Discharge quality from municipal wastewater treatment plants and the Sludge Biotic Index for activated sludge: integrative assessment

Abstract Wastewater treatment plants (WWTPs) are scrutinized by Environmental Authorities particularly regarding the compliance to discharge limit values fixed by national and local regulations. An integrated approach is necessary to achieve the objectives established with Directive 2000/60/EC (WFD) considering the ecological status of the receiving water body and the quality of the discharge. Specifically, documentary, technical, management and analytical controls should be developed. Moreover, integrative information on the behaviour of the activated sludge in the aeration tank can be useful for plant managers as well as for the regulating Authorities. The study presents the experience concerning WWTP regulation considering the analytic assessment of the discharge as well the monitoring of the Sludge Biotic Index (SBI) for activated sludge. Data from monitoring during the period 2008–14 on SBI values and chemical and microbiological data on the discharges of a sample of 35 WWTPs in the province of Venice (north-east Italy, Veneto region) are presented and discussed. Together with chemical and microbiological analysis, the SBI appears to be a highly useful index for the integrative assessment of plant functionality, in particular when monitoring and identifying critical situations that can determine the exceedance of discharge limit values. The SBI method, in an integrated control approach, can be used for small and medium sized WWTPs that only treat domestic wastewaters. In a case by case assessment this may even substitute part of the analytical monitoring carried out in the WWTPs' control process

Contamination of groundwater: obligations of non-responsible parties

In the context of the National Interest Site (NIS) of Venice (North East, Italy), one of the largest petrochemical settlements in Europe, the presence of various significant historical contaminations of soils and groundwater as well as the proximity of different productive sites, have given rise to several complex situations when defining the responsibility for the contamination of groundwater. The identification of the site owner/operator’s duties is of primary importance in defining civil and penal liabilities. In order to favor the recovery of dismissed former production sites, and avoid the propagation of contaminated groundwater in adjacent sites, to highlight any contamination caused by background values (natural contamination) and to apply the European regulation on environmental crimes [EU-Directive 2008/99/EC of 19/11/2008 on the protection of the environment through criminal law. EU O.J. no. L328 6/12/2008], it is fundamental to present a clear operational framework of the prevention measures to be implemented. This also extends to any environmental safety measures that need to be applied and the specific liabilities incurred in view of the decision of the European Court of Justice of 4/03/2015 [ECJ (European Court of Justice). 2015. Decision no. 534 del 4/03/2015. Case C-534/13] which states the need to apply the EU Polluter Pays Principle (PPP). Moreover a historical outlook of the activities carried out on the site and the identification of specific tracers of the contamination source appear to be key elements. The case study of an area heavily contaminated with organo-chlorinated compounds in the NIS of Venice has been chosen, given the different interests of the owners and their concurrent duties, as well as the economic, administrative and technical impediments to recovering the areas for productive use. Organo-chlorinated solvents had been extensively used and can currently supply a fingerprint of the source of contamination. The analytic method applied for this study refers to Italian National guidelines [CNR–IRSA, APAT (Italian National Environmental Protection Agency). 2003. Analytical methods for water, no. 29/2003, Rome. (accessed January 30, 2019)], based on the Gas chromatography technique. The main contaminants detected are the following: Trichlorethylene and Tetrachloroethylene, Vinyl Chloride, 1,1- Dichlorethylene and 1,1,2,2-Tetrachloroethane. Remediation appears bound to complex technical and legal issues which have been analysed in the Italian and EU context of environmental forensics practices