Drinking and 'driving' in Bangkok

Supplying a city of 11 million people with clean water is no easy task. The fluctuating demand must be met uncompromisingly and equipment must perform as expected.

MWA (Metropolitan Water Works Authority), a Thai state enterprise charged with operating the world's biggest tap water treatment plant, supplies the drinking water for Bangkok's 11 million plus citizens. It has a total treatment capacity of 4.3 million m3/day. The treated water is distributed by three transmission pumping stations and 20 distribution pumping stations through a 20,000 km pipeline network.

Most of MWA's pumping stations were equipped with eddy current coupling drives that controlled the speed of the treatment plant's water pumps. Even though they operated with varying speed, MWA had excess energy losses of almost 15-30% because of the out-dated technology. As electricity costs amount to almost 50% of its production cost, MWA was looking for ways to increase the efficiency of its pumping stations. It was decided to replace the coupling drives with ABB's ACS1000 medium voltage drives and by doing this, the treatment plant's system efficiency has increased by 15-30% (depending on the required operating speed).

In the first year of their operation, the first two ABB drives have contributed more than $120,000 to energy cost savings. This figure translates into monthly energy savings of approximately 180,000 kWh and does not take into account any additional savings from improved maintenance.

CO2 emissions have been reduced by about 90,000 kg per month.

Other practical plusses include a more flexible pump operation, increased lifetime of motors and pumps, easier maintenance and full automatic control.