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Approximately eight million tons per year of wet sludge from municipal water and wastewater treatment plants
and septic tanks are generated in Texas.
According to the Environmental Research Foundation "Sludge is a mud-like material that remains after bacteria
have digested the human wastes that flow from your toilet into your local sewage treatment plant."* Human wastes, however, are not the only substances in sludge, because some wastewater treatment facilities also receive industrial waste and some sewage systems mix storm-water runoff with the regular human waste. So, sewage sludge can contain a number of pesticides and chemicals along with human waste.
The EPA has developed regulations governing the use of sludge. At the state level, sludge regulations are
enforced by the Texas Commission on Environmental Quality.. Liquid waste cannot be disposed of in municipal solid waste landfills unless it has been dried. Most permitted water treatment
plants do dry their sludge. The sludge stays at wastewater treatment sites in lagoons that often have a five- to ten-year storage capacity. The sludge is dried and then sent to landfills or
applied to land. In Texas, about 650,000 dry tons of sludge end up in landfills every year.
The following are the state's preferred methods for treating municipal sludge in order of most to least preferred:*
- source reduction and minimization of sludge production;
- treatment of sludge to reduce pathogens and recover energy, produce beneficial by-products, or reduce the quantity of
sludge;
- marketing and distribution of sludge and sludge products;
- applying sludge to land for beneficial use; and
- landfilling.
Because treated sludge is considered by some waste management professionals to have components that can be
useful to the soil—minerals, metals, and plant nutrients, like phosphorous and nitrogen, the land application of sludge (beneficial use) has its proponents. Nationwide approximately 5.6
million tons of sludge (biosolids) a year is collected by wastewater treatment plants, and about 60 percent of that is spread on land---golf courses, farmland,etc.The co-composting of
municipal sludge with brush and yard trimmings is also growing in popularity as a method for dealing with municipal sludge.* (It is also becoming costly to dispose of sludge in landfills.)
The land application of sludge is regulated by the Texas Commission on Environmental Quality, which requires
sludge to be treated before its use. There are two ways to treat sludge: pretreatment, which prevents pollutants such as PCBs and metals from entering the sewer drains; and treatment at the
wastewater facility for organisms that cause disease. Sludge is classified as either Class A or Class B, depending on the type of treatment it has received. Class A sludge has benefited from
both pretreatment and treatment at the wastewater facility. The pathogens in Class A biosolids cannot exceed certain levels set by the EPA. Standards for Class B sludge are less stringent,
and their use is therefore more regulated. A landowner who wishes to use Class B sludge as an alternative to conventional fertilizers must apply to the Texas Commission on Environmental
Quality to register his site. Among other items, the application requires information on the type of land, the amount of buffer zones, and the type of soil. The applicant must also provide
information from the wastewater treatment facility on the type of pollutants and pathogens in the sludge, and calculations of nutrient needs for the crops. The use of Class B sludge on land
has been criticized by the Center for Disease Control and the National Institute for Occupational Safety and Health. A landowner using Class A sludge does not have to register his land.
In the past, cities like Fort Worth, Houston, and Austin have diverted tons of biosolids from the land fill to
beneficial uses. The City of Fort Worth hired a private contractor to distribute 70 tons of dry sludge a day from its wastewater treatment facility to area farmers and ranchers. The
landowners do not pay for the sludge but, as reviewed above, each user had to meet certain land application standards set by the Texas Commission on Environmental Quality. Using a somewhat
different approach, the City of Austin composts and then sells over 50 percent of its sludge (Class A) to wholesale nurseries, which in turn market and sell it as fertilizer—known as Dillo
Dirt—to retail consumers.
In Texas, critics of land application of sludge have made their voices heard. After citizens raised
concern, the Reeves County Commissioners Court issued an order regulating the application of sludge. The order requires that sludge be applied only through subsurface injection and only after
an application has been submitted to the county clerk. In Fort Bend County, residents of the City of Guy appealed to the City and to the Texas Commission on Environmental Quality to stop the
use of sludge by farmers who are spreading it on pastureland. The sludge is from Houston-area wastewater treatment plants. According to complaining residents, the sludge is foul smelling and
nauseating. Some Fort Worth residents, fearing groundwater and surface water pollution, also raised objections to the use of sludge on neighboring farms.
The most common criticism of the use of sludge as an alternative to common fertilizers are as follows:
- Sludge may contain metals, including copper, mercury, and arsenic. The degree to which these metals move into groundwater
and surface water, and the resulting effects on plants and wildlife, are not known, and their movement into and consequences for groundwater, surface water, plants, and wildlife are not
known.
- Toxic heavy metals may build up in soils, and the long-term effects on wildlife and animals have not been assessed.
- The consequences of using the by-products of human waste to fertilize the crops that people eat are unknown.
The National Academies' National Research Council issued a report in July 2002 that said the Environmental
Protection Agency should update the standards that govern using treated sewage sludge on soil. The NRC concluded that not only were current standards
based on outdated science, but that more rigorous enforcement was needed.
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