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Depot uses new gear to strip muck from its wash

Each day more than 800 buses pass through the Kowloon Motor Bus depot in Lai Chi Kok  for a wash.

What comes out from the wash is a mix of dirt and oil.  Laws do not allow companies  such as KMB to dispose of water that contains more than 50 milligrams of oil and grease - an amount  equivalent to a shot of espresso - for every litre of water.

So what does KMB do? It uses an in-house water treatment machine that  removes the grease before  discharging the waste water into the sewage system.

Costing hundreds of thousands of dollars, the Australian-made 'dissolved-air flotation machine' sprays air into waste water to separate out the oil and grease.

KMB's assistant manager of facility management, Rhythm Lai Kwok-fai, explained that this was the 'heart' of the water treatment process.

'The other depots use older machines,' he said, standing next to the processing equipment.  'This is the  newest model, so it's more efficient.'

The machine has a metal screen that is combed through the waste water to filter out solid waste, while a rotating  belt lifts off any oil  floating on top.

A chemical is added to the water to solidify the grease, before the 'heart' pumps air into the mixture to separate the water and oil. What emerges after treatment is a cloudy water mixture, stripped of the black oil and grease.

The waste grease is  dried and turned into  sludge cakes before it is sent to landfills.

'We try to minimise the amount of waste created,' said Mr Lai, but the company still ends up sending dozens of kilograms of sludge cakes to landfills each month.

About 70 per cent of the water used by the bus washing machines is recycled.

Aside from treating water used in washing buses, the  waste treatment equipment also filters water used for cleaning auto parts, the floors of the depot and the  bus interiors.

The Lai Chi Kok depot uses  110,000 litres of water a day. But company executives say that they have been able to  limit grease discharged into sewage at 22 milligrams for every litre of water.



Investing in water treatment helps keep KMB in the clear