Life Cycle Assessment of Technological Shifts in Municipal Wastewater Treatment Plants

Integrated food waste management with wastewater treatment in Hong Kong: Transformation, energy balance and economic analysis

δ15N tracks changes in the assimilation of sewage-derived nutrients into a riverine food web before and after major process alterations at two municipal wastewater treatment plants

In Romania, in the coming years, the amount of wastewater collected by sewage systems will be constantly growing. NTPA-011 in Government Decision 188/28.02.2002, updated until 19.10.2011, provides that until December 31st. 2018 all agglomerations areas between 2000 and 10000 population equivalent to be provided with sewerage networks [1].. Many of these human agglomerations are metropolitan areas located near the county capitals. Wastewater collected in these areas are (will be) transported by gravity or by pumping them in municipal wastewater treatment plants already built. Therefore the amount of treated wastewater will increase, causing at the same time, the increase of the processed sludge quantities, and therefore the increase of the specific energy consumption in wastewater and sludge treatment processes. To compensate this increase of energy consumption, wastewater treatment plants operators must find the best solutions for energy recovery from sewage sludge through anaerobic digestion process with the biogas production and thermal treating with heat and electricity recovery [6; 7; 8; 9; 10]. The purpose of this article is to describe the specific features of an anaerobic digestion process for sludge derived from municipal wastewater. The article presents a calculation summary of mass balance on sludge treatment line.

Advanced wastewater treatment processes and novel technologies are adopted to improve nutrient removal from wastewater so as to meet stringent discharge standards. Municipal wastewater treatment plants are one of the major contributors to the increase in the global greenhouse gas (GHG) emissions and therefore it is necessary to carry out intensive studies on quantification, assessment and characterization of GHG emissions in wastewater treatment plants, on the life cycle assessment from GHG emission prospective, and on the GHG mitigation strategies. Greenhouse Gas Emission and Mitigation in Municipal Wastewater Treatment Plants summarises the recent development in studies of greenhouse gases’ (CH4 and N2O) generation and emission in municipal wastewater treatment plants. It introduces the concepts of direct emission and indirect emission, and the mechanisms of GHG generations in wastewater treatment plants’ processing units. The book explicitly describes the techniques used to quantify direct GHG emissions in wastewater treatment plants and the protocol used by the Intergovernmental Panel on Climate Change (IPCC) to estimate GHG emission due to wastewater treatment in the national GHG inventory. Finally, the book explains the life cycle assessment (LCA) methodology on GHG emissions in consideration of the energy and chemical usage in municipal wastewater treatment plants. In addition, the strategies to mitigate GHG emissions are discussed. The book provides an overview for researchers, students, water professionals and policy makers on GHG emission and mitigation in municipal wastewater treatment plants and industrial wastewater treatment processes. It is a valuable resource for undergraduate and postgraduate students in the water, climate, and energy areas; for researchers in the relevant areas; and for professional reference by water professionals, government policy makers, and research institutes. ISBN: 9781780406305 (Print) ISBN: 9781780406312 (eBook) ISBN: 9781780409054 (ePUB)

In this study the environmental impact of the anaerobic digestion (AD) of sewage sludge within an activated sludge wastewater treatment plant (WWTP) was investigated. Three alternative AD systems (mesophilic, thermophilic, and temperature-phased anaerobic digestion (TPAD)) were compared to determine which system may have the best environmental performance. Two life cycle assessments (LCA) were performed considering: (i) the whole WWTP (for a functional unit (FU) of 1 m3 of treated wastewater), and (ii) the sludge line (SL) alone (for FU of 1 m3 of produced methane). The data for the LCA were obtained from previous laboratory experimental work in combination with full-scale WWTP and literature. According to the results, the WWTP with TPAD outperforms those with mesophilic and thermophilic AD in most analyzed impact categories (i.e., Human toxicity, Ionizing radiation, Metal and Fossil depletion, Agricultural land occupation, Terrestrial acidification, Freshwater eutrophication, and Ozone depletion), except for Climate change where the WWTP with mesophilic AD performed better than with TPAD by 7%. In the case of the SL alone, the production of heat and electricity (here accounted for as avoided environmental impacts) led to credits in most of the analyzed impact categories except for Human toxicity where credits did not balance out the impacts caused by the wastewater treatment system. The best AD alternative was thermophilic concerning all environmental impact categories, besides Climate change and Human toxicity. Differences between both LCA results may be attributed to the FU.

