Greenhouse Gas Emissions from Wastewater Treatment System

Sanitation service chains (SSCs) often consist of a complex mix of different components, frequently involving the coexistence of non-sewered sanitation (e.g., septic tanks) and sewered sanitation. Poorly-maintained components within these chains can lead to substantial, yet potentially avoidable greenhouse gas (GHG) emissions. In this study, we developed a model for estimating the impact of GHG mitigation measures along SSCs that feature overlapping and poorly maintained non-sewered and sewered sanitation, taking the interdependencies of the GHG emissions of these components into account. To this end, we employed mass balance, empirical emission equations, and a carbon footprint estimation model to estimate GHG emissions by component at baseline and under four mitigation scenarios using an example SSC in Hanoi. The results showed that the SSC is predominantly methane-emitting, with poorly-maintained septic tanks and sewers being the primary contributors to the GHG emissions. Annual septic tank emptying was also identified as an effective strategy for reducing GHG emissions and it accounted for a 31-38 % decline in total emissions relative to baseline emission level. Scenario comparison further showed that removing septic tanks and upgrading sewers, even though associated with a slight increase in N2O emissions from the wastewater treatment plant, offer the greatest long-term mitigation potential, yielding 15-24 % lower emissions than annual emptying septic tanks with sewer upgrades. Additionally, if septic tanks are not removed, they will remain the primary source of GHG emissions even after upgraded sewer and centralized treatment is established. However, in cases where septic tank removal poses social challenges, frequent emptying remained a robust and immediately applicable mitigation option. Overall, this study provides a framework for identifying and quantifying major GHG emission reduction strategies for complex SSCs. Additionally, the results obtained indicated that managing septic tanks and sewers are important climate action strategies for ensuring sustainable city-wide inclusive sanitation.

Major US electric utility climate pledges have the potential to collectively reduce power sector emissions by one-third

Nutrient removal and greenhouse gas emissions in duckweed treatment ponds

Global economic development has highlighted the issue of climate change, which is one of the most important environmental issues plaguing human beings. It is widely agreed that excessive greenhouse gas (GHG) emissions are important factors contributing to global warming. Many countries have formulated corresponding GHG emission reduction plans to deal with climate change issues. An important GHG emission source is released from sewage-sludge treatment systems. However, there has not been a comprehensive quantitative GHG emissions evaluation system in the case of sewage-sludge treatment systems, due to multiple emission sources, complex processes, and different standards. In previous studies, the Guidelines for National Greenhouse Gas Inventories (Intergovernmental Panel on Climate Change, IPCC, 2006) and Chinese Greenhouse Gas Inventory (National Center for Climate Change Strategy and International Cooperation, NCSC, 2005) were widely applied to estimate GHG emissions from sewage-sludge treatment. However, IPCC does not consider CO2 emissions from sewage treatment, and NCSC does not consider CO2 emissions from the sewage treatment and N2O emissions from sludge treatment. Therefore, the following have been conducted in this study: (1) A GHG estimation model basing on Life Cycle Thinking (LCT) was constructed, and the research objects were CH4, N2O, and CO2 that were produced by the sewage-sludge treatment system. The estimation model of CO2 and N2O, which were ignored in the IPCC report, were analyzed and discussed. The models of the GHG emission estimation were summarized and improved in the urban sewage-sludge treatment system under the different sewage-sludge treatment process scenarios. (2) The GHG emission load of major urban sewage-sludge treatment processes was analyzed, and the level and key links of environmental impacts generated by different processes were identified. This helps to understand and compare the environmental impacts of different treatment processes and provides suggestions for the sustainable development of wastewater treatment processes. (3) The GHG emission characteristics of nine scenarios of different sewage-sludge treatment processes were analyzed, and the environmental impacts caused by energy consumption and chemicals consumption were studied. Consequently, the sewage-sludge treatment process under low carbonization and low environment impact were proposed.

