MABRs vs MBBRs: membrane-aerated bioreactors vs moving bed bioreactors ('Membrane vs...' series, 7) скачать в хорошем качестве

MABRs vs MBBRs: membrane-aerated bioreactors vs moving bed bioreactors ('Membrane vs...' series, 7)

This video is the seventh in our "Membrane versus.." series, in which membrane processes are compared with the conventional alternatives. This one considers the key differences between the MBBR, that’s the moving bed biofilm reactor, and MABR, the membrane-aerated biofilm reactor. There’s already a comparison of the MABR and MBR technologies in one of our other videos here:    • MBR Insights - MBRs vs MABRs   Biological wastewater treatment is based on either suspended growth or fixed film processes. They are fed with oxygen either actively by pumping with air using a blower or passively by exposure to the atmosphere, and the media may either be agitated - by the bubbles from pumped air - or be static. There a number of media-based fixed-film processes; MBBRs and MABRs are both examples of fixed film processes with immersed media fed by pumped air. The MBBR media comprise pieces of inert materials (or carriers), which can be of various shapes and sizes, on whose surfaces biofilms form. It’s the bacteria in the biofilm which perform the biological treatment in the MBBR process tank - in the same way as the bacteria in the flocs of the suspended growth processes. The biofilm-coated carriers are suspended in the process tank through aeration, which also provides dissolved oxygen to the biofilm. For the MABR the carrier is actually the membrane itself, which can be configured either as a hollow fibre or a spiral-wound sheet. In either case the membrane sits in the process tank and is fed with air. The membrane is perm-selective for oxygen, passing oxygen-enriched molecular (or bubbleless) air through the membrane directly into the biofilm sitting on the membrane. So, the oxygen transfer and utilisation for an MABR is very high. A key difference between the MBBR and MABR technologies is in the biofilm structure. For the MBBR the biofilm sits on the carrier and interfaces with the bulk liquid. The dissolved oxygen, ammonia and COD all enter the biofilm from the bulk liquid. This means that the biofilm region adjacent to the bulk liquid is aerobic and nitrifying, biochemically oxidising the ammonia to nitrate and nitrite. Next to the media surface, the oxygen concentration is much lower. This region is therefore anoxic, and can convert the nitrate to nitrous oxide and on to nitrogen provided there is a sufficient amount of electron donor material - most conveniently the organic carbon. But that's not necessarily the case if the COD has been depleted by its oxidation in the aerobic region. For the MABR the biofilm sits between the membrane, which is also the carrier, and the bulk liquid. The ammonia and COD enter the biofilm from the bulk liquid, as with the MBBR, but the oxygen enters from the other side of the biofilm. This means that the aerobic region, where nitrification takes place, is next to the membrane. The anoxic region, where denitrification occurs, is next to the bulk liquid where the COD concentration is at its highest. This counterflow of nitrogen and oxygen makes simultaneous nitrification and denitrification (or SNDN) more readily attainable and controllable for the MABR. For both technologies, though, controlling the biofilm thickness is crucial. The MBBR and MABR are both examples of fixed film technologies supplied with pumped air. For an MBBR, where the biofilm is attached to solid media (or carriers), the flow of oxygen is in the same direction as that of the ammonia. An MABR uses a membrane to deliver oxygen-enriched air in molecular form directly to the biofilm attached to the membrane, and this flows in the opposite direction to that of the ammonia. The differing biofilm structure and biochemistry makes SNDN more readily achievable for the MABR than for the MBBR. On the other hand, membranes are more expensive than carrier materials. ----------------------------------- Other videos in our 'Membrane versus..' series: 1. Metrics for assessing water and wastewater treatment technology – Introduction:    • Metrics for assessing water and wastewater...   2. MBRs vs CAS - Membrane bioreactor versus conventional activated sludge technology for wastewater treatment:    • Membrane bioreactor (MBR) v Conventional A...   3. Membranes vs. conventional clarification #1 - Principles of membrane filtration versus media filtration and sedimentation for water treatment:    • Membrane filtration vs conventional clarif...   4. Membrane filtration vs conventional clarification - footprint:    • Membrane filtration vs conventional clarif...   5. Membranes vs UV and chemical disinfection for water treatment:    • Membrane filtration vs UV and chemical dis...   6. Reverse osmosis (RO) vs evaporation for desalination:    • Reverse osmosis vs evaporation for desalin...