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The goal of ENVIRO Wiki is to make scientific and engineering research results more accessible to environmental professionals, facilitating the permitting, design and implementation of environmental projects. Articles are written and edited by invited experts (see Contributors) to summarize current knowledge for the target audience on an array of topics, with cross-linked references to reports and technical literature.

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Featured article: Photoactivated Reductive Defluorination - PFAS Destruction

Photoactivated Reductive Defluorination (PRD) is a PFAS destruction technology predicated on ultraviolet (UV) light-activated photochemical reactions. The destruction efficiency of this process is enhanced by the use of a surfactant to confine PFAS molecules in self-assembled micelles. The photochemical reaction produces hydrated electrons from an electron donor that associates with the micelle. These highly reactive hydrated electrons have the energy required to cleave fluorine-carbon and other molecular bonds resulting in the final products of fluoride, water, and simple carbon molecules. Since the reaction is performed at ambient temperature and pressure, there are limited concerns regarding environmental health and safety or volatilization of PFAS compared to heated and pressurized systems. Due to the reductive nature of the reaction, there is no formation of unwanted byproducts resulting from oxidative processes. The PRD reaction rate decreases in water matrices with high levels of total dissolved solids (TDS). The PRD reaction rate decreases in water matrices with very low UV transmissivity. Low UV transmissivity (i.e., < 1 %) prevents the penetration of UV light into the solution, such that the utilization efficiency of UV light decreases. Due to the first-order kinetics of PRD, destruction of PFAS is generally most energy efficient when paired with pre-concentration technologies, such as foam fractionation (FF), nanofiltration, reverse osmosis, or resin/carbon adsorption, that remove PFAS from water.    (Full article...)

Enviro Wiki Highlights

Molecular diffusion slowly transports solutes into clay-rich, lower permeability zones

Typical subgrade biogeochemical reactor (SBGR) layout. The SBGR is an in situ remediation technology for treatment of contaminated source areas and groundwater plume hot spots

An Hydraulic Profiling Tool (HPT) log with electrical conductivity (EC) on left, injection pressure in middle, and flow rate on the right

Diagram of mineral surface exchanging hydrogen ions with varying pH. The surface of most aquifer minerals carries an electrical charge that varies with pH

Comparison of the longitudinal redox zonation concept (A) and the plume fringe concept (B). Both concepts describe the spatial distribution of electron acceptors and respiration processes in a hydrocarbon contaminant plume

Schematic of an Hydraulic Profiling Tool (HPT) probe. HPT were developed to better understand formation permeability and the distribution of permeable and low permeability zones in unconsolidated formations

In situ chemical oxidation using (a) direct-push injection probes or (b) well-to-well flushing to delivery oxidants (shown in blue) into a target treatment zone of groundwater contaminated by dense nonaqueous phase liquid compounds (shown in red)

High-resolution 3D cross-borehole electrical imaging of contaminated fractured rock at the former Naval Air Warfare Center in New Jersey. Cross-borehole resistivity tomography imaging is a geophysical technique that can be used for site characterization and monitoring by observing variations in the electrical properties of subsurface materials

Stable isotope probing (SIP) in use: Loading, deployment and recovery of Bio-Trap® passive sampler with 13C-labeled benzene. Stable isotope probing (SIP) is used to conclusively determine whether in situ biodegradation of a contaminant is occurring

Summary of anticipated, primary reaction pathways for degradation of 1,2,3-Trichloropropane (TCP). TCP is a man-made chemical that was used in the past primarily as a solvent and extractive agent, a paint and varnish remover, and as a cleaning and degreasing agent

Distribution of BTEX plume lengths from 604 hydrocarbon sites. Monitored Natural Attenuation (MNA) is one of the most commonly used remediation approaches for groundwater contaminated with petroleum hydrocarbons (PHCs) and certain fuel additives such as fuel oxygenates or lead scavengers

No-purge and passive sampling methods eliminate the pre-purging step for groundwater sample collection and represent alternatives to conventional sampling methods that rely on low-flow purging of a well prior to collection. The Snap SamplerTM is an example of a passive grab sampler

Conceptualization of Vapor Transport-related Natural Source Zone Depletion (NSZD) processes at a Petroleum Release Site

Conceptual diagram of basic Soil Vapor Extraction (SVE) system for vadose zone remediation. (SVE) is a common and typically effective physical treatment process for remediation of volatile contaminants in vadose zone (unsaturated) soils

Emulsified Vegetable Oil (EVO) mixed in field during early pilot test. EVO is commonly added as a slowly fermentable substrate to stimulate the in situ anaerobic bioremediation of chlorinated solvents, explosives, perchlorate, chromate, and other contaminants

