Nicholas P. Cheremisinoff. Handbook of Solid Waste Management and Waste Minimization Technologies

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within the fields or off-site," says B. L. Harris, associate director of agricultural

science at Texas Agricultural Extension Service. Similarly, Pillai reports "no

indication that pathogens from the sludge application site are blowing beyond the

site."

Although most people consider bad odors more of a nuisance than a health

problem, continuous exposure to strong odors, for example those emanating from

hog farms, has been shown to adversely affect the health of some people. Some

opponents of biosolids recycling have cited odor as a primary incriminating

factor. In fact, biosolids can be closer in appearance and scent to good compost

than to the smelly animal manure that farmers have always used to rejuvenate

their soil. And when biosolids are injected under the soil surface, the process is

virtually odorless. But in northwest New Jersey, residents of Harmony Township

blame sewage biosolids and other residues for the air they claim smells like

diarrhea, vomit, and urine. "People should not have to live this way," says Lois

Markle, a teacher and vociferous opponent of the odors, who recently was

elected deputy mayor of the township. Markle blames the problem on a farm that

accepts biosolids and slaughterhouse and food-processing wastes, and on a

biosolids processing plant next door. With two biosolids facilities side by side,

Markle charges, the "[New Jersey] Department of Environmental Protection is

not [able] to figure out who is making the odor." After years of complaints, the

state is suing one of the operators for air-quality violations.

Questions still remain, however - most prominently, how safe is food grown on

biosolids-amended soils? This question, prompted by concern among food

processors that the public might boycott their products, sparked the NRC study of

biosolids application and waste water reuse. In the most comprehensive report in

many years on biosolids recycling, the NRC generally endorsed the EPA

approach, concluding that "while no disposal or reuse option can guarantee

complete safety, the use of [biosolids and treated effluent] in the production of

crops for human consumption, when practiced in accordance with existing federal

guidelines and regulations, presents negligible risk to the consumer, to crop

production, and to the environment." However, the committee did suggest that

the EPA reconsider its exclusion of toxic organics from Part 503. The NRC

group added that as more croplands "reach their regulatory limit of chemical

pollutant loading from sludge application, additional information will be needed

to assess potential, long-term impacts of sludge on ground water quality and on

the sustainability of soils for crop production." However, since less than 2% of

total U.S. cropland would be enough to recycle all current biosolids production,

and in many cases biosolids can be applied for 100 years before lifetime loading

rates are reached, the day of saturation will not soon be reached.

Given that the scientific literature contains no reports of toxicity or disease due to

sludge, why does the public still seem frightened? In some cases, it's probably

due to regional resentment, a feeling that easterners, or New Yorkers, are

dumping their waste on the rest of the country. There is also a fundamental

feeling that biosolids are unclean. When those feelings are combined with fear

that biosolids are - as, admittedly, was true 20 years ago - carrying unacceptable

levels of heavy metals and toxic chemicals, it's easy to understand the "don't

dump on me" sentiment. Rubin acknowledges that spills, smells, and slip-ups

sabotage public confidence in land application. "If the public feels the aesthetics

are bad, or a sloppy operation is going on and nobody cares, they will feel

something is wrong with their health."

BIOSOLIDS TREATMENT

Biosolids generally require additional treatment at the wastewater treatment

facility before they are disposed of in order to meet regulatory requirements

that protect public health and the environment, facilitate handling, and reduce

costs.

Biosolids characteristics can determine a municipality's choice of use

or disposal methods. Only biosolids that meet certain regulatory requirements

for pathogens, vector attraction reduction, and metal content, for example,

can be land applied or used as compost. Even those biosolids that are

disposed of rather than land applied must meet regulatory requirements.

Also,

with regard to handling and cost, the water content of biosolids can

affect many aspects of biosdids management, such as transportation and the

size of treatment and use or disposal operations. Some biosolids treatment

processes reduce the volume or mass of the biosolids (such as biosolids

digestion processes). The two most common types of biosolids treatment

processes are stabilization and dewatering.

