Economic and environmental assessment of small and decentralized wastewater treatment systems

Abstract

A B S T R A C TThe aim of the present work was the assessment of economic and environmental aspects of decentralized energy-saving wastewater treatment systems. The formulated investment and operation cost functions were adjusted by a power law function. The different wastewater systems serving population settlements between 50 p.e. and 250 p.e., presented associated investment costs varying from €400/p.e. to €200/p.e. and annual operation costs in the range of €70/p.e.-€20/ p.e., respectively. A life cycle analysis approach was used to compare the environmental impact of alternative wastewater treatment systems. The assessment was focused on two energy-saving systems (constructed wetland and slow rate infiltration) and a conventional one (activated sludge process). Low environmental impact of energy-saving wastewater treatment systems was demonstrated, being the most relevant the global warming indicator. Options for reduction of life cycle impacts were assessed including materials used in construction and operation lifetime of the systems. A 10% extension of operation lifetime of constructed wetland and slow rate infiltration systems lead to a 5% and 7% decrease in the abiotic depletion indicator, respectively, and to a 1% decrease in CO 2 emissions in both systems. Replacing steel with HDPE in the activated sludge tank resulted in a 1% reduction in CO 2 emission and 1% in the abiotic depletion indicator. In the case of the Imhoff tank a 1% reduction in CO 2 emissions and 5% in abiotic depletion indicator were observed when concrete was replaced by HDPE. Therefore, considering the huge potential of energy saving wastewater treatment systems, the overall environmental impact of such design alternatives should not be discarded.

A streamlined sustainability assessment tool for improved decision making in the urban water industry

“…Other studies have addressed specific aspects of either wastewater systems (Emmerson et al 1995; Tillman et al 1998; Lundin et al 2000; Beavis and Lundie 2002; Lim and Park 2009; Pasqualin et al 2009), different biosolids management options (Dennison et al 1998; Peters and Lundie 2001; Peters and Rowley 2009), or potable water supply systems (Crettaz et al 1999; Friedrich 2002; Tangsubkul et al 2005; Landu and Brent 2006). Additional studies investigating both environmental and economic impacts of different aspects of the urban water cycle also exist (Nogueira et al 2007; Høibye et al 2008; Lim et al 2008; Sharma et al 2009). All of the aforementioned research has been carried out using the traditional and more detailed methodologies, and published reports detailing the application of “streamlined” sustainability assessment tools in the water industry are rare (Friedrich et al 2007).…”

Life cycle assessment of small-scale constructed wetland and extended aeration activated sludge wastewater treatment system

“…According to the legal standards stated by the Estonian authorities, 1 p.e. equals to 60 g of BOD per 24 h. This functional unit has used in previous LCAs (Dixon et al 2003;Hospido et al 2008;Lundin et al 2000;Machado et al 2006;Nogueira et al 2009) as an alternative to the quantity of inflow water. Since one of the chosen WWTP has a varying yearly water inflow, p.e.…”

“…59 % of WWTPs did not have discharge values as required by the Water Act, and therefore, these WWTPs need to be reconstructed to meet the requirements. Currently, most of the urgent problems are being solved or addressed and the challenge nowadays concerns wastewater treatment of communities located in rural areas (Nogueira et al 2009). In larger municipalities efficient wastewater collection and treatment systems have been built.…”

Design of anaerobic membrane bioreactors for the valorization of dilute organic carbon waste streams

“…74,75 The functional unit for this study was the treatment of 1 m 3 wastewater (300 mg COD·L −1 ) to discharge quality (30 mg COD·L −1 ), with a project lifetime of 30 years. The system boundary included both construction and operation of the plant ( Figure ESI-1 in ESI), but demolition was excluded (consistent with [76][77][78][79] ). First and second order environmental impacts were also examined, where first order impacts were classified as direct emissions (to water, air, and land) from the WTTP and second order impacts stemmed from off-site processes such as electricity production/transmission, material production, transportation, and avoided energy production offset by biogas recovery and utilization.…”