The doubling time is slow, between 10 days to 2 weeks. This makes it difficult to grow enough sludge for a wastewater treatment reactor. Also the recovery time after the loss of sludge by accident is longer than in conventional nitrogen removal systems. On the other hand, this slow growing rate is an advantage due to the reduction of surplus sludge that needs to be removed and treated. Depending on the exact species, the optimum pH level is 8. Therefore, it can be necessary to adjust the pH of the wastewater by adding caustic.