Identification and prioritisation of groundwater contaminants and sources in

South Africa’s urban catchments

Institute for Groundwater StudiesCSIR Environmentek

University of the Western CapeWRC Project No. K5/1326 2004

Overview of PresentationIntroduction and Background ApproachProductsResultsShortcomingsSoftwareImplications to Aquifer Vulnerability project

Where did the project come from ?WRC identified paucity of groundwater contamination research in urban areasSililo et al – WRC report 1008/1/01 in 1998 on vulnerability of urban aquifersRecommendations from this and related WRC projects formed basis of strategies on a “National Information and Aquifer Management Programme”

IntroductionIGS, CSIR and UWC partnershipFilling the gap in the understanding of groundwater contamination in South Africa’s urban environments. Principal pollutants identified and, based on their risk, prioritised. Facilitation of better management of groundwater quality in South Africa by assisting future land use planning and vulnerability studies

Introduction and BackgroundGroundwater contamination can occur, as a result of various activities of manIncreased human settlement and economic development, a range of undesirable waste products are produced This project: filling the gap in the understanding of groundwater contamination in South Africa’s urban environmentsPrincipal pollutants identified and based on their risk prioritisedWill facilitate better managementof groundwater quality through the country

ObjectivesIdentify and prioritise the type of contaminants and sources which present a threat to groundwater, the environment and health in South Africa’s urban catchments;Formulate strategies for better understanding the impacts of polluting activities on groundwater resources in urban catchments;andEstablish a data information system on South Africa’s contaminants.

ApproachLiterature search

Statistics South Africa; Chamber of Mines; State of the Environment Reports; Municipal websites; WRC Reports

Case study examples archives of newspaper articles; conference and workshop proceedings; project reports; monitoring databases

Contact with individuals at various organizationsQuestionnairesContamination incident reports and databases

ApproachDetailed information and data were onlycollected for the major urban areas

Gauteng, Durban, PE, CPT

Problems:Reluctance to supply dataPoor response to questionnairesEfforts directed towards groundwater resource evaluation, rather than groundwater pollution monitoringInorganic analyses but few organicMore surface water data

Framework

Classify Prioritise Risk

SOURCE

TypeReleaseLocation/geometryOrigin

CONTAMINANT

LoadingBehaviourHazardousness

RECEPTOR

VulnerabilityImpact

PrioritisingPrioritising contaminantscontaminantsGeneral ScreeningGeneral Screening

General knowledge of the threat to General knowledge of the threat to groundwater posed by the type of sourcegroundwater posed by the type of sourceNational or regional scaleNational or regional scale

Object SpecificObject SpecificSite specific info for rating/ranking Site specific info for rating/ranking contaminantscontaminantsLocalized scaleLocalized scale

Methods

Over 20 methods referred in literatureSelected methods reviewed in detail

General Screening MethodsKerndorff et al. (1992)

Statistical methods

Foster and Hirata (1988)Subsurface contaminant load

Johansson and Hirata (2000)Modified version of Foster and Hirata

Object Specific MethodsWASP

Waste disposal sites

Methods from minimum requirementsMull et al. (1992)

Rating and weighting

Knox and Canter (1994)Prioritization methods

Mechanisms of contaminationThe contaminant introduced into the soil-rock-groundwater system will only spread if a transport mechanism is available > various processes determine its fate:

physical processes: advection, dispersion, evaporation, filtration, and degassing;geochemical processes: acid-base reactions, adsorption-desorption, ion exchange, oxidation-reduction, precipitation-dissolution, retardation, and complexation; andbiochemical processes: transpiration, bacterial respiration, decay, and cell synthesis

Taken into account in a qualitative and semi-quantitative manner

RiskA risk can be defined broadly as the probability that an adverse event will occur in specified circumstances.

Risk assessmentsEffective decision-making involves the management of risks: the identification, evaluation, selection and implementation of actions to reduce risk. Risk assessment is a technique that

provides such information to the manager, thereby facilitating the complex and integrated decisions required.

Benefits of risk assessments

A clear articulation of the risk.Reveal the uncertaintiesInherently flexible.NB: There is not any single analytical method for combining information

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Hypothetical Example

Sustainability of a boreholeWater strikeRecharge

Fuzzy Rules – Professional knowledge

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Risk Calculation

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Aquifer protection zonesProtection zones have to defend against:• contaminants that decay with time, where

subsurface residence time is the best measure of protection

• nondegradable contaminants, where flowpath-dependent dilution must be provided.

Aquifer protection zones cont• Total source capture area• Microbial protection area• Wellhead operational zone• Further division

Behavior of organic contaminants in aquifers

Organic contaminant transport in subsurface > subject to host of influences (many not important in inorganic contamination hydrogeology)Organic compounds can exist either as pure or mixture or dissolved in waterSeveral physical and chemical properties of organic compounds responsible for behaviour in the subsurface including subsurface characteristics > play a major role in the transport and flow of NAPLs.

