Page 1 of 3
Title / Describe wastewater sludge and biosolids management
Level / 5 / Credits / 10
Purpose / People credited with this unit standard are able to describe: the volumes, types, and characteristics of wastewater sludges produced by wastewater treatmentprocesses; stabilisation and dewatering methods used in wastewater sludge treatment; and the environmental effects of applying biosolids to land, and of heat treatment.
Classification / Water Industry > Wastewater Treatment
Available grade / Achieved
Explanatory notes
1Definitions
Biosolids – sewage sludges or sewage sludges mixed with other materials that have been treated and/or stabilised to the extent that they can be safely returned to the environment.
Sludge – wastewater solids from separation processes including scum.
Wastewater includes stormwater and sewage systems.
2Reference
New Zealand Water and Wastes Association, Guidelines for the safe application of biosolids to land in New Zealand. August 2003. ISBN 1-877134-43-0.
Outcomes and evidence requirements
Outcome 1
Describe the volumes, types, and characteristics of wastewater sludges produced by wastewater treatment processes.
Rangewastewater sludges – primary sludges and scums, secondary sludges, digested sludges.
Evidence requirements
1.1Wastewater treatment processes are described in terms of the volumes and solids content of sludges produced.
1.2Sludges produced in the various wastewater treatment processes are described in terms of their characteristics.
Rangecharacteristics – suspended, dissolved, volatile.
Outcome 2
Describe stabilisation methods used in wastewater sludge treatment.
Rangeprimary sludge and scum, secondary sludge.
Evidence requirements
2.1Aerobic digestion of wastewater sludge is described in terms of the microbiological activity.
Rangemay include but is not limited to – solids loading rates, biological activity, oxygen requirements, temperature and mixing effects, aeration methods, detention times;
evidence is required for at least three.
2.2Anaerobic digestion of wastewater sludge is described in terms of the biological process.
Rangeprocess outputs – volatile conversion rates, gas production;
process inputs – temperature, detention times.
2.3The methods of heat treatment are described in terms of the processes.
Rangeincludes but is not limited to – incineration, vitrification.
Outcome 3
Describe dewatering methods used in wastewater sludge treatment.
Evidence requirements
3.1The measurement of dewatering factors of sludges is described in terms of solids concentration and solids loading rate.
3.2Conditioning techniques are described in terms of their methods of action and effectiveness.
Rangeaddition of – elutriation, coagulants, lime, polymers.
3.3The methods of thickening and dewatering biosolids are described in terms of the processes.
Rangeincludes but is not limited to – drying beds, sludge gravity thickeners, dissolved air thickeners, centrifuges, belt presses, thermal drying.
Outcome 4
Describe the environmental effects of applying biosolids to land, and of heat treatment.
Evidence requirements
4.1The results of applying biosolids to land are described in terms of environmental effects.
Rangemethods – composting and soil additives, landfills, land application;
effects of – nutrients, metals, pathogens.
4.2The results of heat treatment are described in terms of environmental effects.
Rangeeffects of – ash, metals, odours, air dispersion plumes.
Replacement information / This unit standard and unit standard 24945 were replaced by unit standard 29936.This unit standard is expiring. Assessment against the standard must take place by the last date for assessment set out below.
Status information and last date for assessment for superseded versions
Process / Version / Date / Last Date for AssessmentRegistration / 1 / 19 September 2008 / 31 December 2018
Review / 2 / 16 March 2017 / 31 December 2018
Consent and Moderation Requirements (CMR) reference / 0101
This CMR can be accessed at
Please note
Providers must be granted consent to assess against standards (accredited) by NZQA, before they can report credits from assessment against unit standards or deliver courses of study leading to that assessment.
Industry Training Organisations must be granted consent to assess against standards by NZQA before they can register credits from assessment against unit standards.
Providers and Industry Training Organisations, which have been granted consent and which are assessing against unit standards must engage with the moderation system that applies to those standards.
Requirements for consent to assess and an outline of the moderation system that applies to this standard are outlined in the Consent and Moderation Requirements (CMR). The CMR also includes useful information about special requirements for organisations wishing to develop education and training programmes, such as minimum qualifications for tutors and assessors, and special resource requirements.
Infrastructure ITOSSB Code 101813 / New Zealand Qualifications Authority 2018 / / New Zealand Qualifications Aut