Carbon dioxide and methane emissions from Tanswei River in Northern Taiwan

Carbon footprint analysis of chemical enhanced primary treatment and sludge incineration for sewage treatment in Hong Kong

This research focused on the nutrient removal and the simultaneous CO2, CH4, and N2O emission rates of various combinations of vertical subsurface flow constructed wetlands (VSFCWs) and earthworm eco-filters (EEs) under different influent C/N ratios in synthetic wastewater. The optimal parameters for nutrient removal were influent C/N ratios of 5 : 1 and 10 : 1 as well as the combination VSFCW-EE. Relatively low values of greenhouse gas (GHG) emission rates measured in situ were obtained at a C/N ratio of 5 : 1. The emission rates of CH4 and N2O were considerably lower than that of CO2. The VSFCW-EE and EE-VSFCW combinations showed similar GHG emission results. The C/N ratio of 5 : 1 and the VSFCW-EE combination exhibited the highest nutrient removal efficiency with the lowest GHG emission rate. Wastewater nutrient removal and GHG emission were both high during summer (June to August) and low during winter (December to February).

Mitigating Curtailment and Carbon Emissions through Load Migration between Data Centers

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)

This paper evaluates the relationship between ultraviolet‐B (UV‐B, 280–315 nm) radiation enhancement on the earth's surface caused by ozone attenuation and climate change. A pot experiment was conducted to investigate the effects of enhanced UV‐B radiation on greenhouse gas (GHG) emissions from the paddy soil with rice straw incorporation (SI). The paddy soil was sampled from the Yuanyang Terrace, Yunnan Province, Southwest China. There were four treatments: natural light (control check, CK), 5.0 kJ·m−2 UV‐B radiation (UVB), SI, and SI + UVB. The effects of UV‐B radiation (5.0 kJ·m−2) on straw degradation, soil carbon invertase activity, active organic carbon content, and GHG emissions were studied. The results showed that UV‐B radiation promoted the degradation of straw components (lignin, cellulose, hemicellulose, and water‐soluble phenol). The SI treatment significantly increased the activity of soil carbon invertase (P < 0.05), the content of soil active organic carbon (P < 0.05), and the emission rates and amounts of GHGs (P < 0.05). Compared to the SI treatment, SI + UVB treatment reduced soil carbon invertase activity and active organic carbon content, resulting in a 17% reduction in CH4 emission and a 40% and 16% increase in CO2 and N2O emission (P < 0.05), but had no significant effect on the global warming potential (GWP). Correlation analysis showed that the degradation rate of straw components was positively correlated with the activity of carbon invertase, the contents of microbial biomass carbon (MBC), easily oxidized organic carbon (EOC), and the CO2 emission rate; the activities of sucrase and cellulase were positively correlated with the contents of MBC and EOC, which were in turn positively correlated with the emission rates of CH4 and CO2. Under SI, UV‐B radiation reduced the soil carbon conversion, which led to a decreased CH4 emission and increased emissions of CO2 and N2O, but did not alter the GWP of GHGs from the paddy soil. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Methane and methanogen community dynamics across a boreal peatland nutrient gradient

Flooding boreal forest ecosystems for hydroelectric power generation may release substantial amounts of carbon (C) to the atmosphere, contributing to global warming. The objectives of this study were to evaluate CO2 and CH4 production rates using spring/fall (14 °C) and summer (21 °C) temperatures under non-flooded and flooded conditions. incubation temperatures represented the mean annual air temperature in May and September (14 °C), and in July (21 °C). Greenhouse gas production rates were quantified using laboratory incubations of 2 contrasting soil types (Humo-Ferric Podzol [very dry, mineral] and a Histic Folisol [moist, organic]) collected at the experimental lakes area in northwestern Ontario, Canada. The mean production rate of CO2 and CH4 in the headspace of the incubation jars was significantly influenced by temperature, flooding and soil type. results showed that the mean CO2 (65 [Podzol]; 43 [Folisol]) and CH4 (0.06 [Podzol]; 0.06 [Folisol]) production rates (μg·g−1·−1) were significantly higher (P < 0.05) at 21 °C and in flooded treatments from both soil types. The greatest CO2 and CH4 production rates (μg·g−1·d−1) occurred from the Folisol (110 [CO2]; 0.03 [CH4]) and the L and FH horizons of the Podzol (250 [CO2]; 0.05 [CH4]). Q10 values showed that decomposition of soil organic matter was more temperature dependent in non-flooded treatments, with values ranging from 1.57 to 5.03, than in flooded treatments (1.31 to 3.58). The greatest loss of soil organic carbon relative to the original C content (g-m−2) occurred in the Ah horizon of the Podzol in non-flooded (0.01% [14 °C]; 0.02% [21°C]) and flooded (0.02% [14 °C]; 0.03% [21 °C]) treatments and at both temperatures. Information presented in this paper helps to evaluate how 2 contrasting soil types (Podzol and Folisol) responded to flooding and provided further insight into the dynamics of greenhouse gas (GHG) production rates as a result of hydroelectric reservoir creation. This will aid in future planning, construction, and management of hydroelectric reservoirs to help minimize GHG emissions and boreal forest disturbance.