“Non-aqueous phase liquids”Organic contaminants that most commonly are associated with groundwater contamination are classified as NAPLsProcesses to follow to understand transport and risk

Determine NAPL source

Determine NAPL Propeties

Determine Vadose Zone Transport

Determine Groundwater Transport

Determine Risk

NAPL Properties and PlumesDetermine NAPL

Properties

Viscosity Density Chemicals Wetabbility Interfacial tension Volatility Mole fraction

NAPL properties

NAPL plumes

Factors which influence NAPL migration

SolubilityVolatilityDensityMedia parameters

PermeabilityBulk densityRetardation : fraction organic carbon

Mass distributionRelative Permeability

Vadose Zone considerationsSaturation ratioInterfacial tensionWettabilityCapillary pressure

Determine Vadose Zone Transport

Sorption Mass Distribution Volatility

Find Wetability and Interfacial tensions

Determine Capillary Pressure

Calculate Rate of Migration

Determine Changes of Relative Permeability

Van Genuchten approaches Brooks-Corey Approaches

Consider Hysteresis Effects

Determine Travel time to Water Table

Determine Expected Contaminant properties at

Interface

Use as input for Groundwater Transport

Transport below capillary zone

Understanding of NAPL plume behaviour >

Determine Groundwater Gradient

Determine aquifer and soil parametersBulk density, porosity, organic carbon ,

permability

Delineate Expected Plume

Determine Solubilities using Raoults law

Determine Volatility using Raoults law and Henry's Law

Determine mass distribution between phases

Use conventional flow and advective/dispersive equations to determine soluble plume

Determine retardation of organics

Determine decrease in concentration due to degradation according to known kinetics

Based on position of plume determine the date of leak or spill if possible.

Predict long-term behavior

Asses the risk

LNAPL specific parameters

Vertical drainage of LNAPL under gravity and capillary gradients (strongly influenced by soil characteristics)If large enough volume, it migrates down to capillary zoneDepresses water table and invades saturated poresIf spill is discontinuous the lateral spreading of the product will dominate and pool starts shrinking

Hydraulic factors influence shape and occurrence of LNAPL pool through spreading and smearingIn the saturated zone, a plume of dissolved species will develop. Their rate of migration is dependent on degree of retardation and degradation for each species.

DNAPL MigrationDetailed explanation in the reportHave attempted to illustrate the effects of different important factors

Factors facilitating DNAPL penetration Typical circumstances

High DNAPL density Low interfacial tension Low viscosity Large DNAPL volume release High permeability Vertical and sub-vertical geological structure

Chlorinated solvents PCB Aroclors Surfactants or miscible co-solvents such as methanol, methyl ethyl ketone or acetone in the DNAPL. Complex DNAPL mixtures. Chlorinated solvents Disposal of bulk liquid wastes in landfills, lagoons. On-going leakages. Sand, gravel and fractured rock. Angled beddings in sandy aquifers. Fractures, fissures, erosional windows in fine-grained aquitards. Fractured rock.

Product 1: Inorganic and Organic Contaminants and Associated Sources in South Africa’s Urban

Catchments

ClassificationSources (urban settlements, industrial, mining, waste disposal, agriculture, miscellaneous)

Case StudiesContaminant Inventory (generic and urban centers)

Prioritisation (national and urban centers)

Case studiesTitle: Metal plating industryUrban area: Cape TownSource: Leaks and spills in storage and production areas, improper treatment and disposal of wastes. Major contaminants: Cyanide (15-210 mg/kg in soils), and trichloroethene (TCE, 6-4089µg/l). Chromium, nickel, cadmium and zinc are also potential contaminants.Aquifer type: Unconfined primary sand aquifer.General findings: Removal of contaminated soil and pump-and-treat programme (to control the contamination plume) were successful in decreasing TCE concentrations.Lessons learnt: Potentially toxic metal ions react with ligands and alter their behaviour in the subsurface.Reference: Morris et al. (2000)

Case StudiesTitle: Hydrogeology of the Main Karoo Basin Urban area: Free State TownsSource: Leakage from petrol stations and fuel depotsMajor contaminants: Benzene, Toluene, Ethylbenzene-Xylenes.Aquifer type: Weathered fractured rock aquifers.General findings: Concentrations several orders above suggested limits. Dissolved phase contamination severe even where no free phase was detectedLessons learnt: Low permeability rocks can still cause widespread contaminant plumes. Absence of free phase does not indicate there is no pollution. Even in small towns NAPL pollution can be very problematic.Reference: Woodford and Chevalier (eds). (2002)

Classes of industriesUrban settlement MiningAgricultureNon-metallurgical IndustriesMetallurgical and Metal Products Manufacturing43 types of activity considered and potential groundwater contaminant identified

Generic InventoryType of source Expected contaminants Comment

Urban settlement (Domestic/ Commercial):

Wastewater treatmentAmmonium, nitrate, potassium, phosphate, chloride, sulphate, COD, diverse industrial chemicals, faecal pathogens, metals

Depending on the type of water treatment process and management of the system, the likelihood of groundwater contamination may increase.

