Development of PCR for WWTP based on a case study

In order to apply the Environmental Product Declaration (EPD) to products or services, specific rules [Product Category Rules (PCR)] have to be issued to ensure comparability among different declarations within the same service group. The aim of the present study is to describe the reasons leading to each choice in the development of PCR applied to Collecting and Treatment Service of Municipal Wastewater and to evaluate, through life cycle analysis (LCA), their influence on the potential environmental impact of a wastewater treatment plant (WWTP), analysed as a case study. Specific data were collected during the year 2003 from an Italian active sludge treatment plant with separate wastewater and sludge treatment lines.

The PCR 2005:5 (Collecting and treatment service of municipal wastewater (MWW). Product group/service type: refuse disposal, sanitation and similar activities, NACE code:90) document was prepared by the Department of Chemical and Process Engineering “G.B. Bonino” (University of Genoa, Italy). This PCR was tested on the Collection and Treatment Service of Municipal Wastewater in a wastewater treatment plant located in Savona, Italy (Consorzio per la Depurazione delle Acque di Scarico). The PCR 2005:5 document was issued in an open and participatory process between companies and organizations having good knowledge of the specific environmental aspects of the service to be included in the EPD® system. PCR, LCA, and EPD studies were developed according to the document “Requirements for an International EPD Scheme” (EU funded LIFE Env 2003 program, INTEND Project, www.​intendproject.​net).

The following LCA-based information was considered in preparing the PCR: definition of service type, definition of functional unit, choice and description of system boundaries, choice of cutoff criteria, choice of allocation rules, description of quality requirements for data, choice of selected LCI results or other selected parameters for description of environmental performance to be included in the declaration, description of parameters contributing to each preset category, description of specific information to be included in the use stage of the declaration, other environmental information. Ecotoxicity characterization factors, evaluated by the model Uniform System for the Evaluation of Substances (USES-LCA), was added to the PCR as an Annex. The potential environmental impacts of the considered case study were evaluated separately for the following phases: sewer net and plant construction, sewer net and plant management, sludge management. Alternative sludge management techniques were investigated.

PCR of Collecting and Treatment Service of Municipal Wastewater (MWW) was prepared in an open and participatory process between companies and organizations having in-depth knowledge of the specific environmental aspects of the service, in order to safeguard the provision and input of appropriate product-specific knowledge from relevant companies and branch organizations. The main problems characterizing the open consultation regarded are functional unit, system boundaries, boundary in time, parameters to be declared, and other information.

The annual amount of treated wastewater was considered as a functional unit. In order to evaluate water quality aspects, the request for additional information [biochemical oxygen demand (BOD)/chemical oxygen demand (COD) and nutrient removal] was added to the PCR document. These characteristics aim to complete the lack of information about wastewater quality due to the use of a fixed amount of wastewater as a functional unit. The following parameters were identified: resources use (use of nonrenewable resources, use of renewable resources, water consumption, electricity consumption), pollutant emissions as potential environmental impact (global warming, acidification, ozone depletion, photochemical oxidant formation, eutrophication), and new standard parameters (fresh aquatic ecotoxicity, fresh sediment ecotoxicity, marine aquatic ecotoxicity, marine sediment ecotoxicity). The reference model used for the calculation of toxicity potentials was the global nested multimedia fate, exposure and effects model USES-LCA. The comparison of the LCA results obtained for the considered life cycle phases shows that sewer net and plant construction have less than 10% of the total impacts for all the considered categories. Plant management has a higher impact with respect to sewer net and sludge management. In general, sludge treatment for agricultural land application has a lower impact than its treatment in landfill, but the specific results depend on the impact categories.

One of the most important properties of EPDs is that they provide possibilities to add up and accumulate information along the supply chain as well as to make comparisons between declarations with regard to the environmental performance of products and services. Therefore, the PCR 2005:5 document has been prepared to ensure comparability between declarations within collecting and treatment service of municipal wastewater. However, a new revised version of these rules has to be prepared according to the newly published ISO standard for EPD (ISO 14025) and to the incoming revision document of the international EPD® system.