Palm oil mill effluent (POME) treatment in Indonesia is still predominant using an open pond system. This system has the weakness of the unknown and uncontrollable value of greenhouse gas (GHG) emissions into the atmosphere. This study estimated GHG emissions (CH4 and CO2) from anaerobic ponds and their potential as a renewable energy source and obtain GHG emission conversion coefficients for each kg of COD POME and ton of crude palm oil (CPO). Gas samples were collected using a closed static chamber. GHG sample concentration testing was done using Gas Chromatography with a flame ionization detector (FID) and thermal conductivity detector (TCD). The results showed that the emission rate of CH4 and CO2 in the anaerobic pond POME treatment was relatively high, 261.93 and 595.99 g/m2/day, respectively, equivalent to 48.572 t CO2-eq/day or 14,571.5 t CO2-eq/year. CO2 emissions were greater than two times CH4 emissions, both spatially and temporally. There was a process of facultative biodegradation, aerobic and or anaerobic process according to the biotic-abiotic environment and the levels of organic components in the substrate. In anaerobic ponds, the optimal requirements for the biodegradation process tended to be unfulfilled, so the emission rate of CH4 was less than CO2. The GHG conversion coefficient was obtained, namely each kg of COD from POME emitted 6.266 kg CO2-eq of GHG; for each m3 of POME emitted by 0.163 t CO2-eq of GHG; and 0.556 t CO2-eq/t CPO. The maximum potential for POME to energy conversion was 1.045 MWe with a power capacity of 8,603 MWh/year.

BackgroundSoil-derived prokaryotic gut communities of the Japanese beetle Popillia japonica Newman (JB) larval gut include heterotrophic, ammonia-oxidizing, and methanogenic microbes potentially capable of promoting greenhouse gas (GHG) emissions. However, no research has directly explored GHG emissions or the eukaryotic microbiota associated with the larval gut of this invasive species. In particular, fungi are frequently associated with the insect gut where they produce digestive enzymes and aid in nutrient acquisition. Using a series of laboratory and field experiments, this study aimed to (1) assess the impact of JB larvae on soil GHG emissions; (2) characterize gut mycobiota associated with these larvae; and (3) examine how soil biological and physicochemical characteristics influence variation in both GHG emissions and the composition of larval gut mycobiota.MethodsManipulative laboratory experiments consisted of microcosms containing increasing densities of JB larvae alone or in clean (uninfested) soil. Field experiments included 10 locations across Indiana and Wisconsin where gas samples from soils, as well as JB and their associated soil were collected to analyze soil GHG emissions, and mycobiota (ITS survey), respectively.ResultsIn laboratory trials, emission rates of CO2, CH4, and N2O from infested soil were ≥ 6.3× higher per larva than emissions from JB larvae alone whereas CO2 emission rates from soils previously infested by JB larvae were 1.3× higher than emissions from JB larvae alone. In the field, JB larval density was a significant predictor of CO2 emissions from infested soils, and both CO2 and CH4 emissions were higher in previously infested soils. We found that geographic location had the greatest influence on variation in larval gut mycobiota, although the effects of compartment (i.e., soil, midgut and hindgut) were also significant. There was substantial overlap in the composition and prevalence of the core fungal mycobiota across compartments with prominent fungal taxa being associated with cellulose degradation and prokaryotic methane production/consumption. Soil physicochemical characteristics such as organic matter, cation exchange capacity, sand, and water holding capacity, were also correlated with both soil GHG emission, and fungal a-diversity within the JB larval gut. Conclusions: Results indicate JB larvae promote GHG emissions from the soil directly through metabolic activities, and indirectly by creating soil conditions that favor GHG-associated microbial activity. Fungal communities associated with the JB larval gut are primarily influenced by adaptation to local soils, with many prominent members of that consortium potentially contributing to C and N transformations capable of influencing GHG emissions from infested soil.

