Aerobic vs anaerobic which is better for waste treatment?

I have a list of Pros & Cons that I cover with people. This list contains the most common talking points we need to evaluate before selecting a treatment technology. Of course there are many other factors in making the treatment decision, and in many cases a combined anaerobic/aerobic system can often be the best option.




Aerobic Systems
Pros

• Can treat moderate COD waste < 2,000 mg/L more efficiently
• Better removal of fats, oils & grease
• Ammonia oxidation (ammonia removal)
• Good for many xenobiotic compounds
• Less susceptible to low temperatures

Cons

• More biosolids produced per unit of COD removed
• Higher electricity costs for aeration
• Not as efficient at treating high soluble COD loadings

Anaerobic System (with methane production)
Pros

• Low biosolids production (a full magnitude lower)
• Methane can be used to maintain heat for digester & potentially provide some excess power
• Low energy costs
• Very stable once established
• Less susceptible to heavy metals
  
• Smaller footprint
  

Cons

• Works best with concentrated COD wastes
• COD needs to be mostly fermentable materials (Fats & oils can cause problems in excess)
• Outside design temperature range conditions can stop methane formation
• More expensive to construct
• Does not remove nutrients (ammonia & phosphate)

This list is by no means exhaustive, what parameters can you see adding to the list?

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