Trade Waste Charges

The following questions are addressed below:

  • What are trade wastes charges?
  • How are these charges arrived at?
  • How do you determine my charges?
  • What do I pay and when?
  • How reliable is the charging system?

WHAT ARE TRADE WASTES CHARGES?
Trade wastes charges cover the costs of receiving, treating and disposing of wastewater from trade premises on a "user - pays" basis.
The trade wastes charge is an annual charge for the period 1 July - 30 June, based on the customer's actual peak discharges to the wastewater system.

The charges are based on three factors:

  1. Flow (Rate of Discharge)
    This covers the transportation of wastes through sewers and pumping stations to the Treatment Plant, distribution through the various treatment processes, and disposal of the treated effluent to the Manukau Harbour.
  2. Suspended Solids
    This covers the separation of suspended solids from the wastewater, treatment by digestion, and dewatering and disposal of the resulting biosolids.
  3. BOD*
    This covers the treatment of the organic wastes after separation of the solids, by biological processes and includes the treatment and disposal of the resulting biosolids.
    *'Biochemical Oxygen Demand', is a measure of the strength of the waste.

The occupier of a trade premise must pay the greater of:

  • the actual discharge with the charge formula applied, or
  • a uniform annual charge

HOW ARE THESE CHARGES ARRIVED AT?
Each financial year expenditure on the collection system and the various parts of the treatment process are determined. The total loading (flow, solids & BOD) to the system is assessed. The charge rates for flow, suspended solids and BOD are set from this information.
Provisional Charge Rates
Until the financial year is finished, actual expenditure and loads can only be estimated. Therefore provisional charge rates are set based on the previous year's information and estimates for the current year.
Final Charge Rates
Once the financial year is complete, and all information is assessed, final charge rates are determined after consultation with the Employers and Manufacturers Association.

HOW DO YOU DETERMINE MY CHARGES?
At some time each year, and when you are at peak discharge, we will conduct a sampling survey. This involves gaining access to your trade waste drain, where Watercare will set up sampling and flow measurement equipment for a period of time that is deemed necessary.

The flow is determined either by:

  • Flow recorders, or
  • Water consumption figures which are reduced according to agreed usage in process or product or
  • Flow information supplied to you and agreed to by Watercare.

The suspended solids and BOD are measured from a composite sample which represents the total discharge for 24 hours. The analyses are done by Laboratory Services, Watercare's IANZ-registered laboratory. You may request a duplicate sample for your own independent analysis. For some types of waste a nominal concentration is applied.

The following information provides your daily peak discharges required to arrive at your charge:

Flow converted to litres per second in any peak 8 hour period in 24 hours
Suspended
Solids converted to kilograms in the 24 hour period
BOD converted to kilograms of BOD equivalent* in the 24 hour period
*there is a formula which takes into account different types of waste according to their treatability.

The charge is based on the average of the number of 24 hour periods in the survey (less any results which do not reasonably represent peak conditions). If your waste is combined trade plus domestic, you are entitled to the deduction of the Watercare component of the wastewater levy collected by your local council or their agent. When the survey has been completed you will be given a copy of the results.

WHAT DO I PAY AND WHEN?
The annual charge is divided into six "two-monthly" assessments which are invoiced as near as possible to the:
1st July
1st September
1st November
1st January
1st March
1st May
Until the current year's provisional charge rates are set, not later than 30th September, the previous year's charge rates are used in assessing your charges. Until a survey has been completed, your assessments are based on the previous year's discharge unless you have informed us that there has been a significant change in processing. When the survey is finished the difference between estimated and actual is made up for in the remaining assessments for that year. This explains why there is sometimes a variation in assessments.

Final Adjustment
Should the total trade wastes charges collected differ from the actual costs incurred, final charge rates are set. The resulting adjustment to the previous year's total assessment is either due from, or normally refunded to you in, November or December.

HOW RELIABLE IS THE CHARGING SYSTEM?

  • All flow recording and sampling equipment is checked and calibrated to the manufacturer's specifications.
  • All analyses are carried out to IANZ specifications.
  • All charge rates are set in consultation with the Employers and Manufacturers Association.
  • All work is done in accordance with the ISO 9002 accredited Trade Waste operational procedures.


For further information please contact a member of the Trade Wastes Charging Team:
Watercare Services Limited
Tel: 09 539 7655
Fax: 09 539 7601
52 Aintree Avenue
PO Box 107028
Airport Oaks
Manukau 2154
Auckland
Email: tradewasteinfo@water.co.nz

The current trade wastes charge rates are available on request. Refer to the Trade Wastes Bylaw 1991 for details of charging (Sections 19, 20 & 21 and the Third Schedule).