STANDARDS FOR AEROBIC AERATION SYSTEMS FOR THE BIOREMEDIATION OF DAIRY WASTE STREAMS AND OTHER RELATED WASTE STREAMS.

This document gives an overview of aerobic and anaerobic bioremediation technology treating dairy and other related waste streams.

To date the only system with proven results and back up data with complete water analysis reports is the WaterPure-Keeton Specific Design System.

The Waterpure-Keeton Specific Design System is designed by aqua engineers and aquaculture engineers with approved engineering in diff-user aeration, microbial digestion, and wastewater engineering. The biological additives for a WaterPure-Keeton System requires a biologist and microbiologist with expertise in microbial formulation, dosing techniques and treatment of organic wastes.

The principles of WaterPure Technology have over thirty years experience with aerobic systems, waste digestion and waste stream conversion to an enriched plant food effluent and odor control.

The WaterPure-Keeton Aerobic Specific Design System, is explained detail in this document with examples of the quarterly water analysis reports of the incoming and outgo affluent.

It is the goal of WaterPure Technology to be the leader and set standards for the bioremedition technology for the dairy industry and other related waste streams.

WaterPure Technology
Serving Industry Through Science

Standards for Aerobic Aeration Systems for the Bioremediation of Dairy
Waste Streams or Animal Waste Containment lagoons

Overview of aerobic and anaerobic bioremediation technology for treating
Dairy waste streams

Anaerobic animal waste treatments systems are generally characterized by systems with liners or covered lagoons designed to mitigate smell and odor problems or more advanced treatments including large biogas digesters to reduce dairy waste.

Anaerobic processes are very slow at best and do not readily digest the amount of waste produced by large dairies, unless very large and expensive digestors and associated equipment is installed. These systems must be designed to either burn the biogas, produce electricity, or designed to utilize the energy produced in the burning process for heating the facility.

Anaerobic digestion relies on microbial decomposition reactions and processes that break down wastes with nooxygen present. This anaerobic process in very slow and cannot treat theamount of waste without the benefit of specialized, complex, and expensive equipment. Covering lagoons to collect the gasses produced is only a band-aide solution and does not address solid waste disposal problems and water quality problems associated with the use of the remaining solution on crops.

Problems Associated With Open Dairy Waste Lagoons or Covered Animals Waste Lagoons:

1. Anaerobic Systems: Slow treatment of the digestion of dairy waste.
2. Odors: Hydrogen sulfide gas, mercaptans, and other short chain organics compounds with strong odors are produced under anaerobic conditions.
3. Waste: The slow digestion process causes a rapid buildup of solids in the digestion ponds that must be removed and disposed of later.
4. Out-gassing: Ammonia, H2S and other gasses are vented to the atmosphere.
5. Cost: Very costly for little digestion.
6. Cost: More expensive than most farming operation can afford.
7. Solids and Disposal: Solids that eventually fill lagoons must be removed and the solid waste either spread on the dairy's crop land or trucked to other farming facilities.
8. Nitrate/Ammonia: Nitrates and ammonia are not sufficiently reduced.
9. Pollutants: Anaerobic do not digest or oxidize problem pollutants
10. Band-aide: An expensive band-aide effort that in reality does not solve or produce a viable solution for the digestion of dairy wastes.
11. Anaerobic Biogas Digesters: Equipment necessary to handle a typical large 3000 head dairy for biogas production may cost over $500,000 USD.
12. Salts: Does nothing to reduce salt content of run off water.

A properly designed lagoon aeration specification should describe an automatic lagoon animal waste aerobic aeration system. Components of the system should consist of high pressure (greater than 200 inches water pressure) regenerative air blowers, electrical controls, cooling manifold, pressure relief valve, system controls, flow meters, gauges, self weighted air-feeder tubing, duraplate air diffusion system, pipe manifolds, valves, fitting and all other materials necessary for a "knockdown " (turnkey) aeration system.

Aerobic systems vary greatly in the design and efficiency of the system. In general creating and maintaining aerobic, highly oxygenated, conditions in the digestion ponds is the goal of any aerobic system. The design must include continuous transfer of excess oxygen to the lagoon along with continuous mixing of the lagoon manure suspension. For proper operation of the aerobic system, a mixture of specialized aerobic and facultative anaerobic microbes must be used to inoculate the waste lagoons on at least a bi-weekly basis to maintain proper digestion. The pH, electrical conductivity (Ecw), and total alkalinity must be taken on a biweekly basis.

