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Australian Drinking Water Guidelines
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  • Australian Drinking Water Guidelines
  • Copyright
  • Table of updates
  • Contents
  • Figures
  • Tables
  • Boxes
  • Introduction
    • Chapter 1: Introduction
      • 1.1 Guiding principles
      • 1.2 About the Guidelines
        • 1.2.1 Scope of the Guidelines
        • 1.2.2 Purpose of the Guidelines
        • 1.2.3 Structure of the Guidelines
      • 1.3 Water quality characteristics
        • 1.3.1 Introduction
        • 1.3.2 Health-based targets
        • 1.3.3 Microbial health-based targets
        • 1.3.4 Physical and chemical guideline values
        • 1.3.5 Radiological screening and reference values
      • 1.4 Community consultation
      • 1.5 Development of the Guidelines
        • 1.5.1 Acknowledgments
      • 1.6 Future revisions of the Guidelines
      • 1.7 References
  • Part 1: Management of Drinking Water Quality
    • Chapter 2: Framework for Management of Drinking Water Quality: overview
      • 2.1 A preventive strategy from catchment to consumer
      • 2.2 Structure of the Framework
      • 2.3 Benefits of the Framework
      • 2.4 The need for multi-agency involvement
      • 2.5 Applying the Framework
      • 2.6 Correlations of the Framework with other systems
    • Chapter 3: Framework for Management of Drinking Water Quality: the twelve elements
      • 3.1 Commitment to drinking water quality management (element 1)
        • 3.1.1 Drinking water quality policy
        • 3.1.2 Regulatory and formal requirements
        • 3.1.3 Engaging stakeholders
      • 3.2 Assessment of the drinking water supply system (element 2)
        • 3.2.1 Water supply system analysis
        • 3.2.2 Assessment of water quality data
        • 3.2.3 Hazard identification and risk assessment
      • 3.3 Preventive measures for drinking water quality management (element 3)
        • 3.3.1 Preventive measures and multiple barriers
        • 3.3.2 Critical control points
      • 3.4 Operational procedures and process control (element 4)
        • 3.4.1 Operational procedures
        • 3.4.2 Operational monitoring
        • 3.4.3 Corrective action
        • 3.4.4 Equipment capability and maintenance
        • 3.4.5 Materials and chemicals
      • 3.5 Verification of drinking water quality (element 5)
        • 3.5.1 Drinking water quality monitoring
        • 3.5.2 Consumer satisfaction
        • 3.5.3 Short-term evaluation of results
        • 3.5.4 Corrective action
      • 3.6 Management of incidents and emergencies (element 6)
        • 3.6.1 Communication
        • 3.6.2 Incident and emergency response protocols
      • 3.7 Employee awareness and training (element 7)
        • 3.7.1 Employee awareness and involvement
        • 3.7.2 Employee training
      • 3.8 Community involvement and awareness (element 8)
        • 3.8.1 Community consultation
        • 3.8.2 Communication
      • 3.9 Research and development (element 9)
        • 3.9.1 Investigative studies and research monitoring
        • 3.9.2 Validation of processes
        • 3.9.3 Design of equipment
      • 3.10 Documentation and reporting (element 10)
        • 3.10.1 Management of documentation and records
        • 3.10.2 Reporting
      • 3.11 Evaluation and audit (element 11)
        • 3.11.1 Long-term evaluation of results
        • 3.11.2 Audit of drinking water quality management
      • 3.12 Review and continual improvement (element 12)
        • 3.12.1 Review by senior executive
        • 3.12.2 Drinking water quality management improvement plan
      • 3.13 References
    • Chapter 4: Framework for the Management of Drinking Water Quality: application to small water supplies
      • 4.1 Introduction
      • 4.2 Applying the Framework
        • 4.2.1 Assessment of the drinking water supply
        • 4.2.2 Preventive measures for drinking water quality management
        • 4.2.3 Implementation of operational procedures and process control
        • 4.2.4 Verification of drinking water quality
