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February 1999
| Spotlight….by Bill Bickert
VENTILATION: THE DILUTION FACTOR! Both improper design and improper management of ventilation both may compromise animal health. Problems are most likely during winter, spring and fall, especially during rainy weather and warmer days coupled with cold nights. Viewing ventilation as a dilution process may help explain why these periods can be troublesome and why efforts to maintain warmer environments may go awry. Cold barns, generally preferred, present less risk to animal health and are easy to design and manage. In a cold barn, sufficient ventilation maintains indoor temperatures about the same as outdoor temperatures in winter. Of course, ventilation must be adjustable to maintain this minimum temperature difference even as outside conditions change, say from a cold, blustery winter day to a winter day that is calm, sunny and mild. A major reason for air quality problems in a cold barn is adjusting ventilation for the worst case—severe winter weather—and not readjusting to allow increased ventilation when the severe weather passes and milder winter weather appears. During ventilation, outside air is brought into a barn where it collects moisture, heat and other contaminants, all produced by the animals. Air is then exhausted to the outside. Ventilation is an air exchange process—contaminated air inside the barn is exchanged for fresh outside air. To determine ventilation rates, we focus on the moisture content of the air, measured by relative humidity. But moisture is only one aspect. Ventilation removes other undesirable contaminants as well. Ventilation is truly a process of dilution. Air moved through a barn actually serves to dilute the inside air and, very importantly, to dilute all of its components. Dilution reduces concentrations of moisture and heat. Dilution reduces concentrations of airborne disease organisms, harmful gases and dust, and undesirable odors as well. When ventilation is reduced below recommended levels—usually in a misguided effort to warm the barn using animal heat—less moisture is removed. Sometimes the consequences of the resulting moisture buildup are masked by: i) insulating the barn, ii) using a greenhouse effect, iii) providing supplemental heat, or iv) dehumidifying the inside air. But even though excess moisture may not be apparent, the reduced dilution factor does indeed result in increased concentrations of airborne disease organisms, harmful gases and dust, and undesirable odors. If these increases are ignored, animal health problems are inevitable. Essential to maintaining a healthy animal is providing an environment that does not needlessly stress or challenge the animal. Maintaining good air quality is a fundamental aspect of that healthy environment with ventilation providing the key. But air quality is more than just measuring relative humidity. Through ventilation we continually dilute the air inside the barn, assuring that the air the animal breathes has low concentrations of all contaminants that threaten the animal's health
ON THE ROAD TO PRECISION AGRICULTURE Grid sampling is a favored method for site specific soil management because it is unbiased, simple, relatively quick and software exists to facilitate it. After the samples have been pulled, georeferenced and analyzed, a map is made by either filling in the grid cells with the soil test value (grid cell method) or assigning the soil test value to a point and then interpolating between points (grid point method). Grid sampling results in either a "checkerboard" map (grid cell method) or a "smoothed" map (grid point method). Problems of Grid Sampling: Despite the current popularity of grid sampling, it is becoming apparent that there are many deficiencies with this method of within-field soil mapping. These problems include:
Improving Grid Sampling: Simple steps will improve the quality of a grid sampling plan.
When applying fertilizer based on the sample pattern,
incorporate strip plots with fertilizer recommendations based on a
separate whole field soil sample. This allows an on-site evaluation of the
effectiveness of the grid design and fertilizer application.