Stabilization refers to a number of processes that reduce pathogen levels,

odor, and volatile solids content Biosolids must be stabilized to some extent

before most types of use or disposal. Major methods of stabilization include

alkali (lime) stabilization, anaerobic digestion (digestion of organics by

microorganisms in the absence of oxygen), aerobic digestion (digestion of

organics by microorganisms in the presence of oxygen), composting, and/or

heat drying.

The body of technologies within dewatering removes excess water from biosolids

and generally must be performed before biosolids are composted, landfilled,

dried (e.g. pelletized or heat dried), or incinerated. A number dewatering

processes can be used, including air drying, vacuum filters, plate-and-frame

filters,

centrifuges, and belt filter presses.

The improved structural characteristics of stabilized biosolids (compared to

dewatered biosolids cake without lime stabilization) tends to reduce pathogens

and odors, allow for more efficient handling operations, and provide a source of

lime to help neutralize acid soils. While lime is most commonly used, other alka-

line materials, such as cement kiln dust lime kiln dust, Portland cement, and fly

ash, have also been used for biosolids stabilization.

Alkaline stabilization has been implemented using either quicklime (CaO) or

hydrated lime [Ca[OH]

]; which is added either to liquid biosolids before

dewatering or in a contained mechanical mixer. Traditional lime stabilization

processes are capable of producing biosolids meeting the minimum pathogen and

vector attraction reduction requirements found in the 40CFR Part 503 rules

governing land application of biosolids; sufficient lime is added so the pH of the

biosolids/lime mixture is raised to 12.0 or above for a period of 2 hr. The elevated

pH helps to reduce biological action and odors.

In the treatment plant, anaerobic or aerobic bacteria metabolize the solids in

wastewater and settle to the bottom. When these bacteria have finished,

waste water contains about 1% solids, largely organic material from the

decomposing bacteria. In dry-weight composition, biosolids resemble animal

manure, typically containing 3% nitrogen (manure contains 1.7 - 7.8%) and

1.5% phosphorus (manure contains 0.3 to 2.3%). Both materials also contain

sulfur, calcium, magnesium, potassium, and other elements. When applied to

land, the organic matter in biosolids improves the soil's structure, increases its

water-holding capacity, and feeds essential soil microorganisms.

Sewage plants have always had to dispose of biosolids; ironically, better

treatment removes more solids and thus creates more biosolids. One of the first

recycling efforts began in 1926, when Milwaukee began selling dried biosolids to

homeowners and landscapers as fertilizer. According to the EPA, about 12% of

all recycled biosolids are given or sold to the public in containers. Approximately

9% of recycled biosolids are used to revitalize land that's been damaged, usually

by mining. For many years, Chicago's biosolids were spread on former coal strip

mines in Fulton County, Illinois, 190 miles southwest of Chicago. About 2,000

acres of damaged land owned by the Metropolitan Sanitary District of Greater

Chicago has been returned to agriculture and is leased to farmers, says district

soil scientist Scott Nelson. Here and elsewhere, sludge has also been used to

rejuvenate spoils heaps - multi-acre piles of acidic rock where nothing had grown

decades after mining had stopped. An enormous amount of biosolids-up to 1,000

dry tons per acre - increased the organic content of the heaps, and 70 tons of lime

per acre neutralized the acidity. Today the land is prairie, and the runoff of acid

mine drainage, which commonly carries toxic chemicals from abandoned strip

mines, has practically ceased. In Washington State, Seattle's biosolids are

sprayed into forests, a practice that nationwide accounts for about 3% of total

biosolids recycling. In forests, terrain is a key restriction to biosolids use. If the

land slopes more than 10 - 20%, the biosolids may quickly wash into

watercourses.

