This article originally appeared at "Resource or Hazard?" in the September 2019 issue of Water & Wastes Digest
Embracing our excrement has symbolic implications. Human sludge, also termed biosolids, differs depending upon where it is generated and what types of contaminants are exposed to this byproduct. Biosolids may contain heavy metals such as lead and mercury, and other industrial compounds (some biosolids are treated to remove a small number of heavy metals).
Heat-treatments will kill some pathogens, however, it will not kill all of them depending upon the biosolid disposal method (landfilling, land application, incineration and other uses). Thus, best management practices (BMPs) such as testing, pretreating, exploring alternative end uses and other pollution prevention measures are warranted.
Many organic farmers and consumers have objections to this. According to Planet Natural, “the U.S. EPA does not regulate the labeling of compost so manufacturers can call it anything, including organic. While the EPA has given the use of sewage sludge its blessing, some of its own scientists disagree that it’s safe. And for good reason.
“Since 2003, the EPA has allowed marketers to substitute the word ‘compost’ for sewage sludge on ingredient lists. The fact that some sludge is allowed to cure before it is used or treated to remove a handful of the thousands of contaminants it contains, does not make it safe. More amazing is the fact that some makers of compost that include sewage use the word ‘organic’ in their marketing.”
Also, increased awareness of how pharmaceuticals, pesticides, plasticizers, hormones and antibiotics, and other toxins are being properly controlled, and further development of viable reuse options and disposal possibilities for biosolids is an environmental concern.
Advocating for Better Biosolids Management
In 1981, I worked for the Washington D.C. government assisting the Blue Plains Treatment Plant generation of biosolids. Later, working for local governments in northern and western Virginia provided me with a rural perspective regarding biosolids and I proposed certain BMPs.
Years ago, the Virginia Health Department pushed for land application similar to EPA, since there is tremendous business pressure to promote this activity. Regulators have no business promoting any one specific end use technology, especially since land application of biosolids can be a lucrative business.
For example, in 2007, the Carlyle Group bought Synagro for $772 million. Synagro is one of the largest U.S. processors. Land applying in this county is problematic since it has many sinkholes. Such karst areas have serious potential surface and groundwater consequences if toxins leach from such applications. Applicators must exercise vigilant controls to prevent pollution.
For worldwide handling of our collective excrement, there is no one silver bullet. Each person disposes of 1/4 lb of feces each day and about a quart of urine. Promoting BMPs for these biosolids will lessen water pollution and safeguard public health.
In 2013, with almost 7 billion people worldwide, this amounts to about 400 million metric tons a year. Add to this to 1.4 billion cattle, 19 billion chicken, 1 billion pigs, and 1.8 billion goats and sheep, or 14 billion metric tons of animals.
This does not include all the wildlife that also adds to this mountain of organic waste. If you address the major public health issue, about one third of the population (2.5 billion people) lacks clean drinking water while 2 million children die every year from diarrhea.
Around 30% of the world’s biosolids are stockpiled or sent to a landfill each year, while more than 3 billion cu meters of clay soil is dug up for the global brickmaking industry. Using biosolids in
bricks offers a solution to these environmental challenges.
With the tremendous and accelerated erosion of soils, Class A biosolids have an enormous potential to provide essential plant nutrients such as nitrogen and phosphorus. Also, increasing the organic content and drought resistance in plants offers a bountiful supply as a soil amendments. However, all biosolids are different due to the type of contaminants that may have been around them.
Not All Biosolids Are Equal
Today, more than 16,000 wastewater treatment facilities serve nearly 190 million Americans (72% of the U.S. population—not counting those with decentralized septic and wastewater systems). In addition, these sewage treatment and collection facilities serve thousands of industrial and commercial establishments. Integrating biosolids into a new resource requires extensive public education, pollution prevention, pretreatment and political will.
Roughly 8 million dry metric tons of biosolids annually are produced, or about 70 lb per person per year. About 54% of these biosolids are land-applied as fertilizer or as soil conditioner.
Each year in the U.S., 75 billion tons of soil are lost. The rate of erosion is 10 times as high as the natural replenishment rate. In India and China, this rate is 30 to 40 times faster, according to David Wells-Wallace’s “The Inhabitable Earth.”