      • 4.3 Individual household supplies
      • 4.4 Reference
  • Part 2: Description of Water Quality
    • Chapter 5: Microbial Quality of Drinking Water (Updated 2022)
      • 5.1 Introduction
      • 5.2 Microorganisms in drinking water
      • 5.3 Assessing microbial risk
      • 5.4 Enteric pathogens
        • 5.4.1 Enteric pathogens of concern in drinking water
        • 5.4.2 Contamination of source waters with enteric pathogens
        • 5.4.3 Management of risk from enteric pathogens
      • 5.5 Opportunistic pathogens
      • 5.6 Cyanobacteria
      • 5.7 Nuisance organisms
        • 5.7.1 Organisms causing taste and odour problems
        • 5.7.2 Organisms causing colour problems
        • 5.7.3 Deposits due to iron and manganese bacteria
        • 5.7.4 Corrosion problems due to iron and sulphur bacteria
        • 5.7.5 Problems caused by large numbers of microorganisms
      • 5.8 References
    • Chapter 6: Physical and Chemical Quality of Drinking Water
      • 6.1 Introduction
      • 6.2 Physical quality of drinking water
        • 6.2.1 An overview of physical characteristics
        • 6.2.2 Approach used in derivation of guidelines values for physical characteristics
      • 6.3 Chemical quality of drinking water
        • 6.3.1 Inorganic chemicals
        • 6.3.2 Organic compounds (Revised 2011)
        • 6.3.3 Approach used in derivation of guideline values for chemicals
      • 6.4 Differences between Australian and WHO guideline values
      • 6.5 National and international guideline values (2016)
      • 6.6 References
    • Chapter 7: Radiological Quality of Drinking Water (Updated 2022)
      • 7.1 Introduction
      • 7.2 Sources of radiation in the environment and in drinking water
      • 7.3 Health effects of radiation
      • 7.4 Exposure to radiation
      • 7.5 Units of radioactivity and radiation dose measurement
        • 7.5.1 Units of radioactivity and radiation dose
        • 7.5.2 Converting intake to radiation dose
        • 7.5.3 Average dose of radiation
      • 7.6 Approach for derivation of reference levels and screening values for radionuclides
        • 7.6.1 System for radiation protection
        • 7.6.2 Estimation of the dose from radionuclides in water
        • 7.6.3 Estimation of risk from low-level radiation
        • 7.6.4 Reference levels and screening values for drinking water
        • 7.6.5 Application of reference levels
        • 7.6.6 Remedial measures
      • 7.7 References
    • Chapter 8: Drinking Water Treatment Chemicals (Revised 2006)
      • 8.1 Introduction
      • 8.2 Scope and limit of application of this chapter
      • 8.3 Overview of chemical treatment processes
        • 8.3.1 Control of algae
        • 8.3.2 Coagulation and flocculation
        • 8.3.3 Adsorption
        • 8.3.4 Softening
        • 8.3.5 Oxidation
        • 8.3.6 Disinfection
        • 8.3.7 Adjustment of pH
        • 8.3.8 Addition of buffering capacity
        • 8.3.9 Corrosion inhibition
      • 8.4 Public health measures
        • 8.4.1 Fluoridation
      • 8.5 Assessment of Chemicals acceptable for use in drinking water treatment (revised 2016)
        • 8.5.1 Chemicals assessed prior to 2004
        • 8.5.2 New water treatment chemicals
      • 8.6 Quality assurance for drinking water treatment chemicals
        • 8.6.1 Risks associated with drinking water chemicals
        • 8.6.2 Managing risks
        • 8.6.3 Specifications for the supply of drinking water treatment chemicals
      • 8.7 Monitoring and analytical requirements
      • 8.8 Contaminants in drinking water treatment chemicals
      • 8.9 Useful contacts
      • 8.10 References
  • Part 3: Monitoring
    • Chapter 9: Overview of monitoring (Revised 2021)
      • 9.1 Introduction
      • 9.2 Monitoring overview
        • 9.2.1 Monitoring priorities
        • 9.2.2 Principles of monitoring frequency
        • 9.2.3 Catchment-to-consumer monitoring
      • 9.3 Developing a monitoring program
      • 9.4 Operational monitoring
        • 9.4.1 Operational characteristics
        • 9.4.2 Target criteria
        • 9.4.3 Critical limits at critical control points