Fully 67% of recycled biosolids go to farmland, where they are spread on, or

injected under, soil. In Wisconsin, where the Madison Metropolitan Sewerage

District's "Metrogro" program is often held up as a national model, fields are

chosen based on soil type, depth to groundwater and bedrock, and slope. "If

there's high permeability, or potential for

runoff,

we're not allowed to go on

them," says David Taylor, a district soil scientist who directed the Metrogro

program for many years. Since excess nitrogen pollutes groundwater and surface

water, the district applies the amount of biosolids that will supply only enough

nitrogen for the next crop. The farmer's $7.50 per acre payment covers

application with the district's trucks, tests of the soil, plant tissue, well water,

and all required recordkeeping. Although the fee only funds 1 - 2% of the

biosolids program, Taylor says it helps present biosolids "as a resource, not a

waste." Farmers in the surrounding area seem to approve and have offered about

seven times as much land as the district needs for its annual application of 3,000

to 4000 acres per year. The high level of acceptance can be credited to clean

biosolids, a 20-year history of monitoring pollutant levels in biosolids, soil,

water, and plant tissue, and the district's support for university research on

cheaper and cleaner sewage treatment. Importantly, the district has also

shouldered the extra expense of injecting sludge into the soil, preventing odor

and sight problems that enrage neighbors of some land application projects.

APPLICATIONS

The rate at which biosolids are applied to land such that the amount of nitrogen

required by the food crop, feed crop, fiber crop, cover crop or vegetation grown

on the land is supplied over a defined growth period, and such that the amount of

nitrogen in the biosolids which passes below the root zone of the crop or

vegetation grown to groundwater is minimized. Biosolids can exhibit a wide

array of physical and chemical traits. Depending on the extent of dewatering or

drying, the solids content of biosolids can range from less than 5% to more than

New, aggressive pretreatment programs at the source of generation have

dramatically reduced metal concentration in biosolids over the past two decades,

minimizing the possibility of environmental damage. The EPA established

guidelines regarding the quantity of trace elements in biosolids and the amount

that ultimately can be added to soils growing plants (see Table 2). Base metal

90%.

Chemical characteristics of biosolids vary between treatment plants and, to

a limited extent, within the same plant over time. Table 1 lists the typical

chemical composition of biosolids as representative examples. Because biosolids

may contain trace elements, they are classified by their trace-element content due

to their potential impact on public health and the environment.

Table 1: Chemical Properties of Biosolids (Dry Weight Basis)

Parameter, units

dS/m

Organic N, %

-N, %

Phosphorus (P), %

Potassium (K), %

Arsenic (As), mg/kg

Cadmium (Cd), mg/kg

Chromium (Cr), mg/kg

Copper (Cu), mg/kg

Mercury (Hg), mg/kg

Lead (Pb), mg/kg

Molybdenum (Mo),

mg/kg

Nickel (Ni), mg/kg

Selenium (Se), mg/kg

Zinc (Zn), mg/kg

Littleton/Englewood*

11.6

2.88

0.47

0.01

2.52

0.283

558

0.8

942

Fort

Collins

5.0

4.22

0.40

0.01

1.60

0.194

553

6.2

117

776

Metro

Denver

12.7

6.31

1.35

0.01

2.32

0.200

500

3.0

138

915

a Applied to experimental plots near Bennett, Colorado, in August 1993.

b Applied to experimental plots on the Meadow Springs Ranch near Fort Collins,

Colorado, in August 1991.

c Metrogro™ cake chemical analysis, 1993.

d EC is a measure of the soluble salt concentration.

limits on extensive research regarding the effects of biosolids metals on various

pathways of exposure, including plant toxicities and adverse effects on animal

and human health. Biosolids are treated to eliminate pathogens (disease-causing

organisms) that may reside in wastewater. EPA requires domestic wastewater

treatment plants to reduce pathogens and diminish the attraction of insects and

animals before biosolids are applied. Applicators may apply Grade 1 biosolids at

agronomic rates without restrictions regarding trace metal loading limits.

Table 2. Maximum Trace Element Concentrations Allowed for Grades 1 and 2

mg/kg (Dry Weight Basis)

Metal

Grade 1

1200

1500

300

Not finalized

420

2800

Grade 2

3000

4300

840

420

100

7500

Biosolids contain significant amounts of N, P, and K (Table 1). They also can

provide plant micronutrients such as Zn. Many soils exhibit low levels of

available Zn and biosolids help alleviate the deficiency of this essential element.