Wastewater treatment plants produce high environmental impacts on receiving water bodies and pose economic burdens on municipalities or industrial facilities. Their overall operational costs and achieved effluent quality depend very much on the influent type, presence of priority pollutants, treatment technology and required effluent quality (for discharge or for recycle/reuse). Life cycle assessment (LCA), environmental impact quantification (EIQ) and water footprint (WF) are important instruments for sustainability assessments applied for products, production and consumption evaluations in connection with natural resources depletion and pollution threats. This study focuses on the environmental assessment of a municipal wastewater treatment plant (MWWTP) discharges by means of these three evaluation methods with the purpose to understand their (methodological) weak and strong points in capturing the impacts. Such a comparative analysis is necessary to understand how the (individual) advantages provided by each of these instruments can be complimentarily used to improve an assessment framework for various stakeholders concerned with water use cycle management (regional water operators, water management authority, public authorities, research entities, societal organizations, etc.). The three assessment methodologies (LCA, EIQ, WF) are presented, implemented and critically analysed based on a unitary set of data concerning the MWWTP of Iasi city (a municipality of approx. 300,000 inhabitants situated in the North Eastern region of Romania), the wastewater and river water quality indicators as well as all the other relevant data being collected for the year 2012. Although the three methodologies have different principles for environmental impact quantification, the results have shown that most impacts induced to surface waters due to Iasi MWWTP effluents are given by the nutrients (nitrogen and phosphorous compounds), which could induce an eutrophication impact, and to a lesser extent by pollutants responsible for toxicity impacts (such as heavy metals). Based on the results of this comparative study, a critical analysis of these three methods was realized by considering the data requirements, their development and integration status. Furthermore, the strong and weak points that are relevant for each method implementation and their subsequent use by decision-makers and Water Authorities are discussed, in the context of legislative requirements (including the Water Framework Directive), actual development of regional water operators and stakeholders' interests.

Wastewater treatment plants help to reduce negative impact on the environment by improving the quality of effluent. Different technologies are used in wastewater treatment, and one of the tasks is to find the most environmentally sound option, taking into account the use of resources and energy during construction and operation of the treatment system. The aim of the study is to assess environmental impacts from two different types of small-scale wastewater treatment systems, a constructed wetland and extended aeration activated sludge treatment system using Life Cycle Assessment method. The system boundaries include construction and operation phases. Assessment has been carried out using SimaPro software and Impact 2002? and ReCiPe assessment methods with characterisation and normalisation stages. The results show that the main negative impact of constructed wetland is caused by the construction phase and use of lightweight expanded clay aggregate to construct the hybrid filter. Impacts from extended aeration activated sludge treatment system are mainly caused from the use of electricity and the quality of the effluent, therefore, the use phase has a larger impact on the life cycle. Since a large amount of energy is used to produce lightweight expanded clay aggregate, the impact of 1 population equivalent of con- structed wetland is larger than the impact of extended aeration activated sludge treatment system. Constructed wetland dominates in human toxicity, acidification, land use, ozone layer depletion and the use of non-renewable resources categories. Extended aeration activated sludge treatment system dominates in categories associated with eutrophication and ecotoxicity.

New regulations from the Canadian Council of Ministers of Environment, released in 2009, require all wastewater treatment plants in Canada to produce effluent of secondary treatment levels. To comply with the new law, many Canadian municipalities using primary treatment plants must retrofit or renew their old systems. There is an increasing pressure from stakeholder groups and policy makers to select new infrastructure using triple-bottom-line (economic, environmental and social) analyses. The present study aims to illuminate how differing preferences among experts from different stakeholder groups influence what is considered to be the ‘most sustainable' wastewater treatment system. Through the use of policy documents, academic literature, and the use of AHP (a decision support tool: Analytic Hierarchy Process) an objectives hierarchy was constructed. The objectives hierarchy was made up of four criteria and 13 indicators. Five wastewater experts were asked to use pair-wise comparisons to score the indicators and criteria of the constructed objectives hierarchy and provide their opinions on the same. In addition, four low foot-print wastewater treatment alternatives were selected for review. One of the participants was asked to rank the four alternatives with regards to their performance on the selected indicators. This ranking, in combination with the rankings of the indicators and criteria, previously made by the five experts, were used to indicate the preferred alternatives for each of the separate participants. Then, the overall prioritization of the alternatives was used to carry out a sensitivity analysis. In terms of results, this study of sustainability indicators for wastewater treatment selection showed that the most contentious indicators among those studied were Initial Costs and Long Term Costs, Effluent Quality and Aesthetics. Additionally, the study showed that the Sequencing Batch Reactor was identified as the ‘most sustainable’ alternative by the average scores of all five participants and separately by four of the five participants.

