Life cycle assessment (LCA) and techno‐economic analysis (TEA) models are developed for a tertiary wastewater treatment system that employs a biochar‐integrated reactive filtration (RF) approach. This innovative system incorporates the utilization of biochar (BC) either in conjunction with or independently of iron‐ozone catalytic oxidation (CatOx)—resulting in two configurations: Fe‐CatOx‐BC‐RF and BC‐RF. The technology demonstrates 90%–99% total phosphorus removals, adsorption of phosphorus to biochar for recovery, and >90% destructive removal of observed micropollutants. In this work, we conduct an ISO‐compliant LCA of a 49.2 m³/day (9 gpm) field pilot‐scale Fe‐CatOx‐BC‐RF system and a 1130 m³/day (0.3 MGD) water resource recovery facility (WRRF)‐installed RF system, modeled with BC addition at the same rate of 0.45 g/L to quantify their environmental impacts. LCA results indicated that the Fe‐CatOx‐BC‐RF pilot system is a BC dose‐dependent carbon‐negative technology at −1.21 kg CO₂e/m³, where biochar addition constitutes a −1.53 kg/m³ CO₂e beneficial impact to the process. For the WRRF‐installed RF system, modeled with the same rate of BC addition, the overall process changed from 0.02 kg CO₂e/m³ to a carbon negative −1.41 kg CO₂e/m³, demonstrating potential as a biochar dose‐dependent negative emissions technology. Using the C₁₀₀ 100‐year carbon accounting approach rather than C_net reduces these CO₂e metrics for the process by about 25%. A stochastic TEA for the cost of water treatment using this combinatorial P removal/recovery, micropollutant destructive removal, and disinfection advanced technology shows that at scale, the mean cost for treating 1130 m³/day (0.3 MGD) WRRF secondary influent water with Fe‐CatOx‐BC‐RF using the C₁₀₀ metric is US$0.18 ± US$0.01/m³ to achieve overall process carbon neutrality. Using the same BC dose in an estimation of a 3780 m³/day (1 MGD) Fe‐CatOx‐BC‐RF facility, the carbon neutral cost of treatment is reduced further to US$0.08 ± $0.01 with added BC accounting for US$0.03/m³. Overall, the results demonstrate the potential of carbon negativity to become a water treatment performance standard as important and attainable as pollutant and pathogen removal.Practitioner Points: Life cycle assessment (LCA) of a pilot scale tertiary biochar water treatment process with or without catalytic ozonation at a WRRF shows a carbon negative global warming potential of −1.21‐kg CO2e/m3 while removing 90%–99% TP and >90% of detected micropollutants. Biochar‐integrated reactive filtration use can aid in long‐term carbon sequestration by reducing the carbon footprint of advanced water treatment in a dose‐dependent manner, allowing an overall carbon‐neutral or carbon‐negative process. A companion paper to this work (Yu et al., 2023) presents the details related to the process operation and mechanism and evaluates the pollutant removal performance of this Fe‐CatOx‐BC‐RF process in engineering laboratory pilot research and field WRRF pilot‐scale water resource recovery trials. Techno‐economic analysis (TEA) of this biochar catalytic oxidation reactive filtration process using Monte Carlo stochastic modeling shows a forecasted carbon‐neutral process cost with low P and micropollutant removal as US$0.11/m3 ± 0.01 for a 3780‐m3/day (1 MGD) scale installation with BC cost at US$0.03/m3 of that total. The results demonstrate the potential of carbon negativity to become a water treatmentperformance standard as important and attainable as pollutant and pathogen removal.

A subtropical watershed and wetland covering nearly 47,000 km² in the southeastern United States, the Florida Everglades is a degraded, human-dominated environment. As a unique and important ecosystem, the Everglades provide a variety of important environmental services for society and nature. Over the past century and a half, anthropogenic actions have severely impacted the Everglades by disrupting the natural water flow and causing water pollution. As a result, the native flora and fauna have been displaced, important habitats have been lost, invasive species have become prevalent, and water contaminant concentrations have increased. Accelerating efforts are being made towards preserving the Everglades ecosystem by restoring water flow and improving water quality. To explore this complex and important aquatic ecosystem, we critically review the relevant environmental history, major terrestrial and aquatic characteristics and dynamics, engineered changes to water flow, major sources and impacts of nutrient pollution, trends in system response to pollution and mitigation actions, and recent regulatory efforts driving restoration.

Khaidarkan, Batken Province, Kyrgyzstan is home to one of the world’s largest and last primary mercury mines. Doctors without Borders (MSF) and the Ministry of Health (MOH) of Kyrgyzstan have found that the Batken region has an elevated rate of non-communicable diseases (NCD) within the country. NCD can be caused by environmental pollution. A human health risk assessment was conducted to investigate heavy metal exposure. Using a hand-held X-ray fluorescence (XRF) spectrometer for soil screening is faster and less expensive than reliance on bench-scale methods. To establish a site-specific mercury conversion factor between XRF and the local MOH lab’s Atomic Absorption Spectrometry (AAS) with a Pyrolyzer attachment, soil samples were collected in Khaidarkan and surrounding villages. Samples were analyzed by XRF in three stages: in situ, ex situ-bulk, and ex situ-sieved. The ex situ-sieved samples were analyzed by AAS. Analysis results indicate that in situ readings can be used as a qualitative tool for screening, and a conversion factor of 1.7 was most appropriate for converting ex situ-bulk/ex situ-sieved and AAS results. This analysis enables the MOH laboratory and others to use XRF as a quick and cost-effective monitoring tool for Hg contamination in soil.

Dual upflow reactive filtration by a slowly moving sand bed with continuously renewed, hydrous ferric oxide‐coated sand is used for removing polluting substances and for meeting the ultralow 0.05 mg/l total phosphorus discharge permit limits at a 1.2 million liters per day (0.32 million gallons per day) water resource recovery facility in Plummer, Idaho, in the United States. A life cycle assessment (LCA) of this reactive filtration installation was carried out to assess the environmental hotspots in the system and analyze alternative system configurations with a focus on CO₂ equivalent (CO₂e) global warming potential, freshwater and marine eutrophication, and mineral resource scarcity. “What if” scenarios with alternative inputs for the energy, metal salts, and air compressor optimization show trade‐offs between the impact categories. Key results that show a comparative reduction of global warming potential include the use of Fe versus Al metal salts, the use of renewable energy, and the energy efficiency benefit of optimizing process inputs, such as compressor air pressure, to match operational demand. The LCA shows a 2 × 10⁻² kg CO₂e footprint per cubic meter of water, with 47% from housing concrete, and an overall freshwater eutrophication impact reduced by 99% versus no treatment. The use of renewable hydropower energy at this site isolates construction concrete as a target for lowering the CO₂e footprint.Practitioner Points: The main LCA eco‐impact hotspots in this dual reactive filtration tertiary treatment are construction concrete and the ferric sulfate used. Iron salts show smaller impact in global warming, freshwater eutrophication, and mineral resource scarcity than “what if scenario” aluminum salts. The energy mix for this site is predominantly hydropower; other energy mix “what if” scenarios show larger impacts. Operational energy efficiency and thermodynamic analysis show that fine tuning the air compressor helps reduce carbon footprint and energy use. LCA shows a favorable 2 x 10‐2 kg CO2e/m3 water impact with 99% reduction of freshwater eutrophication potential versus no treatment.