Key elements of vapor intrusion pathways

Batch reactor experiments to generate points on a sorption isotherm

Results for metagenomic analysis of a groundwater sample obtained from a site impacted with petroleum hydrocarbons

Perchlorate releases and drinking water detections

Data input screen for ESTCP Mass Flux Toolkit

Amendment addition for biobarrier

Thermal Remediation - Desorption schematic

Key exposure pathways for human health risk from contaminated sediments

The PFAS family of compounds

Table of Contents Attenuation & Transport Processes Biodegradation - 1,4-Dioxane Biodegradation - Cometabolic Biodegradation - Hydrocarbons Biodegradation - Reductive Processes Groundwater Flow and Solute Transport Matrix Diffusion Mobility of Metals and Metalloids pH Buffering in Aquifers Sorption of Organic Contaminants Vapor Intrusion (VI) Vapor Intrusion - Separation Distances from Petroleum Sources Vapor Intrusion - Sewers and Utility Tunnels as Preferential Pathways Characterization, Assessment & Monitoring Characterization Methods – Hydraulic Conductivity Compound Specific Isotope Analysis (CSIA) Direct Push (DP) Technology Direct Push Logging Direct Push Sampling Geophysical Methods Case Studies Groundwater Sampling - No-Purge/Passive Long-Term Monitoring (LTM) LTM Data Analysis LTM Data Variability Molecular Biological Tools (MBTs) Metagenomics Proteomics and Proteogenomics Quantitative Polymerase Chain Reaction (qPCR) Stable Isotope Probing (SIP) Natural Attenuation in Source Zone and Groundwater Plume - Bemidji Crude Oil Spill Climate Change Climate Change Effects on Wildlife Downscaled High Resolution Datasets for Climate Change Projections Infrastructure Resilience Predicting Species Responses to Climate Change with Population Models Restoration of Ecological Function in Terrestrial Systems Impacted by Invasive Species Coastal and Estuarine Ecology Phytoplankton (Algae) Blooms Contaminated Sediments Contaminated Sediment Risk Assessment In Situ Treatment of Contaminated Sediments with Activated Carbon Mercury in Sediments Passive Sampling of Sediments Sediment Capping Light Non-Aqueous Phase Liquids (LNAPLs) LNAPL Conceptual Site Models LNAPL Remediation Technologies NAPL Mobility Munitions Constituents Abiotic Reduction Alkaline Degradation Composting Deposition Dissolution Metal(loid)s - Small Arms Ranges Passive Sampling Photolysis Soil Sampling Sorption Toxicology TREECS™ Monitored Natural Attenuation (MNA) MNA of Chlorinated Solvents MNA of Fuels MNA of Metals and Metalloids Natural Source Zone Depletion (NSZD) Transitioning from Active Remedies Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) PFAS Ex Situ Water Treatment PFAS Soil Remediation Technologies PFAS Sources PFAS Transport and Fate PFAS Treatment by Electrical Discharge Plasma Photoactivated Reductive Defluorination Regulatory Issues and Site Management Alternative Endpoints Mass Flux and Mass Discharge Plume Response Modeling REMChlor-MD Source Zone Modeling Sustainable Remediation Remediation Technologies Amendment Distribution in Low Conductivity Materials Anaerobic Bioremediation Design Considerations Design Tool - Base Addition for ERD Emulsified Vegetable Oil (EVO) for Anaerobic Bioremediation Low pH Inhibition of Reductive Dechlorination Secondary Water Quality Impacts In Situ Chemical Oxidation (ISCO) Design Considerations Oxidant Selection In Situ Chemical Reduction (ISCR) Zero-Valent Iron (ZVI) Zerovalent Iron Permeable Reactive Barriers In Situ Groundwater Treatment with Activated Carbon Injection Techniques for Liquid Amendments Injection Techniques - Viscosity Modification Landfarming Remediation of Metals and Metalloids Remediation Performance Assessment at Chlorinated Solvent Sites Soil Vapor Extraction (SVE) Stream Restoration Subgrade Biogeochemical Reactor (SBGR) Supercritical Water Oxidation (SCWO) Thermal Remediation Combined Remedies Electrical Resistance Heating (ERH) Smoldering Steam Enhanced Extraction (SEE) Thermal Conduction Heating (TCH) Soil & Groundwater Contaminants 1,2,3-Trichloropropane 1,4-Dioxane Chlorinated Solvents Metals and Metalloids N-nitrosodimethylamine (NDMA) Perchlorate Petroleum Hydrocarbons (PHCs) Polycyclic Aromatic Hydrocarbons (PAHs)