Question

Why anaerobic reactors may fail if organic loading rate (OLR) is increased suddenly? and what are the early warnings of the reactor failure and how can such failure be prevented.

Answer 1

it's because the methane producing bacteria (usually the main bacteria in anaerobic reactor) is very sensitive to the change of environment. if organic loading increased suddenly, the methane producing bacteria can't adapt quickly, so the acid that is produced by acid producing bacteria is not consumed by methane producing bacteria as fast as the acid forming rate. it will decreases the pH of the reactor and the risk of failure is higher. how to prevent that condition is by increase the OLR step by step. increase the OLR if the efficiency of the reactor is remain stable, i mean, if you work at OLR 5 kg/m3day then you reach efficiency more and less 50% in 3 days, you can increase the OLR to 5.5 kg/m3day. and repeat the process until the OLR you want.

Answer 2

the warning usually the drop of pH and removal efficiency

Answer 3

The early warning of the reactor if the reactor pH<7, then methane formers will become inactive, and methane production will stop. This will stop COD reduction in the reactor.
Reactor failure in such circumstances may be avoided by adding a buffering agent like soda (Na2CO3) to the reactor to stop decline in pH.
If (OLR) in an anaerobic reactor is increase suddenly the acid formers will become more active and VFA concentration in the reactor will increase, if the buffering capacity in the reactor is insufficient, all alkalinity in the reactor will be exhausted due to the increase acid formation, and reactor pH will go down.

Answer 4

Good answers people.