Reducing odors and fly attraction is an important consideration in land application of septage. Odors, which are emitted from septage when it is agitated and exposed to the air, are carried from the application site by the wind. Flies and other vectors (insects that carry disease-producing organisms to noninfected hosts) are attracted to moist puddles of waste on the ground surface.
Rapid incorporation of raw septage into the soil reduces odors and vector attraction. Immediate incorporation through subsurface injection keeps the septage from being agitated or exposed to the air.
If septage is applied to land in a remote area, where odors are not a concern, surface application may be an alternative. If untreated septage is sprayed onto the ground surface, however, it needs to be incorporated into the soil within six hours to avoid attracting flies and other vectors.
pH-treatment of septage before land application is another way to reduce odors and vector attraction. In areas where odors are a concern and/or incorporation into the soil is not practical, pH-treatment of septage before application is an option. Adding an alkaline material to the septage raises the pH. Alkaline materials commonly used to raise the pH of septage are hydrated lime (calcium hydroxide) and quicklime (calcium oxide). To achieve the benefits of raising the pH, the septage must reach a pH of 12 or greater and remain above pH 12 for at least 30 minutes. This can be accomplished by adding from 20 to 40 pounds of lime per 1,000 gallons of septage. The amount of lime required to raise the pH depends on the solids content of the septage. The higher the solids content, the more lime needed. Do not substitute ground agricultural limestone for hydrated lime or quicklime.
To ensure that the pH has risen to 12 or greater for at least 30 minutes, monitor it. pH meters suitable for field use are available for $50 to $150. pH paper can also be used to measure the pH. A 50-foot roll costs less than $10.
Do not raise the pH too high. Because wastes with a high pH are considered hazardous, using too much lime is both costly and inefficent. Be careful not to raise the pH of the septage above 12.5.
Quicklime is more reactive than hydrated lime. Because heat is released when water is added to quicklime, the following safety precautions must be taken when using quicklime:
- Avoid contact with skin or eyes to avoid severe burns.
- Keep bags of quicklime dry. A wet bag can start a fire.
- Do not put water on a fire involving quicklime. The water will react with the quicklime and cause it to release more heat.
The following safety equipment should be used when handling quicklime:
- Safety goggles
- Half-mask respirator with cartridge
- Shoulder-length, fully coated neoprene gloves
- Emergency eyewash, in case lime gets on the face or in the eyes
- Carbon dioxide fire extinguisher, in the event of a fire
Successful techniques for adding lime to septage include:
- Adding dry lime to the septage in the truck;
- Adding lime slurry to the septage in the truck;
- Adding lime at a septage holding facility.
The simplest method of adding lime to septage is to pour 20 to 40 pounds of lime per 1,000 gallons of septage directly into the pumper truck tank before filling it with septage. As the septage is pumped in, it will mix with the lime and raise the pH. The septage must remain in the truck for at least 30 minutes before it is applied to a field. One limitation to this method is that dry lime may clump in the bottom of the truck and mix poorly into the septage.
Lime may also be drawn into the truck through the vacuum hose. This method, however, has many limitations. For example, dry lime may work its way into the pump, or the lime may react with moisture in the hose and cause heat damage.
Adding a lime slurry to the septage in the truck involves advance preparation. In a plastic drum or tank, mix 13 gallons of water with 50 pounds of hydrated lime-an electric paddle mixer works well for this. The result will be a thick lime slurry, with 5 gallons of slurry equal to 20 to 30 pounds of dry lime. Pour five gallons of lime slurry into the pumper truck tank for every 1,000 gallons of septage pumped.
The lime slurry may also be drawn into the tank with the septage through the vacuum line. The line must first be modified with a "T" fitting, as shown in Figure 1. Insert the "T" fitting into the vacuum hose and attach it to a valved, 1/2-inch-diameter polyethylene pipe. As the septage is pumped into the tank, place the small valved pipe into a bucket or container with 5 gallons of lime slurry for each 1,000 gallons of septage. When you open the valve, the lime slurry will be slowly drawn into the vacuum line and mix with the incoming septage.
Figure 1. Simple system for adding lime slurry to septage as it is being pumped from a septic tank. |
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When field conditions make immediate land application of septage difficult, treat septage with lime at the storage site. Position a receiving tank, large enough to hold an entire truckload, in the unloading area. As the septage is unloaded into the receiving tank, pour dry or slurried lime into the tank. After 30 minutes, discharge the septage into a septage storage basin.
