Resource efficiency and environmental performance of electroplating processes: water consumption aspects
The article analyses opportunities for enhancing resource and environmental efficiency of modern electroplating processes. These parameters highly depend on metal and water use efficiency. Water is consumed primarily for washing details after the plating. Authors analyse reasons for changing water intensity of electroplating processes and opportunities for reducing water consumption while implementing Best Available Techniques (BAT). Data on solution carry-over published in the research literature, norms and standards are compared. Various periods of the technology development and environmental regulation are considered (1939 to date). Specific water consumption grows since 1970s which is caused both by the increase of concentrations of main components of technological solutions and by the introduction of GOST 9.047-75 standard. The standard sets an elevated solution carry-over value: if in 1959-1968, this value varied between 0.055 and 0.073 L/m2, in 1972 the new value was set at 0.2 L/m2. Authors assume that this decision was caused by the environmental regulation requirements which became more stringent at that time. Increased solution carry-over norms allowed using water to dilute wastewater and thereby to reduce concentrations of contaminants. The average solution carry-over value is 0.065 L/m2, while the most probable values vary between 0.04 and 0.08 L/m2 and may be considered as environmentally and resource sound when setting BAT requirements for designing electroplating processes. For the two-stage washing process, parameter (qK1/2) is calculated. This parameter characterises the specific washing water volume. Annual water consumption in the electroplating processes is assessed. The consumption calculated based on existing norms, varies from 3.4 to 6.2 mln m3 per year; it is 2.5 times higher than the consumption reported in the research articles.