Spraying effluent on land has been relatively 
effective in removing nutrients from municipal 
wastewater, but drainage from the land must not 
be allowed to flow into a receiving body of water. 
Membrane processes, primarily for dissolved 
solids removal, have some capability for nitrogen 
and phosphorus removal but are expensive. 
Distillation is efficient for removing nitrogen 
and especially phosphorus. 
Other methods have been proposed, but most 
are still in the research or developmental stages. 
Recent FWPCA hearings on Lake Michigan no 
doubt will accelerate efforts to evolve an efficient, 
inexpensive method for phosphorus removal. The 
Secretary of the Interior stated that phosphorus 
removal from municipal wastewater should be 
maximized, and municipalities that discharge ef- 
fluents to Lake Michigan should accomplish 80 per 
cent phosphorus removal by 1972. 
Agricultural runoff, a significant source of 
nutrients, is more difficult to control. However, 
some measures can be taken to exclude nutrients, 
including land management to prevent erosion and 
subsequent pollution by siltation. 
Measures are being implemented to control 
watercraft wastes, including retention of wastes 
onboard for treatment ashore and onboard proces- 
sing equivalent to secondary treatment and a 
corresponding degree of nutrient removal. Consid- 
erable research and development sponsored by the 
FWPCA, Navy, and Coast Guard is in progress. 
Another measure that can be implemented to 
exclude nutrients from the Great Lakes is the 
cessation of dredge spoil, garbage, trash, and refuse 
disposal in the lakes. Of these, dredging has caused 
concern in localized areas because of the amount 
of nutrients associated with the spoil. 
2. Nutrient Diversion 
Diversion of nutrient-containing effluents (such 
as municipal wastewater) around bodies of water is 
a technique successfully employed in the past to 
prevent accelerated eutrophication. Despite its 
success, this method could prove shortsighted. The 
pollution problem merely is passed to a down- 
stream impoundment, lake, bay, or estuary. This is 
not acceptable resource management unless sub- 
stantial mitigating circumstances exist for which 
the long-term effects are thoroughly understood. 
D. Restorative Measures 
Restorative measures are intended to remove 
nutrients from water. While prevention involves 
millions of gallons per day, restoration in the 
Great Lakes involves hundreds of cubic miles of 
water. This point should be carefully remembered 
when alternative courses of action are considered. 
Some restorative techniques discussed below 
are based on limnologica! theory rather than actual 
experimental or developmental work. Others are 
based on applications to lakes of much smaller size 
than the Great Lakes. 
1. Sealing Bottom Sediments 
If the addition of all nutrients were terminated, 
recycling of nutrients from previously deposited 
sediments would continue accelerated eutrophica- 
tion of the Lakes for a considerable time. One 
solution is to seal the bottom sediments from the 
overlying waters. This seal must be renewed 
periodically, perhaps annually, if accumulation of 
additional nutrients by natural causes continues. 
2. Flushing with Low-Nutrient Water 
Use of low-nutrient water to flush eutrophic 
lakes has been employed with some success to 
restore water quality. This method was used in 
Green Lake near Seattle, and similar experiments 
are planned for Moses Lake, Washington. The great 
quantities of low-nutrient water required make 
application of this method in the Great Lakes 
questionable. Further, downstream waters may be 
adversely affected by the flushed nutrients. 
3. Nutrient Removal 
Although two-thirds of the phosphorus intro- 
duced into Lake Erie is retained in the bottom 
sediments, significant amounts also are retained by 
fish, algae, and rooted vegetation. Removal of fish 
will be considered in later discussions. It is 
essential that algae and aquatic weeds be removed 
from the Lake. Cutting nuisance aquatic weeds 
and leaving them in the water effects no nutrient 
removal. Furthermore, the harvested algae and 
weeds must be removed so nutrients do not 
reenter the lake by leaching and drainage. One 
solution would be to utilize them for added 
benefits as sources of protein, fertilizer, mulch, or 
animal feeds. 
VI-127 