When using this technique, two things happen. First, because ammonia is released quickly from the septage, the receiving tank area must be well ventilated. Second, the septage solids will begin to settle out. An agitator may be needed in the receiving tank to resuspend the solids. The settling of solids will continue to occur in the septage storage basin requiring agitation before pump-out.
Limiting public access to a site is one way to reduce the chance of people coming into contact with the disease-causing organisms in septage. Another way is to allow sufficient waiting time for the disease-causing organisms to die in the soil or be washed off food crops. The recommended number of days or months between septage application and crop harvest are listed in Table 2.
| Table 2. Recommended waiting time for crop harvest and public access after land application of septage | ||
|---|---|---|
| Crop | Waiting time raw septage | Waiting time pH-treated septage |
| Animal feed | 30 days | 30 days |
| Pasture | 30 days | 0 days |
| Fiber crop | 30 days | 30 days |
| Food crop that does not touch ground (example: corn) | 30 days | 30 days |
| Food crop that touches ground (example: melons) | 14 months | 14 months |
| Food crop that grows below ground (example: potatoes) | 38 months | 20 months (if not incorporated within 4 months) |
| 38 months (if incorporated within 4 months) | ||
| Public access-high | 1 year | 1 year |
| Public access-low | 30 days | 0 days |
| Source: Domestic Septage Regulatory Guidance. EPA/832/B-92/005. | ||
Avoiding water pollution from septage is not difficult--using common sense is the best rule of thumb. Ammonia, organic matter, nutrients, bacteria, and color from septage may contaminate water supplies. The problems caused when septage accidentally enters a stream are described in Box 1.
Box 1Avoiding Stream Pollution Although the ammonia in septage is a valuable fertilizer, it is also a water pollutant. Ammonia is toxic to fish and, if conditions are right, the effects are recognizable within a few minutes. Even a small amount of ammonia released to a stream may cause a fish kill. The toxicity of ammonia to fish depends on three factors: pH, oxygen content, and water temperature. The higher the pH of the water, the smaller the amount of ammonia needed to kill fish. The lower the dissolved oxygen content of the water, the smaller the amount of ammonia needed to kill fish. The higher the temperature of the water, the smaller the amount of ammonia needed to kill fish. Because temperature fluctuates with the seasons, the amount of ammonia discharged to a stream in the winter may not kill fish, but the same amount discharged in the summer would. Organic matter in septage is also considered a water pollutant. When organic matter decomposes, oxygen in the water is consumed, leaving less available for fish and other aquatic life. The rate at which a stream can recover from a discharge of organic matter depends on its volume, flow rate, turbulence, and water temperature. Larger streams can accept more organic matter without adverse affects than smaller streams. Rapidly flowing, turbulent streams can recover more quickly from a discharge of organic matter because reaeration occurs as the water moves downstream. Cold water can hold more oxygen than warm water, leaving more oxygen available for decomposition. Also, decomposition of organic matter occurs more slowly at colder temperatures. The worst possible situation is discharge of organic matter into a small, slowly moving stream on a hot day. Nutrients in septage, such as nitrogen and phosphorus, stimulate plant growth both on land and in water. The major impact, however, occurs when the nutrients reach a stagnant part of a stream, lake, or pond. Eutrophic lakes (lakes rich in nutrients) are green with algae and aquatic plants. Bacteria in septage can spread disease to people through a contaminated water supply. Diseases are often transmitted through the fecal-to-oral route. Disease-causing organisms may be present in the waste of an infected person. If the organism is passed to others through contaminated water, they are exposed and risk being infected. Fortunately, disease-causing organisms do not thrive in surface or ground water and eventually die. It is, therefore, important to maintain adequate separation distances between potential pollutants and water sources. This provides an opportunity for disease-causing organisms to be filtered or die before they reach drinking water supplies. Color is a property of septage that is not often considered. Water stained by septage appears black. The color itself may not pose a water quality problem, but may alarm people using the water for recreation or as a water supply. |
Maintain an adequate separation distance and buffer area between the land used for septage application and surface water drainage. A vegetated buffer strip at least 33 feet (10 meters) wide is needed along all streams and ditches. Septage should not be applied within 50 feet of a well.
Restrict application of septage on frozen ground. Hard, frozen ground makes incorporation of untreated septage impossible. Even if septage is treated with lime, application on frozen ground increases the likelihood of septage running off before it has a chance to soak into the soil.
