How does sulphide and carbonates present in water toxic ?

Explanation

Sulphide `(S^(2-))` and carbonate `(CO_(3)^(2-))` present in water undergo anionic hydrolysis. This leads to the formation of weak acids `H_(2)S and H_(2)CO_(3)`. The pH of water increases due to the formation of these acids. Water thus becomes alkaline and hence it will be toxic.