Integration of electrocoagulation, adsorption and wetland technology for jewelry industry wastewater treatment

Jewelry industry wastewater contains heavy metals, organic chemicals, suspended solids, and anions which tend to be toxic to humans and aquatic biota. This study has shown that the integration of chemical, physical, and biological treatment is suitable for these characteristics, with its adaptivity to land limitations and easy operation. The electrocoagulation unit had a capacity of 1.5 m3 and a filtration unit of 250 L for chemical and physical processes, while the constructed wetland (14 m3) was for biological one. The equalization unit collected wastewater from the mold-making process (3 m3/day), chrome plating (8 m3/day), gemstone washing (1 m3/day), gold laundry (0.25 m3/day), silver laundry (0.3 m3/day), and refining silver/gold (0.005 m3/day). The wastewater was then neutralized into pH range 6–8, pumped into the electrocoagulation unit, filtered by a silica–carbon filter, and treated in the wetland before being discharged into the environment. This technology was able to reduce TSS (71%), COD (91%), Cu (95%), CN (96%), and oil & grease (71%). The quality of treated wastewater has met the local water quality standards, thus obtaining a wastewater treatment permit (IPLC) from the local government. This technology was cheaper and convenient because the electrocoagulation process time was short (60 min).