Aluminum is toxic to some fish. Ferric chloride is not recommended due to its high
cost and its potential to leave a residual color.
In order to apply the technique of phosphate removal from a hypolimnion, the
first step would be to determine the volume of the hypolimnion. DAF/filtration
systems of the type used in this study are available up to 13,000 gpm (49,205 L/
min). Knowing the existing phosphorus concentration and the treated effluent
concentration a calculation can be made of how much volume of water would
have to be treated to bring the phosphorus concentration down to an acceptable
level. This may require several years of operation. However, if the lower nutrient
level will reduce the biological growth to a level where the hypolimnion may remain
aerobic, there will be less release of phosphorus from the benthic deposits. A further
consideration is that DAF involves aerating the water. If the effluent is discharged to
the hypolimnion, it may provide sufficient additional oxygen to maintain aerobic
conditions. This should enter into the calculation and influence the final decision to
utilize DAF/filtration (DAFF) to control lake eutrophication. The US Environmental
Protection Agency (US EPA) has summarized the performance data of DAF alone
(Appendix E) and supplemental filtration (Appendix F).
8 Sources, Chemistry, and Control of Acid Rain
Acid rain is a serious environmental problem that affects large parts of the United
States and Canada. Acid rain is particularly damaging to lakes, streams, and forests
and the plants and animals that live in these ecosystems. Acid rain is rain consisting
of water droplets that are unusually acidic because of atmospheric pollution [47]; it is
rain with a higher concentration of positively charged atomic particles (ions) than
normal rain. Acid rain and its frozen equivalents, acid snow and acid sleet, are part of
a larger problem called acid deposition. Acid deposition also includes direct deposition, in which acidic fog or cloud is in direct contact with the ground, and dry
Fig. 7.9 Results of DAF pilot plant study for removal of phosphorus from the hypolimnion of
Devils Lake using alum
278
L. K. Wang et al.
cost and its potential to leave a residual color.
In order to apply the technique of phosphate removal from a hypolimnion, the
first step would be to determine the volume of the hypolimnion. DAF/filtration
systems of the type used in this study are available up to 13,000 gpm (49,205 L/
min). Knowing the existing phosphorus concentration and the treated effluent
concentration a calculation can be made of how much volume of water would
have to be treated to bring the phosphorus concentration down to an acceptable
level. This may require several years of operation. However, if the lower nutrient
level will reduce the biological growth to a level where the hypolimnion may remain
aerobic, there will be less release of phosphorus from the benthic deposits. A further
consideration is that DAF involves aerating the water. If the effluent is discharged to
the hypolimnion, it may provide sufficient additional oxygen to maintain aerobic
conditions. This should enter into the calculation and influence the final decision to
utilize DAF/filtration (DAFF) to control lake eutrophication. The US Environmental
Protection Agency (US EPA) has summarized the performance data of DAF alone
(Appendix E) and supplemental filtration (Appendix F).
8 Sources, Chemistry, and Control of Acid Rain
Acid rain is a serious environmental problem that affects large parts of the United
States and Canada. Acid rain is particularly damaging to lakes, streams, and forests
and the plants and animals that live in these ecosystems. Acid rain is rain consisting
of water droplets that are unusually acidic because of atmospheric pollution [47]; it is
rain with a higher concentration of positively charged atomic particles (ions) than
normal rain. Acid rain and its frozen equivalents, acid snow and acid sleet, are part of
a larger problem called acid deposition. Acid deposition also includes direct deposition, in which acidic fog or cloud is in direct contact with the ground, and dry
Fig. 7.9 Results of DAF pilot plant study for removal of phosphorus from the hypolimnion of
Devils Lake using alum
278
L. K. Wang et al.