Beneficial reuse of biosolids standard
The standard ensures biosolids are treated so they can be safely reused for beneficial purposes.
Note: We are aware of a typographical error in Schedule 2 1 (1)(a) of the Water Services (Wastewater Environmental Performance Standards) Regulations 2025. Grade 1 biosolids should contain more than 2% nitrogen. We are working to have the error corrected.
Biosolids are a nutrient- and energy-rich byproduct of the wastewater treatment process. Made up mostly of water and organic material, they can be safely reused when properly treated for a range of beneficial purposes such as helping rehabilitate land, generate heat energy, and produce biofuels, and other applications. Reusing biosolids also reduces landfill waste.
The standard has four steps to follow.
- Assess the stabilisation and contaminant grades of the biosolids.
- Determine the activity status based on the grades to identify how and when biosolids can be reused or stored.
- Check monitoring and reporting requirements – these align with the biosolids’ grade.
- Include and implement the requirements in the resource consent conditions.
The 2025 Guidelines for Beneficial Reuse of Biosolidsoutbound published by Water New Zealand provides additional detail on how to comply with the biosolids standard, including detail about how to discharge biosolids while managing the impacts on soils, water, plants, animals and people.
Where reuse of biosolids is enabled through the standards, a consenting authority cannot grant a resource consent that imposes requirements that are different from those in the standards. This includes treatment limits for key contaminants as well as monitoring and reporting requirements. Where a consent is approved, it must be issued for a 35-year duration. Consenting authorities maintain discretion over matters not covered by the standards.
Biosolid grading
The grading will reflect how well the product has been treated to reduce harmful pathogens and limit its ability to attract pests, as well as how much metal and chemical contamination it contains.
The activity status for the biosolids is also determined by their grade – A1, A2, B1 or B2.
Stabilisation grade
Biosolids are stabilisation grade A if during processing:
- they have undergone at least one pest reduction method
- they have undergone at least one pathogen reduction process
- and, after processing, they do not exceed a pathogen standard as provided in the table below.
|
Pathogen |
Standard |
|
E. coli |
100 most probable number per gram of biosolid |
|
Campylobacter |
1 most probable number per 25 grams of biosolid |
|
Salmonella |
2 most probable number per gram of biosolid |
|
Human adenovirus |
1 plaque-forming unit per 0.25 grams of biosolid |
|
Helminth ova |
1 egg per 4 grams of biosolid |
Biosolids are stabilisation grade B if during processing:
- they have undergone at least one pest reduction method but have not undergone a pathogen reduction process
- and, after processing, they exceed the pathogen limits specified in the table above.
Where biosolids fail to meet the requirements of either stabilisation grade A or B, the standards do not apply.
Contaminant grade
Biosolids are contaminant grade 1 if the product:
- contains more than 2% nitrogen, calculated by volume
- contains equal to or less than the maximum level of contaminants as provided in the following table (measured in milligrams of contaminant for each kilogram of dry biosolid).
| Contaminant | Maximum level of contaminant (mg/kg) |
|
Arsenic (As) |
30 |
| Cadmium (Cd) | 6.5 |
| Chromium (Cr) | 1500 |
| Copper (Cu) | 750 |
| Lead (Pb) | 300 |
| Mercury (Hg) | 7.5 |
| Nickel (Ni) | 135 |
| Perfluorooctane sulfonate (PFOS) and Perfluorohexane sulfonic acid (PFHxS) (combined) | 0.03 |
| Perfluorooctanoic acid (PFOA) | 0.081 |
|
Zinc (Zn) |
1250 |
Biosolids are contaminant grade 2 where the contaminant grade 1 requirements cannot be met.
The biosolids reuse standard sets out national consenting pathways for applying biosolids to land, based on product quality and environmental risk.
Grade A1 biosolids can be reused as a permitted activity if they meet specific conditions. These conditions ensure environmental effects are managed even when a resource consent is not required.
Permitted Activity Conditions
Grade B1 biosolids can be reused as a controlled activity. Resource consent is required. In these cases, councils can impose conditions to:
- manage environmental effects from contaminants
- protect public health
- control odour
- require monitoring, record-keeping, consultation, reporting or information provision.
Grade A2 or B2 biosolids can be reused as a discretionary activity. Resource consent is required, and specific conditions must be met (e.g. setbacks from waterways or cultural sites). Regional councils may decline a consent application for a restricted discretionary activity.
Activity status
The biosolids reuse standard sets out national consenting pathways for applying biosolids to land, based on product quality and environmental risk.
Grade A1 biosolids can be reused as a permitted activity if they meet specific conditions. These conditions ensure environmental effects are managed even when a resource consent is not required. Permitted Activity Conditions
Grade B1 biosolids can be reused as a controlled activity. Resource consent is required. In these cases, councils can impose conditions to:
- manage environmental effects from contaminants
- protect public health
- control odour
- require monitoring, record-keeping, consultation, reporting or information provision.
Grade A2 or B2 biosolids can be reused as a discretionary activity. Resource consent is required, and specific conditions must be met (e.g. setbacks from waterways or cultural sites). Regional councils may decline a consent application for a restricted discretionary activity.
Monitoring and reporting
Anyone discharging biosolids to land under the biosolid reuse standard must keep records of the:
- date of each discharge
- location of each discharge
- type and grade of biosolids discharged
- volume of biosolids discharged.
These records must be submitted to the relevant consenting authority each year the biosolids are reused.