Background: The primary goal of sewage water treatment is to eliminate or bring down the number of pollutants in the sewage water. This study was needed to assess the efficacy of a sewage treatment plant in reducing contaminants levels to comply with government environmental standards. The wastewater re-use for irrigation approaches must be in compliance with the guidelines and indicators must be tracked and impended consistently, it is therefore essential to give top priority to requirements at the stage of evaluating and development to protect land and water supplies as well as public health. Methods: Chemical and biological approaches were used to regulate the removal efficiency of treatment plants. The performance and effectualness of the Vidyaranyapuram sewage treatment plant (STP) in Mysore are evaluated and analyzed in this report. Novelty: Water quality needs to be regularly checked in wastewater treatment facilities. The current study will aid the treatment facility in its efforts to enhance the process of treatment. One would be able to update the effluent efficiency levels depending on the seasonal variations in wastewater treatment as the assessment explains the number of water quality metrics in waste water plants. The obtained analysis results are very helpful in locating, fixing, and maintaining plant operating and maintenance issues, which may be helpful for next plant expansion to be carried out to get good results. Result: The STP's treatment efficiencies were discovered to have a good treatment level in BOD (96%) and a moderate treatment quality in COD (79%) and TSS (75%) removal efficiency during the year 2018. Conclusion: To ensure correct operation and maintenance, trained and experienced workers must analyze treatment performance at predetermined time intervals. The result explains the quality of effluent water and performance of treatment plant. STPs should be used to their full potential to manage the quality of final effluent, and raw sewage sources should be identified.

Net environmental benefit: introducing a new LCA approach on wastewater treatment systems

Comparative analysis of effluent water quality from a municipal treatment plant and two on-site wastewater treatment systems

Assessment of wastewater effluent quality in terms of physicochemical and microbial parameters is a difficult task; therefore, an online method which combines the variables and represents a final value as the quality index could be used as a useful management tool for decision makers. However, conventional measurement methods often have limitations, such as time-consuming processes and high associated costs, which hinder efficient and practical monitoring. Therefore, this study presents an approach that underscores the importance of using both short- and long-term memory networks (LSTM) to enhance monitoring capabilities within wastewater treatment plants (WWTPs). The use of LSTM networks for soft sensor design is presented as a promising solution for accurate variable estimation to quantify effluent quality using the total chemical oxygen demand (TCOD) quality index. For the realization of this work, we first generated a dataset that describes the behavior of the activated sludge system in discrete time. Then, we developed a deep LSTM network structure as a basis for formulating the LSTM-based soft sensor model. The results demonstrate that this structure produces high-precision predictions for the concentrations of soluble and solid substrates in the wastewater treatment system. After hyperparameter optimization, the predictive capacity of the proposed model is optimized, with average values of performance metrics, mean square error (MSE), coefficient of determination (R2), and mean absolute percentage error (MAPE), of 23.38, 0.97, and 1.31 for , and 9.74, 0.93, and 1.89 for , respectively. According to the results, the proposed LSTM-based soft sensor can be a valuable tool for determining effluent quality index in wastewater treatment systems.

This study aims to evaluate the environmental performance of a hypothetical wastewater treatment plant (WWTP) with activated sludge modeling and life cycle assessment (LCA). In order to simulate the treatment performance of an A2O (anaerobic-anoxic-aerobic) process for low-, medium-, and high-strength municipal wastewaters, activated sludge model no.3 (ASM3) was employed. Simulation results were then used for performing LCA of wastewater treatment plant to assess the environmental impacts associated with wastewater treatment system. Additionally, net environmental benefit (NEB) approach that is useful for wastewater systems was also used to determine the eutrophication potential reduction of the hypothetical WWTP. The LCA results show that global warming, photochemical oxidation, and eutrophication potential impact categories were affected by characteristics of wastewater treated. The highest values of these impact categories (7.87E-01kg CO2-eq., 1.73E-04kg C2H4-eq., and 1.28E-02kg PO4-eq./m3.treated wastewater; respectively) were determined for high-strength wastewater. Considering eutrophication potential reduction, the highest NEB value was found 0.042kg PO4-eq/m3.wastewater for high-strength wastewater, followed by medium-strength (0.027kg PO4-eq/m3.wastewater) and low-strength (0.013kg PO4-eq/m3.wastewater) wastewater. The results of the study is crucial to indicate that combining LCA with other decision support tools ensures achieving predictive and reliable results for proving the performance of WWTPs.

Comparison of contaminants of emerging concern removal, discharge, and water quality hazards among centralized and on-site wastewater treatment system effluents receiving common wastewater influent

Integrating microalgae systems (MAS) at municipal wastewater treatment plants (WWTPs) to produce of bioenergy offers many potential synergies. Improved energy balances provide a strong incentive for WWTPs to integrate MAS, but it is crucial that WWTPs maintain their barrier function to protect water resources. We perform a prospective analysis of energy and emission balances of a WWTP with integrated MAS, based on a substance flow analysis of the elements carbon (C), nitrogen (N), and phosphorus (P). These elements are the main ingredients of wastewater, and the key nutrients for algae growth. We propose a process design which relies solely on resources from wastewater with no external input of water, fertilizer or CO(2). The whole process chain, from cultivation to production of bioelectricity, takes place at the WWTP. Our results show that MAS can considerably improve energy balances of WWTPs without any external resource input. With optimistic assumptions, they can turn WWTPs into net energy producers. While intensive C recycling in MAS considerably improves the energy balance, we show that it also impacts on effluent quality. We discuss the importance of nonharvested biomass for effluent quality and highlight harvesting efficiency as key factor for energy and emission balances of MAS at WWTP.