        • 9.4.4 Corrective action
        • 9.4.5 Operational monitoring frequency
        • 9.4.6 Chlorination as a critical control point: an example
      • 9.5 Verification of drinking water quality
        • 9.5.1 Monitoring consumer satisfaction
        • 9.5.2 Drinking water quality monitoring
      • 9.6 Water quality issues beyond the point of supply
      • 9.7 Investigative studies and research monitoring
      • 9.8 Validation of barrier performance
      • 9.9 Incident and emergency response monitoring
      • 9.10 Reliability of monitoring data
        • 9.10.1 Sample integrity
        • 9.10.2 Methods
        • 9.10.3 Detection limits
        • 9.10.4 Measurement uncertainty
        • 9.10.5 Field testing
      • 9.11 Monitoring advice for small, remote or community-managed water supplies
      • 9.12 Assessing the significance of short-term exceedances of health-based guideline values
      • 9.13 References
    • Chapter 10: Monitoring for specific characteristics in drinking water (Updated 2022)
      • 10.1 Introduction
      • 10.2 Assessing safety: short-term evaluation of monitoring
        • 10.2.1 Short-term evaluation of operational monitoring
        • 10.2.2 Short-term evaluation of drinking water quality monitoring
      • 10.3 Assessing performance: long-term evaluation of monitoring
        • 10.3.1 Long-term evaluation of microbial performance
        • 10.3.2 Long-term evaluation of health-based chemical performance
        • 10.3.3 Long-term evaluation of aesthetic performance
        • 10.3.4 Long-term evaluation of consumer satisfaction
        • 10.3.5 Improvement plan
        • 10.3.6 Performance reporting
        • 10.3.7 Summary of guideline values for microbial, chemical and physical characteristics
        • 10.3.8 Summary of reference levels and screening values for radiological characteristics
      • 10.4 Reference
  • Part 4: Information sheets
    • 1. Disinfection
      • 1.1: Introduction to water treatment
      • 1.2: Overview of disinfection
      • 1.3: Disinfection with chlorine
      • 1.4: Chloramines
      • 1.5: Disinfection with chlorine dioxide
      • 1.6: Disinfection with ozone
      • 1.7: Disinfection with ultraviolet light
      • 1.8: Other disinfectants
    • 2. Sampling
      • 2.1: Sampling Information – handling requirements and preservation
      • 2.2: Radiological monitoring and assessment of performance (updated 2022)
    • 3. Statistics
      • 3.1: Statistics – Visualising data
      • 3.2: Statistics – Assessing data
      • 3.3: Statistics – Statistical principles
      • 3.4: Statistics – Control charts and trends
      • 3.5: Number of samples required
      • 3.6: Guidance for issuing and lifting boil water advisories
      • Attachments
  • Part 5: Fact sheets
    • Microorganisms
      • Microbial indicators
        • Bacteroides
        • Coliphages
        • Clostridium perfringens
        • Escherichia coli
        • Heterotrophic plate counts
        • Intestinal enterococci
        • Thermotolerant coliforms
        • Total coliforms
      • Bacteria
        • Aeromonas
        • Burkholderia pseudomallei
        • Campylobacter
        • Escherichia coli (E. coli) (pathogenic)
        • Helicobacter pylori
        • Klebsiella
        • Legionella
        • Mycobacterium
        • Pseudomonas aeruginosa
        • Salmonella
        • Shigella
        • Vibrio
        • Yersinia
      • Protozoa
        • Acanthamoeba
        • Blastocystis
        • Cryptosporidium
        • Cyclospora
        • Giardia
        • Naegleria fowleri
      • Cyanobacteria and their toxins
        • Cyanobacteria and their toxins
        • Cylindrospermopsin
        • Microcystins
        • Nodularin
        • Saxitoxins
      • Viruses
        • Adenovirus
        • Enterovirus
        • Hepatitis viruses
        • Norovirus
        • Rotavirus
    • Physical and chemical characteristics
      • Acephate
      • Acrylamide
      • Aldicarb
      • Aldrin and Dieldrin
      • Aluminium
      • Ametryn
      • Amitraz
      • Amitrole
      • Ammonia
