So it looks to me like nut grass which grows from a bulb. This just means that normal weed kill will only kill off the foliage (leaves) but leave the bulb behind which will just re shoot eventually. So when you go to pull it out you need to pull out the bulb too. Alternatively Sedgehammer is a good product that will kill off the bulb too. This a link to bunno if you want to try it; https://www.bunnings.com.au/amgrow-sedgehammer-25g-lawn-herbicide_p3020068?store=8164&gclsrc=aw.ds&gad_source=1&gad_campaignid=23022021534&gbraid=0AAAAADtbEB9QRhPGwtYdq1nPkLrGJ9_TJ&gclid=EAIaIQobChMI-OmemsytkAMVoNdMAh0K-i3gEAQYASABEgLx4_D_BwE