Dairy Facultative Lagoons & Koenders Wind Powered Aeration Systems

New Zealand has 16,500 dairy farms (avg. 220 cows), with cows kept on pasture throughout the year. During the 9-month dairy season, the cows are milked twice a day (averaging 2.5-3 h per day in the dairy parlour). Urine and faecal wastes deposited in the dairy parlour are washed away with high pressure hoses, using large volumes of water.

A common method of treatment is in simple two-pond (anaerobic/facultative) lagoon systems, which remove about 95% of suspended solids and BOD5, but only 75% of total-N prior to discharge. High concentrations of ammoniacal-N in the effluent can cause toxicity to aquatic organisms in receiving waters.

Facultative ponds are generally aerobic; however, these ponds do operate in a facultative manner and have an anaerobic zone. Facultative organisms function with or without dissolved oxygen. Treatment in a facultative pond is provided by settling of solids and reduction of organic oxygen demanding material by bacterial activity. Dissolved oxygen is supplied by algae living within the pond and atmospheric transfer through wind action. Facultative ponds are usually 4 – 8 feet in depth and can be viewed as having three layers. The top six to eighteen inches is aerobic where aerobic bacteria and algae exist in a symbiotic relationship. Aerobic stabilization of BOD by aerobic bacteria occurs in the upper oxygenated layer. The aerobic layer is important in maintaining an oxidizing environment in which gases and other compounds leaving the lower anaerobic layer are oxidized. The middle two to four feet is partly aerobic and partly anaerobic, in which facultative bacteria decompose organic material. The bottom one to two feet is where accumulated solids are decomposed by anaerobic bacteria. BOD can be converted to methane by methane bacteria in the lower anaerobic layer. Maintaining a balance between the depth and surface area is important for facultative ponds to function properly. Aerobic reactions in facultative ponds are limited because they do not have mechanical aeration.

Mechanical aeration of the second (facultative) lagoon to promote nitrification. Nitrification, (Nitrification is the biological oxidation of ammonia with oxygen, then into ammonium, then into nitrite followed by the oxidation of these nitrites into nitrates. Degradation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an important step in the nitrogen cycle in soil) improves effluent quality by reducing oxygen demand and potential ammonia toxicity to streamlife. Mechanical aeration however is associated with considerable mixing, which may prevent algae from optimizing photosynthesis in the facultative lagoon. A series of experiments was undertaken which tested the efficiency of mechanical aeration and then attempted to combine it with daytime algal oxygen production in order to maximize ammonia conversion to nitrate, while minimizing costs to the farmer.

An experimental facility was developed by dividing a large facultative lagoon into two, producing a matched pair of lagoons, operated in parallel with influent flow split equally. Over successive dairy seasons, various aeration regimes were compared. Continuous aeration promoted nearly complete nitrification of the ammoniacal-N (99% removal), and effluent BOD was approximately halved. However the continuous mixing reduced algal biomass, and thus daytime algal photosynthesis. Night-only aeration permitted greater algal photosynthesis to occur, as well as halving electrical power consumption. Ammoniacal-N removal reduced to 90% (10 g m(-3) remaining in the effluent), while BOD removal was also lower than in the continuously aerated lagoon (59 and 69% respectively). Providing a series of biofilm attachment surfaces for nitrifying bacteria by suspending geotextile material close to the surface in the pond in consistently aerobic water resulted in improved ammoniacal-N removal efficiency (93%) with night aeration, but still lower removal than continuous aeration

What if it were possible to provide regular aeration that these facultative lagoons require with zero operating costs, well Koenders windmills has done just that, with their Windmill Aeration Systems. Wilf Koenders  invented the windmill aeration system 25 years ago Koender’s Windmills inc, since then have sold over 50,000 windmill aeration systems(I imagine they know just about everything there is to know about windmill aeration), providing water solutions all the way from farm dugouts up to municipality facultative lagoons providing and everything for customers that require cost effective, high performance solutions-not to mention being environmentally responsible. It is no surprise that they are now expanding the use of their product to Dairy farm facultative lagoons where demand is high for a way to reduce the high concentrations of ammoniacal-N in the effluent, which can cause toxicity to aquatic organisms in receiving waters.

How it works is as the windmill blades turn it initiates the air compressor that is located at the top of the windmill. This air is compressed down an airline to 1 or more air diffusers that are located at the bottom of the pond. Their highly efficient airstone is a critical component in the successful aeration of a pond (Aeration is most effective when air bubbles are very small. Small bubbles increase diffusion of oxygen from the air into the water.

A Project done by the National Research Council (NRC) in 2012 on the water quality monitoring of waste water management by windmill aeration (Koenders windmills). It should be made clear that the facultative lagoons being tested were those of a municipality in Canada and not of a dairy farm lagoon. Although the findings are still relative, as statistical measures were used. In addition,  as the influent flow rates and concentrations to both the lagoons were different, they DID NOT compare the test lagoon with the control lagoon. What they did instead was compare each lagoon to its own baseline contamination prior to aeration in order to ensure an accurate comparison. These both being a better measure of the treatment efficiencies of the Koenders Wind Powered Aeration Systems.

The study was conducted on real facultative lagoons. The lagoons chosen have an ideal two primary cell configuration that allowed the use of one cell as a treatment cell that could be compared to the other control cell. Treatment efficiencies were monitored through comparison of water quality changes in both the aeration-treated and control cells. The report done by the NRC concluded that the lagoon using windmill Aeration was significantly better at removing Ammonia-nitrogen and Total Nitrogen. Ammonia-nitrogen removal in the Test Lagoon was 67% compared to 37% removal in the Control Lagoon. Similarly Total Nitrogen removal in the Test Lagoon (24%) was higher than the Control Lagoon (15 %). As well, the increased aeration produced a significantly higher and earlier HAB population which could lead to higher treatment capacity of the lagoon.

Choosing the right Wind Powered Aeration System

A study was conducted by a leading Research establishment in Canada and an eminent academic in the field of environmental sciences. Below is an extract from the report produced by Prof. Gillies. This analysis couples laboratory compressor measurements with actual wind speed patterns purchased from the NOAA. and shows quite clearly that the Koenders Double diaphragm compressor outperforms all others in all wind conditions.

“The Koenders compressors were the most efficient due to their ability to aerate at lower windspeeds than their competitors”…. Prof. J.A. Gillies B.E. M.SC.(Sask) P.Eng (ret.) FEC.

Compressor Model

Average output based on 4 Least Windy States (MO, NC, LA, GA)
(Cubic Feet per month)

Percentage of the month windmill aerating

Koenders Double Diaphragm

20,913

81%

Koenders Single Diaphragm

9,938

81%

Competitor 1

5,594

15%

Competitor 2

357

3%

 

Compressor Model

Average output based on 4 Windiest States  (S.D., N.D., KS, OK)
(Cubic Feet per month)

Percentage of the month windmill aerating

Koenders Double Diaphragm

39,541

93%

Competitor 1

23,073

43%

Koenders Single Diaphragm

19,705

93%

Competitor 2

3,683

16%

Combined photosynthesis and mechanical aeration for nitrification in dairy waste stabilisation ponds.

J P S Sukias, R J Craggs, C C Tanner, R J Davies-Colley, J W Nagels

National Institute of Water and Atmospheric Research Ltd., PO Box 11-115, Hamilton, New Zealand.

Water Science & Technology (Impact Factor: 1.12). 02/2003; 48(2):137-44.

Source: PubMed

 

WATER QUALITY MONITORING OF WASTEWATER TREATMENT BY WINDMILL AERATION (A Project by the National Research Council 2012)