Nuove problematiche e verifiche di funzionalità degli impianti di potabilizzazione

In the last few years, drinking water treatments have become more and more complex due to the worsening of supply sources and the implementation of more restrictive legislation limits. Furthermore, many Drinking Water Treatment Plants (DWTPs) show problems related to technical and operational aspects, especially for small-medium size plants. Moreover, as concerns DWTPs, there is a lack of integrated standard procedures and methodological tools aimed to evaluate their performance and the criteria for their optimization. In order to ensure high water quality and optimize DWTPs operation, a methodological approach that includes performance assessment should be suggested as a viable protocol. Some authors developed different methods for evaluating the operation of DWTPs (Chang et al., 2007; Vieira et al. 2008; Zhang et al., 2012; Lamrini et al., 2013). Furthermore, a performance-based approach to optimize existing DWTPs was developed by US EPA (EPA, 1998). The aim of this study is to define a procedure for evaluating the performance of full scale Drinking Water Treatment Plants (DWTPs) and for defining the optimal solutions for the plant upgrading in order to optimize its operation. The protocol is composed of four main phases: • phase 1 - Routine Monitoring Plan: a routine monitoring is carried out and the historical data concerning DWTP operation are collected, in order to know the effectiveness of the treatment processes (characteristics of raw water, compliance with normative limits, energy consumptions, etc.); • phase 2 - Intensive Monitoring Plan: an intensive monitoring plan is applied to evaluate each process of the DWTP (geometrical data, operative parameters, etc.); • phase 3 - Experimental studies: alternative scenarios are evaluated through experimental tests at laboratory and/or pilot scale (column filtration test, oxidant demand, etc.); • phase 4 - Upgrading and Optimization: one or more upgrading interventions, defined in the previous phase, are implemented in the full scale DWTP and then monitored in order to optimize their operational conditions. The protocol suggested in this study was tested to a full scale DWTP placed in the North of Italy (Mortara, Pavia); the plant is fed with water drawn from a 200 m depth aquifer, treats a maximum flow of 140 m3 h-1 and the main contaminants in raw water are ammonium (0.79 mg L-1), manganese (79 μg L-1) and arsenic (12 μg L-1). The proposed protocol has shown to be useful for the identification of issues related to the DWTP process and planning of the operational and/or structural upgrading. Moreover the modularity of the protocol makes it flexible and easy to apply to other DWTPs.