Liquid trade waste explained

What is liquid trade waste?

The Local Government (General) Regulation 2021 defines 'liquid trade waste' as 'all liquid waste other than sewage of a domestic nature'.

All business activities generating liquid trade waste must have current Council approval and maintain the appropriate equipment necessary to treat any liquid waste before it enters our sewerage system.

Shoalhaven Water regulates liquid trade waste discharges in order to:

  • Protect the health and safety of our staff, the public, and the environment
  • Protect wastewater system infrastructure, assets, and sewerage treatment processes to protect the effluent and biosolid quality for facilitation of recycling
  • Reduce maintenance costs and odour complaints

This includes liquid waste generated from:

  • Industrial premises
  • Businesses and commercial premises such as hotels, motels, restaurants, takeaway stores, butchers, service stations, mechanical workshops, vehicle wash facilities, supermarkets, dentists
  • Community and public premises such as pools, schools, colleges, education facilities, hospitals and nursing homes
  • Any of the above activities carried out at residential premises
  • Septic tank waste, marine pump-out facilities and established sites for the discharge of chemical toilet or pan contents from mobile homes, caravans or portaloos

If your business falls into one of these categories, you will be required to pre-treat your liquid trade waste prior to discharging into our sewerage system.

What is pre-treatment?

Pre-treatment is achieved by using a device or piece of equipment to treat the liquid trade waste prior to discharging into the sewerage system. The type of pre-treatment device required is dependent on the nature of the activity and the volume and strength of the liquid trade waste it generates.

Typical pre-treatment devices used for the treatment of liquid trade waste include but are not necessarily limited to the following:

  • Grease arrestor (grease trap)
  • Basket arrestor with fixed screens (dry basket arrestor)
  • Fixed or removable screens
  • Coalescing plate interceptor (CPI oil separator)
  • Vertical gravity separator (VGS separator)
  • Hydrocyclone separation system (HSS separator)
  • Cooling pit
  • Balancing, averaging, neutralising pit/tank
  • Solids settlement pit/silt arrestor
  • Plaster arrestor

Shoalhaven Water’s pre-treatment requirements are in accordance with the Liquid Trade Waste Management Guidelines 2021 and our Liquid Trade Waste Policy.

Frequently asked questions

I operate a food business, do I need a grease arrestor?

The answer is usually yes! Most food businesses will need to have a 1000L capacity grease arrestor (grease trap) or larger installed to pre-treat the liquid trade waste prior to discharge to the sewer.

The size is determined by a number of factors, such as available seating or kitchen fixture units, and is individually assessed according to the NSW Liquid Trade Waste Regulation Guidelines in force at the time.

Council’s Liquid Trade Waste Discharge policy outlines the type of food businesses that require, and those that may not require, the installation of a grease arrestor.

If you are considering starting up or purchasing a food business, it is important to understand the type of cooking, preparation and serving you will be doing, to determine if a grease arrestor is required. 

If a grease arrestor is already installed on the premise, you need to consider if it is the correct size and in good condition. If there is none at the property, you will need to contact a licensed plumber for advice and a quote. They can also check if there are any installation issues (e.g. due to lack of space).

What are my requirements if I operate a mechanical workshop?

Liquid trade wastes that are discharged from mechanical workshops and vehicle wash businesses are required to be pre-treated using an oily water separator and associated collection pits and pumps. Separators, pits and pumps need to be sized properly for the activity and amount of waste generated. The minimum size for oily water separators is 1000L/hr.

Double and triple interceptor pits and general-purpose pits are no longer appropriate pre-treatment equipment on their own. If liquid trade waste is to be discharged to sewer, the pre-treatment system will need to be upgraded to include an oily water separator.

An alternative is to operate as a dry workshop. This is only appropriate where a very small amount of liquid trade waste is generated.  Any pits need to be disconnected from draining to the sewer. Any waste liquids collected on site need to be removed by a contractor.

Liquid trade wastes collected from service station covered forecourts and other refuelling locations are not permitted to discharge to sewer and will need to find alternate methods of waste water disposal.

Shoalhaven Water’s Regulatory Unit is available to provide advice and assistance to understand the particular liquid trade waste requirements for your business.

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