ANAEROBIC BREAKDOWN

The breakdown of organic wastes like manure or milk solids is anaerobic if it takes place without oxygen.

Biochemical oxygen demand is a common measure of the strength of wastewater containing organic wastes. BOD indicates the amount of oxygen consumed by biological organisms and chemical processes in the oxidation of organic matter to break it down into simpler compounds such as carbon dioxide and water. BOD of wastewater varies with the kind and concentration of pollutants. It is most commonly expressed in milligrams per liter, as exerted over a 5-day period.

In a surface filtration treatment system the soil immediately along the point of application will receive the greatest discharge of waste materials and have the greatest danger of soil clogging. It is thus necessary to distribute the liquid over a wider area. The minimum ratio of slope width to length is considered to be 1:2 with a 1:1 ratio being more desirable. For example, a 60 foot by 85 foot filter area, which might be used with 100 cows, would be in the acceptable width-to-length ratio. Use of a settling tank ahead of the filter will reduce the solids loading and help prevent plugging of soil pores and extend the useful life of the bed.

Infiltration beds should be cropped to remove nutrients taken up by the plants, if site conditions permit. If cropped, two infiltration beds are needed so they may be used alternately. Application of wastewater must consider the ability of the crop to accept the hydraulic and nutrient loads expected.

Special sprinkler heads designed for frost protection of crops operate better during periods of freezing temperatures, but conventional sprinklers have been used successfully. Small low capacity nozzles require more attention to keep them unplugged and free of manure solids.

By-products from livestock production include animal excrement, bedding, wash water, spilled feed, cleansers, and hair.

Nitrogen is an abundant element in the environment and a by-product of animal waste. If animal wastes are overapplied to land, the nitrogen undergoes nitrification which converts it to nitrates which can be harmful to humans if it finds its way into their drinking water.

Oxygen must be continuously present in the lagoon liquid to allow the process to take place. The oxidation uptake of these lagoons is related to their depth. They depend upon penetration of sunlight and wave action to generate and stimulate algal growth to produce oxygen to decompose waste, and thus should be relatively shallow. Because oxygen is available, aerobic bacteria will be the basic organisms affecting decomposition of waste in such lagoons with the result that there should be no odor formation.

If the discharge of waste to the treatment facility exceeds the ability of the facility to decompose the waste, it will malfunction with odors resulting.

Cattle should be fenced out of an infiltration area while it is in use. Pasturing may be permitted on an alternate infiltration area when the soil is dry.

The quantity of wastewater discharged to a treatment system depends on the equipment used in the milking center and the ability of the operator to conserve and reuse the wastewater. A dairy farmer milking 50 cows may use twice as much water as a dairy farmer milking 100 cows who carefully conserves water.

Risers are stands which raise the sprinkler above the height of the crop. Risers 4 to 5 feet tall have been used satisfactorily. In some cases it may be necessary to fasten the riser to a post to keep it in a vertical position.

Settling tanks in commercial usage are designed to hold approximately one or two hours of flow on a continuous basis, and are intended to provide a quiet period during which solids can settle to the bottom of the tank. They are not designed for storage of solids for extended periods of time and may be equipped with some kind of mechanical scraping equipment to remove the solids as they accumulate before they have a chance to become -- septic -- , or anaerobic. Thus the volume of commercial tanks available for liquid holding remains relatively constant.

Shallow, as the term is used in this program, means less then five feet in depth.

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