Self-monitoring Guidelines

COMPLIANCE WITH THE TRADE WASTES BYLAW 1991 AND WATERCARE SERVICES LIMITED TRADE WASTE CONSENTS

INTRODUCTION
In order to manage and operate a safe and successful wastewater collection, treatment and disposal system there must be effective control over the entry of substances which could jeopardise the health and safety of wastewater workers, the integrity of the collection system, wastewater treatment plant processes and the environment.

Watercare has the responsibility of controlling the quantity and quality of industrial waste discharged into the wastewater collection system. Businesses that wish to discharge industrial and other wastewater must apply to Watercare for a trade waste consent. Consent holders have a responsibility to ensure that their wastewater complies with their consent and the Bylaw at all times.

Consents require industry self-monitoring of wastewater discharged. The type and frequency of self-monitoring will vary depending upon the nature of the discharge and is agreed with individual consent holders.

Watercare has provided the following procedure guidelines for the introduction and maintenance of a comprehensive self-monitoring programme.

Watercare's Trade Waste section would be pleased to answer any further queries that consent holders may have with regard to their self-monitoring programme. The email address is tradewasteinfo@water.co.nz.

SAMPLING
The sampling of wastewater discharged is necessary to determine its quality and to establish the category under which it may be classified under the conditions of the Trade Wastes Bylaw.

Watercare's Trade Waste section will audit discharge quality results under the terms of the consent by analysis of samples collected by independent automatic and/or grab sampling.

Samples to determine wastewater quality are normally taken at the point of connection to the public sewer. However, alternative sampling points, for example on individual trade waste streams only, may be specified and adopted in the Discharge Consent.

SAMPLING PROCEDURES
The major source of error in the process of obtaining wastewater quality information occurs during sampling. Samples taken from a portion of the wastewater stream must be representative of the wastewater from which it is taken.

The greatest obstacle to collection of a representative sample is the lack of uniformity of the wastewater itself. For example, grease and oil may float, solids may settle and the concentrations of these may vary from minute to minute.

A testing programme may comprise only a small number of samples. And as these samples (often only one or two litres) are taken from thousands of litres of wastewater, there is a possibility that samples may not be representative unless appropriate sampling techniques are followed.

Laboratory results are only as good as the samples submitted for analysis. As laboratory testing is often expensive and time - consuming, extra care and time taken in sampling will be well rewarded by more reliable and representative results.

Obtaining good results largely depends on:

  1. Ensuring the sample is as representative of the wastewater stream as possible
  2. Using proper sampling techniques and clean equipment
  3. Preparing, protecting and preserving samples prior to analysis, and
  4. Ensuring that correct methods are employed for analysis.



SAMPLING TECHNIQUES
The following guidelines are adequate for many common trade waste discharges. However, specific procedures may be necessary for some discharges. Watercare's Trade Waste staff would be happy to assist with the preparation of such a programme.

  1. Read your water meter (or meters) at the start of the working day and again 24 hours later. This will provide daily water consumption. Water consumption figures should be expressed as cubic metres per day. Conversions of actual water meter readings may be necessary.
  2. Ensure sampling is undertaken at the appropriate location.
  3. The Wastewater at the point at which the sample is being taken should be well mixed to ensure that the sample is representitive of the discharge.
  4. When representatively sampling a non uniform waste stream, it is necessary to take regular grab samples throughout a full days production.

    When grab sampling, it is important that the sample is taken as quickly as possible. This can be achieved by using a wide mouth sampling container of about one litre capacity.

    The contents of the sampling container should then be transferred to a larger clean mixing container which has been pre-rinsed with a quantity of the sample waste.

    At the end of production, the combined grab samples should be thoroughly mixed and a sub-sample taken for analysis.
  5. Care should be taken not to scrape the walls of tanks, gauging pits, boundary traps, troughs etc. and dislodge unrepresentative matter into the sample.
  6. Use only clean sampling equipment and rinse between samples.
  7. Avoid skimming the surface of the liquid being sampled. If possible, fully immerse the sample container to about the middle of the flow depth.
  8. Always thoroughly stir the composite sample before transferring it from the mixing container to the sample jar.
  9. For most analysis, a sample volume of one litre is usually sufficient. Generally, this should be stored and sealed in a polyethylene jar, or glass jar if solvents, hydrocarbons, herbicides or pesticides are in the sample. If the lid is plastic, insulate it using aluminium foil. The sample jar should be filled completely, leaving no air gap in the top.
  10. If there is a delay between sampling and analysis, then the sample should be immediately placed on ice or in the refrigerator. Do not freeze.
  11. Label all sample jars clearly with the date, time and where the samples were taken.



PRESENTATION OF RESULTS
Having received results of analysis from the laboratory and a recording of water consumption figures, a report should be prepared for submission to Watercare's Trade Waste Compliance staff.

An example of a report and suggested layout is shown above. This is only a guide but it should be noted that clear presentation enables easier interpretation of results. A tabular format is preferred. A copy of the Laboratory analysis should also be attached to the report.

PRESENTATION OF RESULTS example:

Watercare's Trade Waste section is dedicated to helping industry dispose of its wastewater in a cost effective and environmentally responsible manner.

FOR FURTHER INFORMATION
Please contact Watercare Trade Waste:
Tel: 09 539 7655
Fax: 09 539 7601
52 Aintree Avenue
PO Box 107028
Airport Oaks
Manukau 2154
AUCKLAND

Email: tradewasteinfo@water.co.nz