Method for removing calcium ions from high concentration organic wastewater

A method for removing calcium ions from high concentration organic wastewater, wherein the method comprises the steps of:

• (1) introducing inorganic carbon, a seed crystal and high concentration organic wastewater containing Ca2+ into a reactor,
• wherein a molar ratio of Ca2+ to inorganic carbon is 1:(3.2-6.2),
• wherein the seed crystal in step (1) is biomass with negative potential on a surface, and a particle size of the seed crystal is 0.2 μm-2 mm;
• (2) adjusting a hydrogen ion activity α(H+) and ionic strength of the solution in the reactors,
• wherein the α(H+) in step (2) is adjusted to 3.16×10−12-6.31×10−9 mol/L, and
• the ionic strength after adjusting in step (2) is in a range of 0.3-2 mol/L;
• (3) sequentially stirring and precipitating in the reactor to convert Ca2+ in the high concentration organic wastewater into calcium carbonate which is then precipitated for calcium removal,
• wherein the precipitating step is followed after the stirring step is stopped.