MBR Sewage Treatment Plant MLSS

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We have received a lot of rainfall in the geographical area where the MBR treatment plant is located. The FOG pond and equi tanks are exposed and have received a lot of dilution from the rainwater.

BOD loading is 75kg/BOD, question is can the dilution affect the MLSS and inturn affect the filtation activities? If so how do we rebuild MLSS and maintain good MLSS in these times?

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6 Answers

  1. Rains will increase the hydraulic load on MBR. This in turn may reduce performance of the Plant.

    Rajendrakumar V Saraf, FIE, FIWWA

    Chairman

     Viraj Envirozing India Pvt. Ltd

    21, Radhakrishna, Near SBI, Paud Road

    Pune 41038

    Tel 02015433445, 9822186763

    www.virajenvirozing.com

     

  2. The dilution effect can cause a reduction in mlss as the overall load arriving at the site may be reduced causing a reduction in solids growth.  If the mlss is not measured and the surplussing times reduced to match the reduced growth, lower mlss will result.  This should not affect the filtration but could result in poor biological treatment when the biological load increases after cessation of the storm.

    1 Comment

    1. On the flip side of exactly what you may experience based on Matthew's comment, you may experience a relatively stable organic load, since the organic load is a function of the inflow quantity and the concentration of COD, so if COD is reduced due to dilution, your increase in flow may well negate the reduction in COD concentration and you end up with a similar organic load (kg/day) number - you should characterise your incoming COD as each site will be reasonably unique, with composite, flow weight sampling. In this way you can also get to understand your biodegradable fraction, etc.

  3. The MBR process is a suspended growth activated sludge system that utilises microporous membranes for solid/liquid separation in lieu of secondary clarifiersMembrane bioreactor (MBR) is the combination of a membrane filtration process with a suspended growth bioreactor. It is a very advanced technology and is now widely used for municipal and industrial wastewater treatment plant. The nominal pore size of the membranes is small (up to 0.15μm), by which not only activated sludge but also coliform bacteria and virus can be shut out. The mixed liquor from the biological treatment can be separated clearly into solid and liquid. It assures almost 100% removal of SS and no carryover of SS into the effluent. This process, therefore, assures stable treated water quality, which enables the treated water to be reused as reclamation water. Most important aspect of MBR technology is production of very high quality Treated Water consistently:

    Process intensification through high Biomass concentration with MLSS (Mixed Liquor Suspended Solids) over 8000 – 10000  ppm

     

  4. To supplement what Christoph Brepols has said, if you have had high rainfall, it may have carried forward fats, oils and grease.  Unfortunately membranes don't like fats and grease and it can increase membrane fouling, which will require cleaning.

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  5. Depends on that whether they are flat sheet or hollowfiber.flat sheet membranes need higher opertional mlss,the hollow fiber are doing lets say better with lower mlss concetrations.

  6. Membrane bioreactors are generally capable of tolerating wider variations of MLSS concentrations inside the bioreactor than conventional activated sludge plants. However there are some boundaries that need to be respected. Do you know these boundary conditions for your plant?

    Generally a too high MLSS increases sludging of your membrane filters and lowers the aeration efficiency in the bioreactor. A too low MLSS may also increase membrane fouling depending on the type of membrane. A loss of biological activity might be another result of a drastic lowering of MLSS concentrations which then would also lead to increased fouling (among other nasty things).

    Maybe you should try to keep your MLSS concentration in check by controlling the rate of excess sludge extraction while you gradually and slowly increase the feed from your rainwater tanks.

    1 Comment

    1. Sounds good....in this case one of the trains is showing 0 MLSS, how do I build biology/MLSS without draining the tank and putting fresh feed?