The Effect of Continuous Laminar Flow Inversion, Micro-organisms, and Calcium on Acidified Lakes

31 Dec
Robert L. Laing
CLEAN-FLO International

There is ever-growing concern about acidified lakes because of acidic precipitation (acid rain and snow). Several acids are present in the atmosphere. Carbonic acid results when carbon dioxide from animal (and human) respiration and the burning of fossil fuels combine with water in the atmosphere. Sulfuric acid also results from the combustion of fossil fuels, forest fires and other sulphur emissions such as volcanoes. Nitrous oxide is formed when lightning ionizes the nitrogen in the air, and is also a by-product of combustion. When nitrous oxide combines with atmospheric humidity it becomes nitric acid. As a result, these harmful acids precipitate into lakes and rivers.

However, there are other sources of acid. Fertilizers, manure, and sewage can contribute nitric, phosphoric, and other acids through runoff.

It is seldom considered that bottom organic sediments can become a major source of acids in lakes. In most lakes, although the surface water remains oxygenated due to wind and wave action, the bottom water is usually anoxic. Anoxic sediments support anaerobic microorganisms that add acids to the water. Benthic (bottom-feeding) anaerobes also produce ammonia. When ammonia is combined with the oxygenated water on the surface, aerobic bacteria will convert it to nitrate. This is another source of nitric acid.

Sulfate-reducing bacteria generate large quantities of highly toxic hydrogen sulfide in an anaerobic environment. Hydrogen sulfide is one of many factors in the death of fish and other aquatic fauna (Stanier, 1976). When mixed with the oxygenated surface water, hydrogen sulfide then converts to sulfuric acid. Anaerobes also produce organic acids such as amino acids and humic acids. In a stratified lake, the concentrations of these undesirable compounds can rise to dangerous levels.

When lakes attain pH values of 6.0 or less during the day, the pH will be further reduced at night. Aerobic faunal organisms produce carbon dioxide which becomes carbonic acid in water. Aquatic plants reverse their respiration at night, and put carbon dioxide into the water. The carbon dioxide instantly converts to carbonic acid. This is when fish kills begin to occur, and other aquatic organisms decline. As the problem worsens, more organisms disappear and the lake loses most of its recreational value. When the pH level drops to about 4.5 or less, floral and faunal life cease.

As previously mentioned, the pH level of a lake will normally fluctuate during any given day. However, these variations can be amplified in speed and intensity by external inputs into the ecosystem such as changes in sunlight, diurnal changes, heavy rainfalls, or man’s intervention. Fish and other aquatic organisms flourish when carbon dioxide is at its lowest levels. This corresponds to a pH of 7.0 to 8.3.

The CLEAN-FLO Process
It is desirable to oxygenate the entire lake (from top to bottom) for several reasons. In an oxygenated environment the sulfur-reducing anaerobes are killed, and the source of hydrogen sulfide and sulfuric acid is removed. Then the sulfate in sulfuric acid already in the lake is assimilated by microorganisms, plants and aquatic animals. Oxygenation also deactivates benthic anaerobes that produce ammonia. As oxygen levels in the bottom water increase, facultative (low oxygen) microorganisms convert nitric acid to inert nitrogen gas. These organisms use nitrate as the electron donor, e.g., Stanier, et al, 1976. Carbon in the sediment is used as an energy source. The end products are nitrogen gas, carbon dioxide and water.

When a system that oxygenates the bottom water is employed, the surface tension of the small bubbles that are introduced at the bottom drags water to the surface. This initiates a flow that we call continuous laminar flow inversion. Continuous laminar flow inversion/oxygenation raises the pH by stripping carbon dioxide from carbonic acid and exhausting it into the atmosphere. Nitrogen gas is also exhausted to the atmosphere by inversion.

CLEAN-FLO International has been in the lake restoration field since 1970. During this time, we have improved over 1,000 ponds and lakes up to 400 acres (160 hectares). We have accumulated copious data, including about 1,000 pages of raw data comprising both in-house and independent studies. Lakes tested varied from acidic to alkaline water. In all projects, the pH moved toward the carbon dioxide-limited condition of pH 8.3. All other water quality parameters improved. For this report, only data taken by independent agencies was used (See Appendix 1). In-house data was then examined and found consistent with the independent data.