Limit septage application on extremely wet soils. Applying septage to soils already saturated with water can result in contaminated runoff or drainage. Check soil moisture before applying septage and adjust application rates to wet soils to avoid runoff. Before applying septage to a field with artificial subsurface drainage or in an area prone to runoff, check the soil moisture conditions using the procedure described in Box 2.
Box 2Checking Soil Moisture to Determine Application Rates for Wet Soils Limit one-time septage application to the water-holding capacity in the top 24 inches of the soil profile. The moisture capacity of different soils is listed in the Ohio Irrigation Guide available from the Natural Resources Conservation Service. Estimate the available soil moisture by the feel and appearance of the soil as listed in Table 3. Example A Kokomo soil (medium soil) has a moisture capacity of 4.5 inches in the top 24 inches of the soil profile. In checking the field condition of the soil prior to applying septage, you learn that this soil ribbons out easily and has a slick feel. Table 3 indicates that soil moisture is about 75 percent of field capacity. Available holding capacity is therefore 25 percent of 4.5 inches, or 1.1 inches of available moisture storage. The maximum amount of liquid septage that may safely be applied at one time is 1.1 inches. Applications greater than that amount are subject to pooling, runoff, or seepage into the drainage system. |
| Table 3. Practical interpretation chart of soil moisture for various soil textures and conditions* | ||||
|---|---|---|---|---|
| Available soil moisturE | Coarse fine sand loamy fine sand | Moderately coarse sandy loam fine sandy loam |
Medium sandy clay loam loam, silt loam | Fine clay loam silty clay loam |
| 0-25% | Dry, loose, will hold together if not disturbed, loose sand grains on finger. | Dry, forms a very weak ball,1 aggregated soil grains break away easily from ball. | Dry, soil aggregations break away easily, no moisture staining on fingers, clods crumble with applied pressure. | Dry, soil aggregations easily separate, clods are hard to crumble with applied pressure. |
| 25-50% | Slightly moist, forms a very weak ball with well defined finger marks, light coating of loose and aggregated sand grains remain on fingers. | Slightly moist, forms a weak ball with defined finger marks, darkened color, no water staining on fingers. | Slightly moist, forms a weak ball with rough surfaces, no water staining on fingers few aggregated soil grains break away. | Slightly moist, forms a weak ball, very few soil aggregation break away, no water stains clods flatten with applied pressure. |
| 50-75% | Moist, forms a weak ball, loose and aggregated sand grains remain on fingers, darkened color, heavy water staining on fingers, will not ribbon.2 | Moist, forms a ball with defined finger marks, very light soil-water staining on fingers, darkened color, will not slick. | Moist, forms a ball, very light water staining on fingers, darkened color, pliable, forms a weak ribbon between thumb and forefinger. | Moist, forms a smooth ball with defined finger marks, light soil water staining on fingers, ribbons between thumb and forefinger. |
| 75-100% | Wet, forms a weak ball, loose and aggregated sand grains remains on fingers, darkened color, heavy water staining on fingers, will not ribbon. | Wet, forms a ball with wet outline left on hand, light to medium water staining on fingers, makes a weak ribbon between thumb and forefinger. | Wet, forms a ball with well defined finger marks, light to heavy soil water coating on fingers, ribbons between thumb and forefinger. | Wet, forms a ball uneven medium to heavy soil water coating on fingers ribbons easily between thumb and forefinger. |
| Field Capacity (100%) | Wet, forms a weak ball, light to heavy soil-water coating on fingers, wet outline of soft ball remains on hand. | Wet, forms a soft ball, free water appears briefly on soil surface after squeezing or shaking, medium to heavy soil water coating on fingers. | Wet, forms a soft ball, free water appears briefly on soil surface after squeezing or shaking, medium to heavy soil water coating on fingers. | Wet, forms a soft ball, free water appears on soil surface after squeezing or shaking, thick soil water coating on fingers, slick and sticky. |
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* From the USDA--Natural Resources Conservation Service, National Irrigation Guide. Part 652. 1 Ball is formed by squeezing a handful of soil very firmly with one hand. 2 Ribbon is formed when the soil is squeezed out of the hand between thumb and forefinger. | ||||
Apply septage carefully to fields with subsurface drainage, especially when the soil is dry and cracked. Septage can follow cracks in the soil and move quickly through drainage pipes to ditches or streams. If deep cracks are visible, till the soil before applying septage. All "blow holes" in the drainage system must be repaired prior to application. Surface inlets and french drains must be avoided.
