Grease is the word

With an increase in volume of greasy wastewater being discharged to sewers, there are two main issues. The first is the discharging of grease to sewers, which results in pipe blockages; the second is the increase in the grease load to downstream sewage treatment plants.

Compounding the problem is the large number of food courts with multiple food outlets and commercial kitchens located together in large shopping centres. Based on the traditional bums-on-seats calculations, most of the larger food courts are required to install multiple grease arrestors to handle the high flows.

Usually fats, oils and greases (FOGs) are removed by conventional grease traps in food courts, but with the increase in the size and number of these food courts, combined with the use of outdated systems, such grease traps may not capture all the FOGs — which can result in the abovementioned issues.

While advances in design are often the solution to such challenges, the design of grease traps has not really changed much at all since the 19th century, when a gentleman called Nathaniel Whiting obtained a patent on the first ever grease trap. That’s where a dissolved air flotation (DAF) system such as the Hydroflux Grease Trap Dissolved Air Flotation (GT-DAF) system comes in.

The capacity of one Hydroflux GT-DAF is equivalent to five or more grease traps and thus takes up considerably less space. For expanding food courts, the system can simply be installed in the existing grease trap room.

Hydroflux realised that while a traditional DAF system can be more effective than a conventional grease trap in a food court environment, such a system is still a compromise. This is because traditional DAF systems are often large in size, consume high levels of energy and can require high loads of chemicals. So the company came up with a separation device that was more energy efficient, smaller in size and designed specifically for the treatment of greasy wastewater from food courts.

The unit is usually installed at a lower level of the complex so that all wastewater from the food outlets gravity flows to the system without the need for multiple pump stations.

Incorporating the best of traditional GT and DAF systems, the Hydroflux GT-DAF features a two-stage separation process which involved a free grease gravity separation stage, followed by the addition of dissolved air and demulsification agents. The purpose-designed unit is said to perform much better than both a grease trap and a typical DAF, minimising the size of the unit by 30%, delivering energy savings of up to 50% and overcoming the operational problems of conventional systems.

Hydroflux has so far installed 10 of these units in Australia, several of them at Westfield shopping centres.

Top image caption: The treated water from a Hydroflux GT-DAF system will comply with current discharge requirements and is a means of futureproofing. The addition of non-hazardous flocculants can further improve the quality should discharge requirements become stricter.