Air Emissions Damages from Municipal Drinking Water Treatment Under Current and Proposed Regulatory Standards

Unveiling the greenhouse gas emissions of drinking water treatment plant throughout the construction and operation stages based on life cycle assessment

The carbon peaking and carbon neutrality targets proposed by the Chinese government have initiated a green transformation that is full of challenges and opportunities and endowed sustainable development strategy for combating global warming issue. It is essential to execute comprehensive identification and carbon reduction measures across all industries that produce greenhouse gas (GHG) emissions. Water supply system, as an energy-intensive sector, plays a crucial role in GHG reduction. This work conducted a life cycle assessment (LCA) to account the GHG emissions associated with the construction and operation phases of the drinking water treatment plant (DWTP). During the construction phase, the total GHG emissions were 19,525.762 t CO2-eq, with concrete work and rebar project being the dominant contributors (87.712%). The promotion of renewable or recyclable green building materials and low-carbon construction methods, such as the utilization of prefabricated components and on-site assembly, holds significant importance in reducing GHG emissions during the construction phase of DWTP. Regarding the operation stage, the DWTP possessed an average annual GHG emission of 37,660.160 t CO2-eq and an average GHG intensity of 0.202 kg CO2-eq/m3. Most emissions were attributed to electricity consumption (67.388%), chemicals utilization (12.893%), and heat consumption (10.414%). By increasing the use of clean energy and implementing strict control measures in the water supply pumps, energy consumption and GHG emissions can be effectively reduced. This study offers valuable insights into the mapping of GHG emissions in the DWTP, facilitating the identification of key areas for targeted implementation of energy-saving and carbon-reducing measures.

Linking the effect of temperature on adsorption from aqueous solution with solute dissociation

Imperative decarbonization of water purification processes entails alternative regeneration methods for activated carbon. Regeneration based on changing dissociation equilibria, i.e. a major influencing factor on adsorption, usually requires the addition of acids/bases, but may also be triggered by temperature swing. Although adsorption and dissociation are both temperature-dependent phenomena, their conjunction has received little attention regarding trace organic compounds (TrOCs) and large temperature intervals, in particular above ΔT ≥ 50 ^∘C. Therefore, we studied the adsorption equilibria of 16 TrOCs onto one granular activated carbon at temperatures ranging from 20 to 95 ^∘C. The majority of compounds (12/16) exhibited an exothermic apparent adsorption enthalpy, while 3 out of 16 exhibited an endothermic apparent enthalpy. The range spanned from - 46 to + 50 kJ mol^-1 (median at - 17 kJ mol^-1). The possible origins of endothermic adsorption were discussed. A rationale of shifting pK_a and thus changing dissociation of TrOCs was introduced and traded off against existing rationales, i.e. changing solute solubility, changing adsorption heat capacity, and saturation effects of the adsorbates. This knowledge may allow designing temperature swing adsorption processes that unlock the dissociation switch. The augmented process efficiency can thus provide the foundation for low-carbon emission, circular water purification processes.

Energy and CO2 Emissions Penalty Ranges for Geologic Carbon Storage Brine Management

Safe and cost-effective geologic carbon storage will require active CO₂ reservoir management, including brine extraction to minimize subsurface pressure accumulation. While past simulation and experimental efforts have estimated brine extraction volumes, carbon management policies must also assess the energy or emissions penalties of managing and disposing of this brine. We estimate energy and CO₂ emission penalties of extracted brine management on a per tonne of CO₂ stored basis by spatially integrating CO₂ emissions from U.S. coal-fired electric generating units, CO₂ storage reservoirs, and brine salinity data sets under several carbon and water management scenarios. We estimate a median energy penalty of 4.4-35 kWh/tonne CO₂ stored, suggesting that brine management will be the largest post capture and compression energy sink in the carbon storage process. These estimates of energy demand for brine management are useful for evaluating end-uses for treated brine, assessing the cost of CO₂ storage at the reservoir level, and optimizing national CO₂ transport and storage infrastructure.