Farm dams are integral part of Australian agriculture and they contain a substantial fraction of inland fresh water on the Australian continent. Storage of water can alter the physical, chemical and biological processes occurring within the dam and subsequently, any downstream receiving water body. However, limited research has been directed into understanding the factors controlling biogeochemical processes in the dam and the effect of the dam on downstream water quality. In this thesis, a dam (11.8 ML) with a catchment area of 1.3 km2 on a dairy farm at Poowong East (ca. 130 km south-east of Melbourne, VIC) was studied to investigate: (1) the seasonal variations in nutrient concentrations and greenhouse gas (N2O and CH4) emissions, (2) the role of aquatic sediments in the emission of the greenhouse gases, and (3) the biogeochemical cycling of nitrogen and phosphorus in the dam. Fluxes of N2O, CH4 and bioavailable inorganic nutrients (NH4+, NOx and FRP) between the sediment and the water column at 3 different sites within the dam were determined over a period of 18 months (from July 2010 to December 2011). Factors controlling the gas and nutrient fluxes (i.e. temperature, dissolved oxygen, nutrient availability and faunal abundance) were analysed. The physicochemical characteristics of the creek upstream and downstream of the dam were also measured throughout the sampling period. This study also involved sediment core incubations, deployment of equilibrium dialysis samplers (pore water peepers) and planar optode experiments. The dam was found to be a major source of N2O during periods when both NOx and O2 concentrations were high in the water column. Sedimentary CH4 flux increased gradually during summer when the overlying water was very close to, or completely, anoxic. The production rate of CH4 was almost 3 times greater in the deeper site (3.5 metres) than in the shallow site (1 metre) and the highest fluxes were associated with the bottom water temperature maxima. The dam was a net source of NH4+ but a net sink for NOx and FRP. The internal load of NH4+ was almost 3 times higher than the external load on an annual basis. Conversely, the dam removed about 14% and 5% of the annual external NOx and FRP loads, respectively. There was a significant seasonal variation in inorganic nutrient fluxes in the dam. The diffusive flux of nutrients across the sediment-water interface, particularly during summer months, emphasized the role of the bottom sediment as an alternative source of bioavailable nutrients into the water column. This study found that benthic macrofauna (here both Chironomidae and Oligochaeta) did not impose any significant effect on in situ N2O production but the results suggested a perhaps important involvement in the cycling of biogenic CH4. Chironomidae larvae significantly increased sediment oxygen consumption rates and decreased the NH4+ efflux. Chironomidae larvae also appreciably increased the water column NOx-derived denitrification (Dw) as well as the coupled nitrification-denitrification (Dn) rates in the sediment. Overall, this study produced three key findings: (1) Farm dams can be a major source of N2O and CH4 depending on the season and nutrient availability. (2) Seasonal variation of nutrient processing within the dam resulted in significant effects on the downstream water quality. In most sampling months, the outflowing water failed to meet the state and regional water quality standards particularly in terms of turbidity, dissolved oxygen and different forms of nutrients. (3) Long term monitoring of the seasonal variation of the nutrient processing in farm dams is essential to predict the influence of such dams on the downstream water bodies and to assess the effectiveness of any management actions.