Sulfide ion-selective electrodes for control of chemical feed of organic sulfide products for metal ion precipitation from waste water

A method of automatically controlling the chemical feed of an organic sulfide chemical precipitant to a wastewater treatment system, comprising the steps of:

• continuously introducing a wastewater containing dissolved metal and having a pH in the range of about 6-12 into a precipitation tank;
• continuously feeding an organic sulfide chemical precipitant by a precipitant feed unit into the precipitation tank in a sufficient amount to precipitate said dissolved metal;
• determining a first set point electrochemical potential between a sulfide electrode and a reference electrode disposed in said precipitation tank corresponding to a precipitant underfeed condition and a second set point electrochemical potential between said sulfide electrode and the reference electrode corresponding to a precipitant overfeed condition programming a controller unit with said first setpoint electrochemical potential and said second setpoint electrochemical potential;
• and,
• automatically controlling the feed of said organic sulfide chemical precipitant by the precipitant feed unit into the precipitation tank by said controller unit which continuously maintains the electrochemical potential of the precipitation tank between the first set point and the second set point, to precipitate said dissolved metal in said precipitation tank.