      • Antimony
      • Arsenic
      • Asbestos
      • Asulam
      • Atrazine
      • Azinphos-methyl
      • Barium
      • Benomyl
      • Bentazone
      • Benzene
      • Beryllium
      • Bioresmethrin
      • Boron
      • Bromacil
      • Bromate
      • Bromoxynil
      • Cadmium
      • Captan
      • Carbaryl
      • Carbendazim/Thiophanate-methyl
      • Carbofuran
      • Carbon tetrachloride
      • Carboxin
      • Carfentrazone-ethyl
      • Chloral hydrate (Trichloroacetaldehyde)
      • Chlorantraniliprole
      • Chlordane
      • Chlorfenvinphos
      • Chloride
      • Chlorinated furanones
      • Chlorine
      • Chlorine dioxide, Chlorite, Chlorate
      • Chloroacetic acids: chloroacetic acid, dichloroacetic acid (DCA), trichloroacetic acid (TCA)
      • Chlorobenzene
      • Chloroketones
      • Chlorophenols
      • Chloropicrin
      • Chlorothalonil
      • Chlorpyrifos
      • Chlorsulfuron
      • Chromium
      • Clopyralid
      • Colour (True)
      • Copper
      • Cyanide
      • Cyanogen chloride
      • Cyfluthrin, Beta-cyfluthrin
      • Cypermethrin isomers
      • Cyprodinil
      • 2,4-D [(2,4-Dichlorophenoxy) acetic acid]
      • DDT (1,1,1-trichloro-di-(4-chlorophenyl) ethane)
      • Deltamethrin
      • Diazinon
      • Dicamba
      • Dichlorobenzenes
      • Dichloroethanes: 1,1-dichloroethane, 1,2-dichloroethane
      • Dichloroethenes: 1,1-dichloroethene (1,1-DCE), 1,2-dichloroethene (1,2-DCE)
      • Dichloromethane (methylene chloride)
      • 1,3-Dichloropropene
      • Dichlorprop/Dichlorprop-P
      • Dichlorvos
      • Diclofop-methyl
      • Dicofol
      • Diflubenzuron
      • Dimethoate
      • Diquat (ion), Diquat dibromide
      • Dissolved oxygen
      • Disulfoton
      • Diuron
      • 2,2-DPA
      • Endosulfan
      • Endothal
      • Epichlorohydrin
      • EPTC
      • Esfenvalerate
      • Ethion
      • Ethoprophos
      • Ethylbenzene
      • Ethylenediamine tetraacetic acid (EDTA)
      • Etridiazole
      • Fenamiphos
      • Fenarimol
      • Fenchlorphos
      • Fenitrothion
      • Fenthion
      • Fenvalerate
      • Fipronil
      • Flamprop-methyl
      • Fluometuron
      • Fluoride
      • Flupropanate
      • Formaldehyde
      • Glyphosate
      • Haloacetonitriles
      • Haloxyfop
      • Hardness (as calcium carbonate)
      • Heptachlor and heptachlor epoxide
      • Hexachlorobutadiene
      • Hexazinone
      • Hydrogen sulfide, Sulfide
      • Imazapyr
      • Iodine, Iodide
      • Iprodione
      • Iron
      • Lanthanum
      • Lead
      • Lindane
      • Maldison (Malathion)
      • Mancozeb
      • Manganese
      • MCPA
      • Mercury
      • Metaldehyde
      • Metham
      • Methidathion
      • Methiocarb
      • Methomyl
      • Methyl bromide
      • Metiram
      • Metolachlor/s-Metolachlor
      • Metribuzin
      • Metsulfuron-methyl
      • Mevinphos
      • Molinate
      • Molybdenum
      • Monochloramine
      • Naphthalophos
      • Napropamide
      • Nicarbazin
      • Nickel
      • Nitrate and nitrite
      • Nitrilotriacetic acid (NTA)
      • N-Nitrosodimethylamine (NDMA)
      • Norflurazon
      • Omethoate
      • Organotins: dialkyltins, tributyltin oxide
      • Oryzalin
      • Oxamyl
      • Paraquat
      • Parathion
      • Parathion-methyl
      • Pebulate
      • Pendimethalin
      • Pentachlorophenol
      • Per-fluoroalkyl and poly-fluoroalkyl substances (PFAS)
      • Permethrin
      • pH
      • Picloram
      • Piperonyl butoxide
      • Pirimicarb
      • Pirimiphos methyl
      • Plasticisers
      • Polihexanide
      • Polycyclic aromatic hydrocarbons (PAHs)
      • Profenofos
      • Promecarb
      • Propachlor
      • Propanil
      • Propargite
      • Propazine
      • Propiconazole
      • Propyzamide
      • Pyrasulfotole
      • Pyrazophos
      • Pyroxsulam
      • Quintozene
      • Radionuclides, Specific Alpha and Beta Emitting
      • Radium (radium-226 and radium-228)
      • Radon-222
      • Selenium
      • Silica
      • Silver
      • Simazine
      • Sodium
      • Spirotetramat
