The Counts and Environmental Risks of Pathogens in Sewage Sludge from Yangtze River Delta

In order to understand land application of sewage sludge, the characterization of fecal coliform, salmonella and helminth in sewage sludge was invested from 45 different wastewater treatment plant in Yangtze River Delta, and
Fecal

coliform
and water content were detected at 7th, 14th, 21st and 28th air-drying days to know the relationship between the counts of
fecal

coliform
and water contents of sludges. The results showed that
fecal

coliform
were found in 89.6% of the sludge samples, the counts of fecal coliform ranged from 0 to 3.4times10
⁶
MPN g
^-1
, average 3.8times10
⁵
MPN g
^-1
. The counts had very high ranges among the tested samples, for the river water sludge and sludge products,
fecal

coliform
counts were much lower than that of domestic and domestic-industrial mixed flow sludge. The detection rate of
ascarid

ova,

entamoeba

histolytica

and

giardia

lamblia
cysts were 24.4%, 22.0% and 7.3%, respectively.
Salmonella
was also found in some sludge samples. Counts of
Fecal

coliform
decreased during early drying days, re-growth phenomenon was seen in about 3-4 weeks.
Fecal

coliform
counts fell down along with the decrease of water content. In conclusion, the pathogens counts were greatly different in all kinds of sludge, they exceeded the guidance level in some sludge samples, and
fecal

coliform
is an important factor to restrict sludge land use in Yangtze River Delta.