水中锰的来源及处理
Source
Manganese ( Mn+2) is present in many soils and sediments as well as
in rocks whose structures have been changed by heat and pressure. It is used in
the manufacture of steel to improve corrosion resistance（耐腐蚀性） and
hardness. Manganese is considered essential to plant and animal life and can be
derived from such foods as corn, spinach, and whole-wheat products. It is known
to be important in building strong bones and may be beneficial to the
cardiovascular(心血管的） system. Manganese may be found in deep well waters at
concentrations as high as 2 - 3 mg/l. It is hard to treat because of the
complexes it can form which are dependent on the oxidation state, pH,
bicarbonate-carbonate-OH ratios, and the presence of other minerals,
particularly iron. Concentrations higher than 0.05 mg/l cause manganese deposits
and staining of clothing and plumbing fixtures. The stains are dark brown to
black in nature. The use of chlorine bleach in the laundry will cause the stains
to set. The chemistry of manganese in water is similar to that of iron. A high
level of manganese in the water produces an unpleasant odor and taste. Organic
materials can tie up manganese in the same manner as they do iron; therefore
destruction of the organic matter is a necessary part of manganese removal.
Treatment
Removal of manganese can be done by ion exchange (sodium form cation - softener)
or chemical oxidation - retention - filtration. Removal with a water softener
dictates that the pH be 6.8 or higher and is beneficial to use countercurrent
regeneration with brine make-up and backwash utilizing soft water. It takes 1
ppm of oxygen to treat 1.5 ppm of manganese. Greensand filter with potassium
will remove up to 10 ppm if pH is above 8.0. Birm filter with air injection will
reduce manganese if pH is 8.0 to 8.5. Chemical feed (chlorine, potassium
permanganate, or hydrogen peroxide) followed by 20 minutes retention and then
filtered with birm, greensand, carbon, or Filter Ag will also remove the
manganese.