Roger Brook
ON THE WASTEWATER FRONT In the November Agricultural Engineering Newsletter we discussed the issue of septic drain field failures. The term "failure" is usually used to refer to systems that are no longer accepting as much wastewater as generated. The symptom of failure is either very slow plumbing in the home, untreated effluent coming to the surface in the yard or both. As indicated in the November article, the problem is very important to determine why the system failed before taking corrective measures. If the cause of failure is not determined and dealt with it may persist and result in premature failure of the repaired or replaced system. The normal solution to a failed drain field is to replace the drain field with a new system following the current code of the local health jurisdiction. If the failed system was installed within the last ten years or so there is probably a designated location for a replacement system on the lot that will show in the original installation permit on record with the health department. If a designated replacement sight exists, it should be used. Before beginning any replacement process it is necessary to contact the local health department and have them assist in determining what needs to be done as well as to issue a replacement system permit. If a replacement system is installed, every possible effort should be taken to avoid any damage to the existing system. A diverter valve should be installed so that in the future the effluent can be switched back to the original system. Over time it will be rejuvenated through biological action. After about two years the old system will be nearly as good as new and alternating between the two systems on a one- to two-year frequency can greatly prolong the life of the replacement system. If there is not room for a complete replacement system, other options may be used. One may add to the existing system in such a way that water will overflow and go into the new trenches only when the existing system is completely filled water will overflow. Chances are, if the system is not in extremely bad shape, existing trenches will continue to take a significant amount of wastewater. Only if the excess is diverted to the new trenches will they retain the ability to dispose of wastewater at relatively high rates. Another option, and one that has been proven to be very effective by research in Wisconsin, is to add an aerobic treatment unit or a sand filter between the septic tank and the existing drain field. It has been shown that providing the added treatment and converting the effluent going to the soil system from anaerobic septic tank effluent to aerobic effluent from a sand filter or aerobic treatment unit can cause the clogging in the soil system to be decomposed. The installation process involves pumping the septic tank, pumping all the water out of the drain field, adding the aerobic treatment unit and putting the unit back and into use. Over 90% of systems corrected in this manner have operated without additional symptoms of failure. The other 10% required some addition to the size of the soil absorption area. In most cases this was because the system was too small to start with. Other processes exist for treating failed drainfields.
These include the use of enzyme products, dried bacteria and physically
opening soil pores by air blasting to lift and fracture the soil which
also opens the clogging mat. We do not have data on the performance of
these processes and cannot recommend either for or against their use. Ted Loudon
CONSTRUCTED Constructed wetlands have emerged as a method of treating dilute wastewaters utilizing natural biological processes. The use of constructed wetlands for wastewater treatment originated in warmer climates and most of the experience and research has been done in those areas. However, in recent years, some of our surrounding states have begun to utilize constructed wetlands. Research has shown that they can work even in colder climates and researchers have begun to define some of the limits. A day-long program on the use of constructed wetlands for dilute wastewater treatment in northern climates has been developed as part of the ANR week program. It is scheduled for Tuesday, March 9, 1999 in rooms 105A and B of the Kellogg Center. The program is sponsored by the Agricultural Engineering Department, Department of Resource Development, Soil and Water Conservation Society, Michigan On-site Recycling Association and the Michigan Septic Tank Association. The morning part of the program will cover the use of constructed wetlands for domestic wastewater treatment including individual homes. The afternoon will deal with constructed wetlands for dilute agricultural wastewaters such as runoff, milk house wastewater and other agricultural and industrial waste. A brochure detailing the agenda for the conference has been sent to all county extension offices. The cost for the full day is $18.00 with lunch or one can register for either morning or afternoon without lunch for $8.00. For additional information or to register contact Barbara Brochu at 800-366-7055 or (.
Ted Loudon
NIOSH REPORTS: The National Institute for Occupational Safety and Health (NIOSH) recently investigated ignition incidents resulting from drilling holes into sealed and filled plow frame sections. A farmer and worker were seriously burned in two separate incidents that occurred in the same county in New York under similar conditions. The best explanation of this rare event was from D. Murphy of PSU who did uncover further details outlined from his latest newsletter below. NIOSH investigated and found the plow frame manufacturer ( Brillion Iron Works in Wisconsin) had filled the hollow frames with scrap metal ballast. The uncleaned assorted machine shop metal scrap apparently reacted electrochemically with water and emulsion-type cutting oils to form hydrogen gas. This concentration of hydrogen gas was found to increase over time under this sealed condition. This gas was nearly pure hydrogen at absolute pressure of 185 psi, more than 12 times atmospheric pressure. Although the reported ignitions involved plows from the same manufacturer, the use of scrap metal fill may not be unique to plows or to that manufacturer. Safety Tip: I checked with two major farm machinery manufacturers; they did not fill the frame with anything or used concrete. This scrap ballast method of adding weight to tool bars/plow frames is not common practice. However, the potential for such ignitions exists in any equipment with similar mixed metal scraps and cutting oils/material used as ballast in sealed compartments during drilling, cutting, welding, or other operations that both release the gases and provide an ignition source.
Howard Doss
Agricultural Engineering Extension Faculty Nancy Aitcheson - Plan Service
Secretary, Co-Editor .
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