Determination of biosolids quality is based on pathogen reduction, disease vector attraction reduction, and trace element concentrations. The regulations contain several additional risk-management requirements designed to limit the potential for pollutants or pathogens to be transported from the application site to groundwater or surface water, or to animals or humans.
Some of these measures include:. Pennsylvania's biosolids regulations contain several risk-management requirements that are more restrictive and stringent than the Federal requirements.
If local, county, and state agencies work together to ensure that all aspects of the regulations are followed carefully, risks from land application of biosolids can be managed at very low levels. The biosolids quality standards and quantity limits were derived from extensive environmental risk assessments conducted by scientists at the E. Department of Agriculture.
The goal of the risk assessments was to provide reasonable "worst-case" protection to human health and the environment, not absolute protection. Worst-case protection in this instance means that the standards and practices established in the regulations would protect a person, animal, or plant that is highly and chronically continuously exposed to sludge pollutants. The rationale was that if a highly exposed individual were protected, then the remaining portion of the population, with lower exposure, also would be protected.
It should be noted that while standards for sludge pollutants were based on risk assessment, standards for pathogen reduction in sludge were based on a "best-available-technology" approach that is described in the next paragraph.
The risk-assessment procedure used by the E. Two other approaches that have been used by other countries are "noncontamination" and "best available technology" BAT. The noncontamination approach does not allow application of any biosolids that would cause an increase in soil concentrations of any pollutant. Any addition of a pollutant to the soil must be matched by removal of that pollutant so that no long-term buildup occurs in the soil.
The BAT approach limits pollutants in biosolids to levels attained by the best current technology industrial pretreatment and separation of sanitary, storm, and industrial sewerage. Each of these approaches is much more restrictive of land application than is the risk assessment approach.
Consequently, with regulation under the noncontamination or BAT approaches, more biosolids will be landfilled or incinerated and less will be land applied. Although this reduces to near zero any environmental risks from land application of biosolids, it increases the environmental risks associated with landfilling and incineration. Landfilling or incinerating a larger percentage of biosolids also reduces the reuse or recycling of valuable resources and may increase the overall cost of biosolids disposal.
The risk-assessment procedures used by the E. Many have concluded that the limits established in the regulations are protective of public health and the environment. Cumulative loading refers to the long-term buildup of trace elements in soil as a result of repeated biosolids applications. As soil levels of these trace elements increase, the elements could become toxic to plants or soil-dwelling animals, or enter the food chain in undesirable amounts.
The debate centers on when applications should cease to prevent this from happening. National Research Council. National Academy Press, Washington, D. Harrison, M. McBride, and D. Cornell Waste Management Institute, The E.
The limit represents the total amount of the element that may be added to a soil before no further addition of biosolids is allowed. The cumulative limits established by the E. Proponents of the rules contend that numerous scientific studies have demonstrated that these levels are protective.
Detractors claim that insufficient data was collected to establish some of the levels, and that in some cases the assumptions built into the risk-assessment procedures were not conservative enough. These questions are being debated actively among scientists including some at Penn State who are involved in biosolids research. Some aspects of the current biosolids regulations are being reassessed by the E.
These changes could include adding one or more organic chemicals to the list of regulated pollutants and modifying the existing cumulative loading limits.
The question that confronts municipalities, farmers, and rural communities in Pennsylvania is whether or not biosolids can be applied to land without creating undue risk to human health and the environment. When considering this question, it is helpful to separate short-term and long-term risk. In the short term, the risk from land application of biosolids can be maintained at very low levels if all applicable regulatory requirements are followed.
The primary short-term risk from land-applied biosolids is similar to that from animal manure: the possibility of nitrate or phosphorus movement to groundwater or surface water. Long-term risks from land-applied biosolids relate to the buildup of trace elements in soil. This buildup is a long-term risk because trace element concentrations in most biosolids are low enough that it would take literally hundreds of years of continuous annual applications to reach the currently established loading limits.
Estimates of the number of years required to reach the cumulative loading limits are shown in Table 3. These are conservative estimates because most sites do not receive biosolids every year and it is highly unlikely that a given field would remain in a biosolids application program continuously for or more years. It must be emphasized, however, that these estimates are based on median trace element concentrations, and any element in any given biosolids sample could be present in much higher or lower quantities than the median value.
