15) groundwater contamination, prevention and remedial techniques as on 27-05-2012- new design
IntroductionImportance of GroundwaterSources of Groundwater ContaminationPrevention from Groundwater PollutionParticipation of Industries and CommunityGroundwater RemediationConventional and Innovative Remediation TechniquesTypical Groundwater ContaminantsPractical Remediation TechnologiesRoyal Commission Environmental Regulations for Groundwater PreventionConclusion
Groundwater is water present below the ground surface thatsaturates the pore space in the subsurface.At least 50% of the world population depends on groundwater as asource of drinking water.Other uses of groundwater includes Irrigation of crops, Industrialuses etc.Groundwater is a part of natural water cycle therefore, it can spreadthroughout the cycle and if contaminated, can cause damage toother entities ( Sea life, lakes, human health etc)Groundwater can be polluted / contaminated as a result of HUMANactivity and Natural conditions.Contaminations found in the groundwater cover a broad range ofphysical, chemical (Organic & Inorganic), bacteriological andradioactive parameters.
Leaking Fuel and Chemical Tanks Improper use of contaminated water Industrial Chemical spills Industrial EmissionsExtensive use of Pesticides, Badly Managed Landfill Herbicides and fertilizers Drainage of house hold chemicals
Once Groundwater gets contaminated, it may be difficult and expensiveto clean it up, therefore,“Thebest way to deal withgroundwater contamination is not tocontaminate it in the first place ”
Participation of Industries:•Minimize use of Toxic / Hazardous Raw Materials•Maintain Integrity of the Storage Tanks, Pipelines, surface impoundments•Adopt Good Engineering Practices for selecting proper material for tanksand pipes.•Implement monitoring programs: Leak Detection and repair program, spilldetection, spill control, emergency response plan etc.•Manage Properly: Waste materials, their transport and disposal.•Install Monitoring Wells•Monitor Periodically: Groundwater quality
Participation of Community:•Minimize use of house hold chemicals containing Hazardous substances.•Avoid draining chemicals, motor oil, insecticides in community areas.•Reduce pesticide application•Use proper procedures for handling chemicals (Paints, Pesticides,Insecticides, polishing materials, cleaning chemicals and detergents).•Immediately clean any spills and report any leakages to concerneddepartment.
Groundwater remediation is the process that is used to remove pollution fromgroundwater.Pollutants and contaminants can be removed from groundwater by applying varioustechniques thereby making the groundwater safe for use.Groundwater remediation techniques are mainly divided into two technologies: Ex-Situ Technology and In-Situ TechnologyEx-Situ Technology involves treatment of groundwater by de-watering the polluted aquifer (pumping out), then treating the water onsurface by Physical, chemical or biological technology and finally re-injecting the treated water to the aquifer.In-Situ Technology involves treatment of groundwater withinthe aquifer (in the sub-surface) by using thermal, chemical andbiological treatment technology.
Ex-Situ Technology:Extraction of groundwater from aquifer , treat above ground. and return the treatedwater to the aquifer. Extraction is done by pumping groundwater from the well ortrench and treat them with a variety of techniques such as :Stream strippingInvolves treatment by introducing steam which extract the contaminants from thepumped out groundwater. The extracted steam (along with contaminants can berecovered from the condensate or treated further by incineration.Oxygen SpargingInvolves introduction of oxidizing/reducing agents ( O3, H2O2, Hypochlorite) tochemically convert the toxic contaminants to less toxic compounds.BioremediationInvolves treatment of pumped up groundwater by air (biodegradation) with carefulcontrol of moisture, heat nutrients, oxygen and pH.Carbon AdsorptionInvolves passing the contaminated pumped up groundwater through activatedcarbon column in which contaminants gets adsorbed.