This tested and proven process and system may be used as a standard for the industry The combined over thirty years experience with aerobic systems and recent specific research on dairy waste digestion and odor control may serve the dairy industry and the states in which the dairies reside. The overall reduction of B.0.D. and reduction in nutrients and salts in the processed water can serve to greatly reduce the possibility of future ground water contamination from modem dairy operations.

The following are some of the observed results of two years of testing and application of the Water Pure-Keeton Aerobic Dairy Lagoon Treatment Process.

1. Proven to reduce overall Biological Oxygen Demand (B.O.D.) by 90-95 %, thus greatly reducing impact on the environment when this water is used for irrigation.
2. Liqueries and digests solid wastes to a point where any remaining small particles are suspended and transported to the irrigated fields.
3. Odors are eliminated or controlled due to aerobic (with oxygen) microbial digestion of the suspended solids and the oxidation of sulfur containing mercaptans and other volatile and odoriferous compounds.
4. EC ratio decreases up to 62% in treated water effluent, reducing salt content by an average of 3.8 tons per acre-foot of water.
5. TKN (Total Kjeldahl Nitrogen), which is a measure of all nitrogen in solution, can be reduced by 95% with the WaterPure-Keeton process.
6. Approximately 30% of all nitrogen in the processed water is in the form of protein and amino acids that can be easily utilized by the soil organisms and subsequently by the plant material.
7. A standard system digests 75 tons of raw wet manure per day on a 3000 cow dairy.
8. Treated product water is a valuable commodity and can increase crop yield without nitrate contamination.
9. Specialized microbes are added to the water that are Sulfur reducing and enzymes are added that inhibit SRB type bacteria from forming. Aerobic type bottom aeration further reduces hydrogen sulfide and methane gas production.
10. Because the BOD is greatly decreased, soils can remain aerobic while still providing a more useable form of organic matter that includes both complex and simple sugars.
11. Product water can be used for irrigation for years without damaging soils. The wastewater is converted into a useful commodity, not a liability and can actually return money to the operation.
12. The nitrate concentration is controlled to an undetectable level in the product water.
13. Weed seeds, which can cause problems for farming operations, are digested in the WaterPure-Keeton Process.
14. Low energy use for size of system; 1000 head dairy (20 IIP) and expandable to any size.
15. The performance of the Water Pure-Keeton Process has been scientifically documented.
16. A database is established and maintained on both inflow water and product water quality allowing the farms utilizing the product water to decrease the use of commercial fertilizers.

Water Pure-Keeton Aerobic Treatment Process System Design and Specifications

There are two general types of dairy waste stream treatment systems; the first for dairies with solid separators in place and the second is for dairies where the waste stream is fed directly into the storage ponds with all solids remaining in suspension. It is necessary to over design the systems where solid separators are not installed. The actual size and aeration demand is scaled to the number of cows and whether pretreatment equipment is in place.

The pond design for these systems should include a minimum of three ponds:

A minimum of 15-day retention time is required in the first pond for a proper initial aerobic digestion of dairy waste stream materials. The size of the ponds must be determined for each facility associated with the flush lane outflow rate, number of animals, expected solids and B.O.D (biological oxygen demand) . The subsequent ponds should be properly aerated to maintain the aerobic digestion and to minimize odors. The three pond process can remove 95% of total B.O.D. utilizing the WaterPure-Keeton treatment system. In layman's terms a 95% reduction in overall biological oxygen demand means that 95 percent of the total waste has been reduced or converted into a more environmentally friendly form.

The depth of the ponds must be a minimum of 15 feet and a maximum of 20 feet. The depth is critical for proper agitation, oxygen transfer efficiency, and proper mixing in the retention ponds. The shape of the ponds is critical for the efficiency of the digestion process. Water Pure Technologies provides design specifications for new ponds and design help to maximize the efficiency of existing operations. Ideally a system will start with clean ponds rather than attempting to retrofit existing ponds. Though good success is observed in retrofit systems, playing catch-up on the solids in the ponds as new waste material is added each day requires that the system be oversized which can increase the cost of the system.

The air system must provide a minimum of 2.5 pound of oxygen for each pound of BOD inflow to the digestion ponds. Specialized WaterPure-Keeton Aerobic and Facultative Anaerobic microbes are used to inoculate the waste lagoons on a biweekly basis. When the inoculation regiment of the ponds is properly maintained, the total amount of oxygen needed to provide proper digestion may be greatly reduced.

In these treatment situations, with and without separators, it is critical to build a subsurface grid of self-cleaning distribution units that are specifically designed to produce extremely small sized air bubbles properly placed to provide the efficient aeration and mixing of the pond.

