Total removal of heavy metal from mixed plating rinse wastewater

A mixed plating rinse wastewater containing zinc, hexavalent chromium, trivalent chromium, and cyanide
with total dissolved solids of 424 mgil was treated by a model consisting of a sand filter and ion exchange
columns. A strongly acidic cation resin in hydrogen form and a strongly basic anion resin in hydroxide form were
used in the columns as cationic and anionic exchangers, respectively. The cationic and anionic exchangers were
regenerated by using 2% H,SO, and 5% NaOH, respectively. A 100% removal of zinc, total chromium, hexavalent
chromium and trivalent chromium was achieved in the studies. Very high removal of total dissolved solids,
cyanide and hardness level was achieved at 98.9%, 99.9% and 96.5%, respectively. The conductivity of
wastewater was reduced from an average of 358 psicm to 5 psicm. The case study has shown that treatment
systems using cationic and anionic resin were able to treat a mixed plating bath effluent to comply with the
standard discharge under the Malaysian Environmental Quality (Sewage and Industrial Effluents} Regulation,
1979.