The CLEAN-FLO process of continuous laminar flow inversion/ oxygenation can be coupled with beneficial microorganisms to accelerate this process. CLEAN-FLO has a variety of different microbial cultures that can be added to feed on organic sediment, ammonia, nitrates, or phosphates which will remove these sources of acids. These microbes occur naturally and are not pathogenic. CLEAN-FLO enhances nature’s ability to deal with undesirable pollutants by increasing the concentration of the microorganisms already present. These cultures flourish and multiply when there are large concentrations of pollutants. After they have assimilated the pollutants, they die and return to their natural levels, depositing the compounds organically at the sediment. Insects feed on the sediment, and on microorganisms, and in turn become food for fish. In this way, harmful pollutants become beneficial food for fish.

To avoid the violent variations in pH which result in fish kills, it is important to add a buffer. Bennett (1970) suggested lime as a strong buffer to keep sulfate from being toxic to fish and other aquatic organisms. Lewis and Summerfelt (1961) added lime to soft water minnow ponds containing high carbon dioxide levels. The pH range was 4.5 at night to 9.5 in bright sunlight. The lime buffered the water enough to prevent the death of minnows. Therefore, CLEAN-FLO developed non-toxic calcium compounds to act as a buffer. However, Swedish conservationists found that a buffer alone is a temporary remediation, and has not produced the desired results. This leads one to the logic of combining continuous laminar flow inversion/oxygenation with either lime or CLEAN-FLO chemicals.

We have found that continuous laminar flow inversion/oxygenation of lakes and other water bodies significantly reduces acidification from all sources. CLEAN-FLO accelerates natural processes that naturally return lakes to a pristine state. When natural life cycles are restored, lakes again become recreational and aesthetically pleasing. This can be attained to some degree without the inclusion of microorganisms and chemicals, but the restoration is enhanced by utilization of the complete program. Oxygenation of the bottom waters is essential for either the microorganisms or the chemicals to be effective. The CLEAN-FLO process is efficient, effective, economical, and completely natural.


Bateman, J. M. and R. L. Laing, 1977. Restoration of water quality in Lake Weston, Orlando, Florida. J. Aquatic Plant Management, Vol. 15, June. pp 69-73.

Bennett, G. W., 1970. Management of Lakes and Ponds. Van Nostrand Reinhold Co., N. Y. p. 221.

Cooley, T. N., P. M. Doris and D. F. Martin, 1980. Aeration as a tool to reduce the growth of Hydrilla Verticillata (L. F.) Royle. Water Research, Vol. 14 pp 485-489.

Cowell, B. C. and C. J. Dawes, 1984. Algal studies of eutrophic Florida lakes: The influence of aeration on the limnology of a central Florida lake and its potential as a lake restoration technique. Final Report, Florida Department of Natural Resources, Tallahassee USA.299pp.

Environmental Quality Laboratory, Inc., 1977. Mechanical mixing – aeration systems for destratifying dead-end finger canals. Port Charlotte, Florida, 52 pp.

Kaleel, R. T., and A. E. Gabor, 1978. Lake Weston restorative evaluation. Orange County Pollution Control Department, Orlando, Florida. 29 pp.

Lewis, W. M. and R. C. Summerfelt, 1961. Adjustment of alkaline reserve of lakes by the addition of hydrated agricultural lime. Illinois State Acad. Sci. Trans. 54(314), 168-174.

Stanier, R. Y., E. A. Adelberg, and J. L. Ingram, 1976. The Microbial World. Prentice-Hall, Inc., Englewood Cliffs, N. J., 871 pp.

Appendix I

Independent Studies
The studies included much more data than is shown below. To simplify this report and save time and space, only the data pertinent to acid is included. An exception is the data for Peavey Lake, which is included to show typical water quality improvement besides the acid-related data. The other data is mostly in bulky raw data form.

