Bio logical -- Biosolids

Word Origin & History

Dr. Bruce Logan, a Bio logical scientist, is credited by WEF with creating the scientific term biosolids for the bacterial
biofilms created during secondary sewage treatment. Biofilms are referred to by the industry as attached growth
systems on trickling filters systems and rotating biological disks. The biofilms are sloughed off the attached growth
systems as sludge, i.e., biosolids. In the activated sludge processes the biofilms attach to floating solid particles and
settle to the bottom as sludge.

However, biosolids was originally a papermill term created about 1978 for treated effluent.
Papermills: Typical Papermills generate tons of lime mud, bark ash and boiler ash as well as significant tons of biosolids
if they have activated sludge plants and have many opportunities for beneficial reuse and co-product development.

Quebec has seen a major increase in the application directly onto farmland of biosolids produced
by municipalities, the pulp and paper industry and food processors. In 1999, about 700,000 tons
of biosolids, of which 83% were pulp and paper mill residuals, were applied to agricultural land.

Water Environment Federation (Water Pollution Control Federation) first published the term biosolids  as used by Costa
et al. in the 1980
"Fate of Suspended Biological Solids Discharged to Receiving Waters" for those solids in effluent. It
was also included in the 1999 American Public Health Association, American Water Works Association, Water
Environment Federation's
"Standard Methods for the Examination of Water and Wastewater" for solids in both water
and wastewater effluent.

This enhanced survival can be attributed to the presence of biological solids which served as food in the higher
concentrations of mill effluent (11).

Biosolids as food. Citation Only Available , Zanella, E.F., Proc Exec Conf Inst Pap Chem, 1978, 42d, p. 28-31.
Subjects: pulp and paper mill effluents

Impact of residual biosolids on receiving water quality. ,
Costa, H.S., TAPPI Environmental Conference Proceedings (Technical Association of the Pulp and Paper Industry),
1978, p. 57-62.

MAY, 1979

The difference in results between filtered and whole effluent (Table I) may have been due to the presence
of biosolids which have been demonstrated as a food source for Daphnia (12).

The tests indicated that some toxicity to Daphnia remained in the filtered effluent. These results were ascribed to lack of
biosolids in the filtered effluent.

Fate of Suspended Biological Solids Discharged to Receiving Waters
Harold S. Costa, James J. McKeown and Dennis L. Borton
Journal (Water Pollution Control Federation), Vol. 52, No. 10 (Oct., 1980), pp. 2432-2441
Published by: Water Environment Federation
Effluent biosolids also were ingested and incorporated into the cellular material of aquatic food-chain organisms."

DAPHNIA LIFE CYCLE ASSAY Project 3355 by Eugene F. Zanella  July 30, 1982
VII Use of Sulfite Mill Suspended Solids (Biosolids) as Food for the Daphnia Life Cycle. Experiment 2.

Production of Food Processing Biosolids  And Their Use As Animal Feed: An Overview  
Charles R. Stack, M.P.H., Charles Stack & Associates Inc.  Prasad S. Kodukula, Ph.D., Woodward-Clyde Consultants  
Presented to the Environmental Issues Committee Association of American Feed Control Officials, Inc. April 24, 1995  
These processes utilize the natural biodegradation by aerobic or anaerobic microorganisms to convert FOG and BOD5
into biological cell mass (biosolids) and waste gases such as carbon dioxide or methane. These gases are easily
handled and discharged into the environment with minimal impact, and the biosolids are disposed through landfilling,
land application, incineration or composting.

Standard Methods for the Examination of Water and Wastewater
"Microbiological examination of biosolids from water and wastewater treatment processes is
desirable to determine the impact of their disposal into receiving waters, ocean dumping, land
application, or burial in landfill operations."


Dr. Bruce Logan is the Kappe Professor of Environmental Engineering at Penn State University, and director of Penn
State’s H2E (Hydrogen Energy) Center and the College of Engineering’s Energy & Environmental Institute. Dr. Logan’s
areas of expertise are in
bio energy production, with emphasis on microbial fuel, microbial electrolysis and microbial
desalination cells;
bio adhesion; environmental transport processes; colloidal dynamics; and bio remediation.

