Microbial analysis

Recycled water and biosolids sampling

Recycled water and biosolids (sewage sludge) contain many microbial contaminants that can affect human health.

Recycled water can be used to irrigate open spaces such as:

• lawns and gardens
• in agricultural and for dust suppression
• toilet flushing
• other beneficial purposes.

Similarly, sewage sludge can be treated to generate biosolids, which can be used as a fertilizer in agriculture and blended in composts.

To ensure the protection of public health, both recycled water and biosolids must be treated to a level that is fit for the intended end use.

A continual sampling program is required to prove that treatment is effective and compliant with either the:

• Guidelines for the non-potable uses of recycled water in Western Australia 2011 (PDF 1.9MB) 
• Western Australia guidelines for biosolids management (external site).

What are recycled waters and biosolids?

Recycled water is water generated from sewage or from industrial sources. It is treated to provide water that is fit for purpose.

Using recycled wastewater that is fit for purpose means it can be safely used for non-potable purposes such as:

• open space irrigation
• agricultural uses
• toilet flushing
• industrial purposes.

Sewage includes:

• Greywater – generated from:
  • washing machines
  • showers
  • baths
  • wash basins
  • spa baths
  • laundry tubs
  • the kitchen (when appropriately treated)
• Yellow water – generated from urinals
• Blackwater – generated from toilets.

A biosolid is sewage sludge generated from a wastewater treatment plant. It is not dewatered sewage.

Biosolids are treated to produce stabilised organic solid residue.

They have different quality ratings designed specifically to comply with fit for purpose quality criteria for their safe end use.

Biosolids may be applied to land as a fertiliser substitute on selected agricultural areas, forestry applications and the production of commercial composts.

Why test for microorganisms?

Indicator microorganisms are used as a simple and reliable measure of the potential risk to human health.

Before recycled water can be approved for reuse you will be required to demonstrate that the water quality (after treatment) complies with the microbial quality standard. This standard corresponds to the end use risk exposure level.

After an approval to recycle water has been issued you will be required to submit microbiological samples periodically. This will verify that the treatment system continually achieves the required water quality standards.

Biosolids can be approved for use once compliance with the pathogen grade for the intended end use has been demonstrated.

After gaining approval to use biosolids, you will be required to submit microbiological samples to verify that the treatment system complies with the required quality standards.

What microbial testing do I need to perform?

The type and frequency of microbial analysis will be specified in the conditions of approval provided to you by WA Health.

WA Health will set the sample location and frequency during the validation process. This will be used for ongoing verification monitoring.

The normal monitoring requirements are as follows:

Recycled Water

• E. coli (an indicator for bacteria) monitoring is required for all risk exposure levels.
• Coliphage (an indicator for viruses) monitoring is required for high risk exposure schemes.
• Clostridia (an indicator for protozoan oocysts) monitoring may also be required depending on the risk assessment provided to the Department of Health.
• Helminths (worms classified as disease-causing organisms) monitoring is required in endemic areas located north of the 20th parallel (mainly the Kimberly region). This monitoring is also required where recycled water is used to irrigate pasture and fodder for beef cattle or dairy animals.

Biosolids

• E. coli and Salmonellae are commonly monitored and results are reported in counts per gram of dry product.
• Coliphage monitoring may also be required before approval to use biosolids depending on the risk assessment provided to the Department of Health.
• Helminth monitoring may be required before approval where biosolids are to be produced/used above the 20th parallel.

Why is E. coli testing required?

In the past total coliform bacteria were used as an indicator of faecal contamination. However, not all coliform bacteria are of faecal origin.

Escherichia coli (E. coli) is an indicator of a number of human pathogens that may be present in faeces.

Therefore, E. coli is the preferred bacterial indicator organism to test wastewater, recycled water, sewage sludge and biosolids for faecal contamination.

Why is Coliphage testing required?

Coliphages are viruses that infect coliform bacteria and are considered to be representative of faecally derived viruses.

Coliphages have been identified as one of the most tolerant to temperature stress over other bacterial and viral indicators. They are useful as indicator organisms to evaluate the effectiveness of treatment technologies to remove potential human pathogenic viruses.

Is a NATA accredited laboratory required?

WA Health requires all microbiological analyses to be conducted by a laboratory accredited by the National Association of Testing Authorities, Australia (NATA).

NATA Laboratories are formally recognised as technically skilled to perform specific types of testing.

To maintain accreditation, the laboratories are reassessed regularly.

NATA accredited laboratories follow standard procedures, methods, inspection, testing and calibration to produce accurate results.

The NATA logo is included in the report of the microbial results.

How much the testing will cost?

The cost varies between different laboratories and over time. Please contact the NATA accredited laboratories listed below to obtain a quote.

Laboratories

• PathWest (external site)
• ProMicro (external site)
• Silliker Microtech (external site)
• MPL Laboratories (external site)
• SGS Australia (external site)
  
• ALS Global (external site)

What do I need to do before taking a sample?

Before you take a sample call the laboratory to obtain sample bottles and information on the correct sampling procedure.

Read about recycled water sampling techniques.

For biosolids sampling, a number of grab samples will be required. Refer to the Western Australian Guidelines for biosolids management before you take a sample.

Your sample will not provide  accurate information unless the:

• correct sample bottles are used
• correct volume is taken
• sample is stored at the required temperature
• sample is transported to and arrives at the laboratory within the correct time period
• correct procedure is used to take the sample.

Analytical methods required by the Department

Table No 1 lists the microbial tests for raw or treated recycled water samples and Table No 2 lists the microbial tests for biosolids or composting products.

* 1 Litre of sample is recommended

*Western Australian guidelines for biosolids management require Salmonella report as counts per 50g of dry product

• Legionella monitoring may be depending on the risk assessment provided to the Department of Health 
• MPN: Most probable number
• cfu: colony forming units
• pfu: plaque forming units

Related sites

• Application process for approval of recycling water scheme
• Recycled water sampling technique