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Household Hazardous Waste
Phosphorus and Nitrates
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City Hall Annex Room 227
800 Center Street
Racine, WI 53403
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The sludge produced in a wastewater treatment plant is converted to “biosolids” through various treatment processes. When applied to land, the biosolids provide valuable nutrients that can improve the condition of soil and yield better crops. Wastewater treatment plants that recycle biosolids must meet stringent regulatory requirements to assure the safe reuse of this material.
The Racine Wastewater Utility entered into an agreement in January 2014 with Synagro Central LLC for the land application of biosolids. Synagro subcontracts some of the work to a local business named Ray Hintz, Inc. Ray Hintz Inc. constructed a biosolids storage facility in Caledonia where he can manage the product until farmers fields are ready for application. For more information on this environmental initiative please click on the following link: www.synagro.com
During wastewater treatment, bacteria and other microorganisms break down components in wastewater into simpler and more stable forms of organic matter. Non-organic matter also settles into sludge. For instance, small amounts (parts per million) of heavy metals and other potentially toxic materials, including flame retardants (PBDEs) and persistent organic pollutants, are commonly found in sewage sludge in parts per million levels. What does not settle into sludge leaves the treatment facility as a treated wastewater effluent. Biosolids in their liquid form look like muddy water and contain 1-10% solids. Biosolids may be dewatered in a second step of the treatment process, which turns it into a "cake" with the texture of a wet sponge. In this stage it contains 20 to 25% solids. Racine dewaters their biosolids using belt filter presses to remove excess water from the product.
According to the United States Environmental Protection Agency (EPA), biosolids that meet treatment and pollutant content criteria of Part 503.13 "can be safely recycled and applied as fertilizer to sustainably improve and maintain productive soils and stimulate plant growth." After the 1991 Congressional ban on ocean dumping, the US EPA promulgated regulations - 40 CFR Part 503 - that continued to allow the use of biosolids on land as fertilizers and soil amendments which had been previously allowed under Part 257. The EPA promoted biosolids recycling throughout the 1990s. The EPA's Part 503 regulations were developed with input from university, EPA, and USDA researchers from around the country and involved an extensive review of the scientific literature and the largest risk assessment the agency had conducted to that time. However, there was no risk assessment for pathogens or chemicals and heavy metals were not considered to be cancer causing agents. The Part 503 regulations became effective in 1993.
United States municipal wastewater treatment plants in 1997 produced about 7.7 million dry tons of biosolids, and about 6.8 million dry tons in 1998, according to sources relying on EPA estimates. As of 2002, about 60% of all biosolids were applied to land as a soil amendment and fertilizer for growing crops. Biosolids that meet the Class B pathogen treatment and pollutant criteria, in accordance with the EPA "Standards for the use or disposal of sewage sludge" (40 CFR Part 503), can be land applied with formal site restrictions and strict record keeping. Biosolids that meet Class A pathogen reduction requirements or equivalent treatment by a "Process to Further Reduce Pathogens" (PFRP) have the least restrictions on use. PFRPs include pasteurization, heat drying, thermophilic composting (aerobic digestion, most common method), and beta or gamma ray irradiation. Processes to reduce pathogens have no effect on heavy metals and may or may not have effects on the levels of other trace pollutants in biosolids. Treatment processes that involve significant amendments such as composting and alkaline stabilization may dilute total trace metals.
Historically, the problem of human waste disposal began when communities first formed. At that time, population densities were low enough that the surrounding land or waterways could handle human wastes. Wastes that were applied to land increased soil fertility. As populations grew, the nearby land could not handle all the wastes, so they were dumped into streams and rivers that carried the problem "away."
Some early cultures put their human waste to good use. For thousands of years, Chinese society returned sewage, called "night soil," to surrounding farmland. This practice helped maintain soil fertility by closing the nutrient cycle. Nutrients from farms were exported to the cities in crops, and the nutrients in the municipal wastes were returned to the farms. This type of system was ideal because two problems were solved at once: maintaining soil fertility and treating a source of pollution. Night soil was valued so highly that those farmers were reputed to compete with one another by locating attractive outhouses along roads to entice users.
