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| Biosolids Recycling What are Biosolids? |
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| Biosolids are the nutrient rich organic materials derived from waste processing. Typical sources for biosolids are public water treatment facilities, food processing operations and industrial operations where production uses organic components such as wood. For many people, the concept of biosolids induces a major emotional response. The response is understandable when you realize that ever since infancy, parents teach their children that human waste is dirty and to be avoided and flushed down the toilet. Compare this with the lifelong experience of most persons familiar with animal byproducts as a material to be managed and used. | |||||||||||||||||||||||||||||||||||||||||||
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| Figure 1 | |||||||||||||||||||||||||||||||||||||||||||
| Like animal byproducts, biosolids are a part of the natural cycle of life. They contain inorganic and organic compounds. Crops that supply our food and animal feed are grown in the soil. To grow, the crops need fertilizer and water. Essential soil fertilizer nutrients include carbon, hydrogen, oxygen, phosphorus, potassium, nitrogen, sulfur, calcium, iron, magnesium, molybdenum, boron, copper and zinc. Plants take up these essential soil-borne nutrients that are necessary for their normal growth. Using these nutrients and sunlight, plants manufacture organic carbon-rich foodstuffs such as carbohydrates, fats, and proteins. | |||||||||||||||||||||||||||||||||||||||||||
| The same nutrients that are essential for plant growth also are essential for the growth of humans and animals. We gain many of these essential nutrients, along with carbohydrates, fats, and proteins, by eating plants and 'plant eating' animals. The byproducts excreted from humans and animals contain these same essential nutrient elements that are in the foods we consume. They go into the municipal sewer system along with other household wastes. | |||||||||||||||||||||||||||||||||||||||||||
| Municipalities also gather byproducts from industrial and commercial sources. The residual solids generated during wastewater treatment, called biosolids, when properly prepared provide a rich source of the essential fertilizer elements needed by plants to produce food. It only seems natural to return this rich source of nutrients and organic matter back to the soil to perpetuate the cycle of life. | |||||||||||||||||||||||||||||||||||||||||||
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| What can they be used for? Agricultural Use |
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| The most common use of biosolids is for fertilizer in the agricultural community. In fact man has been using these products since the beginning of farming. States like Ohio and Maryland are using over 55% and 90% respectively of all biosolids produced for land applications. Since 1974, all the biosolids from metropolitan Washington DC (3 million population) have been used on land. As of 1993, 75% of Washington's land application was on agricultural land. The other 25% was composted and used by horticulturists, landscapers, and the general public.
An additional benefit of biosolids is its suppression of pathogenic soil organisms such as nematodes that damage plant roots as well as specific plant root diseases that otherwise cause damage to commercially grown potted plants. |
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| Nonagricultural Use | |||||||||||||||||||||||||||||||||||||||||||
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| Biosolids are also used in silviculture to increase forest productivity and to revegetate and stabilize lands that have been harvested or disturbed by mining, landslides, or other natural disasters. | |||||||||||||||||||||||||||||||||||||||||||
| The application of biosolids to forest land can shorten pulp wood and lumber production cycles by accelerating tree growth, especially on marginally productive soils. Studies by the University of Washington in the Northwest, and the US Forest Service in the Southeast, on the use of biosolids as a fertilizer in silviculture have shown as much as a threefold increase in tree growth compared to controls for certain tree species.
