What is anaerobic digestion PH range?

What is anaerobic digestion PH range? Correct Answer 6.0 – 8.0

Low pH inhibits the growth of the methanogenic bacteria and gas generation and is often the result of overloading. A successful pH range for anaerobic digestion is 6.0 – 8.0; efficient digestion occurs at a pH near neutrality.

Related Questions

Statement (I): Anaerobic sludge digester, by itself, is considered to be the better method than other methods of sludge treatment: Statement (II): During anaerobic sludge digestion, CH4 is produced; also rodents and other pests are attracted when digester sludge is dried. 
Which of the following is correct regarding anaerobic digestion in the sludge digestion process?
In what PH range does anaerobic digestion occurs at best?
What is the range of retention time during anaerobic digestion?
For what range of COD level anaerobic digestion is carried out?