HARVEST: Dr Azuhan steps up to the challenge of tasting water in Changwon recently

MALAYSIA has traditionally sought its supply of water from sources referred to as surface water which include rivers and dams.

Currently, surface water accounts for more than 98 per cent of the national public water supply and the high level of dependence on surface water needs to be diluted due to the impending climate change.

Malaysia must also look for other sources of water as the demand for the natural commodity in the country is expected to increase significantly next year to approximately 17,000 million litres per day.

To cater to this growing need, Sime Darby Bhd is embarking on a RM1.2 million groundwater project at Batang Padang, Perak. The project site covers an area of approximately 2,700 square kilometres and is expected to supply 500 million litres of groundwater per day for public consumption by Dec 31, 2012.

Batang Padang, Perak was chosen as the location because of its high annual rainfall of between 2,500mm and 3,300mm. It also has large tracts of undeveloped land, including forest reserves and water catchment areas, said Dr Azuhan Mohamed, Sime Darby's head of water management, energy and utilities.

During a recent media familiarisation visit to South Korea on the groundwater technology, Dr Azuhan said the project would be undertaken in two stages.

The first would involve a development of a 50 million litres per day capacity pilot well, which is expected to be ready by year-end. The second stage development will uncover the remaining 450 million litres per day capacity supply from nine wells.

The first supply of drinkable water is expected to reach the public in January 2013 as well as to the industrial areas in Selangor.

Relevant to Sime Darby's groundwater project, the first site visited by members of the media was a project site by Da Joo Construction Co Ltd, which uses the radial collector well system.

Da Joo's director of the overseas projects department, Dr Jae Ha, said this green technology contributes 20 per cent of the treated water supply to the citizens of Seoul (including horizontal wells). The city has a population of 12 million.

Unlike surface water harvesting, this process means one need not worry about depletion of water supply since the ground water abstraction takes place at unconfined aquifers away from rivers and other surface water bodies.

The recharge rate for the alluvial aquifer was rapid in conditions where the ground water head was higher than the river head.

Dr Ha also said the possibility of industrial waste seeping into the ground water was minimal as the radial collector wells were dug deep into the bed rock. He added that this system was also used to rehabilitate rivers and streams.

Each well takes six months to construct and once the system is up and running, little maintenance is needed. The wells, which can measure between four and eight metres in diameter, depending on the number of pumps, can harvest between 20,000 to 40,000 cubic metres of water per day.

During dry seasons, water is pumped at a level considered optimum based on studies and analysis to prevent over-abstraction of water.

Due to the natural filtration that occurs when rainwater travels down the ground levels, it also will cost less for the purification process, said Dr Ha.

Changwon's clean bank water filtration

CHANGWON City in South Korea is located about 40km west of Busan on the Namhae Expressway. It 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 naturally sinks into the ground via the river bed or bank and is recovered via a pumping well.

It takes between 50 and 100 days for groundwater to reach the pumping well. Through bank filtration, micro-organisms and other particles are removed by contact with the aquifer minerals.

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

Compared with an ordinary water treatment system, which harvests 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 smell and taste of the water).

It is therefore 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 by product 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 with bank filtration is greatly reduced, compared with the ordinary water cleaning process.

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 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. Note that for Kuala Lumpur, the Cheras 11th Mile water treatment plant in Hulu Langat is still closed to this day due to high ammonia levels in 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 no effect on the river's water level nor does it 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. Changwon 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, but is currently producing only 16 million. In its second phase of developing the system, the centre hopes to increase the capacity to 60 million.

Star City's water wonder

GROUNDWATER harvesting is not the only method used in South Korea to boost its fresh water supply system. Other methods and systems are used in harvesting water and improving the quality of the water harvested.

The Star City in Seoul is an interesting case study of a luxury housing complex that uses a rainwater management system for the purpose of flood control, water economy and emergencies.

Rainwater is collected from two catchment areas apartment roofs and the ground. Each of Star City's apartment blocks houses three 1,000-cubic metre water storage tanks at its underground floors, where the carparks are located.

Rainwater from the ground goes into the first tank, thus enabling the mitigation of flood in the area which used to suffer from frequent downstream flooding in the past, due to its location in a monsoon region.

Water collected is emptied into the nearby Hang river to allow for the tank to accommodate the collection of groundwater on rainy days.

The second tank stores rainwater from the roofs, channeled through some 58 floors downwards until it reaches the tank located underground.

As Star City does not have a purification system installed, the water although clean and of high quality is not used for drinking purposes. Instead, the water is used for gardening, for public toilets and swimming pools.

Meanwhile, unlike the first tank for flood mitigation, the third tank is always kept full and is used for emergency situations such as in the case of fire in the residential area or the nearby commercial districts and drought.

The Star City rainwater management system is the brainchild of Mooyoung Han, a professor with Seoul National University's department of civil and environmental engineering.

He is also president of the Korean Rainwater Catchment Systems Association. He said that, although the entire cost of piping alone for the project is estimated to be around US$400,000 (RM1,354,000), its long term benefits had far surpassed the initial costs for setting up the system.

In 2007, rainwater usage in Star City was 40 million litres per day with a rainwater use efficiency of 66 per cent. This was reflected in the reduction of water bills for residents.

The first and only system to be used in a housing complex in South Korea, Han hopes the usage of Star City's rainwater management system can be further expanded upon in the future.

“The system works very well in areas with a relatively high average annual rainfall (Korea’s average annual rainfall is 1,283mm) and is also effective in controlling urban flood problems without the need to resort to costly and lengthy operations in increasing the capacity of storm sewerage.”