Liquid trade waste explained

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. 

Activities that generate and discharge liquid trade waste will fall into one of the following discharger categories:

Low Risk

Category 1A - Nil or minimal liquid trade waste pre-treatment equipment required (e.g. hairdresser, florist, beautician)

Category 1B - Still low risk but require more sophisticated prescribed liquid trade waste pre-treatment equipment (e.g. vehicle wash, laundry activities)

Medium Risk

Require prescribed liquid trade waste pre-treatment equipment (e.g. Grease arrestor for restaurant or cafe, oily water separator for a mechanical workshop).

Category 2A - The prescribed pre-treatment equipment is installed and maintained to Council’s requirements (e.g. correct type and size grease arrestor pumped out to Council’s set frequency)

Category 2B - The prescribed pre-treatment equipment is not installed or is not appropriate or is installed but not maintained to Council’s requirements.

Category 2S - Dischargers of pan contents, septic wastes, chemical toilet waste and ship-to-shore pump-outs into the sewerage system. Includes septic tank pump outs and septage transported and discharged directly to a sewerage treatment plant. 

High Risk

Referred to as Category 3A or 3B (depending on the complexity of the pre-treatment system) and includes:

• Industrial dischargers
• Large volume (greater than 20kL/d) dischargers
• Dischargers that do not fall into Category 1 or 2 above
• Contaminated groundwater or stormwater

Best practice pricing is implemented to ensure dischargers bear a fair share of the cost of providing sewerage services and to facilitate appropriate pre-treatment, waste minimisation and water conservation.

Ongoing liquid trade waste fees and charges are issued on the property owners’ quarterly water account. They include:

Annual fee to help recover costs incurred by council for ongoing administration and scheduled inspections, and to ensure that the discharge complies with the approval conditions.

Usage charge is a price per kilolitre applied to the volume of wastewater discharged to the sewerage system. The discharge amount is based on a percentage of the amount of incoming water. The usage charge will depend on the charging category and the business activity.

Please note that liquid trade waste usage charges are in addition to non-residential sewer usage charges. 

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 Management 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).

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.