The nature of nutrients in biosolids is different from those found in commercial

fertilizers. Stabilization of biosolids during waste treatment produces organic N

forms that are not available to plants until they are decomposed by soil

microorganisms. When added to soils, microorganisms break down biosolids and

release 10 to 50% of the organic N as available N (ammonium, NH

) in the first

year following application. Soil microorganisms rapidly convert the NH

nitrate (NO

"). Plants quickly absorb NO

". It also is mobile in soils, irrespective

of whether it originates from commercial N fertilizer or biosolids.

The mobility of NO

' increases the potential for groundwater contamination. In

essence, biosolids are slow-release N fertilizers that contain low concentrations of

plant nutrients. Frequently, biosolids promote physical changes in soil that are

more significant than the plant nutrients they supply.

The greatest challenge in using biosolids for beneficial reuse on crop- and

rangeland is to prevent NO

' leaching to groundwater. As biosolids

nutrient

value may vary depending on the form (i.e., liquid, dewatered, or dried),

determining the correct agronomic rate remains a challenge. However, if the

agronomic rate is applied under nonirrigated (dryland) cropping in a semiarid

environment, where water table depths generally are over 100 feet, the potential

for groundwater contamination is negligible. Under irrigated conditions, if

agronomic rates of biosolids based on site specific soil-test and crop-management

information are applied, groundwater contamination with NO

" should not occur.

Annual monitoring of residual soil NO

-N levels will help guard against

groundwater pollution.

A SHORT REVIEW

Biosolids applications are often touted as a pollution prevention technology;

however in many ways this is an inappropriate labeling for this application. It is a

form of recycling that may carry some long-term health risks, depending upon

the nature and characteristics of the solids. Conceptually it is a more cost-

effective strategy that incineration and straight landfilling, but this in part

depends on local market conditions which support the uses of this material. As a

form of recycling, it represents a more logical strategy for long-term solid waste

management. It is not, however, a preventive strategy as is often presented to the

public.

RECOMMENDED RESOURCES

Barbarick, K.A., R.N. Lerch, D.G. Westfall, R.H. Follett, J. Ippolito, and

R. Jepson. Application of anaerobically digested sewage sludge to dryland

winter wheat. Colorado Agricultural Experiment Station, TR91-5, 1991.

Barbarick, K.A., R.N. Lerch, J.M. Utschig, D.G. Westfall, R.H. Follett, J.

Ippolito, R. Jepson, and T.M. McBride. Eight years of application of

sewage sludge to dryland winter wheat. Colorado Agricultural Experiment

Station,

TB92-1,

1992.

Colorado Department of Health. Biosolids Regulation 4.9.0, 1993.

Harris-Pierce, R. L., E. F. Redente, and K. A. Barbarick. The effect of

sewage sludge application on native rangeland soils and vegetation: Fort

Collins - Meadows Springs Ranch. Colorado Agricultural Experiment

Station, TR93-6, 1993.

Ippolito, J., K. A. Barbarick, D .G. Westfall, R. H. Follett, and R. Jepson.

Application of anaerobically digested sewage sludge to dryland winter wheat.

Colorado Agricultural Experiment Station, TR92-5, 1992.

6. Ippolito, J., K. A. Barbarick, D. G. Westfall, R. H. Follett, and R. Jepson.

Application of anaerobically digested sewage sludge to dryland winter wheat.

Colorado Agricultural Experiment Station, TR93-5, 1993.

Ippolito, J., K. A. Barbarick, D. G. Westfall, and R. Jepson. Application of

anaerobically digested sewage biosolids to dryland winter wheat. Colorado

Agricultural Experiment Station, TR94-6, 1994.