Each WaterPure-Keeton subsurface aeration unit is designed to circulate up to 2,500 gallon per minute of water to the surface of the ponds while at the same time adding oxygen to the effluent water. The airlift principal is very important in moving large volumes of water to the pond surface with extreme efficiency. The airlift principal provides major oxygen exchange at the air water interface as the water with lower dissolved oxygen is repeatedly moved to and exposed to the surface. Each WaterPure-Keeton subsurface aeration unit is designed to produce laminar flow and best oxygen transfer rate efficiency at 2.5 cubic feet per minute design airflow. Recirculation of water from the bottom up is essential to prevent anaerobic conditions from developing which promote rapid microbial decomposition when the correct microbes are added on a biweekly basis. These units are designed to be retrievable if maintenance is required but are essentially nonclogging. An oxygen transfer rate efficiency of 25-28 % is achieved at a depth of 14 feet and appreciably greater efficiency is observed at depths from 15-20 feet.

The key to the Aerobic WaterPure-Keeton process requires treatment lagoons to be completely vertically mixed by our WaterPure-Keeton subsurface aeration unit (Duraplate) bottom aeration devices. This process of vertical mixing does not allow the waste to accumulate or to remain on the bottom and become anaerobic. Microbial digestion finishes the solid waste decomposition. As soon as any lagoon is allowed to become anaerobic, the rapid digestion process essentially stops. The BOD reduction and the denitrification processes that are integral to the success of the Water Pure Technologies digestion process must be monitored for efficiency. Any interruption in aeration or the inoculation process may retard the digestion process.

In the case of digestion ponds fed from unseparated flush-lanes, it may be necessary to provide additional directed surface aeration to minimize low-density solids from building on the surface of the ponds. If these solids were allowed to build the solids may be raised above the surface of the pond liquid, and the digestion of the solids would become much less efficient or even stop completely. The mixing of any floating solids back into the pond suspension is necessary for the process to remain efficient and guides the solids back into the mixing stream of the subsurface diffusers. Surface aerators may be required to remix the solids back into the digestion solution.

WaterPure-Keeton Aeration System and Microbial System Design and Specifications

The WaterPure-Keeton lagoon aeration specification describes an automatic lagoon animal waste aerobic aeration system. Components of the system consist of high pressure (greater than 200 inches water pressure) regenerative air blower, electrical controls, cooling manifold, pressure relief valve, system controls, flow meters, gauges, self weighted air-feeder tubing, duraplate air diffusion system, pipe manifolds, valves, fitting and all other materials necessary for a "knockdown " (turnkey) aeration system.

System must be designed by an aqua engineer, aquaculture engineer or approved engineer with diffuser aeration, microbial digestion and wastewater engineering background. Other biological requirements for system design stipulate a biologist or microbiologist with expertise in microbial formulation, dosing techniques and treatment of organic wastes. Each WaterPure-Keeton system must be specifically engineered and designed to meet the site-specific conditions and biological parameters for each dairy and based upon the biological parameters necessary to achieve an average of 90% reduction in biological oxygen demand and reduction of other water quality parameters as outlined in this document.

Any aerobic system must incorporate a microbial dosing scenario with a scientific formulation of beneficial microbes. This formulation must have been demonstrated to achieve a high degree of solids digestion in dairy or other animal containment lagoons. Digestion effectiveness must be backed by documented field test results from a certified laboratory.

The turnkey onshore air system is designed to produce high volume low-pressure air and deliver air via a pressurized manifold to various valved manifold locations. The air is then carried via specialized "heavy set" non-leaded self-sinking flexible tubing, (Keeton weighted feeder tubing). This weighted tubing delivers air to each Duraplate flexible membrane diffuser that are spaced according to design parameters for uniform water mixing and oxygen diffusion throughout the complete pond.

Testing and Documentation:

The flush lane water and the outflow water from both the first pond and the irrigation storage pond must have the following parameters tested quarterly. Both the inorganic and organic parameters must be tested so that the water quality may be documented for long-term usability on crops. A record of both the bio-load and saft concentration of the outflow water used for irrigation must be maintained. The testing should include the evaluation of nitrogen compounds in the irrigation water as well as the phosphorus and potassium ion concentrations in the outflow water. These records will allow the long-term evaluation of the dairy water when used on crops and allow the farming operations using this processed water to decrease the other fertilizers added to their crops. Sampling also provides a record of the degree of water quality treatment, insures the proper functioning of the system and will be important in the future to meet discharge water quality requirements.