Biosolids range from 70% to greater than 98% water content. The dry matter in biosolids consists mostly of inert minerals (that is to say, sand and silica) or biological materials comprised of fat, protein, fiber and carbohydrates. Biosolids also contain trace amounts of heavy metals and organic chemicals.
This waste contains varying levels of metals, pathogenic organisms, vector (e.g., insects and rodents) attractants and odor-causing substances that may be harmful as well. The metals, organic chemicals and pathogens can pose a threat to human health unless the biosolids are sufficiently processed and properly managed.
Below is a summary from a Clemson University study:
“Millions of tons of residual by-products, such as urban wastes (biosolids, recycled water, food scraps and other municipal solid waste), agricultural waste (manure) and industrial sludges are produced in the U.S. On average, approximately 50% of biosolids, 98% of food scraps, and 45% of yard trimmings are currently disposed of in
landfills or incinerated at substantial cost to the industry and public.
“Reuse of residuals as soil amendments offers the potential to substitute beneficial agronomic and environmental uses for disposal costs. Treated liquid wastes, such as wastewater effluent, recycled water and other non-potable waters, also present opportunities for beneficial reuse in lieu of surface water discharge or expensive treatment.
“There have been many obstacles to optimized use of residuals. These include a lack of research to optimize residual based product development, conflicting regulations or the absence of regulations on residuals use, and lack of public outreach and communication.”
The 503 Biosolids Rule
EPA’s Part 503 Biosolids Rule allows land application of sewage sludge as fertilizer or to condition the soil. EPA has focused on promoting the use of sludge for land application. In 1993, the agency published the 503 Biosolids Rule setting standards for the use or disposal of sewage. This created controversy in the science, agricultural and public sectors.
Although this rule establishes minimum quality standards for biosolids for land application, there have been concerns whether these standards are stringent enough. Should they require additional source separation and greater pretreatment of contaminants? Numerous citizens that work with or live near sludge have voiced these same concerns.
Several years ago, the EPA Inspector General found that, “EPA does not have an effective program for ensuring compliance with the land application requirements of the 503 rules. While EPA promotes land application, [it] cannot ensure the public that current land application practices are protective of human health and the environment.”
Personal Care Products & Pharmaceuticals in Biosolids
Most people do not think about how as they flush everyday chemicals and drugs down the drain it ends up in biosolids. However, U.S. Geological Survey scientists found biosolids contain relatively high concentrations (hundreds of milligrams per kilogram) of the active ingredients commonly found in a variety of household products and drugs.
“Since biosolids are rich in plant nutrients, farmers, landscapers and homeowners use about 50% of the annual production of biosolids as fertilizer for plants,” according to Science Daily. “Biosolids must meet standards for nutrient, metal and pathogen content before they can be used to fertilize plants and to improve the quality of soil. Because a variety of pharmaceuticals and other household chemicals have been found in the wastewater discharged from WWTPs, questions have been raised about the presence of these chemicals in biosolids.
“To help answer the questions, scientists obtained nine different commercially or publicly available biosolids and analyzed them for 87 organic chemicals found in cleaners, personal care products, pharmaceuticals and other products. They found: 55 of the 87 organic chemicals measured were detected in at least one of the nine biosolids collected, with as many as 45 chemicals found in a single sample.”
Biogas & Biodigestion in China
One innovation is happening in China. It has more than 173 large biogas plants and 748 large to medium bio-digesters that handle 20 million metric tons of sewage producing 200 million cu meters of methane gas. And one promising organization is the Resilience Alliance, a research organization comprised of scientists and practitioners from many disciplines who collaborate to explore the dynamics of social-ecological systems.
Because some land applications of biosolids were improperly performed, some localities have either banned the practice or have developed stricter regulations.
Safe application of biosolids requires assertive pretreatment, pollution prevention, vigilant monitoring, testing, soil surveys, and screening of the application area so as to safeguard contamination to water resources and other measures to ensure sludge does not impact public health or the environment.
It is incumbent on the industry to fully invest in the many viable forms of reduction, reuse, composting, incineration and disposal options to best manage