Bio logical scientists study living organisms and their relationship to the environment. They perform research to gain a
better understanding of fundamental life processes and apply that understanding to developing new products or
processes. Research can be broken down into two categories: basic and applied. Basic research is conducted without
any intended aim; the goal is simply to expand on human knowledge. Applied research is directed towards solving a
particular problem. Most bio logical scientists specialize in one area of biology, such as zoology (the study of animals) or
microbiology (the study of microscopic organisms). (Medical scientists, whose work is closely related to that of biological
scientists, are discussed elsewhere in the Handbook.)

from Gk. bio-, comb. form of bios "one's life, course or way of living, lifetime" (as opposed to zoe "animal life, organic
life"), from PIE base *gweie- "to live" (cf. Skt. jivah "alive, living;" O.E. cwic "alive;" L. vivus "living, alive," vita "life;" M.
Pers. zhiwak "alive;" O.C.S. zivo "to live;" Lith. gyvas "living, alive;" O.Ir. bethu "life," bith "age;" Welsh byd "world").
Equivalent of L. vita. The correct usage is that in biography, but in modern science it has been extended to mean
"organic life."

early 16c., "pertaining to logic," from logic + -al. Attested from 1580s as "conformable to laws of reasoning;" 1860 as
"following as a reasonable consequence." Related: Logically.

biofilm  (bī'ō-fĭlm')    A complex structure adhering to surfaces that are regularly in contact with water, consisting of
colonies of bacteria and usually other microorganisms such as yeasts, fungi, and protozoa that secrete a mucilaginous
protective coating in which they are encased. Biofilms can form on solid or liquid surfaces as well as on soft tissue in
living organisms, and are typically resistant to conventional methods of disinfection. Dental plaque, the slimy coating
that fouls pipes and tanks, and algal mats on bodies of water are examples of biofilms. While biofilms are generally
pathogenic in the body, causing such diseases as cystic fibrosis and otitis media, they can be used beneficially in
treating sewage, industrial waste, and contaminated soil.

The adaptive and genetic changes of the micro-organisms within the biofilm make them resistant to all known
antimicrobial agents. Thus, the diagnostic and therapeutic strategies used to fight acute infections are not effective in
eradicating medical device biofilm-related infections or chronic biofilm diseases.

WEF -- 2000

"Biosolids, a twist on the use of bio logical processing of wastewater solids, was one of 300 responses to WEF’s call
for suggestions. Dr. Bruce Logan of the University of Arizona created the word. WEF’s Executive Committee formally
recognized the term in 1991. The U.S. Environmental Protection Agency (U.S. EPA) began using the word soon
thereafter, and “biosolids” is used by most federal and many state agencies today. A new word was coined for
the same reason the word is used today: to describe the primarily organic byproduct of wastewater treatment which can
be beneficially recycled."

EPA -- 1993

The chemical composition and
bio logical constituents of the sludge depend upon the composition of the
wastewater entering the treatment facilities and the subsequent treatment processes. Typically these constituents may
include volatile organics, organic solids, nutrients, disease-causing pathogenic organisms (e.g., bacteria, viruses, and
others), heavy metals and inorganic ions, and toxic organic chemicals from industrial wastes, household chemicals, and

Secondary treatment produces sludge generated by
bio logical treatment processes. Bio logical treatment
processes (e.g.,
activated sludge systems, trickling filters, and other attached growth systems) utilize
microbes to break down and convert the organic substances in the wastewater to microbial residue. [biosolids]

Bio logical treatment processes remove up to 90 percent of the organic matter in the wastewater
and produce a sewage sludge that typically contains from 0.5 to 2 percent solids. Sewage sludges produced during
secondary treatment generally are more difficult to dewater than are primary sewage sludges. The organic content of
secondary treatment sewage sludge ranges from 50 to 60 percent. Secondary treatment processes increase the
volume of sewage sludge generated over the volume generated in primary treatment by 15,000 to 20,000 liters of
sewage sludge per million liters of wastewater.

Achieving desired national levels of environmental quality depends on the reduction and elimination of the
substantial volumes of waste and wastewater generated at home and at work. Without a significant reduction in these
volumes (e.g., by home composting food scraps rather than putting them down a garbage disposal),
and a corresponding reduction in the residual from wastewater treatment (sewage sludge is also often referred to as
“biosolids”) that must then be either used or disposed of, attaining these goals is severely hampered.

The organic and nutrient content of sewage sludge (
biosolids) makes it a valuable  resource to use both in
improving marginal lands and as a supplement to fertilizers and soil conditioners.

