Chapter Six


The NRC's second point discusses the

(2)  wastewater treatment technologies and procedures
for agricultural use of these materials;

The wastewater collected from households, business

and commercial establishments and industrial facilities

which contain organic matter, disease causing agents,

nutrients (which can also be toxic), toxic and hazardous

pollutants (both organic and inorganic), and dissolved

minerals, which are concentrated during the treatment

process to produce sludge, are treated by one or more of

the following technologies:

(1)  preliminary treatment, includes the screening of

course solids and grit removal of heavy solids that

would interfere with the treatment process.

(2)  primary treatment "involves the gravity

sedimentation of screened, degritted wastewater to

remove settled solids; slightly more than one-half

of the suspended solids ordinarily removed."

"At one time during the evolution of domestic

wastewater treatment in the United States,

facilities only practiced primary wastewater

treatment and the primary effluent was commonly

discharged to surface waters offering appreciable

dilution. Now, primary treatment is used as an

economical means for removing some contaminates

prior to secondary treatment. The residue from

primary treatment is concentrated suspension of

particles in water called "Primary Sludge."

(P. 48)

(3)  secondary treatment is generally accomplished by

using a biological treatment process in a trickling

filter, or ponds or some other process to remove

biodegradable material.

The NRC Report is rather vague on the results of

the biological process producing "carbon dioxide

and other end products." The "other end products"

include methane and hydrogen sulfide, a very deadly

gas. The Report is also vague on the "constituents"

"incidentally associated" in the secondary sludge

such as pathogens (disease causing organisms),

"trace elements" (toxic and hazardous substances)

and "organic compounds (PCB's as well as other

unknown compounds). (p. 49)

(4)  advanced or "tertiary" treatment is used when a

high quality effluent is required. According to the

report, "Disinfection for control of pathogenic

microorganisms and viruses is the most common type

of tertiary treatment." (p. 49).

   Sludge may be "conditioned" by "polymers" or

"ferric chloride" of "lime" to help in the

dewatering process or it may go through a

stabilization process which further reduces the

pathogens. (pp. 52-3)

The raw wastewater (domestic sewage) entering a

treatment plant "undergoes preliminary, primary,

secondary, and in some cases additional treatment to

yield treated effluent and a concentrated stream of

solids (generally about 1%) in liquid, called sludge."

The NRC Committee are claiming the wastewater

treatment technologies and procedures are adequate to

control: bacteria, viruses and parasites.

Yet, According to the study, "There are three kinds

of microorganisms in sewage sludge which are of concern

for their effects on human health: bacteria, viruses,

and parasites. All have been found in treated secondary

effluent and sludges"...."Using traditional methods of

virus sampling and assay of water from soil lysimeters

at sites irrigated with undisinfected secondary water

effluent, Moore et al.  (1981), have found coliphage

virus particles at a depth of 1.37 meters. Using more

sensitive detection methods, several ground water

samples were taken 27.5 meters below wastewater soil

application sites and were found to be positive for

animal viruses." (p. 79) Couldn't there be a similar

problem when sludge is used for irrigation purposes or

through multiple applications at 98 percent liquid?

The treated wastewater is either discharged into

the surface waters or used to irrigate crops. "Following

treatment, sludges may be disposed of (for example, in a

landfill) or used for food crop production....." (p. 45)

Sludge for use on farmland near a plant is

generally thickened by gravity in a lagoon (5-6%

solids), or dewatered for transport (20-45% solids) or

dried by a number of processes to achieve between 45 to

near 100% solids.

Class B sludge is either thickened or dewatered

sludge processed to "reduce fecal coliform levels to

less than 2,000,000 (two million) colony forming units

per gram of total dry solids." (p. 34)

Class A sludge is processed to further reduce fecal

coliform levels to below detectable levels, not destroy


According to the NRC report, there are also  127

priority pollutants that the Clean Water Act attempts to

regulate under a pretreatment program for industrial

plant wastewater before it gets to the treatment plant:

"Section 307 of the Clean Water Act regulates 127

hazardous compounds, (1) 14 heavy metals and cyanide,

(2) 28 volatile organic compounds, (3) 58 semi-volatile

organic compounds and (4) 25 pesticides and

polchlorinated biphenyls (PCBs) (40 CFR 123.21)." (p.