      • Styrene (vinylbenzene)
      • Sulfate
      • Sulprofos
      • Taste and Odour
      • Temephos
      • Temperature
      • Terbacil
      • Terbufos
      • Terbuthylazine
      • Terbutryn
      • Tetrachloroethene
      • Thiobencarb
      • Thiometon
      • Thiram
      • Tin
      • Toltrazuril
      • Toluene
      • Total dissolved solids
      • Triadimefon
      • Trichlorfon
      • Trichlorobenzenes
      • 1,1,1-Trichloroethane
      • Trichloroethylene (TCE)
      • Triclopyr
      • Trifluralin
      • Trihalomethanes (THMs)
      • Turbidity
      • Uranium
      • Vernolate
      • Vinyl chloride
      • Xylenes
      • Zinc
    • Drinking water treatment chemicals
      • Aluminium chlorohydrate
      • Aluminium sulfate (alum)
      • Ammonia
      • Ammonium sulfate
      • Calcium hydroxide
      • Calcium hypochlorite
      • Calcium oxide
      • Carbon, granulated activated
      • Carbon, powdered activated
      • Chlorine
      • Copper sulfate
      • Ferric chloride
      • Ferric sulfate
      • Hydrochloric acid
      • Hydrofluorosilicic acid
      • Hydrogen peroxide
      • Hydroxylated ferric sulfate
      • Ozone
      • Polyacrylamide
      • Polyaluminium chloride
      • Polyaluminium silica sulfates
      • Polydiallyldimethylammonium chloride
      • Potassium permanganate
      • Sodium aluminate
      • Sodium bicarbonate
      • Sodium carbonate
      • Sodium fluoride
      • Sodium fluorosilicate
      • Sodium hexametaphosphate
      • Sodium hydroxide
      • Sodium hypochlorite
      • Sodium silicate
      • Sodium tripolyphosphate
      • Sulfuric acid
      • Zinc orthophosphate
  • Appendices
    • Appendix 1: Additional guidance
      • A1.1 Introduction
      • A1.2 Water supply system analysis
      • A1.3 Assessment of water quality data
      • A1.4 Hazard identification
      • A1.5 Risk assessment
      • A1.6 Preventive measures and multiple barriers
      • A1.7 Critical control points
      • A1.8 Chlorination as an example of a critical control point
      • A1.9 References
    • Appendix 2: Further sources of information on drinking water quality management
      • A2.1 Drinking water quality management - general
      • A2.2 Catchment management and source water protection
      • A2.3 Groundwater protection
      • A2.4 Risk assessment and management
      • A2.5 System analysis and management process control and optimisation
      • A2.6 Monitoring and verification
      • A2.7 Materials and chemicals
      • A2.8 Incident and emergency management
      • A2.9 Employee training and awareness
      • A2.10 Research and development
      • A2.11 Documentation and reporting
      • A2.12 Community consultation and communication
      • A2.13 Hazard analysis and critical control point (HACCP)
      • A2.14 Quality management continuous improvement
      • A2.15 Reference web sites
    • Appendix 3: Derivation of microbial treatment targets for enteric pathogens
      • A3.1 Introduction to Quantitative Microbial Risk Assessment (QMRA)
      • A3.2 Adopting the QMRA approach in the Guidelines
      • A3.3 QMRA framework for the calculation of log₁₀ reduction values (LRVs)
      • A3.4 Defining the health outcome target
      • A3.5 Selection of reference pathogens
      • A3.6 Level of reference pathogen contamination in Australian source waters
      • A3.7 Consumption volume of unheated (unboiled) water per person per day
      • A3.8 Dose response relationships
      • A3.9 Disability Adjusted Life Years (DALY) burden per case
      • A3.10 Calculation of LRVs using the QMRA framework
      • A3.11 Interpretation of calculated LRVs for practical treatment guidance
      • A3.12 Understanding log₁₀ reductions
      • A3.13 References
  • Glossary
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On this page
  • General description
  • Chemistry
  • Typical use in Australian drinking water treatment
  • Contaminants
  • Residual and by-product formation in drinking water
  • Status
  • References
  1. Part 5: Fact sheets
  2. Drinking water treatment chemicals