Biosolids have been used to reclaim over 3,000 acres of lands devastated by mining and smelting activities in Pennsylvania. Biosolids are being used in combination with fly ash to revegetate soils at the Palmerton, PA, site which has been included on the EPA's list of Superfund Sites. The Palmerton site was so highly contaminated from 90 years of smelting zinc that all the vegetation in the surrounding area was destroyed. The research team members from Allentown, PA, and the Pennsylvania State University, who were responsible for demonstrating the viability of the reclamation procedures, were recognized as the winners in EPA's first National Beneficial Use of Biosolids Awards Program in 1988. |
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| The treatment of biosolids through anaerobic digester operations produces methane gas as a byproduct. Plants such as the Tampa, FL water treatment facility are using the methane to generate electricity. Tampa recovers about $700,000 worth of electrical costs annually. In addition, Tampa uses the heat recovered from the generators to aid the digester operation and to heat-dry the biosolids. They then sell them for $85 to $120 per dry ton. |
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| Do they have value? | |||||||||||||||||||||||||||||||||||||||||||
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| Biosolids may be used separately or in conjunction with chemical fertilizers. The use of the biosolids can significantly reduce the need for chemical fertilizers. Private contractors such as Burch Hydro Inc. often provide the biosolids and the application to the farmer at low costs making them an outstanding value | |||||||||||||||||||||||||||||||||||||||||||
| Soils low in organic matter receive additional benefits unavailable from chemical fertilizers. The biosolids' organic matter content enhances the soil rooting media thus providing for better water retention, improved air exchange around plant roots, and increased ability of the soil to hold nutrients in a plant-available state. Not only is the crop yield improved, but also use of pesticides and herbicides was reduced due to the more vigorous plants' ability to compete with weeds and withstand damage from insect pests. | |||||||||||||||||||||||||||||||||||||||||||
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| How do biosolids benefit the environment? | |||||||||||||||||||||||||||||||||||||||||||
| Municipalities that do not utilize biosolids recycling operations usually must either incinerate the beneficial byproducts or haul them to land fills. Incineration raises concerns over air quality. Landfills are rapidly filling everywhere and the public rarely wants to approve new ones. By recycling the biosolids, the strain on existing landfills is reduced significantly. | |||||||||||||||||||||||||||||||||||||||||||
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| By returning the nutrient rich organic compounds of biosolids to the soil, a loop is closed in the cycle of life. What was removed by the growth of plants, consumed by humans and animals, is returned for the plants to grow again and again. | |||||||||||||||||||||||||||||||||||||||||||
| Will biosolids cause odor problems? | |||||||||||||||||||||||||||||||||||||||||||
| Some treatment operations such as composting or drying completely eliminate offensive odors in biosolids. Digester and lagoon operations reduce the offensive odors to a level barely discernible. For particularly sensitive areas of use, direct injection below the soil surface will completely eliminate any odors. | |||||||||||||||||||||||||||||||||||||||||||
| Are biosolids safe? | |||||||||||||||||||||||||||||||||||||||||||
| The primary concerns regarding biosolids are the levels of unwanted pollutants and pathogens. Also of concern are the flies and rodents that could result from application of biosolids. By applying controls and treatment throughout the process, a safe and effective product can be assured. The pre-treatments mandated by Federal, state and local laws ensure the wastes entering the water treatment facilities won't exceed established pollutant levels. This prevents the unwanted pollutants from becoming a part of the resultant biosolids. | |||||||||||||||||||||||||||||||||||||||||||
| Treatment methods such as heat drying, composting, and treatment with alkaline materials convert biosolids into useful products that can be considered 'exceptional quality'. In fact, these treatment methods allow for unrestricted use by the general public as long as the generator maintains an ongoing monitoring program to ensure that the biosolids continually meet the 'exceptional quality' requirements. | |||||||||||||||||||||||||||||||||||||||||||
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| The most common form of biosolids treatment is through 'anaerobic digester' and 'lagoon' operations. Biosolids from these operations are defined as Class B and have been spread for years on agricultural land in liquid form and as a de-watered product. By limiting the rates of application and the methods, fly and rodent populations won't increase. Class B biosolids represent one of the most economical and agriculturally beneficial methods for using biosolids. Application of these biosolids are closely monitored and regulated, adding another level of safety to the process. | |||||||||||||||||||||||||||||||||||||||||||
| Who regulates this industry? | |||||||||||||||||||||||||||||||||||||||||||
| The safety and environmental soundness of utilizing biosolids is a matter that isn't taken lightly. Both the Ohio EPA and the US EPA have stringent rules to protect the public health and the environment from all reasonably anticipated adverse effects of using biosolids as a fertilizer. These regulations require that biosolids be frequently analyzed at the source to ensure that the trace elements, pathogen levels, and nutrients are quantified. State and Federal regulations allow only those biosolids with extremely low trace element content and pathogen levels to be land applied. Maximum application rates are structured such that applications can be made safely for decades. Follow up soil testing at the application site provides an additional level of safety to biosolids use. All application sites must be approved by the Ohio EPA. Factors such as slope, drainage patterns, proximity to dwellings, and current soil conditions are used to determine site suitability. The entire process is much more tightly controlled than that of the chemical fertilizer industry. |
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