The term
biosolids has been used to distinguish sewage sludge that has been treated and can be beneficially
recycled. Improving the productivity of our land using the soil conditioning properties and nutrient content of sewage
sludge has human health and environmental advantages beyond those that are directly associated with applying
sewage sludge to the land. Secondary or related benefits of reusing sewage sludge result from a reduction in the
adverse human health effects of incineration, a decreased dependence on chemical fertilizers, a reduction in the
emissions associated with incineration that may contribute to the “greenhouse effect” and a reduction in fuel or energy
costs associated with incineration.

Adoption of the part 503 standards as a minimum baseline for sewage sludge use or disposal will protect public health
and the environment. In addition, widespread adoption of part 503 standards would facilitate beneficial use of sewage
sludge (
biosolids) by establishing uniform standards from State to State.

EPA -- March 25, 1996
To Interested Parties:
The Water Science and Technology Board (WSTB) of the National Research Council/National Academy of Sciences
recently issued an important new report, "Use of Reclaimed Water and Sludge in Food Crop Production." The effort
leading to this new report provides a timely critique of the practice of using treated municipal wastewater effluents and
biosolids in the production of crops for human consumption.
It has been recognized in Germany, at least since D. Strauch published his 1991,"
Survival of pathogenic micro-
organisms and parasite in extreta, manure and sewage sludge", that" most pathogenic agents can survive the treatment
process" and the sewage treatment process causes some of the pathogenic disease organisms to be absorbed or
enclosed in faecal particles during the treatment process. "Therefore," according to Strauch, "sewage sludge is rightly
described as a concentration of pathogens." Strauch concluded in his study that, "In any case, the agricultural utilization
of hygienically dubious sewage sludge poses a risk for the whole national economy."

"The problem of pathogen detection in sludge,
according to EPA's David Lewis, 1998,  "is that the sewage treatment
process changes the outside crust of the aggregates in sludge and only the pathogens on the outside of the
aggregates are measured by standard tests." He says that most of the microbes are trapped inside the aggregates.  
When ultrasound was used to break open the aggregates of sludge the trapped microbes were revealed. In effect, it
appears that the treatment processes hide most of the pathogens rather than destroying them."

EPA has told us what it was supposed to do to protect public health and the environment. It also told us it was not going
to do those things because it did not have the data to create a safe regulation.

EPA -- 1993

Section 405(d) of the CWA directs the Agency to control the quality of sewage sludge by establishing limits for
pollutants in sludge applicable to methods of use or disposal. Preventing the contamination of sewage sludge
before it is used or disposed of is more equitable than requiring others to contain the contaminated sewage sludge
or to deal with the consequences. When it is not feasible for the Agency to set pollutant limits, section 405(d)(3)
authorizes EPA to establish a design or equipment standard, management practice, or operational standard or
combination of these in lieu of numerical limitations. This is the approach EPA took in the criteria promulgated for
municipal solid waste landfills (MSWLFs). There, EPA adopted a containment approach rather than numerical limitations
for solid waste, including sewage sludge disposed of in MSWLFs, in part because of the infeasibility of developing and
enforcing numerical limitations for mixtures of sewage sludge and other solid waste materials disposed of in
MSWLFs (56 FR 50978, October 9, 1991).

A POTW has a number of options to dispose of sewage sludge, including applying it to land, incineration,
disposing of it in a landfill, or selling it to the public for use as a fertilizer or soil nutrient. However, the composition of
the sludge can limit these choices. One important avenue for sewage sludge disposal is through beneficial use
and recycling projects.

However, if sewage sludge containing high levels of pathogenic organisms (e.g., viruses, bacteria) or high
concentrations of pollutants is improperly handled, the sludge could contaminate the soil, water, crops,
livestock, fish, and shellfish. The major human health, environmental, and aesthetic factors of concern in the land
application of sewage sludge are related to pathogens, metals and persistent organic chemicals content, and odors.

At the same time, in some situations, disposal of sewage sludge may present an environmental concern because of
contamination by harmful pollutants. Greater focus on surface water toxics control, as well as Resource
Conservation and Recovery Act (RCRA) provisions such as the ban on land disposal of certain hazardous wastes
(section 3004(d)) and the exclusion of discharges into municipal sewers from RCRA requirements (section 1004(27)),
may result in increased volumes of toxic and hazardous pollutants that reach POTWs and consequently may
adversely affect sludge quality when these pollutants are removed from the wastewater.

