15. Atmospheric Quality Deterioration 
The carbon dioxide content of the world’s 
atmosphere has increased a small amount, and the 
temperatures of the atmosphere have increased 
likewise. Consequent temperature increases in the 
water cause a small drop in dissolved oxygen. 
It is virtually impossible to predict what would 
happen to the eutrophication trend by removing 
any single nutrient source. While priorities should 
be established for preventive and restorative tech- 
niques, many methods must be implemented 
before restoration can be achieved. 
Factors contributing to accelereated aging are 
ranked below according to their importance in the 
problem. Hence, they serve as the targets for both 
preventive and restorative measures: 
High Impact 
Municipal wastewater 
Agricultural runoff 
Sediment interchange 
Medium Impact 
Industrial wastewater 
Combined storm sewage 
Urban land drainage 
Dredging 
Nutrient-laden inflow from tributaries 
Fisheries 
Low Impact 
Watercraft wastes 
Oil discharges 
Thermal discharges 
Waterfowl 
Subsurface waste disposal 
Atmospheric quality deterioration 
Can the eutrophication process in the Great 
Lakes be reversed? This is an extremely significant 
question, because the effort and funds expended 
on Great Lakes restoration will greatly influence 
the answer. In referring to Lake Erie, Dr. Ralph L. 
Brinkhurst of the University of Toronto said, “It’s 
the healthiest corpse I’ve seen.” He firmly believes 
that eutrophication can be reversed, citing specific 
studies that demonstrate eutrophication reversal 
has occurred in other smaller lakes. The fact that 
the FWPCA and other agencies are working to 
control elements contributing to eutrophication 
and to restore water quality reinforces Dr. 
Brinkhurst’s conclusion. 
Technology to control eutrophication may be 
classified as preventive or restorative. Preventative 
measures remove nutrients from the water before 
discharge to a receiving body, and restorative 
measures remove the nutrients or the products of 
eutrophy from the affected body of water. Meas- 
ures which reduce nutrients usually improve other 
water quality parameters, (e.g., bacterial content) 
which may have little effect on eutrophication. 
C. Preventive Measures 
1. Nutrient Exclusion 
Most research has been to develop suitable 
methods to remove nutrients from municipal 
wastewater. Most methods, however, can be 
applied also to other nutrient-containing aqueous 
flows. The soap and detergent industry is seeking 
substitutes for the phosphate in detergent formula- 
tions, because detergents account for a substantial 
part of the phosphorus in municipal wastewater. 
Activated sludge secondary treatment plants 
can be operated to optimize nutrient removal. 
Aeration rate, aeration time, aeration solids, and 
return sludge ratios are critical to effective phos- 
phorus removal. These plants also can be operated 
to accentuate denitrification, employing a variety 
of operating procedures. 
Capitalizing on the principle that nutrients in 
municipal wastewaters cause prolific growth of 
algae, algae are cultured under controlled condi- 
tions in the treatment plant. The algae then are 
harvested to remove the incorporated nutrients, 
leaving the effluent low in nutrient content. The 
limiting factor in the removal of nitrogen and 
phosphorus by this method is the efficiency of 
algal harvesting. 
Chemical co-precipitation with lime and 
hydrous aluminum and iron oxides is highly 
effective in removing phosphorus from municipal 
wastewater, but nitrogen removal is less effective. 
Of all removal processes, ion exchange is the most 
effective for removing both nitrogen and phos- 
phorus. Ammonia stripping also has been effective 
in removing nitrogen. 