In-Situ Remediation Technology:Involves treatment of groundwater (in-place) without extracting the water from aquifer. There areseveral treatment techniques used for in-situ groundwater treatment such as:Air Sparging:Involves the injection of contaminant-free air into the subsurface saturated zone, enabling a phasetransfer of hydrocarbons from a dissolved state to a vapor phase.Bioremediation:Involves injection of oxygen to enhance the biodegradation. This treatment also combines injection ofdegrading bacteria and nutrients into aquifer to stimulate biodegradation.In-well air stripping:Involves injection of air in double screened well, lifting the water up the well and force it out in upperscreen. VOCs in the contaminated water are transferred from dissolved phase to vapor phase in airbubbles and drawn off and treated.Chemical Oxidation:Involves Reduction-Oxidation reactions that chemically converts hazardous contaminants to less toxiccompounds. Cyanide oxidation and de-chlorination are the typical examples of chemical oxidation.Thermal Treatment:Involves increase in temperature of the source zone to increase the mobility of the pollutants. Themobility facilitate removal of pollutants and can also results in In-Situ destruction of contaminants.PhythoremediationIt involves the use of macroscopic plants to destroy, remove, immobilize and treat contaminants.This process does not use microorganisms.
The selection of the remedial technology depends upon severalparameters such as:Contaminant Profile:Types of compounds ( DNAPL, LNAPL, Ammonia, Virus, Bacteria)Quantity and Solubility ( Solubility in Water)Toxicity and volatility ( VOCs , SVOCs, Metals, etc)BiodegradabilityAquifer Profile:Soil Type (permeability, homogeneity, chemistry, confined or open, etc)Groundwater Flow directionWater Table locationRecharge location ( seasonal Rainfall)Feasibility Profile:Cost of technologyTime of completion
Several man made chemicals are referred to as Groundwatercontaminants because of their extensive use, accidental spills andleaks, mismanagement and illegal dumping. Some of the popularcontaminants are the following:DNAPL (Dense Non Aqueous Phase Liquids )LNAPL (Light Non Aqueous Phase Liquids)Inorganic Chemicals ( Ammonia, Cyanide, Fluoride)MetalsBacteria and Viruses
DNAPL :Dense Non Aqueous Phase Liquids are organic compounds heavier thanwater and having less absolute solubility. These compounds includechlorinated solvents (EDC) and halogenated aromatics (TCB)DNAPLs migrate very fast through the soil formation and reach watertable because of their high density and low viscosity. They sink steeply tothe bottom of the aquifer till they reach the impermeable bed rock.Treatment of DNAPLThe following types of technologies are increasingly being used to treat DNAPLs: In situ thermal treatment In situ chemical oxidation Surfactant/co-solvent flushing In situ bioremediationGround water extraction (P&T or recirculation) ExcavationContainment (Engineered caps and slurry walls).
LNAPLLight Non Aqueous Phase Liquids are organic compounds lighter thanwater and having low solubility. These liquids include Gasoline, fuel oiland other petroleum products.LNAPL Remediation:Remediation may require the use of more than one technology.It is likely that several remediation techniques, used in series and/orparallel applications, will be required for maximum contaminant removal.This collaborative effort may be referred to as a treatment train approach.A conceptual example of a treatment train which might be effective at anLNAPL site includes:Pump and Treat for mobile LNAPL removal followed by vaporextraction for removal of residual LNAPL .Additional technologies such as bioremediation might be used to furtherreduce contaminant concentrations.
Contaminant Main Source Treatment Technology Degreasing of Metal and Electronic parts, •Pump and TreatTrichloroethylene Extract for oil and waxes, fumigant, carries in •Activated Carbon(TCE) paints and adhesives •Thermal and Biological MTBE can be released to groundwater by •Air Sparging leaking underground storage tanks and •In-Situ oxidation ( H2O2 and Fe)MTBE piping, atmospheric deposition, spills during •Bioremediation/Bioaugmentation transportation, and leaks at refineries •Pump and Treat. From EDC and VCM Plants, storage tanks, •In-situ Bioremediation.EDC (DNAPL) pipelines etc. Gasoline and other petroleum fuels tanks, •In-situ BioremediationGasoline (LNAPL) petrol stations, storage tanks and pipelines. •Vapor extraction Ammonia Storage Tanks, Landfill leaks, •Pump and TreatAmmonia Waste stockpile, etc. •Combination of Air Stripping, Nitrification, Ion Exchange.