Chinese society was unique in its development of an ecologically sound system for recycling waste. Most other early urban civilizations focused on improving ways to dispose of wastes from cities. Many civilizations developed sewer systems that helped protect local public health but usually created problems downstream.
Large-scale cropland application of municipal wastewater was first practiced about 150 years ago after flush toilets and sewer systems were introduced into cities in Western Europe and North America. The wastewater was discharged without any treatment, and receiving watercourses became heavily polluted. The problem was illustrated by the situation in London in the 1850s when the "stink" from the River Thames obliged the House of Parliament to drench their drapes in chloride of lime. Water supplies drawn from the river below the sewage outfall were found by Dr. John Snow to be the source of the cholera outbreaks of the period. A partial solution to the problem was the construction by Sir John Bazalgete of a vast interceptor along the north bank of the River Thames, creating the famed Thames Embankment. This gave relief to central London, but moved the pollution problem downstream.
Sir Edwin Chadwick, a lawyer and crusader for public health and a strong advocate of separate sanitary sewers, coined the slogan, "the rain to the river and the sewage to the soil." In this spirit, and to reduce pollution of the Thames downstream, "sewage farms" were established to take the discharges from the interceptor. The agricultural benefits from the farms were incidental to their service in the disposal of the wastewater.
The practice of sewage farms quickly spread. By 1875, there were about 50 such farms providing land treatment in England, and many similar farms served major cities in Europe. By the turn of the century, there were about a dozen sewage farms in the United States. However, the need for a reliable outlet for wastewater was not entirely compatible with the seasonal nature of nutrient and water requirements of crop production. While sewage farms alleviated pollution in the receiving streams, they created a different set of environmental sanitation problems. Hydraulic and pollutant overloading caused clogging of soil pores, soil water logging, odors, and contamination of food crops. The performance improved over the years as operators gained experience with balancing the needs of wastewater disposal and crop growth. Nevertheless, the farms were gradually phased out when the land areas required to accommodate wastes from large cities grew too great to be practical and more effective technologies were developed to remove pollutants from wastewater.
In the United States, federal legislation aimed at controlling water pollution first appeared in 1899 and was strengthened during each decade since the 1950s. Thousands of municipal sewage treatment systems, or Publicly Owned Treatment Works (POTWs) were built, although ocean disposal of residual solids was still permitted. The Federal Water Pollution Control Act Amendments of 1972 (PL 92-500, 1972) placed further restrictions on the discharge of pollutants to waterways and encouraged beneficial uses such as land application. Subsequent legislation encouraged land application of biosolids while simultaneously increasing the regulations surrounding such application. Recent restrictions on ocean disposal and landfilling now make land application one of the best, if not the only, option for most municipalities.
In the U.S., the magnitude of the municipal wastewater treatment and biosolids management challenge is partly understood by realizing that municipal wastewater is generated at an estimated rate of 182 gallons per person per day. Municipal wastewater treatment plants currently serve around 75 percent of the U.S. population. The remainder are largely served by individual household septic systems. Overall, these values mean that about 45 billion gallons per day of wastewater is treated and safely managed in the U.S.
Before the era of wastewater treatment, municipal wastewater was untreated and biosolids did not exist. Biosolids are an end product of municipal wastewater treatment and contain many of the constituents removed from the influent wastewater. Biosolids are a concentrated suspension of solids, largely composed of organic matter and nutrient-laden organic solids, and its consistency can range in form from slurry to dry solids, depending on the type of treatment.
Agricultural utilization of biosolids was practiced since residual solids were first produced. Given our experience with the use of human excrement, sewage, and animal manure on croplands, the application of biosolids to agricultural lands was a logical development. As an early example, municipal biosolids from Alliance, Ohio was used as a fertilizer as early as 1907. During the same period, Baltimore, Maryland used domestic septage in agricultural production.
Over the past 30 years, there has been an intense and concerted effort of scientific research worldwide to better understand the fate of potentially toxic and pathogenic constituents in biosolids when biosolids are applied to agricultural soils. The surge of technical information regarding agricultural application of biosolids led to the development of pollutant loading guidelines by the United States and western European countries.
