Chemicals used for treatment of water intended for human consumption Phosphoric acid. This includes the following specified in Table1 below: Table 1 Phosphoric acid content Greater than 75% ( m/m ) H3PO4 . Within +/- 1% of stated concentration. Density 1.57 g/ ml @ 200C for 75% ( m/m ) H3PO4 Sulphuric acid content Maximum 500 mg/ Kg in H3PO4 Iron content ( Fe ) Maximum 20 mg/ Kg in H3PO4 MAXIMUM ACCEPTABLE LEVELS OF TOXIC SUBSTACES Contaminants Maximum Prescribed Concentrations in Drinking Water ( ug/l ) Maximum Acceptable Level Limit in mg/Kg of H3PO4 Arsenic ( as As ) 10 2 Cadmium ( as Cd ) 5 0.5 Chromium ( as Cr ) 50 4 Mercury ( as Hg ) 1 0.5 Nickel ( as Ni ) 20 4 Lead ( as Pb ) 25 4 Antimony ( as Sb ) 5 4 Selenium ( as Se ) 10 1