A new approach to the evaluation of biological treatability of industrial wastewater for the implementation of the “waste design” concept

An intrinsic characteristic of the Italian industrial production system is the presence of several industrial districts with a prevalent manufacturing typology, in which several small and medium enterprises dealing with the same or similar products are concentrated in a small territory. An important textile district is localized in Como area, north of Italy. In many cases, industrial districts are served by large treatment plants that receive the majority of the pollution loading from several small and medium enterprises that do not have internal treatment facilities. The treatment fee is determined by regional regulations; commonly, the single wastewater stream connected to the sewer is billed by the sewer manager to the source industry on the basis of the flow rate and of a complex formula that takes into account a series of parameters. This method is unable to properly evaluate the relationship between treatment fee and actual treatment costs, since conventional physical-chemical and biochemical parameters are not necessarily linked to wastewater treatability. New advanced respirometric methodologies could be used as wastewater characterization techniques, since they are particularly suited to represent the effect of a given wastewater on the final wastewater treatment plant. Hence, they could be better correlated to treatment costs. The instrument developed is composed of two parallel moving bed continuous flow completely mixed reactors of the working volume of about 5 l each, equipped with oxygen sensors connected to a computer that acts as a controller and as a data acquisition and processing unit. Some examples of experimental results obtained with synthetic waste and with real sewage are presented.