Drains, separators and washing cars

We've all seen the gutter drains marked with green slogans; "The drain is meant for rain" or "What you drop the rivers cop. The spray painted pictures of dolphins and fish remind us that if something goes down that drain, it will run into the stormwater system and we’ll find ourselves swimming in it next time we are at the beach. We know that these drains are stormwater drains.

But in a workshop, how do we know which drain goes to the stormwater or the sewer, and if it really matters anyway? Why is it okay to put wastewater through a separator and into the sewer, when nothing is allowed to go into the stormwater?

Stormwater VS. sewer

The core difference is that the stormwater drain goes straight to the waterways (whether that be the ocean or a local river system) without any filtering or treatment. Whatever goes into a stormwater drain gets released into nature in exactly the same form that it entered. Stormwater drains are always found outside (except in very old premises) and are for the sole purpose of removing excess rain water from a property to prevent flooding. The contents of sewer drains, however, are processed at the sewerage treatment plant before the treated water is released into the waterways. The sewer

Protecting stormwater drains

Nothing except rainwater should go down a stormwater drain. This means that run off from a vehicle, oil and other liquid wastes must be prevented from entering the stormwater system. This is required by law. In NSW, any contaminant is designated pollution; there is no minimum amount. All staff must be aware of this, although it may seem straightforward it is worthwhile ensuring all new staff understand the difference between the stormwater drain and any drains that go to the separator in the workshop, as both individual staff and businesses can be penalised in NSW. To protect the stormwater drains on your premises:

- Identify all stormwater drains onsite (if you are unsure, check plumbing information that you may have)

- Make sure that there are no oily trails or residue around the drains (this is something that councils will look for in an audit, as it shows past pollution)

- Mark any drains, either with a slogan or just bright coloured paint

- Install protective drain equipment to filter material entering the drain

- Only conduct repair work inside the workshop

- Install bunding across the front entrance of the workshop to stop spills from leaving the workshop (bunding is a barrier that prevents liquid from spreading, it could be a rubber speed bump or similar)

- Make sure all liquid storage containers or old parts or engines containing oil are kept inside or in a bunded, undercover area away from any drains.

Washing cars

If you wash vehicles commercially, it is usually a requirement that it is done in a dedicated wash bay that is bunded, undercover, on sealed ground and drains to an oil water separator. When vehicles are washed, the runoff contains several materials that need to be kept away from waterways. Runoff contains degreasers, detergents, oil, grease, heavy metals, rubber and sediment and needs to be pre-treated with an oil water separator before it is discharged to the sewer. Wastewater from washing vehicles cannot be allowed into stormwater drains or onto soil where it can seep to the waterways.

A good way of dealing with this wastewater (as usually it is in high volumes) is by processing it through an oil water separator, which is attached to the wash bay.

Oil water separators

An oil water separator ('separator' or 'pre-treatment equipment') is a system designed to remove oil based pollutants from wastewater. It is pre-treatment equipment that allows wastewater to be discharged to the sewer. It works by separating oily water into oil and treated water, with the oil being collected for removal by a licensed waste removal company, and the treated water being pumped into the sewer.

Usually businesses are required to operate a separator if they wash vehicles, produce a high amount of liquid waste or if a new site is being developed.

The operation of separators may require a permit, as it does in NSW which ensures that the separator meets the required standard, can handle the volume of wastewater produced, has been installed properly by a licensed plumber and is operating correctly. (To check the laws in your state, contact your MTA).

Stormwater and sewer drains are extremely different, and it is worth knowing which is which. Don't assume that everyone is aware and take small steps to make sure that no contaminants from your workshop go down into stormwater.

Contributed by Sophie Luttrell

Environmental Manager, Motor Traders' Association of NSW