mercury salt - containing discharge effluents such as from b - 5 fixatives and pva fixatives are treated to remove mercury therefrom . the present method contemplates plates the addition of aluminum to the effluent to cause the precipitation of elemental mercury therefrom . the remaining effluent , after precipitation , can be decanted and post treated while recovering precipitated elemental mercury . the decanted effluent , once subjected to post treatment , by first rendering the effluent highly basic , is the neutralized . neutralization causes the precipitation of sodium chloride . a water conditioner is then added thereto . subsequently , the so - treated decanted effluent is then filtered through a filtering medium such as filter paper or the like . a second filtration step may then be carried out by passing the so - filtered effluent through a mixed bed or through a filter paper .