Stormwater/ sewer systems Ammonium, nitrate, potassium, chloride, sulphate, DOC, hydrocarbons, faecal pathogens, diverse industrial chemicals

Likelihood of groundwater contamination dependant on the type and integrity of the network

On-site sanitation Nitrate, potassium, chloride, COD, faecalpathogens, phosphate, boron

Present in all urban areas where rapid urbanisation / informal settlement takes place, typical of SA conditions

Cemeteries Ammonium, potassium, microbial pathogens Often located on outskirts of urban area

Transport

Benzene, toluene, xylenes (BTEX), oxygenates (alcohols, MTBE), metals (lead, nickel), sulphur, alkanes, TPH, PAH, any other chemicals transported resulting from accidents or spills

Accidents and spills in urban area often cleaned up quickly after reporting

Gauteng as egType of source Expected contaminants Examples/ Comments

Urban settlement (Domestic/

Commercial):

Wastewater treatment Ammonium, nitrate, potassium, phosphate, chloride, sulphate, COD, diverse

industrial chemicals, faecal pathogens, metals

No figure is available on the number of waste water works in

Gauteng. 345,000 cubic meters of effluent is treated daily at several

water treatment works in Pretoria

Stormwater/ sewer systems Ammonium, nitrate, potassium, chloride, sulphate, DOC, hydrocarbons, faecal

pathogens, diverse industrial chemicals

On-site sanitation Nitrate, potassium, chloride, COD, faecal pathogens, phosphate, boron

About 88% of Gauteng households used a flush/chemical toilet in

1999, with 10% using a pit latrine and 1% using a bucket or other

system. (In 1996, 83% used a flush toilet in Gauteng.) The bucket

system will be eradicated by 2007 in the whole of Gauteng. 13% of

Pretoria have on-site sanitation.

Product 2: Guidelines for assessing and evaluating impacts of human activities

on groundwater resources in urban catchmentsCharacteristics of urban contamination of groundwater (Recharge and Mechanisms)Physiochemical properties affecting migration of groundwater contaminantsMethods for prioritising groundwater contaminants and sourcesPrioritisation of contaminants and sources in South African urban environments (ranking and risk)Example Case Study – CPT

National ranking ofsources based on aweighting system

National ranking of contaminants based on a weighting system

TIERS

Level 0Prioritisation of sources on a regional/local scale based on:

• Possible contaminants • Frequency of occurrence • Level of management

Prioritisation of contaminants based on • Source • Physio-chemical behaviour • Health impacts

Level 1Prioritisation of contaminants on a regional/local scale based on:

• Source • Physio-chemical behaviour • Exposure duration • Health impacts • Vulnerability of the aquifer

Level 2Prioritisation of contaminants on a local scale based on same aspects as level 1. However more field data is necessary and calculations are more complex. Urban recharge is also taken into account.

Protection zones for production boreholes

Product 3: Excel database

Structure and contents of databaseRanking of priority contaminantsUser manual (step-by-step)Case Study - CPT

Data information systemI. An inventory of inorganic and organic contaminants and associated sources in major urban areas of South Africa (Gauteng, Durban, Port Elizabeth, Cape Town)II. An inventory of properties of inorganic and organic contaminantsIII. A simple model for site-specific ranking of priority contaminants

Rao et al. (1982) model was included in the Excel database as a tool for prioritization and site-specific ranking of contaminantsattenuation and retardation factors of specific contaminantsHenry’s constant, half-life and organic carbon partitioning coefficient and user’s input of hydrogeological characteristics taken into account

Source PriotisationSource prioritisation (from highest to lowest risk) Source prioritisation (continued)On-site sanitation Marine maintenance industry Agricultural Chemicals (fertilisers, herbicides, pesticides) Dry cleaning activities