Since the late 1970s and early 1980s source control and industrial wastewater pre-treatment programs were initiated to limit the discharge of industrial constituents into municipal sewers. These programs resulted in a dramatic reduction of trace elements in wastewater and biosolids. Municipal wastewater biosolids, particularly from industrialized cities, now contain significantly lower levels of trace elements than in earlier decades when much of the research on biosolids application to cropland was conducted. EPA first developed biosolids management regulations under the 1972 Federal Water Pollution Control Act to prevent biosolids-borne constituents from entering the nation's navigable waters. In 1977 Congress amended the Act to add a new section, 405(d) that required EPA to develop regulations containing guidelines to identify alternatives for biosolids use and disposal and to specify what factors must be accounted for in determining the methods and practices applicable to each of these identified uses. Also to identify concentrations of pollutants that would interfere with each use.
In 1978, U.S. EPA established regulations limiting concentrations of cadmium, PCBs and pathogens. In 1987, Congress amended section 405 again and established a timetable for developing biosolids use and disposal guidelines. Through this amendment, Congress directed EPA to identify toxic pollutants that may be present in biosolids in concentrations that may affect the public health and the environment. and to promulgate regulations that specify acceptable management practices and numerical concentration limits for these pollutants in biosolids.
The intent of the 1987 amendment was to "adequately protect human health and the environment from any reasonably anticipated adverse effect of each pollutant." This section also states that any permit issued to a POTW or other treatment works for wastewater discharge should specify technical standards for biosolids use or disposal.
Biosolids are created through the treatment of domestic wastewater generated from sewage treatment facilities. The treatment of biosolids can actually begin before the wastewater reaches the sewage treatment plant. In many larger wastewater treatment systems, pre-treatment regulations require that industrial facilities pre-treat their wastewater to remove many hazardous contaminants before it is sent to a wastewater treatment plant. Wastewater treatment facilities monitor incoming wastewater streams to ensure their recyclability and compatibility with the treatment plant process.
Once the wastewater reaches the plant, the sewage goes through physical, chemical and biological processes which clean the wastewater and remove the solids. The wastewater treatment processes work to control pathogens (disease-causing organisms, such as certain bacteria, viruses and parasites) and other organisms capable of transporting disease.
Biosolids are used to fertilize fields for raising crops. Agricultural uses of biosolids, that meet strict quality criteria and application rates, have been shown to produce significant improvements in crop growth and yield. Nutrients found in biosolids, such as nitrogen, phosphorus and potassium and trace elements such as calcium, copper, iron, magnesium, manganese, sulfur and zinc, are necessary for crop production and growth. The use of biosolids reduces the farmer's production costs and replenishes the organic matter that has been depleted over time. The organic matter improves soil structure by increasing the soil's ability to absorb and store moisture.
The organic nitrogen and phosphorous found in biosolids are used very efficiently by crops because these plant nutrients are released slowly throughout the growing season. This enables the crop to absorb these nutrients as the crop grows. This efficiency lessens the likelihood of groundwater pollution of nitrogen and phosphorous.
To determine whether biosolids can be applied to a particular farm site, an evaluation of the site's suitability is generally performed by the land applier. The evaluation examines water supplies, soil characteristics, slopes, vegetation, crop needs and the distances to surface and groundwater.
There are different rules for different classes of biosolids. Class A biosolids contain no detectible levels of pathogens. Class A biosolids that meet strict vector attraction reduction requirements and low levels metals contents, only have to apply for permits to ensure that these very tough standards have been met. Class B biosolids are treated but still contain detectible levels of pathogens. There are buffer requirements, public access, and crop harvesting restrictions for virtually all forms of Class B biosolids.
Nutrient management planning ensures that the appropriate quantity and quality of biosolids are land applied to the farmland. The biosolids application is specifically calculated to match the nutrient uptake requirements of the particular crop. Nutrient management technicians work with the farm community to assure proper land application and nutrient control.
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