The independent studies were:

1. The City of St. Petersburg, Florida studied the CLEAN-FLO process on 400-acre (160-hectare), 3.5-ft (1.5-m) deep Lake Maggoire. The City of St. Petersburg Department of Environmental Affairs took monthly data on Lake Maggiore for three years. CLEAN-FLO treated the lake with continuous laminar flow inversion/oxygenation and CLEAN-FLO Lake Cleanser.

2. E.A. Hickok and Associates of Wayzata, Minnesota studied the effect of inversion/oxygenation and Lake Cleanser on 6.5-acre (2.6-ha) 90-ft (27.5-m) deep Peavey Lake. This was a six-year study for the Twin City Metropolitan Sewage Commission. Five sites on 15,000-acre (6100-ha) Lake Minnetonka and one on Peavey Lake were tested. These were used as a control for the Peavey Lake experiment. Peavey Lake is attached to Lake Minnetonka by a channel. Continuous laminar flow inversion/ oxygenation was used during the second to fifth years, and buffered alum added in years two and three.

3. The Orange County Pollution Control Department, Orlando, Florida (Kaleel, et al, 1978, and Bateman et al, 1977), studied the effect of inversion/oxygenation and CLEAN-FLO Lake Cleanser on 11.3 hectares, 15m deep Lake Weston. Monthly tests were made on Lake Weston for one year before treatment, and three years after. This was followed by two years testing during continuous laminar flow inversion/oxygenation and CLEAN-FLO Lake Cleanser applications.

4. The University of South Florida did a simulated multiple inversion laboratory experiment (Cooley, et al, 1978);

5. Environmental Quality Laboratory, Inc. of Port Charlotte, Florida studied aeration of four brackish water finger canals (1977). They compared continuous laminar flow inversion with perforated tubing aeration, a venturi aerator, and a control canal over a two-week period.

6. Analytical Laboratories, Inc. of Sioux Falls, South Dakota studied CLEAN-FLO inversion/oxygenation on a 1ha, 2m fish pond. Tests were made 9 January 1983 before continuous laminar flow inversion/oxygenation was initiated and microorganisms added to the water, and again on 24 June 1983.

7. The University of South Florida studied the results of CLEAN-FLO inversion/oxygenation on 10.5-ha, 5.2-m Lake Brooker (Cowell, et al, 1984). Biweekly sampling was conducted for one year before treatment, and for two years after continuous laminar flow inversion was initiated. Samples were taken at 1.5-m intervals, and were composites for most variables.

Appendix III

Continuous laminar flow inversion/oxygenation in combination with CLEAN-FLO Lake Cleanser caused the decline of nitrogen, carbon dioxide, sulfates, chlorides, and fluorides in all lakes studied. Acids were neutralized. Acid salts were assimilated by aquatic organisms. Carbon dioxide and nitrogen from carbonic and nitric acids were exhausted to the atmosphere.

These programs used calcium-buffered alum instead of lime. A comparative study of continuous laminar flow inversion/oxygenation in combination with lime is warranted.

CLEAN-FLO International tested the results of using calcium hydroxide, CLEAN-FLO Lake Care, a proprietary calcium compound, and buffered alum in aquaria having aeration bubblers. All three raise the pH. But Lake Care was far superior in improving the health of fish, while buffered alum was the best phosphate precipitant. Without oxygenation and inversion, all three compounds produce only temporary results.

All the test lakes received continuous laminar flow inversion/oxygenation. All but Brooker Lake, the fish pond, the finger canal, and the University of South Florida laboratory tests received CLEAN-FLO Lake Cleanser. Lake Maggiore and Lake Brooker both had pH higher than 8.3 before the process, while the other water bodies had pH less than 8.3. The fish pond in South dakota had a low pH value of 5.3. Brooker Lake had a low pH value of 5.6.

The pH increased in all the lakes whether buffered alum was used. Exceptions were Lake Maggiore, which had high pH initially and received buffered alum, and Lake Brooker. Lake Brooker had considerable pH fluctuation from alkaline to acid before treatment, and did not receive buffered alum. The pH stabilized after treatment. Where buffered alum was used, pH did not fluctuate as widely from day to day.