Limit application of septage nutrients to meet crop needs. Excess application of septage results in the buildup of soil nutrients. Excess application of phosphorus or nitrogen increases the chance for nutrients to be carried into streams with surface runoff. Excess applications of nitrogen increase the possibility of nitrate leaching into groundwater.
For maximum use of nutrients, match septage application to crop needs. Use the following guidelines to achieve maximum nutrient use with minimal environmental hazard:
- Test soil to establish existing fertility levels.
- Establish nutrient content of septage. Typical nutrient content is listed in Table 1.
- Select an application rate that does not exceed crop nutrient requirements.
- Calibrate equipment to obtain desired application rate. Rain gages or straight-sided cans and containers placed in the field before application work well to measure the depth of liquid applied. Table 4 lists the gallons per acre for different liquid depths.
- Incorporate raw septage to reduce nitrogen losses.
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Table 4. Liquid depth to gal/acre conversions (use to calibrate liquid application equipment and determine application rates) | |
|---|---|
| Inches applied | Gallons/acre |
| 1/8 | 3,394 |
| 1/4 | 6,789 |
| 3/8 | 10,183 |
| 1/2 | 13,577 |
| 5/8 | 16,971 |
| 3/4 | 20,366 |
| 7/8 | 23,760 |
| 1 | 27,154 |
| 1 1/8 | 30,548 |
| 1 1/4 | 33,943 |
| 1 3/8 | 37,337 |
| 1 1/2 | 40,731 |
| 1 5/8 | 44,125 |
| 1 3/4 | 47,520 |
| 1 7/8 | 50,914 |
| 2 | 54,308 |
| 2 1/8 | 57,702 |
| 2 1/4 | 61,097 |
| 2 3/8 | 64,491 |
| 2 1/2 | 67,885 |
| 2 5/8 | 71,279 |
| 2 3/4 | 74,674 |
| 2 7/8 | 78,068 |
| 3 | 81,462 |
Services for soil testing, septage testing, and calculation of application rates are provided through the Ohio State University Research-Extension Analytical Laboratory (REAL) at the Wooster campus. Calculations to determine application rate require a soil sample, a waste sample, and crop information. REAL testing forms are available at county Extension offices. A computer program available from Ohio State University Extension can also assist in selecting appropriate application rates. ECP 102, Crop Nutrient Management, is available from your local county Extension office.
Nitrogen (N) is required for crop growth, but nitrogen applied in excess runs off into surface water or leaches into groundwater. The amount of nitrogen from septage, fertilizer, manure, and other sources should be matched to the needs of the crop. The nitrogen needs of specific crops are listed in the Ohio Agronomy Guide, Bulletin 472, available from your local county Extension Office. An example of the nitrogen recommendations for corn are listed in Table 5.
| Table 5. Example of annual nitrogen application (expressed as lb N/acre/year) recommended for corn | |||
|---|---|---|---|
| Previous crop | Yield goal (Bu/acre) | ||
| 120 | 150 | 180 | |
| Annual application (lb N/acre) | |||
| Forage legume | 60 | 110 | 150 |
| Grass crop | 65 | 170 | 200 |
| Soybeans | 85 | 190 | 200 |
| Continuous corn or other crops | 115 | 200 | 200 |
| Source: Ohio Agronomy Guide, Bulletin 472, Ohio State University Extension. | |||
Estimate the annual application rate of septage based on the nitrogen needs of the crop using Formula 1.
Formula 1Annual application rate (gallons/acre/year) = Nitrogen required for crop yield (pounds N/acre)/ 0.0026 |
All of the nitrogen and about one-third of the organic nitrogen in septage is available to crops during the year of application. The remaining two-thirds of the organic nitrogen, or residual organic nitrogen, becomes part of the soil organic matter. The organic forms of nitrogen found in septage, manure, and sludge will mineralize at a rate of about 5 percent per year for several years, making it available to crops. If a field receives septage, sludge, or manure every year, you should account for this slowly released nitrogen when calculating application rates. Box 3 describes how to account for residual nitrogen.
