Whereas algae may be undesirable in lake water treatment, algae are also being
harvested in some places for their nutrient value. The use of dissolved air flotation
for harvesting cultivated algae for animal feed has been shown to be an efficient
means of separating algae from their watery growth medium. The algae have been
used as a livestock feed since they have a high nutrient and protein content and are
reported to be highly acceptable to livestock. Another important benefit of the algae
harvesting from lake water is reduction of chlorine dosage as an algicide, in turn,
reduction of trihalomethanes, taste, and odors in drinking water when the lake water
is used as the freshwater supply [45].
Acid rain and acid mine drainage pollute lake waters everywhere and have
become a serious international problem. In order to develop alternative remedial
methods for recovery of acid lakes believed due to acid rain and/or acid mine
drainage, many engineering and management studies have been conducted on
various chemical manipulation methods for lake water neutralization [45]. The
materials evaluated for lake water neutralization include calcium hydroxide, sodium
carbonate, agriculture limestone, fly ash, water treatment softening sludge, cement
plant bypass dust, di-calcium silicate, calcium oxide, and magnesium oxide. It has
been known [45] that the use of lime products is an effective way to neutralize
acidified lake waters if properly administrated.
If acid lakes are contaminated by acid mine drainage, not only the water’s high
acidity shall be neutralized, but also its heavy metal concentrations (copper, zinc,
cadmium, lead, iron, manganese, etc.) shall be reduced to safe or desirable levels.
Chemical precipitation is a common process for inactivation of soluble metal ions.
The precipitated insoluble metals in floc forms can be further separated by sedimentation, dissolved air flotation, and/or filtration.
The dissolved air flotation (DAF) investigated in this research is of an innovative
process [83–87]. The treated effluent containing an almost saturated concentration of
dissolved oxygen can be discharged to the lake bottom for hypolimnetic aeration.
The use of aluminum sulfate, sodium aluminate, and lime in a flotation system can
accomplish phosphate removal, biotic separation, and harvesting. Either sodium
aluminate or lime can be used in the flotation system for neutralization of acidity
caused by acid rain and acid mine drainage. A DAF plant built on a boat is one
method that should be considered for phosphate removal, acid neutralization, or
algae harvesting in a lake. Lake restoration may be effective in extending the service
life of a lake. Other lake restoration technologies, such as chemical feeding, mixing,
acid neutralization, chemical precipitation, coagulation, flocculation, filtration, nitrogen removal processes, dredging, algae harvesting, etc. can all be found from the
literature [32, 42, 43, 77–83, 88]. AquaDAF was investigated for lake restoration.
The AquaDAF process is introduced in detail in the literature [87]. Although
AquaDAF has been demonstrated successfully for lake water treatment, all other
manufacturers’ DAF equipment, such as Supracell, Sandfloat, KAMET, Clari-DAF,
etc., may also be used for successful lake restoration under the conditions that the
types and dosages of chemicals must be correct, and the operators must know what
they are doing.
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L. K. Wang et al.
harvested in some places for their nutrient value. The use of dissolved air flotation
for harvesting cultivated algae for animal feed has been shown to be an efficient
means of separating algae from their watery growth medium. The algae have been
used as a livestock feed since they have a high nutrient and protein content and are
reported to be highly acceptable to livestock. Another important benefit of the algae
harvesting from lake water is reduction of chlorine dosage as an algicide, in turn,
reduction of trihalomethanes, taste, and odors in drinking water when the lake water
is used as the freshwater supply [45].
Acid rain and acid mine drainage pollute lake waters everywhere and have
become a serious international problem. In order to develop alternative remedial
methods for recovery of acid lakes believed due to acid rain and/or acid mine
drainage, many engineering and management studies have been conducted on
various chemical manipulation methods for lake water neutralization [45]. The
materials evaluated for lake water neutralization include calcium hydroxide, sodium
carbonate, agriculture limestone, fly ash, water treatment softening sludge, cement
plant bypass dust, di-calcium silicate, calcium oxide, and magnesium oxide. It has
been known [45] that the use of lime products is an effective way to neutralize
acidified lake waters if properly administrated.
If acid lakes are contaminated by acid mine drainage, not only the water’s high
acidity shall be neutralized, but also its heavy metal concentrations (copper, zinc,
cadmium, lead, iron, manganese, etc.) shall be reduced to safe or desirable levels.
Chemical precipitation is a common process for inactivation of soluble metal ions.
The precipitated insoluble metals in floc forms can be further separated by sedimentation, dissolved air flotation, and/or filtration.
The dissolved air flotation (DAF) investigated in this research is of an innovative
process [83–87]. The treated effluent containing an almost saturated concentration of
dissolved oxygen can be discharged to the lake bottom for hypolimnetic aeration.
The use of aluminum sulfate, sodium aluminate, and lime in a flotation system can
accomplish phosphate removal, biotic separation, and harvesting. Either sodium
aluminate or lime can be used in the flotation system for neutralization of acidity
caused by acid rain and acid mine drainage. A DAF plant built on a boat is one
method that should be considered for phosphate removal, acid neutralization, or
algae harvesting in a lake. Lake restoration may be effective in extending the service
life of a lake. Other lake restoration technologies, such as chemical feeding, mixing,
acid neutralization, chemical precipitation, coagulation, flocculation, filtration, nitrogen removal processes, dredging, algae harvesting, etc. can all be found from the
literature [32, 42, 43, 77–83, 88]. AquaDAF was investigated for lake restoration.
The AquaDAF process is introduced in detail in the literature [87]. Although
AquaDAF has been demonstrated successfully for lake water treatment, all other
manufacturers’ DAF equipment, such as Supracell, Sandfloat, KAMET, Clari-DAF,
etc., may also be used for successful lake restoration under the conditions that the
types and dosages of chemicals must be correct, and the operators must know what
they are doing.
306
L. K. Wang et al.