TABLE 1. Average slopes of the mid-lake site on Lake Maggoire over a 3-year period. Data was taken monthly.
MeasurementRate of Change/Year, Mid-lake
Temperature, C-0.2
Ammonia (N), mg/l-0.1
Total N, mg/l-0.2
TKN, mg/l-0.4
Sulfate, mg/l-43.0
Chloride, mg/l-105.0
Fluoride, mg/l-0.1
Conductivity, micromhos/cm-109.0
TABLE 2. Peavey Lake four-year Regression statistics for ammonia, nitrite, nitrate, Total Kjeldahl Nitrogen, and pH on five test sites using Lake Minnetonka as a control. Values given are the rates of change per year. Peavey Lake received both continuous laminar flow inversion/oxygenation and buffered alum treatment. Values in parenthesis are initial Peavey Lake values.

Brown’s Bay, Wayzata Bay, Gale Island, Crane Island, Deering Island, Peavey Lake
Measurement: Bay, Bay, Island, Island, Island, Lake


Item SurfaceBottom
Brown’s Wayzata Gale Crane Deering Peavey I.V. Brown’s Wayzata Gale Crane Deering Peavey I.V.
Ammonia (N)-0.2, -0.2, -0.1, -0.2, -0.2, -1.1, (6.2)0.7, 0.2, 0.5, 1.0, 0.4, -5.3, (27.8)
Nitrite (N),-0.0, -0.0, 0.0, 0.0, -0.0, -0.0, (0.2)0.0, -0.0, 0.0, 0.2, -0.0, -0.0, (0.2)
Nitrate (N)-0.0, -0.0, -0.0, -0.0, -0.0, -0.2, (0.8)-0.0, -0.0, -0.0, -0.0, -0.0, -0.3, (1.0)
TKN-0.1, -0.1, -0.3, -0.3, -0.1, -1.8, (8.4)0.1, 0.0, 0.1, 0.2, 0.1, -8.9, (42.0)
pH 0.2, 0.2, 0.1, 0.1, 0.1, 0.2, (6.5) -0.0, -0.0, -0.1, -0.1, -0.0, 0.1, (6.7)
Ortho P-0.0, 0.0, -0.0, -0.0, 0.0, -0.3, (0.9)0.0, 0.0, 0.0, -0.1, 0.1, -1.1, (6.2)
Total P-0.0, -0.0, -0.0, -0.0, 0.0, -0.6, (1.9)0.0, 0.0, 0.0, -0.0, 0.0, -2.1, (10.1)
D.O.-0.2, -0.2, -0.3, -0.1, -0.1, 1.1, (6.2)-1.9 ,-1.9, -1.9, -1.1, -0.8, 0.1, (1.3)
B.O.D. 0.4, 0.2, -0.1, 0.7, 0.9, 0.3, (9.1)0.5, 0.3, 0.7, 0.5, 1.1, -2.3, (16.0)
Secchi Disk, ft.-0.5, 0.1, -0.5, -0.3, -0.6, 0.9, (1.9)
Chlorophyll-a1.3, 1.3, 3.0, 2.0, 8.5, 4.4, (18.6)
Total Coliform MPN/10015.9, 14.8, 6.4, 5.2, 92.7, -61.6, (355)
TABLE 3. Regression analysis of data on Lake Weston, 24-month period. Composite readings.
Measurement Slope per Year
TKN, mg/l-0.1
Ammonia, mg/l-0.2
Alkalinity, mg/l as CaCO3-4.0
Conductivity, micromhos/cm-8.5
Table 4. Results of CLEAN-FLO-treated fish pond study by Analytical Laboratories, Inc., Sioux Falls, SD. Data is mg/l unless otherwise noted.
Measurement 9 Jan. 1983 24 June 1983
9 Jan. 198324 June 1983
Sulfates100 48
Manganese 0.34 0.06
Fluoride 0.250.21
Chloride 8.6 7.5
Nitrate 0.27 0.1
pH units 5.3 6.0
Hardness (as CaCO3) 106 60
Total Coliform/100 ml 3000 <1
Total Solids 501 150 150


Peavey Lake before CLEAN-FLO

Peavey Lake after CLEAN-FLO

Lake Weston – Orlando, FL