Water Pure Technologies list of variables currently being tested and documented on both the flush-lane solution product water to be used for irrigation:

Field Testing:

At the time of inoculation, at least twice a week, the following variables must be field-tested and proper records maintained on the flush-lane solution and the stored water that is to be used for irrigation.

PH

Electrical Conductivity (EC)
Nitrate ion concentration

The independent laboratory testing of both the flush-lane inflow water and the product water used for irrigation should be completed at least quarterly. This will allow verification of the quality of the product water and evaluation of the efficiency of the aerobic digestion system. Records must be maintained to allow verification of the water nutrient load to be documented on product water used for irrigation. The Water Pure Technologies (WPT) standards for variables to be regularly tested are listed below. Many of the standards set by WaterPure-Keeton are not required by existing programs, however these variables are useful in the evaluation and long term use of the product water for irrigation.

Nitrogen: Nitrate, Ammonium, Kjeldahl Total Nitrogen
Phosphorus
Potassium
Calcium
Magnesium
Sodium
Bicarbonate
Chloride
Sulfate
Boron
Electrical Conductivity (EC)
Total Dissolved Solids (TDS)
PH
Biological Oxygen Demand (BOD)

Water Reports to the Dairy Management

In the future dairy waste strewn water used for irrigation must be documented for nutrient load. This is part of programs now being initiated by the University of California Cooperative Extension with funding from the USDA CSREES Water Quality Program. The program is an attempt to minimize any over application of fertilizers applied to farming operations. This program requires the nutrient load of the water from waste stream ponds used on crops to be included in any crop nutrient programs. Because the water is used on fields near the dairy to both produce silage crops for use on the dairy and also on other farming operations, the documentation of the quality of the product water is critical to the long-term use of this water.

The reports are produced quarterly for the dairies along with the actual testing data. The staff of Water Pure Technologies has completed the short course, Using Dairy Lagoon Water for Crop Production, conducted by the University of California Cooperative Extension Service in February 2000. The data that WaterPure Technologies has documented and will continue to collect for the dairies and for farming operations will serve to establish a database that will be useful to the industry in minimizing the over application of commercial fertilizers. The information associated with the irrigation water used from the dairy waste lagoons will help to insure the long-term safe operation of the dairies.

Usage of the Product Water from the WaterPure-Keeton Aerobic Digestion Process

The database will allow any changes in nutrient load to be noted and be part of the information made available to the farming operations near the dairy utilizing the product water for irrigation. The farming operations can use this data to regulate any commercial fertilizers needed to produce their crops. This can result in savings to the farmer and minimize the chance of problems occurring because of excess fertilizer applications. If commercial fertilizer applications are made knowing the total nutrients available in the product water, the ground water table will be safeguarded from nutrient contamination. The standards set by Water Pure Technologies for the testing and record keeping could provide a universal set of standards and a database which can be utilized by both dairy and farming in future evaluation.

Fanning Evaluation

If the data from the applied nutrients is coupled with the normal testing of both soil and tissue of the crops grown, a good picture of the efficiency of the nutrient management from this point on can be observed. The minimization of nutrient contamination is part of the good stewardship of our resources allowing long-term success of the modem dairy operations. It should be noted that the fertilizer components in the product water are efficiently incorporated into the irrigated plant materials and the quantity of this water used on a particular crop type should be monitored. In many cases the nutrients in this water is more than adequate for most crops. Because of this efficiency of utilization of the nutrients the possibility of contamination of the soil and ground water is minimized.