Box 3Accounting for Residual Organic Nitrogen Septage contains an estimated 700 mg/l total nitrogen where 80 percent (560 mg/l) is organic nitrogen and 20 percent (140 mg/l) is ammonia. In the first year of application all of the ammonia and 33 percent of the organic nitrogen are available for crop growth (140 mg/l + 0.33 * 560 mg/l = 325 mg/l available nitrogen). In the second year, 5 percent of the remaining nitrogen (Table 6) is available ((700 - 325) * 0.05 = 20 mg/l available nitrogen). A small amount of residual nitrogen will be available in the third year ((700 - 325 - 20) * 0.047 = 17 mg/l). 1000 mg/l is equal to 0.0085 lb /gallon. |
| Table 6 . Percent of residual organic nitrogen made available from organic materials applied in previous years | |
|---|---|
| Years after application | Percent of residual nitrogen available |
| 1 | 5.0 |
| 2 | 4.7 |
| 3 | 4.5 |
| 4 | 4.3 |
| 5 | 4.1 |
| 6 | 3.9 |
| 7 | 3.7 |
| 8 | 3.6 |
| 9 | 3.4 |
| 10 | 3.2 |
| Source: Ohio Livestock Manure and
Wastewater Management Guide, Bulletin 604, Ohio State University Extension. | |
Phosphorus (P) is also required for crop growth, but phosphorus applied in excess accumulates in the soil. The amount of phosphorus applied should match the needs of the crop. The phosphorus needs of specific crops are listed in the Ohio Agronomy Guide, Bulletin 472, available from your county Extension office. Examples of the annual phosphorus removal rates for corn, wheat, and oats are listed in Table 7.
| Table 7. Examples of phosphorus (expressed as lb P2O5 /acre/year) crop removal rate for corn, wheat, and oats | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Crop | Yield goal (Bu/acre) | ||||||||
| 50 | 70 | 90 | 100 | 120 | 130 | 150 | 160 | 180 | |
| Crop removal (lb P205/acre/year) | |||||||||
| Corn | 45 | 60 | 70 | ||||||
| Wheat | 35 | 45 | 60 | ||||||
| Oats | 35 | 45 | 60 | ||||||
| Source: Ohio Agronomy Guide, Bulletin 272, Ohio State University Extension. | |||||||||
Agronomic crops grown in Ohio rarely respond to applications of additional phosphorus when soil-test levels exceed 60 pound of phosphorus per acre. Crops grown in soils with high phosphorus levels may actually produce a lower yield because of nutrient imbalances. Therefore, septage should not be applied to a field with high phosphorus soil-test level (measured as Bray P1). Test the top 8 inches of soil when determining phosphorus levels. If septage is applied to fields with soil test level above 60 pounds per acre, follow the precautions described in Box 4.
Box 4Precautions for Septage Application on Fields with Phosphorus Levels in Excess of 60 Pounds P per Acre Always test soils to determine phosphorus levels. If phosphorus levels exceed 300 pounds per acre in the top 8 inches of soil, do not apply septage. If a test reveals a phosphorus level greater than 60 pounds, but less than 300 pounds, per acre (measured as Bray P1) in the top 8 inches of soil, the following special precautions must be taken when applying septage:
Based on soil testing, shallow tillage may be necessary to reduce surface phosphorus levels that have increased because of crop-residue deposition. Producers should be aware that incorporation of septage deeper than 8 inches may promote development of a soil zone with extreme nutrient concentrations. If this layer is brought to the surface, phosphorus runoff may occur. On soils with high nutrient levels, septage application should be skipped for one or more seasons to allow depletion of accumulated nutrients. Recommended application rates for various soil test levels are summarized in Table 8. |
| Table 8. Recommended maximum septage application rates at different soil test levels | ||
|---|---|---|
| Bray P1 Level | Surface applied on high runoff potential sites (1) | Incorporated or low runoff potential sites (2) |
| 0-60 lb P/A | N needs of non-legume crops. N removal rate of legume crops. | N needs of non-legume crops. N removal rate of legume crops. |
| 60-250 lb P/A (3) | N needs or P removal rates for non-legume crops, whichever is less. N or P removal rates for legume crops, whichever is less. | N needs of non-legume crops. N removal rate for legume crops. |
| 250-300 lb P/A (3) | Septage application for crop production purposes not recommended. | N needs or P removal rate for non-legume crops, whichever is less. N or P removal rate for legume crops, whichever is less. |
| more than 300 lb P/A (3) | Septage application for crop production purposes not recommended. | Application of septage for crop production purposes is not recommended. If application is necessary, apply no more septage than supplies N or P removal for the next crop, whichever is less. A site plan which addresses erosion control and runoff is recommended. |
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