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.