Biodegradability of Potential Organic
Substitutes for Phosphates
ROBERT L. BUNCH, Chief
Biological Treatment Research Activities
M. B. ETTINGER, Chief
Chemistry And Physics
Cincinnati Water Research Laboratory
Cincinnati, Ohio
INTRODUCTION
Excessive growths of algae and rooted plants are appearing more frequently in
bodies of water throughout the country because of the increased load of fertilizing
elements which can De traced directly or indirectly to man's activities. Wastewater, whether treated or not, contains considerable quantities of phosphorus,
nitrogen, and other plant nutrients. These elements find their way into rivers,
lakes, and estuaries and give rise to obnoxious algal blooms.
In recent years, the phosphate content of wastewater-treatment plant effluents has -been rising appreciable presumably traceable to the use of phosphates in
detergents. The quantity may have reached a plateau. Levin (1) in 1963 made
a survey of the orthophosphate levels in wastewater-treatment plant effluents
throughout the United States and found levels in the range of 6.5 to 9.0 mg P/l.
In 1958 Stone and Merrell (2) reported that the average amount of orthophosphate
in wastewater-treatment plant effluents of seven California towns was 8.5 mg P/l.
These were considerably higher than the average value of 0.22 mg P/l that
Rudolfs (3) found in the trickling-filter effluents from 12 American plants during
the year 1947. Other surveys such as those of Johnson (4), Owen (5), and Hume
(6) snow the same trend.
Phosphorus content in wastewater is derived from human excretion, garbage,
industrial waste, street runoff and detergent builders. It is estimated (7) that the
total excretion of phosphorus from an average man is 1.5 to 2.0 g P/day. If we
use the upper estimate of 2.0 g/day and assume a total population of 186 million
with an average use of 150 gals of water per capita, we find that the total amount
of phosphorus contributed by man in the USA is 3.0 x 10° lb/yr or 3.7 mg P/l of
wastewater. In 1963, approximately 4.0 x 10^ lb/yr as P were used in detergent
formulations (8,0). Although the amount and proportions of different phosphates
a sewage receives varies from time to time, it appears that in domestic sewage as
much as one half of the phosphorus could come from detergents.
The amount of nitrogen and phosphorus reaching waters that can be attributed
to fertilization of agricultural lands is as yet largely unknown. Many believe the
phosphates are avidly held by most soils and are not as easily leached by rainwater
as are the nitrates. Weibel et al (10,11) studied runoff from both urban and rural
land. The average values for the total hydrolyzable phosphates was 0.4 and 1.7
mg P/l, respectively. He estimated that the amount of phosphate from urban
runoff was only nine per cent of that contributed by sewage from the same area.
It is not the purpose of this paper to discuss the quality of nutrients necessary
for maintaining algal species and the quantity necessary to produce a sharp increase in the population because each species has its own optimum.   Phosphorus
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