Heavy metal removal by coagulation with seawater liquid bittern

Soluble heavy metals present in water could be deleterious to health, and as a result, their discharge into surface waters has been regulated internationally. Many processes for the removal of heavy metals from water and wastewater have been investigated. Coagulation and precipitation are the processes that have been reported to be most effective in the removal of heavy metals. In this study, seawater liquid bittern (LB), as an inexpensive source of magnesium, added to wastewater alkalized with lime or caustic soda is investigated as a possible coagulant. The experiments covered tests on eight metals: arsenic, cadmium, chromium, copper, lead, mercury, nickel, and zinc. The lime-LB process culminated in high removals (>90%) for cadmium, chromium, lead, mercury, and zinc and reasonably good removals (71, 82, and 75%) for arsenic, copper, and nickel, respectively. These results were superior to those obtained using the caustic-soda-LB process. The concurrent presence of different metals in solution has been shown to have a minor effect on removal efficiencies for most metals. However, in the case of nickel, removal was appreciably increased by 18.5%. Also, higher concentrations of a single metal showed higher removal efficiencies.