A1.4 Hazard identification

Adoption of a risk-based approach that includes the identification of hazards from catchment to consumer and the assessment of the potential impact on drinking water quality and human health (i.e. risk) is essential to effective system management. Hazard identification and risk assessment are useful for understanding the vulnerability of a drinking water supply and planning effective risk management strategies to assure drinking water quality and safety.

The purpose of this element is to identify and document all potential hazards and the hazardous events and sources that might give rise to the presence of these hazards.

Summary of actions

• Define the approach and methodology to be used for hazard identification. Devise an evaluation team with appropriate representatives.

• Review hazardous agents in drinking water and ensure that their link to public health is understood (see Section V — Fact Sheets).

• Identify and document hazards, sources and hazardous events for each component of the water supply system (see Tables A1.2 and A1.3).

• Periodically review and update the hazard identification to incorporate any new hazards.

A structured approach is important to ensure that significant issues are not overlooked and that areas of greatest risk are identified. There is no single right way to perform these activities; however, the process should involve a structured and comprehensive evaluation of the water supply system.

For each component of the water supply system, all hazards and hazardous events and sources that might affect drinking water quality and safety (what can happen and how) should be identified and documented. Table A1.2 provides examples of various pollution sources and the potential hazards they produce.

All potential hazards, hazardous events and sources should be included in the assessment, regardless of whether or not they are under the direct control of the drinking water supplier. Continuous, intermittent or seasonal pollution patterns should also be considered as well as extreme and infrequent events such as droughts or floods. Table A1.3 provides examples of potential sources and hazardous events, from catchment to consumer, to be considered.

Table A1.2 Examples of sources and potential hazardsᵃ

Potential sources	Potential hazard
Septic tanks	Pathogensᵇ, nitrates/nitrites
Sewage treatment plants	Pathogens, nutrients
Animal husbandry	Pathogens, nutrients, turbidity, colour
Horticulture	Pesticides, fertiliser nutrients, turbidity, colour
Rural stormwater	Pathogens, turbidity, colour
Forestry	Pesticides, turbidity, colour
Industry	Heavy metals, organic chemicals including halogenated organics; specific industries can be associated with specific types of contaminants (e.g. arsenic and copper associated with wood preserving, cadmium and chromium with electroplating and chromium with leather tanning)
Mining	Acid mine wastes from pyrites tailings can release and transport metals such as aluminium, iron and manganese; other naturally occurring metals such as cadmium and copper can also be leached; arsenic can be associated with old goldfield areas
Urban stormwater	Lead and zinc from roads, turbidity, colour, petrol/oil products, microorganisms from pets (lower range of pathogens than from humans or livestock waste)
Stormwater/sewer overflows	Pathogens, nutrients, turbidity, colour

ᵃ Human and animal waste represent the largest sources of potential hazards in drinking water. Both can include high numbers of enteric pathogens and large amounts of nutrients. Due to the scale of primary production in Australia, the total amount of livestock waste would greatly exceed the amount of human waste.

ᵇ The potential range of pathogens present will vary according to the type of waste involved. Many enteric pathogens, and in particular viruses and protozoa, infect only one species. In general, human enteric viruses are only carried and excreted by humans. Human infectious Cryptosporidium parvum can be carried by humans and livestock, but the current state of knowledge suggests that the species of Cryptosporidium that infect birds do not infect humans.

Table A1.3 Examples of hazardous events and their potential sources

Catchments and groundwater systems

Catchments and groundwater systems (continued)

Rapid variations in raw water quality Sewage and septic system discharges Industrial discharges Chemical use in catchment areas (e.g. use of fertilisers and agricultural pesticides) Major spills and accidental spillage Public roads Human access (recreational activity) Wildlife (native and feral) Unrestricted livestock Inadequate buffer zones Surrounding land use (e.g. animal husbandry, agriculture, forestry, industrial area, waste disposal, mining) Changes in surrounding land use

Poorly vegetated riparian zones, failure of sediment traps and soil erosion Stormwater flows and discharges Existing or historical waste-disposal or mining sites/ contaminated sites and hazardous wastes Unconfined and shallow aquifers Groundwater under direct influence of surface water Inadequate well-head protection and unhygienic practices Uncased or inadequately cased bores Saline intrusion of coastal aquifers Contaminated aquifers Climatic and seasonal variations (e.g. heavy rainfalls, droughts) Bushfires, natural disasters, sabotage

Storage reservoirs and intakes	Storage reservoirs and intakes (continued)
Open reservoirs and aqueducts, uncovered storages Human access/absence of exclusion areas around shorelines Animal access including birds and vermin Short-circuiting of reservoir Depletion of reservoir storage No selective withdrawal No alternative water sources Unsuitable intake location Cyanobacterial blooms	Stratification Soil erosion Inadequate buffer zones and vegetation Climatic and seasonal variations (e.g. heavy rainfalls, droughts) Public roads / accidental spillage Failure of alarms and monitoring equipment Bushfires and natural disasters Sabotage

Treatment systems	Treatment systems (continued)
Significant flow variations through water treatment system Incapable equipment or unit processes Inadequate backup Inappropriate treatment processes Process control incapability or operational inflexibility Use of unapproved or contaminated water treatment chemicals and materials Chemical dosing failures Inadequate mixing	Failure of dosing equipment Inadequate filter operation and backwash recycling Ineffective disinfection Equipment malfunctions Poor reliability of processes Failure of alarms and monitoring equipment Power failures Sabotage and natural disasters Formation of disinfection byproducts

Service reservoirs and distribution systems

Service reservoirs and distribution systems (continued)

Open reservoirs and aqueducts / uncovered storages and unprotected pipe system Human access, absence of exclusion areas around shorelines Animal access including birds and vermin Short-circuiting of reservoir, stagnation zones Buildup of sediments and slimes Inappropriate materials and coatings or material failure Aged pipes, infrastructure Corrosion of reservoirs and pipe system Mixing of different source waters Infiltration and ingress of contamination from cross-connections, backflow (soil and groundwater)

Biofilms, sloughing and resuspension, regrowth Pipe bursts or leaks Inadequate repair and maintenance, inadequate system flushing and reservoir cleaning Commissioning new mains Inadequate disinfection after construction, repairs Flow variability, inadequate pressures Treatment dosing failure Inadequate maintenance of chlorine residual Formation of disinfection byproducts Failure of alarms and monitoring equipment Sabotage and natural disasters

Consumers	Consumers (continued)
Potential consumer misuse Leaching of metals	Inappropriate plumbing and construction materials