Chemicals

 


 

Phosphate

in the

Little Miami River



Background
As indicated in the web page of Little Miami, Inc., the Ohio Environmental Protection Agency has implicated phosphate as contributing to excessive algae growth in the Little Miami River, thus depriving fish of sufficient oxygen. The tests described here were undertaken in an attempt to determine the levels of phosphate and perhaps isolate the sources.

The Little Miami, Inc. web page cites 10 ppb (parts per billion) as an upper recommended limit for phosphate in fresh water. Algae blooms can occur at levels of 5 to 10 ppb, and become readily apparent at levels of as little as 50 ppb. The usual criteria are 30 ppb for running waters and 20 ppb for lakes, reservoirs and other slow moving water bodies. No national criteria have been established for concentrations of phosphorus compounds in water; however, to control eutrophication, the EPA makes the following recommendations:

The United Kingdom Environment Agency proposed the following interim standards for phosphorus in standing and running fresh waters (December 1998):


Standing
(µg/l total P)
Running
(µg/l soluble reactive P)
Oligotrophic
8
20
Mesotrophic
25
60
Meso-eutrophic
-
100
Eutrophic
85
200

Ohio EPA (1999) Potential TP Criteria (mg/L) for Ohio Rivers.

Watershed S ize Aquatic Life Designations W W H E W H M W H
Headwaters (drainage area < 20 mi2) 0.08 0.05 0.34
Wadable Rivers (20 mi2 < drainage area < 200 mi2) 0.10 0.05 0.28
Small Rivers (200 mi2 < drainage area < 1000 mi2) 0.17 0.10 0.25
Large Rivers (drainage area > 1000 mi2) 0.30 0.15 0.32

WWH - Warmwater Habitat; EWH - Exceptional Warmwater Habitat; MWH - Modified Warmwater Habitat.

Test Method
Samples were taken from the riverside using a sampling cup attached to a 4-ft extensible rod. 8-oz. containers were triply rinsed with sample, and stored at room temperature for not more than 6 hrs prior to analysis.

Phosphate measurements were made with a Hach Pocket Colorimeter for reactive phosphorus. Reactive phosphorus is determined in essentially two steps by the Ascorbic Acid Method. The first step involves reaction of orthophosphate with molybdate in acid solution to form a yellow-colored phosphomolybdate complex:

12 MoO3 + H2PO4- --> (H2PMo12O40)-

The phosphomolybdate complex is then reduced by ascorbic acid, causing a characteristic molybdenum blue species.

10 ml samples were reacted with PhosVer 3 powder pillows for 2 minutes prior to taking a reading. The reference cell was also 10 ml, and contained untreated sample. The Colorimeter's resolution is 10 ppb. A check with distilled water gave a reading of 0 +/-10 ppb. A check with Hach phosphate reference standard (3.00 +/- 0.03 mg/l) gave a reading of 3.08 mg/l, so the readings below are believed to be accurate within about 3%. Tap water in Maineville on July 6, 1996 measured 220 ppb. Readings were taken in singlicate or duplicate as noted below.

Sampling Locations
The Little Miami River flows southward to the east of Cincinnati into the Ohio River. The main stream is fed in part by Caesar's Creek Lake. More information on the Little Miami River can be found at the sites of the US Geological Survey and the Ohio Division of Natural Areas and Preserves.

Sites are shown in the linked sampling map.

Results
Full results for all phosphate measurements made in the Little Miami River, mostly in Warren County, are contained in the linked page.

Discussion
Phosphate results showed an increasing trend as measurements were made further upstream (see chart). Readings from 12/1/96 were taken while the river was exceptionally high, and so the lower phosphate readings may reflect a dilution effect in addition to a seasonal variation. During readings taken 1/3/97, after an immoderately warm week, it was noted that the river had a greenish hue.

Tributaries, such as Todd's Fork, Caesar's Creek, Bear Run, Wolfe Creek, Salt Run, Cane Run, Plum Run, Bigfoot Run and Halls Creek, generally had lower readings than the river itself. The exception to this was Simpson Creek, which gave readings nearly three times higher than the highest observed in the main river. Readings taken further up Simpson Creek, near and at Landen lake, showed typically low phosphate levels. The highest levels were observed from the effluent of the Warren County Lower Little Miami River Waste Water Treatment Plant (WWTP), which flows directly into Simpson Creek.

Likewise, Muddy Creek and Turtle Creek have excessively high phosphate levels. Upstream of the WWTP's, which empty into the creeks, the concentration returns to more typical levels.

An extensive study of the Little Miami River was performed by the Ohio EPA in 1993. This report (MAS/1994-12-11) is available from the State of Ohio EPA, Division of Surface Water, 1685 Westbelt Drive, Columbus OH 43228. In this report the flow through the Lower Little Miami River WWTP is given as approximately 2 million gallons/day. For a phosphate concentration of 4.7 mg/l, this is equivalent to 37 kg of phosphates per day.