Making wastewater obsolete: Selective separations to enable circular water treatment

By 2050, the societal needs and innovation drivers of the 21st century will be in full swing: mitigating climate change, minimizing anthropogenic effects on natural ecosystems, navigating scarcity of natural resources, and ensuring equitable access to quality of life will have matured from future needs to exigent realities. Water is one such natural resource, and will need to be treated and transported to maximize resource efficiency. In particular, wastewater will be mined for the valuable product precursors it contains, which will require highly selective separation processes capable of capturing specific target compounds from complex solutions. As a case study, we focus on the nitrogen cycle because it plays a central role in both natural and engineered systems. Nitrogen occurs as several species, including ammonia, a fertilizer and precursor to many nitrogen products, and nitrate, a fertilizer and component of explosives. We describe two applications of selective separations: selective materials and electrochemical processes. Ultimately, this perspective outlines the next thirty years of modular, selective, resource-efficient separations that will play a major role in enabling element-specific circular economies and redefining wastewater as a resource.

Biofilter with mixture of pine bark and expanded clay as packing material for methane treatment in lab-scale experiment and field-scale implementation

Low methane (CH₄) emission reduction efficiency (< 25%) has been prevalent due to inefficient biological exhaust gas treatment facilities in mechanic biological waste treatment plants (MBTs) in Germany. This study aimed to quantify the improved capacity of biofilters composed of a mixture of organic (pine bark) and inorganic (expanded clay) packing materials in reducing CH₄ emissions in both a lab-scale experiment and field-scale implementation. CH₄ removal performance was evaluated using lab-scale biofilter columns under varied inflow CH₄ concentrations (70, 130, and 200 g m^-3) and corresponding loading rates of 8.2, 4.76, and 3.81 g m^-3 h^-1, respectively. The laboratory CH₄ removal rates (1.2-2.2 g m^-3 h^-1) showed positive correlation with the inflow CH₄ loading rates (4-8.2 g m^-3 h^-1), indicating high potential for field-scale implementation. Three field-scale biofilter systems with the proposed mixture packing materials were constructed in an MBT in Neumünster, northern Germany. A relatively stable CH₄ removal efficiency of 38-50% was observed under varied inflow CH₄ concentrations of 28-39 g m^-3 (loading rates of 1120-2340 g m^-3 h^-1) over a 24-h period. The CH₄ removal rate was approximately 500-700 g m^-3 h^-1, which was significantly higher than relevant previously reported field-scale biofilter systems (16-50 g m^-3 h^-1). The present study provides a promising configuration of biofilter systems composed of a mixture of organic (pine bark) and inorganic (expanded clay) packing materials to achieve high CH₄ emission reduction. Graphic abstract ᅟ.

Air Emission Reduction Benefits of Biogas Electricity Generation at Municipal Wastewater Treatment Plants

Conventional processes for municipal wastewater treatment facilities are energy and materially intensive. This work quantifies the air emission implications of energy consumption, chemical use, and direct pollutant release at municipal wastewater treatment facilities across the U.S. and assesses the potential to avoid these damages by generating electricity and heat from the combustion of biogas produced during anaerobic sludge digestion. We find that embedded and on-site air emissions from municipal wastewater treatment imposed human health, environmental, and climate (HEC) damages on the order of $1.63 billion USD in 2012, with 85% of these damages attributed to the estimated consumption of 19 500 GWh of electricity by treatment processes annually, or 0.53% of the US electricity demand. An additional 11.8 million tons of biogenic CO₂ are directly emitted by wastewater treatment and sludge digestion processes currently installed at plants. Retrofitting existing wastewater treatment facilities with anaerobic sludge digestion for biogas production and biogas-fueled heat and electricity generation has the potential to reduce HEC damages by up to 24.9% relative to baseline emissions. Retrofitting only large plants (>5 MGD), where biogas generation is more likely to be economically viable, would generate HEC benefits of $254 annually. These findings reinforce the importance of accounting for use-phase embedded air emissions and spatially resolved marginal damage estimates when designing sustainable infrastructure systems.