A portable apparatus for adding a dechlorination agent into a fluid stream prior to discharge and a method for treatment of chlorinated water. The portable apparatus can connect in any part of a fluid flow system. A bypass is provided such that a controlled portion of the fluid stream is diverted to a dechlorination agent. The dechlorination agent dissolves in the bypassed fluid flow. The bypassed, dechlorination agent enriched fluid re-enters and mixes with the fluid flow that was not bypassed. As the two streams mix, the total flow receives the required amount of dechlorination before being discharged into the environment. A valve controls proportional flow of the fluid stream through the bypass.