56)  [Treatment] Standards have been set for the first

29 of the 34 categories of industries that the EPA has

identified "based on the best available technology".

(p. 59)

Yet, the EPA does not regulate wastewater used for

irrigation or sold to water lawns; it is only regulating

10 pollutants in sewage sludge for food crop production.

There are two items that should be considered when

evaluating any treatment of sludge.  (1) the EPA

acknowledges that anaerobic digestion for stabilization

of sludge is controlled putrefaction. "If sludge is held

for ten to thirty days in a digester, methane

fermentation converts up to half of the organic matter

to gases. A mixture of methane and carbon dioxide is

produced that has about one half the heating value of

natural gas and is contaminated with hydrogen sulfide

and other odorous substances. There is enough energy in

the gas to operate normal mechanical equipment and air

compressors in a sewage treatment plant." The NRC report

notes that approximately 50 percent of sludge applied to

crops is organic matter.  When the sludge decays in the

field, it will also produce methane gas, carbon dioxide

and hydrogen sulfide gas. Methane and carbon dioxide

gases have been identified as pollutants which are

effecting the earth's temperature, and creating a

greenhouse effect.  Hydrogen sulfide gas is only a

little less deadly than hydrogen cyanide gas.  In

effect, large sludge farms are being created which

produce enormous amounts of "greenhouse gases" as well

as other very deadly gases.

(2) The EPA also acknowledges that, "Sludge is

sometimes treated with large doses of chlorine that

produces hydrochloric acid and chlorinated compounds and

destroys ammonia and pathogens." Hydrochloric acid is

the same acid that is used in car batteries.

The EPA acknowledged these two problems in the

Proceedings of the Joint Conference on Recycling

Municipal sludges and effluents on Land, July,  1973.

Furthermore, according to the NRC report, the Clean

Water Act regulates 127 hazardous compounds, (1) 14

heavy metals and cyanide, (2) 28 volatile organic

compounds, (3) 58 semi-volatile organic compounds and

(4) 25 pesticides and polchlorinated biphenyls, yet, the

part 503 sludge regulation doesn't regulation them.

Pretreatment standards have been set for 29 of 34

categories of industries. According to "Sources of Heavy

Metals and Their Impact on Wastewater Treatment and

Receiving Water Bodies' Quality --- Case Study of

Metropolitan Area",  "The 1970 to 1972 study of the

sources of heavy metals in New York City wastewater

concluded that even with zero discharge by industry, 94

percent of the zinc, 91 percent of the copper, 84

percent of the cadmium and 80 percent of the chromium

being discharged would continue to be discharged by

sources virtually immune to treatment." (p.133)

Yet, "The National Research Council (1977) reported

that pretreatment has the potential to alleviate

problems of sludge disposal due to heavy metal and toxic

organic compounds. In a study of operating POTWs in

Chicago, Illinois and in a pilot study at a POTW in

Buffalo, New York where significant amounts of

industrial wastewater discharge were received, it was

found that industrial pretreatment programs reduced

toxic heavy metal concentrations by a range of 50 to 90

percent (Zenz, et al., 1975, EPA, 1977)." (p. 59)

While there is little doubt that pretreatment

programs will help eliminate some pollutants from the

wastewater treatment plants, it may not be the answer

the NRC claimed that would make the major difference,

particularly, for New York City.  "After pretreatment,

either through local limits or categorical standards,

83% to 84% of New York City sludges would still be

unacceptable for land application."  ..."the reason for

this is that non-domestic sources of pollutant loading,

not industrial sources, are primarily responsible for

interfering with this sludge use." (p.  142) (Wat. Sci.

Tech. Vol.19, No.  9, 1987) After Reilly had the

sludge regulation revised, only 6% of New York City

sludge is unacceptable for land application.

NRC says sludge is safe for use on crops, except,

the treatment process does not destroy all of the

bacteria, viruses or parasites. Moreover, no accounting

is made for the deadly gases that form during the decay

process of organic matter in sludge on large farm areas.

In effect, the treatment process produces the

potential for serious health damage from sludge after

it leaves the treatment process, particularly, if the

sludge dump is in a low depression area with little wind

to disperse the deadly gases that will accumulate.

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Review of National Academy of Science's (NAS) 1996 literary review report by
its National Research Council (NRC) Committee :

"Use of Reclaimed Water and  Sludge in Food Crop Production"