**2.1 Sample characterisation**

 The study site is located on Sungai Kerian at Lubok Buntar Kedah, Malaysia (**Figure 4**). The sample was collected during dry and wet seasons from Sungai Kerian and tube well. One hundred samples were collected; 50 sample for column test. Tube well water samples were collected in sterile amber glass bottles of 125 ml without headspace in order to prevent the formation of air bubbles and were airtight sealed. All laboratory analytical analysis was according to Standard Method [37]. Ten litres of river raw water sample was collected in polyethylene bottles. These samples were preserved in accordance with Water and Wastewater Standards and then stored at a temperature of less than 4°C. Laboratory apparatus used in this study were prewashed with 5% nitric acid (HNO3) and rinsed with deionised water prior to testing.

#### **2.2 Experimental setup**

 In this study, 13 runs of test with different magnetic field exposures were conducted. The horizontal transparent polypropylene cylindrical columns test with inner diameters of 50 mm were used. The coiled column test was built on the horizontal axis, and the magnetic field was generated by means of a solenoid, obtained with overlapping windings of copper wires, at 500 mm in length. The coils wrapped around the column transformed the magnetic fields controlled by the magnetic field power generating system. The maximum of effective current was 2 A at 50 Hz frequency. The magnetic generator consisted of a pair of solenoid coils, a current amplifier, and a waveform generator controller. The samples were exposed and placed in a horizontal column where uniformity of the magnetic field was optimal. Then, the LF-EMF coiled column experiment was started by pumping water samples in a horizontal direction into the column in order to ensure complete wetting of the particles [54]. A constant discharge rate was maintained using the peristaltic pump model Masterflex L/S HV 07522–20 at 50 and 100 mL/min to allow sufficient contact time between the magnetic field, and for the removal of *E. coli*.

**Figure 4.**  *The location of Kerian River in map of peninsular Malaysia.* 

#### **Figure 5.**

*Set-up for LF-EMF column study on E. coli removal by using magnetic fields exposure with alternating current.* 

The water sample was continuously fed into the column for a total experiment time of 6 hours. A total of 18 effluents were collected every hour directly into 100 mL sterilised vessels. The experimental setup is shown in **Figure 5**.
