Waste management company NSL Oilchem Logistics was fined $17,000 last month for the illegal discharge of liquid waste into public sewers on two occasions (Waste management firm fined $17,000 for illegal discharge into Tuas sewers, Nov 24). It was fined $12,200 in 2018 for a similar offence.

National water agency PUB said such acts disrupt Singapore's used water reclamation processes, an important pillar of water sustainability.

The fine previously meted out to NSL Oilchem Logistics did not seem to have enough of a deterrence effect.

I beseech the relevant authorities to hand out a custodial sentence for such irresponsible practices which may one day cause immense harm to Singapore's water security.

Foo Sing Kheng