Small MapThe Caesar's Creek tributary had a markedly lower phosphate level (190 ppb) than did the river at that point (1030 ppb). Using a mass-balance calculation with phosphate as a marker,

Nixon Bridge + Caesar's Creek = Oregonia

(1030)(x) + (190)(1-x) = 760

x = 0.679

shows that about one-third of the Little Miami River at Oregonia is coming from Caesar's Creek. A similar calculation could be performed on the 5/11/97 data measuring the confluence of the River with Simpson Creek at the Carl Rahe access point, however the access point may not be sufficiently downstream to ensure complete mixing.

The Little Miami, Inc. website has recently provided preliminary phosphate and oxygen data for the East Fork of the Little Miami River as determined by researchers at the University of Cincinnati.

The phosphate levels for the East Fork are generally lower (mostly below 200 ppm) than those noted above in the main branch of the river. This may be a real difference, or may be due to analytical biases. No temporal trend is evident in the data, but in general the phosphate level appears to increase as one moves downstream (see chart).

The oxygen levels in the East Fork do not vary perceptibly along the length of the river, but a temporal variation is clearly evident (see chart). During the winter months, the oxygen levels average about 13 mg/l, while during the summer they descend to about 7 mg/l.

Human waste accounts for a large portion of the phosphate deposited into the Little Miami River. It has been estimated that human urine alone contains 60% of the phosphorus in househould wastewater (H. Jönsson et al., Wat. Sci. Tech. 35 (9) 145-152, 1997), or that 80% of phosphorus in urban wastewaters come from 1% of the input waters: toilets (T. Herrmann & U. Klaus, Wat. Sci. Tech. 36 (8-9) 167-172, 1997). Ingestion of carbonated beverages, which often contain phosphoric acid as an acidifier, contributes to our phosphate throughput. Coca-Cola was assayed at approximately 0.5% phosphate, or 1.75 g phosphate per 12-oz. can. If an individual drinks an average of one can of cola per day, a community of 10,000 would be delivering 17.5 kg of phosphate to the River. The contribution from milk is probably not too far behind, as fat-free milk assays at just under 0.2% phosphate.

It would be difficult to change the amount of phosphate coming from humans, as the Recommended Daily Dietary Allowance (RDA) for adults is 800-1200 mg phosphorus. Assuming this phosphorus value refers to phosphate, then a typical human using 100 gallons of water per day would raise the phosphate concentration of their wasterwater to 2.5 mg/l (2500 ppb). This is close to what is coming out of the Simpson Creek wastewater facility.

Traditional wastewater treatment plants using thickened sludge do not exceed phosphorus removal efficiencies of 30% (C. Sommariva et al., Desalination, 255-260, 108, 1996). Remaining phosphorus can be removed via chemical additives at additional cost. Sommariva has developed a technique to remove over 85% of phosphorus at influent levels up to 90 mg/l by adapting biomass to high phosphorus levels. Zhao and Sengupta have developed a polymeric ligand exchanger system based on DOW3N that achieves bed outflows of <0.1 mg/l phosphorus ("Ultimate removal of phosphate from wastewater using a new class of polymeric ion exchangers", Wat. Res. 32 (5) 1998). Operating costs, for a reduction from 4 mg/l to less than 0.5 mg/l, ranged from $25 to $35 per 1000 gallons.

The European Urban Waste Water Treatment Directive (21 May 1991) requires phosphorus removal at all sewage works serving conurbations of more than 10,000 person equivalents.This treatment must remove at least 80% of phosphorus and reduce concentrations in the outflow to below 2 mg/l (1 mg/l if >100,000 person equivalents). In May 2007, phosphate removal began at Edmonton, Alberta. Phosphate is removed as struvite (ammonium magnesium phosphate) which can be used as fertilizer. A pilot plant is being tested at Mill Creek in Cincinnati.


Other sites of interest, from local to international:

Chateau La Roche, the Castle on the Little Miami
Little Miami River Partnership
Little Miami Flow at Milford
Greenacres Foundation
Sierra Club, Miami Group
Greenacres Foundation
Clermont County Office of Environmental Quality
ORSANCO, Ohio River Valley Water Sanitation Commission
Greenlink
Ohio EPA, State Environmental Protection Agency
US Geological Survey, Water Resources in Ohio
RMS, River Management Society
United States EPA, Federal Environmental Protection Agency
Scope, the Newsletter of the Scientific Committee on Phosphates (mostly Europe)
Phosphate Recovery
Washed Phosphate • S.E.T Alshoweky for Engineering & Trading (Syria) • showeky2 <at> scs-net.org
UNGEMS, United Nations Global Environment Monitoring System/Water Programme


Debut: 11/1/96. Revision No. 39, October 27, 2012.
Please send comments to Jeffrey Clymer. Other pages by the author.
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