Proper disposal of sewage sludge is important because contaminated or improperly handled sludge can result in
pollutants in the sludge re-entering the environment, and possibly contaminating a number of different media through a
variety of exposure routes. Further, improper sludge management could lead to environmental degradation of land and
air. Failure to dispose of sludge properly or contaminated sludge could also have adverse effects on surface and
ground water and wetlands, as well as human health.

EPA’s rules must also establish numerical limitations for each such pollutant. EPA’s rules must protect public
health and the environment with an ample margin of safety, and must take care to protect the health of individuals or
populations which are at higher risk than the population as a whole.

The regulatory thresholds do not purport to define a concentration that would be safe if used for growing food or feed

Sewage sludge with high concentrations of certain organic and metal pollutants may pose human health problems when
disposed of in sludge-only landfills (often referred to as monofills) or simply left on the land surface, if the pollutants
leach from the sludge into the ground water. Therefore, the pollutant concentration may need to be limited or other
measures such as impermeable liners must be taken to ensure that ground water is not contaminated.
The Agency believes, therefore, that it must determine the “safe level” of a pollutant before removal credit authority can
be granted for that pollutant

However, its exposure assessment models relied, in part, on data from field studies on sewage sludge
applied to agricultural land that represented a range of sewage sludge of different concentrations. The models do
not look exclusively at data from the most heavily contaminated sludges or consider ecological systems impacts
from sludges applied to non-agricultural lands.

Results of a ground-water monitoring program developed by a qualified ground-water scientist or a certification by a
qualified ground-water scientist shall be used to demonstrate that sewage sludge placed on an active sewage sludge
unit does not contaminate an aquifer.

By requiring
“adequate protection” of public health and the environment did Congress intend to leave to EPA’s
discretion the determination of what adverse effects public health and environmental protection required? Is a
consideration of whether the effects are widespread, particularly with respect to non-public health effects, part of the
determination of what constitutes adequate protection.

EPA concluded that
adequate protection of public health and the environment did not require the adoption of
standards designed to protect human health or the environment under exposure conditions  that are unlikely and where
effects were not significant or widespread.

Methodologies and data do not yet exist, except for lead, to correlate differing levels of exposure to
non-carcinogenic pollutants with incidence of an effect. The only measure for threshold pollutants other than lead is the
number of people exposed to a level above a RfD. This, in fact, may have little meaning for individual risk since risk
above the RfD cannot be determined using the RfD methodology.

For example,
if the Agency lacked data from sludge field studies on metals up take in crops grown for human
consumption, data from sludge/pot studies or salt/pot studies was used in the MEI risk assessment analysis.

The margin of safety associated with the data from salt/pot studies is greater than the margin of safety associated with
data from sludge/pot studies and far greater than the margin of safety associated with data from sludge/field studies.

The Agency agrees with the public and the scientific peer review committees that the 98th-percentile
approach is inconsistent with the MEI approach and that numerical limitations derived from the 98th-percentile approach
do not ensure protection of public health and the environment because they lack a formal pathway risk

At this time, limited
sludge field data exists that indicate the level at which inorganic pollutants become
toxic to soil biota. However, Hartenstein et al. (1980) routinely raised earthworms using sewage sludges, which provided
a limited source of data. Evidence does not prove that they are highly sensitive species; however, because of the lack
of data for other species, the criteria for this pathway have been set using earthworm data.

In addition, the
Agency lacks any national information on the consumption of homegrown meat
products that would enable it to adjust the data in the non-metropolitan category, previously done for vegetable food

Protozoa are no longer included as one of the organisms subject to pathogen requirements because of the
lack of an analytical method for protozoa.

For pollutants other than those in appendix G,
it cannot be determined, however, whether pollutants were not
selected for regulation because they were believed to be “safe” or because
there are not adequate data to
determine a “safe level”.

Dioxins, which may be present in sewage sludge, are not regulated not because they are believed safe but
because at the time EPA initially screened pollutants for regulation
it lacked data to evaluate dioxins for

Some commenters assumed incorrectly that the pollutants on Table 111-3 in the preamble for the proposed
part 503 regulation were the only pollutants for which EPA lacked adequate data to establish a “safe level”.
Table 111-3 listed the pollutants that were recommended for further study but
for which a positive determination
was made subsequently that EPA lacked sufficient data to establish a safe level.
There are other pollutants
that may have not been recommended for study because
EPA lacked data regarding the risk they presented.