Cemeteries General/ Domestic waste sitesMetallurgical Wastewater treatmentMetal mining and coal mining Textile manufactureTransport Rubber and plastics Petrol Service Stations (Underground Storage Tanks) Non-metallic Mineral products - CementWood processing and preserving Leather manufacturing Feedlot/poultry farms Food and beverage manufacturingManufacturing - Chemicals Printing industry Workshops (Mechanical and electrical) Diamond, sand, calcrete and gravelStormwater/ sewer systems Shale, sandstone and graniteAutomotive refinishing and repair Auto Salvage/Metal RecyclersOther metal product manufacturing Electrical and electrical products manufacturingRailroad yards Electricity generationNon-metallic Mineral products Photographic manufacturing and uses Abattoir Paint/ink manufacturing and coatings Agriculture (General and crop cultivation) Pharmaceuticals and Cosmetics manufacturing Paper/pulp industry Adhesives and sealentsResearch and educational institutions Automotive parts manufacturingPetroleum refining and reuse Automotive manufacturingSolvents, chlorinated Wool processingSolvents (nonchlorinated) Hospitals / Health CareMunitions manufacturing Glass manufacturing Hazardous waste sites Incinerators

Contaminant prioritisation (from highest to lowest risk)

Contaminant prioritisation (from highest to lowest risk)

Contaminant prioritisation (from highest to lowest risk)

Contaminant prioritisation (from highest to lowest risk)

Chlordane Methylene Chloride Antimony PCEHCH Tebuthiuron Diuron Oxylic AcidLindane Phosphoric Acid Heptane NaphthaleneDDD Monosodium-Methyl

ArsenateChlorobenzene Methane

Butadiene Isopropanol Dioxin IronTrichloroethylene Acetone Hexane AsbestosTCE Strontium Tetrachlorobenzene GlycolDichloromethane Mercury Sulphate Fluorocarbon 113Tetrachloromethane Cadmium Nickel FloridebenzenePhenol Nitrite Methanol DOCAtrazine Nitrate Manganese CODTCA Aldicarb Fluoride ChloropyrifosFormaldehyde Xylene Ethylbenzene ChlorofluoroethaneCreosote Trichloroethane 1,1,1,- Ethyl Alcohol ChlorideDichlorobenzene Pentachlorophenol Ethyl Acetate CalciumMEK Lead Cobalt ButaneAmmonium Ethylene oxide Ammonia BismuthEthanol Ethylene Dibromide Vanadium AcetyleneAcrylonitrile Dioxane 1,4 Tri-n-Nutyltin Oxide PhthalatesVinyl Chloride Chlorine Dioxide Asbestos AluminiumUranium Carbon Tetrachloride Titanium ZincTrichlorophenol 2,4 Beryllium Styrene TinDichloropropane 1,2 Benzidine Sodium SilverDichlorophenol 2,4 Trichlorobenzene Silver Bromide SeleniumCyanide Toluene Silane Hydrochloric acidChromium VI Sulphur Potassium Dichromate CopperChlorine Dichloroethylene Potassium Chromium IIIBenzene DDE Phosphate BoronArsenic Chloroform Perchloroethylene

ConclusionsOf great concern is the fact that for many of these the currently available datasets show that very little attention has been paid to the constituents in most groundwater monitoring programs

Petroleum products, industrial thinners and mineral oils and other non-aqueous phase liquidsmicrobial contaminantspesticidesHigh nitrate

• Petroleum products, industrial thinners and mineral oils and other non-aqueous phase liquids represent a category of potential pollutants that have been largely overlooked by regulatory agencies and legislature, despite their harmful effects at small concentrations. There is an urgent need for published research into NAPL contamination in South Africa. • Based on the paucity of groundwater-related microbial data encountered in this project, the inclusion of these aspects in urban groundwater management must be regarded as a priority. •

A general lack of data on groundwater pollution from pesticides is evident.There is therefore need to monitor groundwaters and to develop modeling tools for the prediction of the fate and behaviour of pesticides.• High nitrate concentrations have been found to occur from sources ranging from agricultural fertilizing (especially the application of sludge to land) to pit latrines and explosives companies. There is, no directed programme to monitor nitrate in urban and peri-urban areas and hence the gap in information.

•Based on the recommendation of the Steering committee, aquifer vulnerability considerations have not received detailed attention in this project. It is recommended that the national vulnerability and prioritisation results be merged at some point in the future to improve site-specific and regional identification and prioritisation of areas of concern.

SoftwareUrban Risk Assessment Software (URA)

PrioritisationTier 0 to Tier 2 Risk assessmentRisk LogProtection Zones

Excel databaseAn inventory of contaminants and sources in major urban areas of South Africa An inventory of properties of contaminantsA simple model for site-specific ranking of priority contaminants

Some thoughts for AVAP

The need for vulnerability aspects has been highlighted by the prioritisation projectOrganics should be a big part of the projectThe special purpose vulnerability classification is vital (general approaches will only go so far !)Data is hard to come by !Most site owners are reluctant to share experiencesDWAF has not yet given unequivocal indication that research sites will be given leeway

And more…

Thank You