Pro's and con's of sending RO reject water to STP for treatment

Can we send the RO reject and softener re-generation water for treatment in STP? Normally the RO reject and water discharged during softener regeneration gets wasted or we need to send to ETP, but when ETP facilities are not available what is the best course of action?

My idea is to confirm that the hardness and sodium content in the softener re-generation water does not harm the bacterial growth of the STP and the water can be utilized for use in garden or process cooling towers. This will save cost on treatment of such water in ETP as this is not process generated effluent. Kindly give your views based on the given facts.