A) Activated sludge
B) Trickling filter
C) Septic tank
D) Lagooning
E) All of the choices are correct.

A) primary treatment.
B) secondary treatment.
C) advanced treatment.
D) quaternary treatment.
E) All of the choices are correct.

A) presence of heavy metals and similar pollutants AND inhibitory effect it has on plant growth.
B) presence of heavy metals and similar pollutants AND presence of pathogenic organisms and viruses.
C) presence of pathogenic organisms and viruses AND inhibitory effect it has on plant growth.
D) inhibitory effect it has on plant growth AND stimulatory effect it has on methane production.
E) stimulatory effect it has on methane production AND presence of pathogenic organisms and viruses.