The water stories: Changwon City's bank filtration water system

Changwon City, about 40 kilometres west of Busan on the Namhae Expressway, relies on a riverside or bank filtration water system managed by the Daesan Water Cleaning Centre.

Bank filtration is a water treatment process that makes use of surface water that is naturally infiltrated into ground water via the river bed or bank(s) and is recovered via a pumping well. It takes between 50 and 100 days for groundwater to reach the pumping well.

Through bank filtration, microorganism and other particles are removed by contact with the aquifer minerals.

This system, which was completed in 2001, rely on wells, both radial collector wells and horizontal wells, that are dug some 100m away from the Nakdonggang river.

Compared to an ordinary water treatment system, which harvest water directly from the river via a pump, there are less steps to the bank filtration one.

Water from the intake pumping station goes through an aeration reactor, a rapid sand filter basin (to remove harmful minerals such as iron and manganese) and an activated carbon filter basin (to neutralise the water's smell and taste) and is not subjected to chemical treatments as is in the case of the ordinary water treatment process.

The water is finally disinfected before being stored in a service reservoir.

Sludge is produced as a byproduct of the bank filtration process. Approximately 150mg of sludge is produced per cubic metre of treated water, a problem faced by water treatment plants in Malaysia due to the high cost of treating the waste.

However, the amount produced is greatly reduced compared to when the ordinary process is used.

Due to the nature of the system, which harvests river water from the ground as opposed to directly from the river, the system is able to continue its supply of water in Changwon City even in the event of water pollution or unexpected disaster.

With this system, the shutting down of water treatment plants due to pollution can be prevented.

The Cheras 11th Mile water treatment plant in Hulu Langat is still closed to this day due to high ammonia levels in the Sungai Langat, which serves as the plant's raw water intake point.

The Changwon Waterworks and Sewage Agency guarantees the stability of the bank filtration water system.

It has not effect on the river's water level nor does it also cause the ground to sink or vegetation to die.

Only the groundwater level changes within the 1m range, depending on how much water is pumped out.

The cost for treated water via bank filtration is only 850 won (RM2.48) per cubic metre of water.

The city currently has 50 vertical collector wells and six radial collector wells, with another five wells under construction.

The centre has the capacity to harvest up to 20 million litres of water per day (mld) but is currently producing only 16mld.

In its second phase of developing the system, the centre hopes to increase the capacity to 60mld.

NOTE TO READER: The writing of this story was made possible thanks to Sime Darby's media familiarisation tour to some locations in South Korea which utilise different methods of water harvesting. It was a brilliant trip, I learned so much and because sharing is caring (and we can always make use of new knowledge), I have decided to share what I have learnt with you.

XOXO, Masami.