Dear,

This will depend on the nature of your effluent (dyeing, printing, finishing, etc.). I think the simplest method is physico-chemical (settling-coagulation-flocculation, etc.).

for a bleaching bath you use enzyme to decompose the hydrogene peroxide.

for desizing solution you can use them to produce biogase.

the main question ist, what are the rules and limits in a contry. for some effulents the public waste water treatment plane is enough.