Biosolids Treatment Processes: Handbook of Environmental Engineering, Volume 6

J.G. LLaurado (Deputy Editor, MEQ)

Management of Environmental Quality

ISSN: 1477-7835

Article publication date: 18 April 2008



LLaurado, J.G. (2008), "Biosolids Treatment Processes: Handbook of Environmental Engineering, Volume 6", Management of Environmental Quality, Vol. 19 No. 3, pp. 402-405.



Emerald Group Publishing Limited

Copyright © 2008, Emerald Group Publishing Limited

Biosolids are organic materials obtained through wastewater treatment that may be put to useful applications. Because ocean and lake disposal is no longer thought of as an appropriate alternative to utilization, land disposal of the biosolids after treatment has been increasingly accepted. Impetus in this use has been given by the United States Environmental Protection Agency [US EPA], which under Title 40 Code has established the minimum national standards for the use and disposal of municipal biosolids.

Although not categorically stated the leader from the editors' triad appears to be L.K. Wang presently a retired Dean and Director of the Lenox Institute of Water Technology, Lenox, Massachusets who has also occupied distinguished positions in industry. Chapter 12 on Elutriation and Polymer Conditioning was written in honor of Professor M.L. Granstrom, former Chairman of the Department of Civil and Environmental Engineering, Rutgers University, Piscatawy, New Jersey, who dedicated “his entire academic career to promote environmental engineering education”. He directed more than 100 PhD dissertations from students around the world. Dr Wang is among those who received supervision and guidance from Professor Granstrom and has continued spreading his message.

This tome comprises 23 chapters of unequal length written by an ensemble of 20 authors [with a lengthy appendix (55 pp.) on conversion factors, where I learned that the US inch is shorter than the British inch by the factor 0.999972]. However in 22 chapters and the appendix the lead editor is a co‐author. This tends to give a unity of purpose to the book, even though in the preface the editors make the caveat that, because of the multiple authorship, repetitions among the various texts are unavoidable. Rather than perceiving this fact, I noted in many chapters repetitions within a chapter itself. The book abounds in illustrations, pictorial and tabular, that appear in almost every page, mostly transferred from the EPA, though this is not to be construed as an uncomplimentary observation. The editors make a pledge to write down throughout the text units in both the “Imperial”‐American system and the SI; this commitment is not universally carried through and even the abbreviation for second is taken as sec instead of s. This volume is voluminous [pun intended] and with dimensions 25 × 16 × 5 cm (9.84 × 6.30×.97in.), over 800 pages and a verified weight of 4lb (1.82 kg) it is not easy to carry around.

The EPA in its Standards for the Use and Disposal of Sewage Sludge “requires that wastewater solids be processed before they are land applied. This processing is referred to as stabilization and helps minimizes odor generation, destroys pathogens … and reduces vector attraction potential”. Among the methods to stabilize wastewater solids one finds adjustment of pH by lime, anaerobic digestion, aerobic digestion, composting and heat drying. Not only does the book describe the above and other procedures in detail, but it also presents real and theoretical examples. The authors make use of mathematical equations, involving differential equations in some cases, as well as properties of chemistry, microbiology and physics. It is thus implied that civil and environmental engineering is in our times entrenched in scientific bases as contrasted with empirical accumulation of facts in earlier periods. The point is made, however, that some engineering systems do not yield to strict scientific analysis and “in these instances we [the authors] have resorted to less science in favor of more art and empiricism”.

Owing to the book's extension it is impossible to comment in detail on the contents of each chapter, so I shall try to give an overview of the different topics. After a chapter on the characteristics of biosolids, the following chapters are devoted to gravity thickening, filtration thickening, and centrifugation manipulation. Chapters 5 and 6 deal correspondingly with anaerobic and aerobic digestion. Next is lime stabilization where the characteristics of quicklime [CaO] and hydrated lime [Ca(OH)2] are summarized in a table. Attention is drawn to the causticity of these products that requires strict safety equipment: eyewash fountains, emergency showers and protective clothing.

Chapter 8 deals with pressurized ozonation. Ozone is a more powerful oxidant than oxygen but is an unstable material that must be produced at the point of use. It has been employed for disinfecting drinking water in Europe for many years. It has also been employed for treating some industrial wastes such as cyanides and phenols. Oxygenation‐ozonation systems are very powerful but the relatively high cost of ozone generation necessitates a high ozone‐utilization efficiency if ozone treatment is to be economically competitive. This is a prolix chapter where every step is analyzed carefully and in a detailed manner: from the chemical equations for ozone generation to application methods with equipment and systems for handling the operation. The reactions of ozone with inorganic and organic substances in different materials are amply documented by chemical equations with structural formulæ when required. Ozone is characterized as the strongest disinfectant as well as the strongest oxidizing agent. It seems that the new ozone generation technology will render the cost of ozonation competitive with the cost of chlorine oxidation.

Since time and temperature are important factors in determining the degree of organic waste stabilization to be obtained, a chapter is devoted to low‐temperature thermal treatment processes.

