Treatment of highly contaminated waste waters in a continuous cascade line reactor

Abstract

This paper presents research work done on complex copper bearing effluents from the Serbian RTB-Bor plant. The INTREAT project, funded by the European community, addresses environmental pollution problems associated with solid and liquid wastes produced by complex sulphide ore mining and metallurgical activities. In order to offer a cost-effective and environmental friendly technology, a continuous precipitation system for selective neutralization and chemical precipitation was designed as cascade line reactor. However, since the minimum solubility for the dissolved metals occurs at different pH-values and the hydroxide precipitates are amphoteric in nature, the highest removal efficiency cannot be achieved at a single precipitation pH level, respectively in one reactor. Thermochemical analysis predicted three effective pH ranges: 4 to 4.5 (mainly iron hydroxides), 7 to 7.5 (mainly copper hydroxide/sulfate-mix), and gt 10 (mainly nickel hydroxide). For this reason, the waste water was treated in multiple stages. During the testwork the influence of temperature and such pH-values on the metal removal degree was investigated in a continuous operation mode. The consumption of NaOH was monitored in dependence of its feed concentration. Obtained results show that the metal removal efficiency is very satisfactory and the recovered purified solution meets international discharge water standards.