How to Design MBBR and MBR Process for Sewage Treatment Plant?

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How to design MBBR and MBR process for Sewage treatment plant?

How to do the basic process calculation for the equalization tank, anoxic tank, aeration tank, clarifier or sedimentation tank, sludge holding tank, air requirement for aeration, RAS and WAS.

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  1. s no strait forward answer to your question.  Process design of wastewater treatment works is complex with a large number of input variables.  Also just want to check that you grasp the difference between a MBBR process and a MBR process, the 2 being quite different.  Furthermore just as there is a range of BNR activated sludge processes, so too there are a range of MBBR and MBR process configurations.  So to be able to answer your question with say 10 calculations is not possible.  Kim has referred to Metcalf and Eddy (the "Bible" of wastewater treatment), and this is a detailed book for the understanding and design of wastewater treatment works - but as Liang says - "will take a few years to get the point".  The main aspects of MBBR and MBR process configurations is that you can operate at higher MLSS concentrations or longer sludge age in the aeration basin, which then impacts on the aeration tank design (you also need diffused air aeration rather than mechanical aerators), RAS and WAS calculations.

  2. As a rough rule of thumb,  the equalisation or balance tank should be big enough to do its job of balancing pH levels, loads and volumes, so there are no hard and fast rules.  It does depend on whether there are other materials other than domestic sewage from industrial or food sources.  I prefer to have a minimum of 24 hours when there is a food or dairy feeding the waste.  If the volumes vary throughout a day, then the volumes need to be balanced in the first tank.  I also prefer to mix this tank with air to prevent it from becoming septic.   As far as anoxic tanks is concerned, I like to have between 30-60 minutes contact time where returned sludge can be mixed with fresh liquor.  MBR plants do not require settlement tanks because the membranes carry out the separation process.  It also means that the plant can run at higher suspended solids levels and can  use many forms of aeration.  MBBR systems are a cross between fixed film and aerated systems.  In theory, they are supposed to have a smaller volume than an activated sludge plant.  Because my experience has been with industrial plants after the plant has been upset, I am not a fan of them.  I cannot see an real advantage of MBBRs.  As far as aeration is concerned, I avoid oxygen systems, because the carbon dioxide is not removed and causes the pH to run below ideal levels below 7.  With the advent of fine-bubble aeration systems, I prefer them to coarse air systems such as helixers.  If you have a plant, which uses a settlement tank, then I avoid jet mix or pumped venturi systems because it disrupts the bacterial floc and makes separation more difficult.  Good oxygen levels are needed to allow ammonia oxidising bacteria to produce nitrate, on which other bacteria may grow.  For design of plant I refer to Medcalf and Eddy. 

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  5. Start by reading i.e the relevant chapters in Metcalf and Eddy

  6. Hi Arun,

    As all the biological treatment, the questions is how much BOD and NH4 you have to treat. The best primary treatment you have, the less MBBR you need. SS play a big role in the MBBR efficiency. It is important to remove a important part of it. Then, the question is : what is the regulation you must comply with. If you need a denitrification, it costs more. 

    After the MBBR, I recommend you a DAF, because the sludges are light and small.