Enterprise Rent-A-Car Redspot Car Rentals - Case Study



In 2016, Enterprise Redspot were setting up a new car rental facility in Auckland and had a requirement to wash cars on site. The Auckland trade waste bylaw requires car washes to have an appropriate oil/ water separator to ensure total petroleum hydrocarbon and suspended solids levels are within prescribed discharge levels. Discharge of stormwater to sewer is generally prohibited and similarly to protect the natural environment, discharge of wastewater to stormwater drains also prohibited.

Fortunately, the new premises had an undeveloped space under an overhanging office area large enough for the wash bay, with a water supply and connection to sewer.    

IWS proposed a bunded concrete pad, falling to a central slot drain and sump, an above ground pump and oil/ solid separator, discharging to sewer.

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Equipment supplied


IWS distributes Baldwin coalescing plate separators in New Zealand as part of our wastewater treatment plant installations. These separators have been tested to remove free oil droplets as small as 20 microns and achieve effluent discharge levels of 10ppm and below.

The separator is tough and compact, made from polyethylene and polypropylene, with a stainless steel frame. The electric diaphragm pump is non emulsifying by design, robust and simple in construction. With simple, regular maintenance they will give many years of reliable service.

IWS provided the bunded concrete wash slab, draining to a central slot drain, easily cleaned to remove dirt etc, a pump sump, electrical controls and all pipework. The system is fully automatic, treated wastewater is discharged to sewer and free oil is collected in a container for disposal.

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The plant is tough, robust and simple. Equipment is easily installed, and relocatable, should this be required in the future.

As most components are above ground, oil is removed and stored automatically and sludge can be simply drained without need for specialist contractors. The pump sump may require occasional sludge removal depending on contaminant levels, this can be minimised by a couple of minutes of daily cleaning of the slot drain.      

An unused area of the site has been transformed into an efficient, productive facility.                                                                                                                                                                                                                                                                                                 

IWS provide complete turn key packages including consents, supply, installation and ongoing support.

"Mason at IWS, along with his team, were innovative in their approach to our idea. Due to the size and angle of the building any constraints were considered and addressed easily. Dealing with IWS was easy, relaxed and professional, and you always felt all bases were covered, and no stone left unturned, in coming up with a solution that suits our company perfectly. All contact with consenting agencies, engineers, Watercare, on-going maintenance, training and training manual development etc was handled as part of the process and I would recommend the IWS team for any similar project, large or small."

Steve Whyte

General Manager

Enterprise Rent-A-Car and

Redspot Car Rentals

0272 368 377