Humic acids and their derivatives can be used for removing toxic metalsand their ions from wastewater. Humic acids can be applied as an adjunct in dissolved air flotation cells to assist in the removal of trace amounts of grease, oil, liquid organics and suspended matter. They should be considered as a special coagulant aid to be used in conjunction with watersoluble polymeric flocculants for removal of soluble organics. They can also be used as potential fluid loss additives in certain types of organic liquids to prevent seepage from lagoons or pit containment areas.
Humic acids are used most effectively in particular in the stage subsequent to chemical treatment of water. A chemical treatment leads to the precipitation of metals by means of calcium hydroxide or sodium hydroxide. Adding humic acids improves the process and lowers the concentrations of undesirable ions below the permissible limit. As stated above, it is also possible to use humic acids for removing toxic metals from water. The residual concentration of toxic metals in waste water after such a treatment is lower than 0.03 mg/L. The highest effect can be observed in the removal of lead (Pb), mercury (Hg), cadmium (Cd), copper (Cu), zinc (Zn), nickel (Ni) and chromium (Cr). Not a heavy metal but toxic, humic acids also remove aluminium from wastewater successfully.
The humic acid solution to be applied is obtained through a special extraction from highly oxidized lignite. The product is composed of high-molecular humic acids, which can be coagulated through neutralization and polyvalent cations. Humic acid solution for water treatment should not be mistaken for humic acids and their metal complexes which are considered as disturbing water impurities from water works. The latter are low-molecular humic acids and their rudiments.
Due to their outstanding properties of adsorption of liphophilic substances, their high cation exchange capacity, their ability to form hardly soluble complexes with polyvalent cations and heavy metals and their high electron exchange capacity, humic acids are ideal as sorption medium for a number of water impurities and especially for heavy metals and liphophilic substances.
In wastewater treatment, the process is based on the injection of a fluid humic acid solution in ground water channel. There humic acids create a reactive wall in which harmful substances in ground water are dismantled. Requiring low investment and maintenance levels, this method proves to be cost-effective, secure and environmentally friendly.