Chapter 10 presents irradiation and solid substances disinfection through two basic techniques: electron irradiation or γ‐irradiation. It is very inclusive of pathology and enumerates the commonly found infectious agents in waters: adenovirus, coxackie virus, ECHO virus, poliovirus, etc. followed by Escherichia coli, Salmonella, fecal streptococci, Shigella and continued with lists of protozoa, nematodes, helminthes, and fungi such as Actinomyces, Aspergillus and Candida albicans. The efficacy of high‐energy electrons projected through wastewater sludge is being tested at the Deer Island Wastewater Treatment Plant in Boston, Massachusets. Since the penetration of a high‐energy electron is at the most 0.5 cm, to be on the safe side it requires that the thickness of the sludge layer undergoing irradiation does not exceed 0.2 cm. Experimental data have shown that the larger pathogens are more susceptible to electron “hits” by being bigger targets. As compared to pasteurized sludge, electron radiation has less odor problems and the energy requirements (fuel and electricity) for an irradiation system are 90‐98 percent less than those for heat pasteurization. For disinfection with γ‐radiation two radionuclides, namely 137Cs and 60Co, have been considered as “fuel” sources. The isotope 137Cs has a half‐life of 30 years and is a byproduct from processing nuclear weapons waste. The 60Co has a half‐life of five years and is made by bombarding stable 59Co with neutrons. A system in active operation is in Geiselbullach [by Munich] in Germany. The 60Co‐rays are very penetrating: it takes 64 cm of thick water layer to stop 90 percent of radiation from a 60Co source and this is many times more than the penetration of an electron. However, in comparing the advantage of one system vs. the other, it must be considered that the decaying source of γ‐rays is continuous and can only be varied by exposure time whereas the electron beam generator can be turned off and on.

Other chapters deal with inorganic chemical conditioning and stabilization; elutrication [“A process of sludge conditioning whereby a sludge is washed either by fresh water or plant effluent, to reduce the sludge alkalinity and fine particles, thus decreasing the amount of required coagulant in further treatment steps, or in sludge dewatering”], and polymer conditioning; drying beds; animal wastes treatment using anaerobic lagoons [where a detailed solution to an agricultural waste treatment system for 6,000 pigs employing an anaerobic lagoon is given]; vertical shaft digestion, flotation and biofiltration; vacuum filtration; belt filter presses; pressure filtration; evaporation processes; high temperature thermal processes; and biosolids composting (the last comprising 43pp.)

Chapter 22 is devoted to vermicomposting process, i.e. “a novel municipal biosolids and solid waste treatment process that uses earthworms (Oligochaete annelids) for the biodegradation of the biosolids and/or solid waste”. An example of successful application of this technique began at Wright‐Patterson Air Force Base in Dayton, Ohio in 2002 starting with 250,000 worms “to consume a daily average of 500lbs of solid waste”. The earthworms digest vegetable matter and old newspapers. As the number of worms grows, so does the amount of waste they digest. The worms'casings replace chemical fertilization at the base's golf course. A plea is made by this chapter's authors to encourage governments to adopt this technique in the field of environmental engineering and International agencies to encourage and fund the transfer of vermicomposting [or vermistabilization] among different countries.

The last chapter, 23, describes the land application of biosolids. It is an excellent way to recycle wastewater solids as it returns valuable nutrients to the soil and favors conditions for vegetative growth, while at the same time being relatively inexpensive. This option has encountered public opposition in some sectors because of odor if the use site is near residential areas. Moreover, although beneficial to the environment, land application may have negative impacts on water, soil and air if not practiced correctly. Nevertheless, in 1995 about 54 percent of wastewater treatment plants managed biosolids through land application. To counteract the “social” opposition to this enterprise, the US Department of Agriculture, the US Food and Drug Administration, public regulators and academic researchers developed a body of regulations to “protect public health and the environment from all reasonably anticipated adverse effects”. A former official from US EPA stated in 1998: “In fact, in all the years that properly treated biosolids have been applied to the land, we have been unable to find one documented case of illness or disease that resulted”.

In this handbook there are numerous references at the end of each chapter listing complete titles and all authors for each publication, including some for 2007. While the appendix for units' conversion appears an overkill, the alphabetic subject matter index at the end of the book is skimpy. It would also be helpful to have a complete alphabetic list of abbreviations used in the text. Although many international plants and procedures are mentioned, understandably the bulk of the contents refers to United States' sites and procedures, albeit many of them are of universal application.

I detected a few errors: in p. 24, equation 7 is dimensionally incorrect; in p. 334 one reads “Pathogenic protozoa and the disease caused are listed in Table 1, together with the diseases they cause”, this is not only a repetitious statement, but is also jejune because the diseases are not listed therein; in pp. 359‐360 the sentence “This test is performed by taking tour to six large beakers” is likely to mean “… by taking four to six … ”; in p. 364 relating capital costs of ferric chloride storage and feeding facilities “if a designer needed to feed 100lb/h (45.4 kg/h) of ferric chloride the estimated cost would be 330,000USD” [editors' symbol for US$], but the price would be in fact $33,000 by accurately reading Figure 8 [p. 365]; in p. 698 mention is made of a Section 4.2, but there is no such section; in p. 701 when describing “worms in their climate‐controlled home (at a constant 70oC temperature)” probably it is intended 70oF, otherwise the worms would be “pasteurized” [this illustrates once more the hazard inherent in allowing for two different systems of units in USA!].

In pointing out the errors, their presence almost unavoidable in a book of such magnitude, I do not want to detract from its value. For each procedure or modality of biosolids treatment the purpose of a system, the listed specifications, the theoretical considerations, the necessary equipment, the operation and maintenance, the costs in power sources and number of staff, and the advantages and disadvantages of the procedure are discussed at length and in easy language. When there is a mathematical analysis it is always done with extreme clarity and step by step.

This book will be extremely useful to advanced undergraduate and graduate students – and I should also add to their teachers, preceptors and mentors –of civil and environmental engineering, to designers of wastewater treatment, biosolids and sludge treatment systems, and to scientists and researchers dealing with biosolids management operations. It is printed in acid free paper for a long duration and its format makes for a pleasant reading. Moreover, given the actual exchange for the US$, this book is a bargain for the non‐dollar area public.

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