Part I

Overview

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1Introduction

Wastewater collection and treatment have greatly reduced the number of outbreaksof disease in the United States each year. Wastewater treatment consists of a com-bination of biological, chemical, and physical processes to degrade organic andnitrogenous wastes and destroy or inactivate a large number of pathogens. Usually,chlorine (Cl2) or chlorinated compounds, ozone (O3), or ultraviolet light (uv) is usedto disinfect the treated effluent before its discharge to receiving waters.

Every stream and lake has some limited capacity to degrade wastes and reducethe number of pathogens by natural inactivation and destruction processes. Inacti-vation or destruction is achieved through adsorption, predation, dilution, change inwater temperature, and solar radiation. Because of the large quantity of effluent dis-charged to the receiving waters, the natural processes of pathogen reduction areinadequate for protection of public health. In addition, industrial wastes that alterthe water pH and provide excessive bacterial nutrients often compromise the abilityof natural processes to inactive and destroy pathogens. Therefore, the disinfectionof effluent has assumed critical importance.

The degradation of organic and nitrogenous wastes by biological wastewatertreatment plants (activated sludge and trickling filter) results in the production oflarge quantities of sludge. Numerous pathogens are contained in the sludge. Manyof the pathogens are inactivated or destroyed by additional biological, chemical, andphysical processes before its disposal.

Pathogens in wastewater and sludge represent health hazards to individualsworking at wastewater treatment facilities and sludge disposal sites. The pathogensalso represent health hazards to community members living downwind of waste-water treatment facilities and near sludge disposal sites.

A large number and diversity of pathogens are found in wastewater and sludge.The pathogens include viruses, bacteria, fungi, protozoans, helminths (worms),

Wastewater Pathogens, by Michael H. Gerardi and Mel C. ZimmermanISBN 0-471-20692-X Copyright © 2005 John Wiley & Sons, Inc.

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allergens, and toxins.The most prevalent are viruses, bacteria, fungi, protozoans, andhelminths. The pathogens are a reflection of the common diseases in a communityand may be present in numbers as great as 100,000,000 per milliliter. The pathogensof greatest concern to wastewater personnel are enteric viruses, enteric bacteria,especially Campylobacter, the bacterium Leptospira, the fungus Aspergillus, the pro-tozoans Giardia and Cryptosporidium, and the tapeworm Hymenolepis.

Pathogens enter wastewater treatment facilities from several sources. Pathogenicagents are found in fecal waste and urine from humans and animals. They can enterwastewater treatment facilities from humans who are sick or are carriers of disease.Wastewater from baths, dishwashers, showers, sinks, and washing machines also maycontain pathogens. Viruses in the feces of an infected host may be present at con-centrations as high as 10,000,000,000 per gram of wet weight of feces. Pathogenicbacteria in the feces of an infected host may be present at concentrations as highas 1,000,000 per gram of wet weight of feces.

Pathogens in animal waste on the ground can enter wastewater treatment facil-ities through inflow and infiltration (I/I). Animal wastes from meatpacking and pro-cessing facilities and from rats in sanitary sewers also serve as sources of pathogens.

Waterborne, foodborne, bloodborne [hepatitis B virus and human immunodefi-ciency virus (HIV)], and sexually transmitted pathogens are found in wastewater.Along with these pathogens, microbial toxins and allergens also are found. Viruses(Table 1.1) commonly found in wastewater include hepatitis and the human immun-odeficiency virus.

Pathogenic bacteria (Table 1.2) commonly found in wastewater include Lep-tospira and Salmonella. Pathogenic fungi (Table 1.3) commonly found in wastewaterinclude Aspergillus and Candida.

Disease-causing or parasitic protozoans (Table 1.4) commonly found in waste-water include Giardia lamblia and Cryptosporidium parvum. Parasitic helminths(Table 1.5) that have been found in relatively large numbers in wastewater includecestodes (tapeworms) such as Taenia and nematodes (roundworms) such as Ascarisand Trichuris. The U.S. Environmental Protection Agency (U.S. EPA) and Centers

4 Introduction

TABLE 1.1 Viruses/Viral Groups Commonly Found inWastewater

Virus/Viral Group Disease

Adenovirus Upper and lower respiratory tract distressCoxsackievirus Common cold and pharyngitisEnterovirus Upper respiratory tract distress and

gastroenteritisHepatitis HepatitisHIV Acquired immunodeficiency syndrome

(AIDS)Influenza “Flu”Norwalk GastroenteritisPoliovirus PoliomyelitisReovirus Upper respiratory tract distress and

gastroenteritisRotavirus Gastroenteritis

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Introduction 5

TABLE 1.3 Pathogenic Fungi Commonly Found inWastewater

Fungus/Fungi Disease

Aspergillus fumigatus “Farmer’s lung” (allergic lung disease)Candida spp. Candidiasis

TABLE 1.4 Parasitic Protozoans Commonly Found inWastewater

Protozoan Disease

Balantidium coli BalantidosisCryptosporidium parvum Cryptosporidiosis (diarrhea)Entamoeba coli Diarrhea, ulcerationEntamoeba histolytica Amebiasis (amebic dysentry)Giardia lamblia Giardiasis (diarrhea, malabsorption)

TABLE 1.2 Pathogenic Bacteria Commonly Found in Wastewater

Bacterium/Bacteria Disease

Actinomyces israelii ActinomyocsisBacillus anthracis AnthraxBrucella spp. Brucellosis (Malta fever)Campylobacter jejuni GastroenteritisClostridium spp. Gas gangreneEnterotoxigenic Escherichia coli (ETEC) Gastroenteritis, diarrheaFrancisella tularensis TularemiaLeptospira interrogans icterohemorrhagiae Leptospirosis (Weil disease)Mycobacterium tuberculosis TuberculosisNocardia spp. NocardiosisSalmonella enterica paratyphi Paratyphoid feverSalmonella spp. Salmonellosis (food poisoning)Salmonella typhi Typhoid feverShigella spp. Shigellosis (bacillary dysentery)Vibrio cholerae Cholera (Asiatic cholera)Vibrio parahaemolyticus GastroenteritisYersinia enterocolitica Yersiniosis (gastroenteritis)

TABLE 1.5 Parasitic Helminths Commonly Found in Wastewater

Helminth Type of Worm Disease

Taenia saginata Tapeworm TaeniasisAncylostoma spp. Roundworm AnemiaAscaris spp. Roundworm AscariasisEchinococcus granulosus Tapeworm EchinococcosisEnterobius spp. Roundworm EnterobiasisNecator americanus Roundworm Hookworm disease (anemia)Schistomsoma spp. Flatworm Schistosomiasis (swimmer’s itch)Strongyloides stercoralis Roundworm StrongyloidiasisTaenia spp. Tapeworm TaeniasisTrichuris spp. Roundworm Anemia, diarrhea

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for Disease Control and Prevention (CDC) maintain data on many of these proto-zoan and helminthic diseases as well as viral, bacterial, and fungal diseases. Thisinformation as well as data on other diseases also is maintained by CDC and stateand local health departments.

6 Introduction

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