The most conservative scientists in the debate over risk from biosolids application have recommended cumulative loading limits approximately one-tenth of those in the current regulations for all trace elements except lead. Under this highly conservative scenario, it would take one-tenth the number of years given in Table 3 to reach the various loading limits. An application site, therefore, could receive about 28 applications of biosolids before the more conservative suggested loading limits would be reached for copper.
Because most biosolids application sites in Pennsylvania have had fewer than 10 applications, this practice can continue for at least 18 years before even these highly conservative limits would be reached. During this year period, some resolution of the scientific debate over these issues should be reached. Over the long term, public health and environmental risks can be reduced even further by decreasing the quantity and increasing the quality of the biosolids that are produced.
Table 1 Disposal situation of sewage sludge in Shanxi in 1. Open in a separate window. Materials and Methods 3. Sampling To assess the risk of heavy metals in sewage sludge that is disposed through land use, 9 municipal WWTPs, with a daily output greater than tons in Shanxi Province, China, were selected to collect sewage sludge, as indicated in Figure 1. Figure 1. Determination of the Total Heavy Metal Concentration The collected samples were dried at room temperature, grounded, and homogenized in an agate mortar; then, they were sieved through a sieve mesh pore size: 0.
Geoaccumulation Index I geo The geoaccumulation index I geo had been defined in the s to assess the pollution of heavy metals in bottom sediments [ 29 ]. Results and Discussion 4. Geoaccumulation Index Values for Heavy Metals in Sewage Sludge The values of I geo for the seven heavy metals were listed in Table 3 , and, on the basis of the classification by Muller, heavy metals in sewage sludge were divided into 5 pollution groups, class 0 to 4.
Table 3 Geoaccumulation index values for heavy metals in sewage sludge. Table 5 Potential ecological risk assessment results of heavy metals in sewage sludge for land use. Conclusions The disposal situation of sewage sludge was investigated in Shanxi Province. Author Contributions Yushan Bu and Baoling Duan conceived and designed the experiments; Haixia Zheng, Chunyang Wu and Qiang Zhang sampled and performed the experiments; Wuping Zhang provided the analysis tools and technical assistance; Baoling Duan analyzed the data and wrote the paper.
Conflicts of Interest The authors declare no conflict of interest. References 1. Liu J. Concentrations of heavy metals in six municipal sludges from Guangzhou and their potential ecological risk assessment for agricultural land use. Dong B. Changes of heavy metal speciation during high-solid anaerobic digestion of sewage sludge.
Bioresour Technol. Kendir E. Risk Assess. Heavy metal concentration, emission flux and potential ecological risk assessment for agriculture in Guangzhou. Cole L. Using Collembola to assess the risks of applying metal-rich sewage sludge to agricultural land in western Scotland.
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Earth Sci. Shafie N. Application of geoaccumulation index and enrichment factors on the assessment of heavy metal pollution in the sediments. Health Part A. Kouidri M. Enrichment and geoaccumulation of heavy metals and risk assessment of sediments from coast of Ain Temouchent Algeria Arab. Abrahim G. Assessment of heavy metal enrichment factors and the degree of contamination in marine sediments from Tamaki Estuary, Auckland, New Zealand. Heavy metal contamination and ecological risk in Futian mangrove forest sediment in Shenzhen Bay, South China.
Islam M. Heavy metals in the industrial sludge and their ecological risk: A case study for a developing country. Xiao Z. Risk assessment of heavy metals from combustion of pelletized municipal sewage sludge. For further information, see PPG 4 on treating and disposing of sewage sludge when no foul sewer is available. You cannot dispose of liquid waste at landfill. Liquid waste includes wastewater, but does not include sewage sludge. If you dewater sewage, you can:.
You can only dispose of sewage sludge at a landfill that is permitted to accept this waste. The sludge must also meet the waste acceptance criteria for the landfill. If you send your waste to landfill, you must check that the landfill has a pollution prevention and control permit or waste management licence.
Ask the landfill site operator to show you a copy of their permit. The permit will specify whether the site can accept hazardous, non-hazardous or inert waste. It may also include or exclude specific types of waste. For further information, see our landfill guidance. If you use sewage sludge to produce energy, see our energy-from-waste guidance. About Sewage Sludge. Join the Food Movement! Help us grow the food movement and reclaim our food. What is Sewage Sludge?
Share this:. On April 15th the Senate Environment and Public Works Committee, chaired by Senator Barbara Boxer, will be holding hearings on recent studies documenting pharmaceuticals found….
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