Groundwater contaminated by Ethylene Dichloride and Chloroform can betreated through in-situ bio remediation by using certain types of Enzymesunder proper conversion parameters.This In-Situ process is applicable to both fresh and brackish waters.50 to 80 percent biodegradation can be achieved by injecting Enzymes inthe aquifer within 5 to 10weeks.Applicability:EDC (1.3 g/cc), Chloroform (1.5 g/cc) , Chlorobenzene, Vinyl Chloride,VOCs.Limitations:Permeability of the groundAquifer MatrixPractical ExecutionThis In-Situ Bio remediation is practically implemented by two industrialfacilities in Jubail to reduce EDC and other chlorinated compounds from thegroundwater.
Treatment of MTBE (Methyl Tertiary Butyl Ether )MTBE is broadly used as Gasoline additiveand is one of the popular contaminant ofthe groundwater.The solubility in water is as high as 4.3%comparing to Solubility of benzene andtoluene 0.18% and 0.05% respectively.MTBE is very mobile and can spread tovery large subsurface area very quickly.Groundwater contaminated with MTBE can be treated by :In-Situ OxidationBioremediation (Enhanced by Oxygen and Nutrients injection)Pump and Treat by Air Stripping & Activated Carbon AdsorptionCombination of Catalytic Chemical Oxidation with UV Presence.
Ammonia is one of the major pollutants which contaminates groundwater.Ammonia contamination could lead to Sea Water Pollution. Being Toxic toAquatic Organism, Remediation of Ammonia is very important.US Department of Energy has successfully conducted pilot studies on theInnovative Remedial Techniques on an Aquifer near Moab, Utah, USA. Whichshows that technologies are available for treating groundwater contaminatedwith high levels of Ammonia to a safe level of 3 mg/LThese technologies includes:Pump and Treat by Ammonia StrippingPump and Treat by Air Stripping and further NitrificationPump and Treat by Ion ExchangeLimitation: Needs pH Adjustments,
Royal Commission has always been concerned about Public Health andEnvironment including Surface and Subsurface groundwater.At Royal Commission Environmental Control Department(RC-EPCD), we believe inPrevention from groundwater contamination as the very first rule of remediation.Therefore, Royal Commission Environmental Regulation (RCER) has made itobligatory for all industries to stringently follow RCER Groundwater Regulationsuch as:At least 3 Groundwater Monitoring Wells in each industrial facility.Periodical Monitoring Groundwater Quality.Periodical Reports to RC.Mandatory use of Impervious Liner (1.5 mm thick HDPE liners) for : Tank foundations, Secondary Containments(Dikes) and Storm Water PondStorage Tank Regulations: Spill Control Devices , Leak Detection and Overfill System Containments and Double Walls, Material of Construction
Implementation of Leak Detection and Repair System to ensure the integrity of the pipelines and components.Separate Location for Landfills: Inert Waste Non Hazardous Waste Hazardous Industrial Wastes Sanitary Wastes.Landfill Design Double Liners Groundwater Monitoring wells Near Landfill Leachate Collection SystemMonitoring Groundwater Quality from 60 Monitoring Wells outsideindustrial facilities in Jubail Industrial City.Reviewing Groundwater Quality Reports submitted by Individual Industries from over 500 Wells in the Jubail Industrial City.Checking Quality of Groundwater used for Re-mineralization of drinking water which is supplied in Royal Commission Area.
1. Prevention from groundwater contamination is the best Remedial Option.2. Mostly, groundwater contaminants are of industrial origin.3. Royal Commission is closely monitoring the quality of Groundwater through out the Jubail Industrial City and also have implemented strict regulation for the prevention of groundwater pollution.4. Environmental Awareness Programs Including groundwater prevention should be Implemented for Community.5. Innovative Technologies are available for the groundwater remediation, for several common contaminants including EDC and Other Chlorinated Compounds, MTBE and Ammonia.
Prevention Pays - Remedy Costs and The Prevention is in Our Hands