Reuse of Sludge and Minor Wastewater Residuals

Alice Outwater, Berrin Tansel

• Publisher: CRC Press
• Year: 2020
• Topic: Technology & Engineering
• eBook ISBN:
  9781000157871
• Subtopic: Environmental Science
• Index: Technology & Engineering

Starting with sludge and scum characterization, this practical guide provides least cost methods of improving sludge quality, options for beneficial reuse, the costs of implementing those options, and case studies of sludge reuse programs around the country. From the pitfalls of site selection to pairing sludge products with their markets, this is a comprehensive resource for anyone working to establish a successful sludge reuse program. Each sludge processing option is presented in depth, including costs, operational difficulties, odor control, and application of the sludge product. The land application of liquid sludge, traditional and innovative methods of natural and mechanical dewatering, and lime stabilization processes are covered in detail. Composting options including aerated static pile composting, vermicomposting, windrow composting, and in-vessel composting are investigated. Sludge pelletizing processes and innovative technologies for sludge reuse are discussed, along with the Part 503 regulations.

1	INTRODUCTION

The land application of sludge is as old as agriculture. The Chinese have used human waste as a fertilizer for thousands of years. The Japanese called it nightsoil and carried it out of town under the cover of darkness to apply to their orchards and gardens. The special role of the Untouchable caste in India was to gather up human waste from the towns and transport it out to the countryside. Before the 1940s, land application of sludge was common in the United States. In those simpler, less squeamish times the “manurial” benefits of sludge were appreciated, and local farmers were glad to use wastewater residuals to improve crop yields. However, as soon as synthetic fertilizers became affordable and available, sludge was seen as a disposal problem rather than a resource.

After a hiatus of nearly 50 years, the amount of sludge that is applied to U.S. forests, crops, and disturbed land is steadily increasing. Seattle sprays sludge on forests to promote tree growth, Maryland sludge compost is used to enhance the turf on the White House lawn, Omaha spreads its sludge on nearby farmland, Pennsylvania rehabilitates strip-mined land with sludge compost, and Florida uses sludge from around the country to fertilize the orange groves. Nearly all of the major cities in the U.S., including Philadelphia, Chicago, Baltimore, Denver, Madison, Phoenix, Los Angeles, and Portland, are processing their municipal sludge into fertilizers and soil conditioners.

When sludge products are used judiciously, the risk to human health and the environment is negligible. There are rarely reports of harmful effects to humans, livestock, and pets or to the environment resulting from the land application of sludge products when recommended application rates and good management practices are followed, in spite of the fact that we live in a litigious society and sludge has been land applied for generations. With the promulgation of the U.S. Environmental Protection Agency (EPA) 40 CFR Part 503 regulations,¹ the beneficial reuse of sludge has become a viable alternative for almost all wastewater treatment plants in the U.S.

1.1 SLUDGE PRODUCTION IN THE UNITED STATES

There is a tremendous amount of sludge produced in this country. A typical family of four discharges 300 to 400 gal of wastewater per day, using 75 to 100 gal per person. Domestic wastewater contains material flushed into household drains from sinks, toilets, and tubs. Components of domestic sewage include soaps, shampoo, human excrement, toilet paper, foodstuffs, detergents, pesticides, household hazardous waste, and oil and grease. Domestic wastewater may be treated (or partially treated) at its source in septic tanks, cesspools, or portable toilets or in publicly or privately owned treatment works. These treatment works may accept domestic wastewater alone or a combination of domestic and industrial wastewater.

Municipal wastewater treatment works may use one or more levels of treatment — primary, secondary, or tertiary — to clean this wastewater. Each level of treatment provides both a higher level of wastewater cleanup and a larger quantity of sewage sludge. Unprocessed sewage sludge contains from 93 to 99.5% water, as well as the solids and dissolved substances that were present in the wastewater or that were added or cultured by the wastewater treatment process.

Approximately 12,750 publicly owned treatment works (POTWs) generate 5.4 million dry metric tons of sludge annually, or 47 dry pounds of sewage sludge for every person in the U.S. This sewage sludge is commonly used or disposed of in a number of ways. Sludge is applied to agricultural and nonagricultural lands; it is sold or given away for use in home gardens, lawns, horticulture, and landscaping (often referred to as sludge distribution and marketing); it is disposed of in municipal landfills, sludge-only landfills (known as monofills), and surface disposal sites; and it is incinerated.

Table 1-1 shows the amount of sludge generated based on the size of the facility and on the amount of sewage sludge that is disposed of by a use or disposal practice. Table 1-2 shows the number of facilities employing a particular method of use or disposal. Only about one third of the sewage sludge generated in the U.S. is effectively reused by land application or is sold or given away for use in home gardens.² In comparison, Japan uses 42% of its sewage sludge for coastal reclamation and home gardening or farming uses, while the U.K. applies 51% of its sewage sludge to the land.

Table 1-1 Estimated Mass of Sludge Disposed Annually in the U.S.^a

Use or disposal practice	Reported flow rate (MGP)^b				Total^a
	>100	>10 to 100	>1 to 10	≤1
Incineration	382.9	346.5	124.8	10.5	864.7
Land application: agricultural	203.0	400.8	423.9	143.2	1170.9
Land application: compost	22.4	65.3	31.7	30.8	150.2
Land application: forests	4.5	24.5	1.0	1.3	32.3
Land application: public contact	62.1	60.5	40.3	6.3	166.1
Land application: reclamation	52.6	9.8	2.4	1.0	65.8
Land application: sale	30.6	27.8	11.9	0.8	71.1
Land application: undefined	12.7	76.4	27.2	13.0	129.3
Co-disposal: landfill	518.6	674.0	495.6	110.4	1818.7
Surface disposal: dedicated site	34.2	124...

Table of contents

• Cover
• Title Page
• Copyright Page
• Author
• Table of Contents
• 1. Introduction
• 2. Sludge
• 3. Improving Sludge Quality
• 4. Minor Residuals
• 5. Designing a Sludge Recycling Program
• 6. Land Application of Liquid Sludge
• 7. Sludge Dewatering
• 8. Lime-Stabilized Sludge
• 9. Sludge Composting
• 10. Sludge Pelletizing
• 11. Innovative Technologies for Sludge Reuse
• Index