Aluminium sulfate (alum)

(endorsed 2005)

PreviousAluminium chlorohydrateNextAmmonia

Last updated 11 months ago

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Australian Drinking Water Guidelines 6 2011, v3.9

  • Go back to NHMRC website

Aluminium sulfate (alum) is a general purpose coagulant that is used in water treatment to remove turbidity, natural organic matter (NOM) (including colour), microorganisms and many inorganic chemicals. Removal of NOM reduces the formation of disinfection by-products, because it removes the organic precursors of the by-products.

General description

For use in water treatment, aluminium sulfate (alum) is generally supplied as a bulk liquid, but it can also be supplied in granular form. The concentration of the supplied liquid solution varies, and users should establish the concentration with the supplier. Typically, alum solutions contain 7.5–8.4% Al2O3\text{Al}_{2}\text{O}_{3}Al2​O3​ w/w (i.e. 43–50% w/w Al2(SO4)3⋅14H2O\text{Al}_{2}\text{(SO}_{4}\text{)}_{3}\cdot\text{14H}_{2}\text{O}Al2​(SO4​)3​⋅14H2​O, and have a specific gravity of 1.28–1.34 at 20°C. Solutions at the upper end of the available strengths may become unstable at low temperatures.

Alum is also available as a crystalline solid with varying degrees of hydration (14–18 H2O\text{H}_2\text{O}H2​O). It has a pH of 1.2–3.0 and can be stored in rubber-lined containers or in fibreglass, stainless steel (type 316) or plastic.

Chemistry

Alum is produced by the reaction of sulfuric acid with an aluminium-rich ore such as refined bauxite.

In water, the aluminium ion reacts with natural alkalinity (hydroxyl or bicarbonate) or added alkalinity (lime, caustic soda or soda ash) to form aluminium hydroxide species. The hydrolysis proceeds as follows:

Al2(SO4)3⋅6H2O↔2Al(OH)3+6H++3SO42−\text{Al}_{2}\text{(SO}_{4}\text{)}_{3}\cdot\text{6H}_{2}\text{O}\leftrightarrow\text{2Al}\text{(OH)}_{3}+\text{6H}^{+}+\text{3SO}_{4}^{2-}Al2​(SO4​)3​⋅6H2​O↔2Al(OH)3​+6H++3SO42−​

As the hydrolysis reactions proceed, mononuclear products can form polynuclear species. The reactions are complex and the species formed are quite variable. Examples of the species formed are:

  • mononuclear: Al OH2+\text{Al OH}^{2+}Al OH2+, Al(OH)2+\text{Al}(\text{OH})_2^+Al(OH)2+​, Al(OH)3\text{Al}(\text{OH})_3Al(OH)3​ (solid precipitate), Al(OH)4−\text{Al}(\text{OH})_4^-Al(OH)4−​

  • polynuclear: Al8(OH)204+\text{Al}_8(\text{OH})_{20}^{4+}Al8​(OH)204+​, Al13O4(OH)247+\text{Al}_{13}\text{O}_4(\text{OH})_{24}^{7+}Al13​O4​(OH)247+​

The generally positively charged Al species are available to interact with negatively charged colloidal matter in water. Such matter includes inorganic turbidity particles and the high molecular weight fraction of organic compounds present in NOM. The interaction destabilises the repulsive forces between the negatively charged particles, allowing them to collide and agglomerate to form microfloc (a process referred to as adsorption–destabilisation).

