Development and field testing of heavy metal monitor prototype for pollution detection in untreated waste water
Wastewaters in municipal sewerage systems are frequently polluted by heavy metals from industrial discharge violations. To discover these pollution peaks lasting only 0.5-2 hours mostly in night times and weekends, a new analytical monitor principle is required. Due to the high organic (FOG: fat, oil, grease) and inorganic suspended matter contents of these water streams the well known and sensitive analytical sensors and methods are not fit for the 24 hours/day and 7 days/week operation. Based on a new analytical measuring principle (the electrolyte-cathode-atmospheric-glow-discharge-emission-spectroscopy) the development of a metal monitor was possible for direct analysis of the untreated wastewater for heavy metal pollution level. Its characteristics are : no sensor surface or optical window in contact with the sample, measures all free ionic, complexed and hydrolysed metal forms without strong mineralization process, measuring ranges are approximately 0.1/0.2/0.3 - 10 - 100 mg/L, multi-metal measurement without special reagents, no fine filtering required (below 0.2-0.3 mm), accepts fat emulsion loaded sample, low power consumption, 1-5 measurements/hour. The long term monitor operation required one more innovation in the self-cleaning raw sample filtering unit which allows the assay of the total metal content (dissolved + colloidal + fine suspended components). Field testing of the constructed metal monitor was conducted with the inflow stream at a wastewater treatment plant and the 4 days monitor operation successfully proved the pollution peak observation power of the instrument in the 0-5 mg/dm3 total concentration range.