Can you please provide more information in order to be able to give you a hand. What is your Q? What are the concentrations of pollutants?
With the information you provided, I would suggest the simplest process and probably choose the lagoons but you will need other equipment to complete the treatment (it cannot be accomplished only by the lagoon).
UASBR and CSTR can also apply. They require a bit more attention and will also need to be combined w/ another process to complete the treatment.