However, it must be recognized that the decision to regulate some pollutants and not others was in part based on the
availability of information on the pollutants. EPA solicited comments and data to support whether additional or fewer
pollutants should be regulated but received little response.
The decision not to regulate does not necessarily
mean that the unregulated pollutants may not threaten public health and the environment

Attached growth systems

The concept of flowing wastewater across some natural material for treatment is the basis of
attached growth processes, also referred to as fixed film.

In contrast to activated sludge processes where the waste-consuming bacteria grow in suspension in
water tanks, the active bacteria in attached growth processes cling to some surface, natural or manmade, to
perform the cleaning.

There are two basic designs of attached growth or fixed film systems: those that hold the media in
place, allowing the wastewater to flow over the bed (such as trickling filters), or those where the media is
in motion relative to the wastewater ( e.g., rotating biological disks).

Disadvantages are a larger land requirement, poor operation in cold weather, and potential odor problems.

i. Biological filters (fixed film systems)
Here, an inert supporting medium is impregnated with microorganisms and is packed into a tower or tank. Using organic
matter and oxygen, microbial slime develops on media support. The thickness of the slime increases and the extra
thickness is sloughed off as sludge, which is collected in a sedimentation tank below, and is treated and disposed off.

ii. Trickling filters

Through the drainage system below, sludge as well as treated effluents are collected. The microorganisms growing on
the fixed inert support, decompose the organic matter. Facultative bacteria (Achromobacter, Pseudomonas, etc.),
filamentous form (Sphaerotilus natans), nitrifying bacteria (Nitrosomonas), few fungi, algae and protozoa, etc., are of
common occurrence.

iii. Rotating biological contactors (RBC)

Rotating biological contactors are aerobic systems with a fixed film of microorganisms growing on discs on a rotating
shaft. The disc is made of polystyrene, polyethylene, polypropylene, stainless steel, cement, aluminium, glass, PVC,
rubber, teflon, wood, wire screen, etc.
What are Biosolids?
2005 -- Burch Hydro Incorporated,
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.

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.

Village of Plover, Wisc  WASTEWATER DEPARTMENT  
The process provides optimum growth conditions for the bacteria, and there is an ample food source in the wastewater.  
The bacteria grow and reproduce in the system.  The most efficient removal is obtained at a certain balance between
the bacteria in the system and the amount of food entering the process.   As the bacteria grow and reproduce, a portion
of the bacteria must be removed on a regular basis.   

Excess bacterial solids or “biosolids” generated by the process are diverted from the RAS piping into an aerated
storage tank.  The biosolids from the storage tank is fed to a gravity belt thickener where 94 to 96% of the water is
removed.   Thickened biosolids is discharged into the auto-thermal aerobic digesters.  The biosolids entering the
digesters is quite active, viable, and have a high proportion of organic material incorporated into its cell mass.  The
biosolids in this state are unstable and could create strong odors, attract flies, and be generally undesirable.  The
biosolids are treated further to reduce their organic content in digesters. The digesters stabilize the biosolids by blowing
air through the mixture, and raising the temperature to about 110 degrees F.  The biosolids are held under these
conditions for 40 to 80 days.

Sewage Treatment Plants
Chemtronics Technologies

By progressively converting dissolved material into solid , usually a biological floc and settling this out, an effluent
stream of increasing purity is produced.

Phosphorus removal can be effected biologically in a process called enhanced biological phosphorus removal. In this
process specific bacteria, called Polyphosphate accumulating Organisms, are selectively enriched and accumulate
large quantities of phosphorus within their cells. When the biomass enriched in these bacteria is separated from the
treated water, the bacterial biosolids have a high fertilizer value.

Innovative Remediation Technologies Inc. uses a bioremediation process that is unique to the industry.
The Biosolids Enhanced Remediation (BER) approach takes advantage of aerobic and facultative
metabolic pathways utilized by specifically cultured microorganisms and inoculation levels which far
exceed the numbers of bacteria which can be typically attained by stimulating the natural population of
selected petroleum hydrocarbon degraders.