Water Pure Technologies Results of the Aerobic Bioremediation of Dairy Waste

The January 2001 results of the Water Pure aerobic bioremediation of dairy waste include the analysis of three dairies, one with a solid separator. The analysis of all three dairy pond systems includes the same data as in the previous evaluations with the additional determination of the Biological Oxygen Demand (BOD) and the Total Kjeldahl Nitrogen (TKN) for each sample taken. The results of these analyses have allowed the Water Pure Technologies method of bioremediation to be more easily explained and verified. In previous analyses without the BOD and TKN data, only suppositions could be made as to why the quantity of soluble salt was decreased and how much of the organic matter was actually being digested.
	It is determined that the decrease in the Electrical Conductivity of the water (ECw) was mainly because of the calcium ion and magnesium ion forming precipitates as carbonates and phosphates. It is assumed that the decrease in the sodium and potassium ion was associated with the incorporation of these more soluble ions into the bodies of the organisms involved in the digestion of the organic matter in the waste. Another observed decrease in cation concentration is associated with the ammonium ion eliminated by the denitrification, reduction to nitrogen gas, N2 discussed later.
	The average decrease in the ECw is 44% corresponds to an average reduction of the over-all salt by 3.4 tons of salt per acre-foot of the digested product water. The restrictions placed on the number of dairy animals based on the salt output from each animal may be able to be reevaluated. This method of bioremediation if applied to dairy waste streams may provide a way to decrease groundwater contamination. The lower the ECw of the product water, the safer the product water becomes as an irrigation source. The agricultural operations at or near the dairies utilizing the Water Pure Techniques for aerobic digestion should be able to more safely continue the long -term use of this water while minimizing salt and extra nutrient in the irrigation water.
	The nitrogen sources in the undigested flush lanes solution contain a complex mixture of nitrogen compounds, which includes anything from proteins, individual amino acids, free ammonical nitrogen including either ammonia, and ammonium ion as well as urea and nitrate ion. The Water Pure Technologies process includes the digestion and denitrification of the original flush lane solution. The Graph to the right gives a visual representation of the efficiency of the processes run under different conditions. The Visser Dairy, which does not have a solid separator, is the most efficient system and has been in operation for the longest time. The digestion ponds at the Visser Dairy are deeper and have the longest retention time of any of the systems tested.
	Because of the control and monitoring of the product water nutrient output, which is part of the Water Pure bioremediation program, nutrient contamination of ground water may be minimized. Because the overall nutrient load in the product water will be known, the farming operations should be able to eliminate unnecessary applications of other fertilizers. This can provide a cost savings in nutrients as well as a savings in the labor associated with the application of these nutrients. As the regulatory agencies require more control and documentation of all nutrients applied to farming operations, the utility of the use of this type of product water sources may become even more valuable. The utility has been proven so far in silage grown on fields using the product water, which has undetectable nitrate concentrations. The corn silage grown with this water has provided 30% higher tonnage of silage and 40% higher protein content. The uptake of the nitrogen of all sources as well as the uptake of micronutrients such as zinc and manganese has been observed.
	The denitrification of the ponds, the reduction of the more complex nitrogen compounds to nitrogen gas, N2, decreases the potential contamination of the groundwater. The 87% reduction in the Total Kjeldahl Nitrogen and the 35% reduction in the ammonical nitrogen at the Visser Dairy provide a measure of the efficiency of this process when ideal conditions are maintained. The DeHoog Dairy, which has very shallow ponds, still shows 66% efficiency in the reduction of the TKN and a 29% reduction of the ammonical nitrogen has no solid separator. The JCJ Dairy, which utilizes a solid separation system, shows a 40% TKN reduction and a 26% reduction of the ammonical nitrogen. The reduced efficiency at the JCJ operation may be associated with the ECw being 2.3 times as high in the digestion pond than at the other dairies. The product water at the JCJ Dairy is also reused in the flush lanes leading to the higher salt concentration in the digestion ponds. It should be noted that the product water from all three dairies continues to have undetectable concentrations of nitrate ion.
It should be noted that the product water still contains some complex nitrogen compounds such as amino acids. These amino acids have been shown to help to complex or chelate micronutrient metal ions and allow them to be more easily transferred across the root's membrane. In earlier tissue analysis of silage corn, it has been shown that both the zinc and manganese concentrations were greatly enhanced when the aerobically digested water was used for irrigation resulting in 40% higher protein content and 30% greater yield.
	The Biological Oxygen Demand, BOD, a measure of the organic matter in solution was determined for the flush lane solutions and the product water for each of the dairies. The results of these analyses are shown in the following graph. It should be noted that each of the dairy operations shows fairly efficient BOD reduction, but as might be expected the Visser system is the most efficient and the JCJ the least efficient. The JCJ Dairy operation was still over 80% efficient in the digestion of the original organic matter in the pond solution. The digestion process depends on a number of factors only one of them being the salt concentration. The process is observed to be even more efficient during the warmer months.
	As the organic matter is efficiently digested in the Water Pure Technologies Process the BOD is decreased by as much as 95% The organic matter that might have loaded the soil and decrease the available soil oxygen has been greatly reduced and the soil oxygen remains more available With more availability of oxygen in the soil a much healthier soil environment can be maintained for the critically important aerobic soil organisms If oxygen rich conditions are maintained in the soil ecosystem, the critical balance of all organisms can not only exist but also thrive. Once these balanced conditions are established and maintained most soil born diseases are held in check by these healthy competing organisms.

