Organic Waste Recycling

Characteristics of organic wastes 59

Concentration per liter in town sewage

b^10120

Total excreted daily by town

5 × 10

8

6 × 10

9

Total excreted daily per infected person

c

10

4

2 × 10

5

Average number of organisms per gram of feces

b^10

4

2 × 10

3f

Prevalence of infection in country (percentage)

a

(^160)
Table 2.22 Possible output of selected pathogens in the feces and sewage of a tropical community of 50,000 in a developing countrPathogen Taenia saginata Trichuris trichiura
y(
continued
)
a The prevalences given in this column refer to infection and not to morbidity b It must be recognized that the pathogens listed have different abilities to survive outside the host, and that the concentrati
on
of some of them will rapidly decline after the feces have been passed. The concentrations of pathogens per liter in the sewageof the town were calculated by assuming that 100 liters of sewage are produced daily per capita, amd that 90 percent of the pathogens do not enter the sewers or are inactivated in the first few minutes after excretion c To calculate this figure it is necessary to estimate a mean fecal weight for those people infected. This must necessarily be t
he
roughest of estimates because of the age-specific fecal weights and the age distribution of infected people in the community. It was assumed that people over 15 years old excrete 150 g daily, and that people under 15 excrete, on average 75 g daily. It was also assumed that two-thirds of all infected people are under 15. This gives a mean fecal weight for infected individuals of 100 g d Includes polio-, echo-, and coxsackieviruses e Includes enterotoxigenic, enteroinvasive, and enteropathogenic
E.coli
f The distribution of egg output from people infected by these helminthes is extremely skewed; a few people excrete very high egg concentrations gAncylostoma duodenale
and
Necator americanus
From Feachem
et al.
1983; reproduced with permission of the World Bank