8. Logan, T. J., and R. L. Chaney. Utilization of wastewater and sludges on

land - metals, pp. 235-323. In A.L. Page (ed.) Proc. of the 1983 Workshop

on Utilization of Municipal Wastewater and Sludge on Land. Univ. of

California-Riverside, 1983.

Chapter 7

INDUSTRY PRACTICES

INTRODUCTION

The last decade has brought about a significant change in industry attitude and

practices in the handling of wastes and pollution. The concept of environmental

management systems, personified by ISO

14001,

the chemical industry's

Responsible Care program, and Western Europe's EMAS, have raised the

awareness and level of responsibility of industry to act in a more responsible

manner that protects the public and preserves the environment. Despite this

awareness, industry sectors continue to struggle innocently and in some cases act

irresponsibly in their handling of waste and pollution issues.

This chapter provides an overview of industry practices in different heavy

manufacturing sectors. The conventional waste handling practices, along with

some of the pollution prevention strategies that are being implemented more

frequently today, are covered.

THE CHEMICAL INDUSTRY

The U.S. chemicals and allied products industry consists of some 9125

multinational corporations whose primary business is the development,

manufacturing, and marketing of industrial chemicals, Pharmaceuticals, and other

chemical products. The U.S. chemical industry is vital to the U.S. economy. It

produces 1.9 percent of U.S. gross domestic product (GDP). It is the nation's

number one exporter. It supplies more than $1 out of every $10 of U.S. exports

and consistently runs large international trade surpluses. It is a high-tech,

research and development (R&D) oriented industry that is awarded about one out

of every eight U.S. patents. It employs more than 1 million persons and it

produces more than 70,000 different products. Most importantly, chemicals is a

"keystone" industry ~ one critical to the global competitiveness of other U.S.

industries. Because so many modern products and businesses depend on

chemicals, the international competitiveness of other U.S. industries requires a

high-tech, globally competitive U.S. chemical industry that can supply new

products at prices that give U.S. producers an edge.

Chemicals in many ways can be described as the foundation of a modern,

progressive society. They are an integral and ever-increasing part of our complex

technological world, making it possible for us to enjoy a high standard of living.

Not only do pollution prevention (P2) practices in the chemical process industries

(CPI) offer reduced costs in manufacturing operations, but they are essential in

developing more efficient and safe means of manufacturing many of the chemical

products we have grown to depend on.

PETROCHEMICAL MANUFACTURING PRACTICES

Natural gas and crude distillates such as naphtha from petroleum refining are

used as feedstocks to manufacture a wide range of petrochemicals that are in turn

used in the manufacture of consumer goods. Basic petrochemicals are

manufactured by cracking, reforming, and other processes, and include olefins

(such as ethylene, propylene, butylenes, and butadiene) and aromatics (such as

benzene, toluene, and xylenes). The capacity of naphtha crackers is generally of

the order of 250,000 to 750,000 metric tons per year (tpy) of ethylene

production. Some petrochemical plants also have alcohol and oxo-compound

manufacturing units on site. The base petrochemicals or products derived from

them, along with other raw materials, are converted to a wide range of products.

Among them are:

• Resins and plastics such as low-density polyethylene (LDPE), high-density

polyethylene (HDPE), linear low-density polyethylene (LLDPE),

polypropylene, polystyrene, and poly vinyl chloride (PVC);

• Synthetic fibers such as polyester and acrylic engineering polymers such as

acrylonitrile butadiene styrene (ABS);

• Rubbers, including styrene butadiene rubber (SBR) and polybutadiene rubber

(PBR);

• Solvents;

Industrial chemicals, including those used for the manufacture of detergents such

as linear alkyl benzene (LAB) and of coatings, dyestuffs, agrochemicals,

Pharmaceuticals, and explosives.

Chemical compounds manufactured at petrochemical plants include methanol,

formaldehyde, and halogenated hydrocarbons. Formaldehyde is used in the

manufacture of plastic resins, including phenolic, urea, and melamine resins.

Halogenated hydrocarbons are used in the manufacture of silicone, solvents,

refrigerants, and degreasing agents.