We are improving the way we manage trade waste and are proposing some new changes to the nitrogen-based trade waste parameters (TKN and Ammonia).

We have been seeking trade waste customer feedback on the proposed changes, which are being considered to reflect risk more accurately at both the Eastern and Western treatment plants (ETP & WTP respectively).

This change only affects former City West Water (CWW) customers.

Why the changes?

Due to various upgrades at the treatment plants, the risk that nitrogen compounds pose to the sewerage system has changed.

The proposed changes in acceptance criteria (limits) of both TKN (Total Kjeldahl Nitrogen) and Ammonia are recommended so that they more accurately reflect the current risk they pose to the sewer system

Testing equipment

What are the benefits of these changes?

The benefits include the following:

  • Reduces the consequence of a trade waste customer breaching compliance to the trade waste acceptance criteria and having to implement improvements and/or capital costs to meet the limit.
  • Reduced administrative burden for retail water companies, Melbourne Water and trade waste customers where non-compliance is identified and if the customer needs to apply for a Customer Specific Acceptance Criteria (C-SAC).
  • Trade waste customers that meet new criteria will not need to apply for a C-SAC and avoid C-SAC processing fees and needing to re-apply every three years.
  • Easier to understand TKN and Ammonia limits for trade waste customers.
  • Equitable limit requirements for trade waste customers across both the WTP and ETP catchment zones.

A water industry working group (Yarra Valley Water, South East Water, Greater Western Water and Melbourne Water) assessed the current nitrogen limits (TKN and Ammonia) against the treatment plants’ (ETP and WTP) risk tolerance to nitrogen loads.

The two limits were chosen which would minimise customers incurring non-compliance and/or requiring to apply for a Customer Specific Acceptance Criteria (CSAC) but would allow the treatment plants to safely maintain process performance and their licence limits.

For these changes to take effect, the Essential Services Commission (ESC) requires a customer impact assessment to be completed, based on customer communication and feedback as part of the submission to change the acceptance criteria.

All water businesses are communicating with customers about the proposed changes and what they will mean for them.

What are the proposed changes?

From section 2.3 (Nitrogen) of the Trade Waste Acceptance Criteria

Current Acceptance Criteria

Proposed Acceptance Criteria

The Occupier must not discharge trade waste with a concentration of Total Kjeldahl Nitrogen greater than 500 mg/ litre.

The Occupier must not discharge trade waste with a total mass load of TKN exceeding 788 kg/day (expressed as N) unless its concentration is no greater than 500 mg/L.

The Occupier must not discharge trade waste with a concentration of Ammonia, plus ammoniacal ion (expressed as N) greater than:

i. 50 mg/litre, except as provided this clause.

ii. 200 mg/litre, where -

A. the trade waste discharge can only be received by Melbourne Water’s Western Treatment Plant

B. a risk assessment has been conducted

C. the occupier can comply with a restricted pH range of 6.0 to 8.0, and

D. the Occupier has demonstrated to the RWC Representative, that commonly available waste minimisation technology has been applied to the best extent practicable.

The Occupier must not discharge trade waste with a concentration of ammonia, plus ammoniacal ion (expressed as N), greater than:

1. 50 mg/L or

2. 200mg/L if the pH is within the range 6 to 8.

Please provide your feedback

We are collecting your feedback as part of our consultation.

The results will be published once finalised, and will form part of our submission to the ESC.

We will communicating updates to affected customers at key milestones.