidizes. In addition we must not overlook the presence of hazardous chemicals that react microphones in the oxygen supply. I have the solution, but I can not communicate as long as I'm not protect its intellectual property. lyseconcept jean Marius

  8. The issue in this situation is one of air flow and not pressure. The aeration system (pipe, manifold, diffusers and water depth) has its own performance curve for air flow and pressure. Consider a tire analogy - albeit not a great one. When you use a high pressure compressor to inflate a tire, the pressure in the tire is not the same as the compressor pressure feeding the air into the tire. Because the volume of air you feed into the aeration system with a compressor is lower than it would be for your blower, you will have less mixing energy and lower dissolved oxygen levels in your aeration tank.

  9. DO levels

    I presume you meant DO level in the tanks. It's achieved by distributing air generated by the blowers through the air grid and the set of diffusers in a diffused aeration system.

    Alternate means is the use of surface aerators. In case of surface aerators appropriate sizing and positioning is critical to avoid dead spots in the tanks.

  10. Aeration needs flow, not pressure

    For Aeration you generally need high flow and low pressures. That is why we use blowers. A compressor will give you high pressures and low flow. If you have fine bubble diffusers, like I always spec for Aeration tanks, then you will run the risk of damaging your diffusers. With high pressures and low flows you will probably find is that you have flow at the diffusers closest to your air input, but the ones further away are not functioning properly. And those that are not functioning properly will likely be starting to foul. In a pinch with a good regulator maybe you can get away with a compressor for a few hours but I would get a new blower immediately. If this is a common problem then maybe you should consider either keeping a spare on hand or wiring in an extra one for redundancy.

  11. blowers

    Maybe, when you connect compressed air line to the aeration tank you increased velocity of bubbles of air, (because you increased air flow) and contact time is shorter so you dont have good results.

    Regards.