Abstract
The aim of this study is to use the life cycle assessment method to measure the environmental performance of the sludge incineration process in a wastewater treatment plant and to propose an alternative that can reduce the environmental impact. To show the damages caused by the treatment processes, the study aimed to use an endpoint approach in evaluating impacts on human health, ecosystem quality, and resources due to the processes. A case study was taken at Bissell Point Wastewater Treatment Plant in Saint Louis, Missouri, U.S. The plant-specific data along with literature data from technical publications were used to build an inventory, and then analyzed the environmental burdens from sludge handling unit in the year 2011. The impact assessment method chosen was ReCipe 2008. The existing scenario (dewatering-multiple hearth incineration-ash to landfill) was evaluated and three alternative scenarios (fluid bed incineration and anaerobic digestion with and without land application) with energy recovery from heat or biogas were proposed and analyzed to find the one with the least environmental impact. The existing scenario shows that the most significant impacts are related to depletion in resources and damage to human health. These impacts mainly came from the operation phase (electricity and fuel consumption and emissions related to combustion). Alternatives showed better performance than the existing scenario. Using ReCipe endpoint methodology, and among the three alternatives tested, the anaerobic digestion had the best overall environmental performance. It is recommended to convert to fluid bed incineration if the concerns were more about human health or to anaerobic digestion if the concerns were more about depletion in resources. The endpoint approach may simplify the outcomes of this study as follows: if the plant is converted to fluid bed incineration, it could prevent an average of 43.2 DALYs in human life, save 0.059 species in the area from extinction, and make a 62% reduction in the plant’s current expenses needed by future generations to extract resources per year. At the same time it may prevent 36.1 DALYs in humans, save 0.157 species, and make a 101% reduction in current expenses on resources per year, if converting to anaerobic digestion.
Highlights
The growing of the world's population and the improvement in standards of living across the world causes higher demand for efficient treatment of wastewater
The second highest impact is related to climate change affects human health (4.75 × 10−7 disability adjusted life years (DALY) equal to 14.1 mPt per each dry kg), while the third highest impact is on particulate matter formation (3.65 × 10−7 DALY equal to 10.7 mPt per each dry kg) which is mainly related to emissions from incineration plus the emissions from electricity and
If the decision makers have more concerns about human health and ecosystem quality in the region, they are recommended to convert to fluid bed incineration, while they should convert to anaerobic digestion if they are concerned more about a resources issue
Summary
The growing of the world's population and the improvement in standards of living across the world causes higher demand for efficient treatment of wastewater. This demand can be met either by using more efficient treatment processes in wastewater treatment plants (WWTPs) or establishing new plants. The new generations of WWTPs have to integrate the concerns of energy efficiency, carbon footprint and other sustainability issues with the concerns of water quality A wastewater treatment plant is considered efficient if it is capable of harvesting the potential energy available in the organic matters and nutrients found in the wastewater (Lazarova et al, 2012). The sludge treatment unit in the plant is a place where the organic matters and nutrients can be processed for energy and nutrients recovery. Johansson et al (2008) showed that it is important for the environmental outcome of sludge treatment options to minimize the direct gaseous emissions and recover nutrients. Hong et al (2009) showed that the global warming potential generated from incineration and melting processes can be significantly reduced when the heat is used for electricity generation
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