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Title / Describe wastewater activated sludge treatment processes, and critical points
Level / 5 / Credits / 10
Purpose / People credited with this unit standard are able to: describe the type and design; describe the microbiology;describe and interpret tests; describe performance optimising; and identify critical points, adverse effects, preventive actions, and corrective actions, of activated sludge processes.
Classification / Water Industry > Wastewater Treatment
Available grade / Achieved
Explanatory notes
Definitions
Optimising – adjusting plant input variables to make the process as effective as possible to achieve the desired output, taking into account the constraints of cost, human input, effluent quality, and resource consent requirements.
Critical points – points in a process or in equipment where failure to function correctly can lead to a public health hazard adverse effects which may affect the treatment process or other processes in the treatment plant.
Organisational procedures – instructions to staff, and procedures which are documented in memo or manual format and are available in the workplace. These requirements include but are not limited to – site specific requirements, manufacturers’ specifications, product quality specifications, and legislative or regulatory requirements.
Wastewater includes stormwater and sewage systems.
In the context of this unit standard, activated sludge treatment includes the separation process.
Outcomes and evidence requirements
Outcome 1
Describe the type and design of activated sludge processes.
Evidence requirements
1.1Activated sludge processes are described in terms of their type and design.
Rangeconventional activated sludge, extended aeration, biological nutrient removal.
1.2The recycling of solids is described in terms of solids concentrations.
Rangemixed liquor suspended solids, the return of activated sludge, sludge volume index, sludge age during the process.
1.3The introduction of dissolved oxygen into the process is described in terms of process operation.
Rangeprocess types – surface aeration, diffused aeration.
Outcome 2
Describe the microbiology of activated sludge processes.
Rangeloading rates, sludge volume index.
Evidence requirements
2.1The micro-organisms in activated sludge wastewater treatment are identified and described in terms of their functions and effects.
Rangefunctions – sludge bulking, burnout, filamentous bacteria, biological and physical processes;
food to micro-organism ratio.
2.2Microbiological activity which affects process parameters is described.
Rangeoxidation, sludge volume and density indices, sludge age, enzyme addition, pH effects.
Outcome 3
Describe and interpret tests of activated sludge processes.
Evidence requirements
3.1Activated sludge processes are described in terms of the timing and types of tests to be undertaken.
Rangetests include but are not limited to – pH, suspended solids, phosphorus, nitrogen, Biochemical Oxygen Demand (BOD), temperature, dissolved oxygen, microscopic evaluation, mixed liquor, sludge volume index, settleability.
3.2Test results are interpreted in relation to process variations.
Rangeloading, time, environmental manipulation.
Outcome 4
Describe performance optimising of activated sludge processes.
Evidence requirements
4.1Results of monitoring are described in terms of the adjustments that may be carried out.
Outcome 5
Identify critical points of activated sludge processes, adverse effects, preventive actions, and corrective actions.
Evidence requirements
5.1The critical points in activated sludge processes are identified in accordance with organisational procedures.
5.2The adverse effects at each critical point are identified in terms of the causes or the events leading to their occurrence.
5.3The preventive and corrective actions for problems or events related to each adverse effect are identified.
Replacement information / This unit standard and unit standard 24947 were replaced by unit standard 29935.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