Summary January 2001:

1. The average 44% decrease in the Electrical Conductivity, EC, between the flush lanes and the product water, corresponds to a decrease of 3.4 tons of salt per in an acre-foot This should allow the dairy to maintain more animal units at a particular dairy site if the Water Pure Technologies method of aerobic digestion is maintained
2. The continued efficient operation of the Water Pure Technologies System Process is documented by the aerobic BOD reduction An average of 90% reduction of the organic material suspended in the water from the flush lanes continues to be observed
3. The denitrification, the conversion of the more complex nitrogen compounds to inert N2 gas, shows an average efficiency of approximately 64% and as high as 87% reduction. The decrease in the total nitrogen minimizes the possibility of nitrate contamination of ground water when the product water is used for irrigation purposes. The nitrogen utilized by irrigated crops can further reduce the possibility of nitrate contamination of the ground water.
4. The average documented 90% decrease in the Biological Oxygen Demand, BOD, and the average lowering of the ECw by 44%, a decrease of 3.4 tons of salt per acre-foot of water, allows this product water to be used for irrigation without creating anaerobic or problemsaline conditions in the soil.

Dissolved Oxygen and Airlift Mixing in the
Water Pure Technologies Process of Aerobic Waste Digestion.

Water Pure Technologies

The vertical lift caused by the introduction of the air at the bottom of the waste pond moves the waste suspension in a circular motion. This mixing and associated transfer of oxygen is attained by the utilization of specifically designed WaterPure-Keeton subsurface aeration units that can continue to operate efficiently even in heavy waste stream slurries. Around each WaterPure-Keeton subsurface aeration unit a convection like current is created as the air moves upward through the suspension. At the bottom of the pond the circular movement of the liquid moves solids from the bottom and causes the solids to be suspended in the waste slurry. The oxygen is made available to the digesting organisms in the slurry. Any areas of the pond where continuous movement is not maintained may become depleted of oxygen. In these small areas on the bottom of the pond, gasses are formed as the facilitative organisms undergo anaerobic digestion. The anaerobic digestion process causes the solids to become flocculent allowing the solids to again become involved in the dominant aerobic process.

Each WaterPure-Keeton subsurface aeration unit is designed to circulate up to 2,500 gallons per minute of water to the surface of the ponds while at the same time adding oxygen to the effluent water. The airlift principal is very important in moving large volumes of water to the pond surface with extreme efficiency. The airlift principal provides major oxygen exchange at the air water interface as the water with lower dissolved oxygen is repeatedly moved to and exposed to the surface. Each WaterPure-Keeton subsurface aeration unit is designed to produce laminar flow and best oxygen transfer rate efficiency at 2.5 cubic feet per minute design airflow. Recirculation of water from the bottom up is essential to minimize anaerobic conditions from developing which promote rapid microbial decomposition when the correct microbes are added on a biweekly basis. These units are designed to be retrievable if maintenance is required but are essentially non-clogging. An oxygen transfer rate efficiency of 25-28% is achieved at a depth of 14 feet and appreciably greater efficiency is observed at depths from 15-20 feet.

The data that has been taken over the last two years while monitoring the three digestion systems has shown that the oxygen level in the pond varied from being at as high as 80% of saturation near the aerator to less than 1% of saturation in the middle of summer near the bottom of the pond at 15 feet from the unit. The oxygen from the air added at the bottom of the pond mixes with water as the air moves toward the surface forcing the water to move vertically and back to the bottom. The organisms that utilize this oxygen as they digest the waste material use the great majority of the oxygen provided in this cyclic pattern. The movement mixes the solids and helps to keep the solids in suspension where aerobic digestion can take place. The oxygen concentration decreases in the flow pattern when the water is moving in the radiating pattern away from the maximum vertical lift directly over the WaterPure-Keeton subsurface aeration units. As the water circulates back to the bottom of the digestion pond, the organism's metabolic processes continue to use the dissolved oxygen. If the solids are not kept in suspension and solid masses were allowed to form whether on the surface or on the bottom of the pond, the aerobic processes would be minimized. In the flow patterns around the WaterPure-Keeton subsurface units the actual dissolved oxygen varies greatly depending on where in the pattern the sample is taken, but the oxygen is continuously replenished and utilized allowing the digestion process to remain efficient. Physical movement of the solids without the addition of the oxygen will not provide the desired rapid aerobic digestion.

Example Data: Visser Dairy Pond #1 (Data taken 5/3012001 ) Oxygen Levels