At higher concentrations of alum, metal hydroxides precipitate and can enmesh any colloidal particles in a process known as ‘sweep coagulation’, which renders water suitable for clarification. Alum has an optimum pH for coagulation of 5.5–7.5, with the lower end of the range (pH 5.5–6.2) being used for organics removal and enhanced coagulation (see below), and the higher end (pH 6.5–7.5) being used for sweep coagulation. Adsorption–destabilisation to form small floc, which can be removed by contact and direct filtration, typically occurs in the pH range 6–7.

‘Enhanced coagulation’ refers to coagulation at low pH with high doses of alum, and is used to remove NOM. The pH and alum dose need to be optimised, to maximise the removal of dissolved organic carbon (DOC).

Typical use in Australian drinking water treatment

The dose of alum used depends on the properties of the raw water, including (but not limited to) the turbidity, DOC, temperature and alkalinity. Waters of low turbidity often need higher doses of alum to bring about coagulation than more turbid waters. Indeed, waters of low turbidity and high colour are the most difficult to treat.

The dose rate for alum is expressed in different units throughout Australia, and it is important to take this into account when comparing rates.

Contaminants

The purity of chemicals used in Australia for the treatment of drinking water varies, depending on the manufacturing process. In Australia, alum is produced by reacting aluminium trihydroxide or refined bauxite with sulfuric acid, and most of the impurities in the alum are derived from these raw materials.

The following chemical contaminants may be present in alum (NRC 1982):

  • antimony

  • arsenic

  • barium

  • beryllium

  • cadmium

  • chromium

  • copper

  • fluoride

  • iron

  • lead

  • magnesium

  • manganese

  • mercury

  • nickel

  • phosphorus

  • selenium

  • silver

  • thallium

  • zinc

Residual and by-product formation in drinking water

When employed in drinking water treatment, alum should be used in such a way that any contaminant or by-product formed by the use of the chemical does not exceed guideline values in the Australian Drinking Water Guidelines.

Aluminium residuals after filtration can cause floc to form in the distribution system, which can cause customer complaints. To minimise residual levels of aluminium, alum should be used at pH and dosage conditions that exceed the solubility of aluminium. At 25°C, aluminium is least soluble at a pH near 6. At colder temperatures, the pH of minimum solubility increases. For example, at 4°C, aluminium is least soluble at pH 6.5–7. Hence, if water is treated at pH 6 throughout the year, levels of residual dissolved aluminium will be higher in winter. Poor dosage selection or inadequate mixing also leads to elevated aluminium residuals.

Status

Aluminium sulfate was endorsed by the NHMRC for use as a drinking water treatment chemical in 1983. The 2003 revision did not change the status of this chemical for the treatment of drinking water.

References

Amirtharajah A and Mills KM (1982). Rapid Mix Design for Mechanisms of Alum Coagulation. Journal of the American Water and Wastewater Association 74(4):210–216.

ANSI (American National Standards Institute)/AWWA (American Water and Wastewater Association) Standard no B403-98. AWWA CD-ROM (April 2003). Available at <www.awwa.org>

Clesceri LS, Greenberg AE and Eaton AD (eds) (1998). Standard Methods for the Examination of Water and Wastewater, 20th edition. American Public Health Association, Washington, DC.

Letterman RD, Amirtharajah A and O’Melia CR (1999). Coagulation and Flocculation. In: Water Quality and Treatment, A Handbook of Community Water Supplies, Letterman RD (ed), American Water Works Association, 5th edition. McGraw-Hill Professional, New York, 6.1–6.66.

NRC (National Research Council) (1982). Water Chemicals Codex. Committee on Water Treatment Chemicals, Food and Nutrition Board, Assembly of Life Sciences, NRC, Washington, DC.

Typical alum doses (expressed as mg/L Al2(SO4)3⋅14H2O\text{Al}_{2}\text{(SO}_{4}\text{)}_{3}\cdot\text{14H}_{2}\text{O}Al2​(SO4​)3​⋅14H2​O) range from 5 to 200 mg/L and may even be as high as 500 mg/L if the water is particularly dirty.