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Enviro Wiki aims to be the go-to website for environmental information. US environmental programs such as the Strategic Environmental Research and Development Program (SERDP) and Environmental Security Technology Certification Program (ESTCP) fund cutting-edge environmental research projects. Here, articles written by invited experts (see Contributors) and edited by leaders in this field (see Editors) aim to introduce and summarize current knowledge for environmental project professionals on an array of topics, with cross-linked references to reports and technical literature.	Your Environmental Information Gateway

Featured article / Biodegradation - Hydrocarbons

High-pressure membrane filtration such as nanofiltration (NF) or reverse osmosis (RO) is a filtration process that separates dissolved inorganic and organic solutes from liquid solvents, typically water. As opposed to porous and more permeable low-pressure membranes (i.e., microfiltration and ultrafiltration), NF and RO membranes are widely considered semi-permeable and therefore require higher operating pressures to force water against an osmotic gradient to produce a purified permeate stream. NF and RO systems are separation processes that yield two streams: the treated permeate and the concentrated retentate. Typical parameters used to describe operational performance of high-pressure membrane systems include solvent recovery and solute rejection. Recovery is defined as the percentage of feed water that becomes permeate. Solute rejection is defined as the percent of concentrated feed water retained by the membrane. Significant advancements in membrane material development have led to development of NF and RO membranes with varying pressure requirements and solute rejection characteristics.
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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

Table of Contents Attenuation & Transport Processes Advection and Groundwater Flow Biodegradation - Hydrocarbons Biodegradation - Reductive Processes Cometabolism Dispersion and Diffusion Mobility of Metals and Metalloids pH Buffering in Aquifers Vapor Intrusion (VI) Characterization, Assessment & Monitoring Compound Specific Isotope Analysis (CSIA) Direct Push (DP) Technology DP Logging DP 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 Quantitative Polymerase Chain Reaction (qPCR) Stable Isotope Probing (SIP) Soil & Groundwater Contaminants Chlorinated Solvents Metals and Metalloids Perchlorate PFAS Polycyclic Aromatic Hydrocarbons (PAHs) Trichloropropane (TCP) Munitions Constituents Deposition Dissolution Sorption Toxicology TREECS™ Monitored Natural Attenuation (MNA) MNA of Chlorinated Solvents MNA of Metals and Metalloids MNA of Petroleum Hydrocarbons Natural Source Zone Depletion (NSZD) Regulatory Issues and Site Management Alternative Endpoints Mass Flux and Mass Discharge Plume Response Modeling Source Zone Modeling Sustainable Remediation Remediation Technologies 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) Injection Techniques - Viscosity Modification Landfarming Liquid Amendments in Groundwater Remediation of Metals and Metalloids Remediation Performance Assessment at Chlorinated Solvent Sites Soil Vapor Extraction (SVE) Subgrade Biogeochemical Reactor (SBGR) Thermal Remediation Combined Remedies Desorption Electrical Resistance Heating Smoldering Steam