The best approach is ...
Published by Jeremy Biddle, Engineering Director at Bluewater Bio
The best approach is generally chemical coagulation and then filtration. If there are significant settleable solids in the effluent, you should include a gravity settlement stage first to reduce the load on the filters. For further information see http://www.sciencedirect.com/science/article/pii/S2212371713000085
Depending upon the coagulation characteristics of the effluent, and on the chromium limit for the receiving sewer, you should design the filtration process to ensure that limits are met reliably. Coarse sand filters are cheapest but will require better coagulation to create large flocs. If you need a fine filter, I can assist you with a design for our patented FilterClear system, which has been used successfully to remove metals from industrial effluents.