MBBR Denitrification for Salty Water

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I have an interesting case of MBBR treatment for denitrification process. I have experience with this process, but in this case the water is salty: 15 to 35 ppt.

I don't know how much the salinity will affect efficiency, need for carbon, removal rates, etc.

Do you have experience with salty water denitrification?

Can you give me some info or suggest books and articles on the topic?

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10 Answers

  1. Dear Francesco,

    The MBBR process enables total nitrogen removal in compact spaces through high-density nitrifying and denitrifying bacteria populations. ... MBBR denitrification processes are commonly used in decentralized wastewater treatment systems for their ease of operation and elimination of bulking problems.

    1. Nitrate in drinking water can cause Blue Baby SyndromeIncreased .
    2. levels of nitrate in water supplies can increase the acidity of the water and make toxic metals such as mercury more soluble.
    3. Growth of nuisance algae blooms can cause decreased water quality and cause fish kills.

     

    Advantages of MBBR

    1. Smaller Footprint
    2. Utilize whole tank volume for biomass
    3. Less Sludge Produced (Better Settling)
    4. No Return Activated Sludge
    5. Easy Expansion (more media)
    6. No Media Clogging
    7. Reliability and Ease of Operation
    8. Easy to Retrofit Existing Basins
    9. MBBR can handle Saline water easily.
    10. For more detail please see following art. & links

    https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwicsMeQ3YXTAhXJro8KHUTOA0gQFggiMAE&url=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpubmed%2F16023699&usg=AFQjCNHIqnphtTd4BOrbI_7MYd6TNAV0Eg&sig2=IFt6vMUygKzp2sOUYqICHg

  2. Francesco.  The activated sludge process is resilient to saline but this is dependent both on the concentrations and the variability of that concentration.  The micro-organisms to acclimatise to higher levels but if concentrations are variable, the plant will struggle.  The concentrations that you refer to (15 to 35 parts per thousand?), are extremely high and would have a significant adverse effect on the microbial population aswell as adversely affecting membrane permeability.

  3. While not using an MBBR, we have both nitrified and denitrified in water with salinities that you described. The nitrifiers at 30+ ppt are from different species than the typically described  Nitrosomonas  & Nitrobacter . The denitrification species tend to favor the more halotolerant versions of standard WWT organisms. As long as salinity is consistent, the system should naturally adjust well in your range. Our big problems have happened when we cross the 45 ppt threshold.

  4. I haven't any direct knowledge of nitrification and denitrification of wastewater with high TDS using an MBBR  process, but I have encountered the situation of high TDS with a MBR and a conventional activated sludge process.  In both these cases full nitrification and denitrification was adversely impacted resulting in nitrification to nitrite only, and virtually no denitrification.  The MBR process was part of a water reclamation and reuse system with the recycle ratio greater than 50 percent, resulting in the accumulation of nitrite to over 300 mg/L,  identified by an extremely high disinfection chlorine demand.  This suggested that ammonia-oxidizing bacteria were unaffected by high TDS levels but nitrite-oxidizing bacteria (NOB) and denitrifying bacteria were affected by high TDS concentrations. 

    Eliminating the unintentional source of seawater inflow to the sewer feeding the treatment plant resolved the problem in both cases.  

    Based on this experience, I concluded that nitrification and denitrification were inhibited by high TDS concentrations but I later learned through a literature search that both complete nitrification and denitrification can be accomplished under high TDS concentrations in the order of 3 to 5 percent salt (30,000 - 50,000 ppm) if the TDS is gradually increased to allow the bacteria to acclimatize.   I expect this would be the same for a MBBR process.   

  5. Francesco, it may sound off-topic a bit, I am interested in your case and have a question for you:

    What kind of anoxic MBBR mixer are you using for denitrification? Do you have any issues with it? Let me know. Feel free to contact me at ishin kaya  gmail com

  7. Saltwater has no affect on microorganism, we have MBBR plants treating wastewater with 30,000 ppm TDS however, it wont remove any salt, for that you would need membranes

    Regards www.eecusa.com

    1 Comment

    1. It depends on the species of microorganism, e.g. some bacteria can't tolerate salt (sodium chloride), others have an absolute requirement for it. I suspect that what happens in a  biological wastewater treatment process is that the environmental conditions (e.g. salinity) select for a sub-set of microbes that grow well under those conditions. 

  8. Activated sludge systems along the coast often get saltwater intrusion and in the worst cases chloride levels can be greater than 3,000 mg/L.   I have had the impression that below 3,000 mg/L or so the systems are not terribly effected (the microbiology adapts) but that at levels of 4, or 5,000 mg/L and up there are negative impacts.  The levels you're describing are quite low and I'd expect little impact.

  9. Denitrification is used in salt water applications (aquariums for example) often and it works very well. I would look up salt water aquarium references.