Control of industrial discharges into the sewerage system

The high level of industrialisation in Italy has led to the application, since 1976, of stringent regulations on the quality of industrial discharge- s not only in surface waters, but also in the public sewerage system. A total of 51 quality parameters are imposed by national legislation and in many cases the companies responsible for urban water treatment plants themselves impose limits to technological discharges into the public sewerage system in order to make them acceptable to the characterist- ics of the terminal treatment plant and incoming waters. The metropolitan area of Turin represents a basin with a high level of industries which discharge into the public sewerage system where over 70 million m3 of waste is collected and treated by the terminal treatment plant every year from industrial sources, accounting for over one-third of the total waste water treated. Since 1984 a series of prevention and control systems have been introduced for the treatment plant, leading to an improvement in the yield of treatment sections and guaranteeing the quality of the final discharge into the river Po. The first activity carried out to oblige companies to pretreat techno ogical discharges was the creation of a control programme based on risk parameters for the various types of industry and the subsequent organisation of a control task force which collected samples from those companies with the highest risk. In addition, the fiscal samples taken from production plants have fallen from a total of over 54% exceeding the limits imposed on discharges into the public sewerage system in the first year to 10% in 1997. Recently screening of industrial waste water was also included in the control activity, aimed to prevent nitrification inhibition in active sludge oxidation basins, using the MINNTOX test. Another protection device for the terminal treatment plant is an alarm system based on toxicity and total organic carbon monitoring on the in-flowing stream of sewage, which is described together with its management.