Encyclopedia of Environmental Science and Engineering, Volume I and II

EUTROPHICATION 399

the exchange capacity due to sulfates and other ions. The

former may be reduced by removing the organic matter from

the resin with sodium hydroxide, hydrochloric acid, methanol

and bentonite.

The effi ciency and cost of nitrogen and phosphorus

removal by ion exchange depends largely on the degree of

pretreatment and/or the quality of the water to be treated.

Removal of nitrogen ranges from between 80 to 92%.

A number of ions exchange resins are available for nitro-

gen removal alone. These include zeolites, strong base anion

resins (Amberlite IRA-410) and nuclear sulfonic cation

resins (Nalcite HCR and Amberlite IR-120).

Algae Harvesting

A two-phase process which involves (1) growing algae in

special shallow wastewater ponds where they feed on the

absorb nutrients, and (2) removing the algae which then con-

tain the nutrients within their systems. Algal predominance

will depend upon the type of nutrients available and the con-

centrations. Frequently the fl agellates euglena and chlorella

will predominate where the nutrient concentration is high,

and fi lamentous green algae such as spirogyra, vaucheria

and ulothrix will predominate where the nutrient concentra-

tion is more moderate. The most desirable algae would be

those that are large, those that would grow rapidly and those

that would require vast quantities of food for energy, such

as the swimming algae. In addition to removing nutrients,

algae produce oxygen which reduces the B.O.D., and certain

fl agellates which ingest inorganic solids, are able to stabilize

some of the organic material.

One of the major diffi culties experienced with this

process involves the harvesting procedure. A number of

methods have been tried which include screening, settling,

centrifuging and chemical screening. All have been found

to present some form of diffi culty, although it appears from

the standpoint of performance and economy, the screening

method may be the least unsatisfactory. Another problem is

that complete nitrogen removal is seldom achieved unless a

carbon source, such as carbon dioxide or methanol, is sup-

plied. Still another problem is the need for disposing of a

huge, sloppy mass of slimy and odoriferous dead algae.

Pilot studies show that a high-rate continuous-fl ow pro-

cess is feasible when light is not limiting, and that orthophos-

phate concentrations can be reduced 90% to less than 1.0

ppm within 6 to 12 hours. Nitrogen removal is variable with

estimates ranging from 40 to 90% effi ciency depending upon

the feed rate, pond design, and climatic conditions. The major

drawbacks to this process aside from those mentioned, are the

large land requirements needed and the necessity to rely on

climatic conditions. In the latter case, artifi cial illumination

may prove of value depending on power rates in the area.

CONCLUSIONS AND OBSERVATIONS

It might be concluded after examining a vast array of mate-

rial that the bio-physical and bio-chemical factors which

affect algae are extremely complex, and it is diffi cult to pre-

dict, with exacting certainty, future events relating to algal

growth. The complexity is greatly magnifi ed by the interac-

tion which apparently exists between the numerous factors

themselves. When these factors are examined and evaluated,

the conclusions reached by one observer are not always in

complete agreement, or may disagree entirely, with the con-

clusions reached by another observer. Commonly, specifi c

organisms may produce different reactions because of their

phase of life, seasonal changes, or because of other complex

and little understood metabolic functions.

In few areas is there less accord than in the literature

written about algae. (See references—The Physical Nature

of Algae, #1 to 33, at the end of this article.) Authorities

vary sharply in their opinions as to classifi cation, physical

descriptions, toxicity thresholds, etc. When this disagree-

ment is added to the previously expressed uncertainties, it

can be seen that our current knowledge is subject to various

interpretations. Thus it is evident that there is a need for more

work; work to develop new and useful information which

will receive universal acceptance and which will clarify and

expand our present knowledge. Conferences dealing with

unique and local problems involving algae and eutrophica-

tion are ongoing. (See References—Eutrophication, #53, 55,

56 and 57, at the end of this article.)

ACKNOWLEDGMENTS

My sincere appreciation is extended to Mr. Robert G. Wieland

who helped in the preparation of the manuscript and to the

Research Foundation of the Newark College of Engineering

for their aid in the typing of the manuscript.

REFERENCES

THE PHYSICAL NATURE OF ALGAE

1. Palmer, Mervin C., Algae in Water Supplies, Robert, A., Taft Sanitary
   Engineering Center, Cincinnati, Ohio, Public Health Service Pub. No.
   657, 1959, p. 8.


2. Babbitt, H.E. and J.J. Doland, Water Supply Engineering, McGraw-Hill,
   N.Y., 1955, p. 457.


3. Kudo, R. R., Protozoology, Chas. C. Thomas Publisher, 3rd Ed., 1950.


4. Palmer, Mervin C. and W.M. Ingram, Suggested classification of algae
   and protozoa in sanitary science, Sewage and Industrial Wastes, 27,
   1955, pp. 1183–1188.


5. Silvey, J.K.G. and A.W. Roach, Studies on microbiotic cycles in sur-
   face waters, Jour. of the Amer. Water Works Assn., Jan., 1964, p. 61.


6. Lackey, James B., Two groups of flagellated algae serving as indicators of
   clean water, Jour, of the Amer. Water Works Assn., June, 1941, p. 1000.


7. Patrick, Ruth. A proposed biological measure of stream conditions,
   Proc. of the 5th Industrial Waste Conference, Purdue, Univ. Engineer-
   ing Bull. No. 34, 1950, pp. 379–399.


8. Rafter, G.W., The Microscopial Examination of Potable Water, Van
   Nostrand Co., N.Y., 1960.


9. See Reference 1. above, pp. 41 and 42.


10. See Reference 1. above, p. 38.


11. Lackey, J.B., Plankton as related to nuisance conditions in surface
    waters, Amer. Assn, for the Advancement of Science, 1949, pp, 56–63.


12. Krauss, Robert W., Fundamental characteristics of algal physiology, Sem-
    inar on Algae and Metropolitan Wastes, Robert, A., Taft Inst., Cincinnati,
    Ohio, Apr., 27–29, 1960, p. 41.

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